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Koga S, Okushima D, Barstow TJ, Rossiter HB, Kondo N, Poole DC. Near-infrared spectroscopy of superficial and deep rectus femoris reveals markedly different exercise response to superficial vastus lateralis. Physiol Rep 2018; 5:5/17/e13402. [PMID: 28912130 PMCID: PMC5599862 DOI: 10.14814/phy2.13402] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2017] [Revised: 08/08/2017] [Accepted: 08/08/2017] [Indexed: 12/13/2022] Open
Abstract
To date our knowledge of skeletal muscle deoxygenation as measured by near-infrared spectroscopy (NIRS) is predicated almost exclusively on sampling of superficial muscle(s), most commonly the vastus lateralis (VL-s). Recently developed high power NIRS facilitates simultaneous sampling of deep (i.e., rectus femoris, RF-d) and superficial muscles of RF (RF-s) and VL-s. Because deeper muscle is more oxidative with greater capillarity and sustains higher blood flows than superficial muscle, we used time-resolved NIRS to test the hypotheses that, following exercise onset, the RF-d has slower deoxy[Hb+Mb] kinetics with reduced amplitude than superficial muscles. Thirteen participants performed cycle exercise transitions from unloaded to heavy work rates. Within the same muscle (RF-s vs. RF-d) deoxy[Hb+Mb] kinetics (mean response time, MRT) and amplitudes were not different. However, compared with the kinetics of VL-s, deoxy[Hb+Mb] of RF-s and RF-d were slower (MRT: RF-s, 51 ± 23; RF-d, 55 ± 29; VL-s, 18 ± 6 s; P < 0.05). Moreover, the amplitude of total[Hb+Mb] was greater for VL-s than both RF-s and RF-d (P < 0.05). Whereas pulmonary V˙O2 kinetics (i.e., on vs. off) were symmetrical in heavy exercise, there was a marked on-off asymmetry of deoxy[Hb+Mb] for all three sites i.e., MRT-off > MRT-on (P < 0.05). Collectively these data reveal profoundly different O2 transport strategies, with the RF-s and RF-d relying proportionately more on elevated perfusive and the VL-s on diffusive O2 transport. These disparate O2 transport strategies and their temporal profiles across muscles have previously been concealed within the "global" pulmonary V˙O2 response.
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Affiliation(s)
- Shunsaku Koga
- Applied Physiology Laboratory, Kobe Design University, Kobe, Japan
| | - Dai Okushima
- Applied Physiology Laboratory, Kobe Design University, Kobe, Japan
| | - Thomas J Barstow
- Departments of Anatomy and Physiology, and Kinesiology, Kansas State University, Manhattan, Kansas
| | - Harry B Rossiter
- Rehabilitation Clinical Trials Center, Division of Respiratory & Critical Care Physiology & Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California.,Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Narihiko Kondo
- Applied Physiology Laboratory, Kobe University, Kobe, Japan
| | - David C Poole
- Departments of Anatomy and Physiology, and Kinesiology, Kansas State University, Manhattan, Kansas
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Ward SA. Open-circuit respirometry: real-time, laboratory-based systems. Eur J Appl Physiol 2018; 118:875-898. [PMID: 29728765 DOI: 10.1007/s00421-018-3860-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 03/30/2018] [Indexed: 11/28/2022]
Abstract
This review explores the conceptual and technological factors integral to the development of laboratory-based, automated real-time open-circuit mixing-chamber and breath-by-breath (B × B) gas-exchange systems, together with considerations of assumptions and limitations. Advances in sensor technology, signal analysis, and digital computation led to the emergence of these technologies in the mid-20th century, at a time when investigators were beginning to recognise the interpretational advantages of nonsteady-state physiological-system interrogation in understanding the aetiology of exercise (in)tolerance in health, sport, and disease. Key milestones include the 'Auchincloss' description of an off-line system to estimate alveolar O2 uptake B × B during exercise. This was followed by the first descriptions of real-time automated O2 uptake and CO2 output B × B measurement by Beaver and colleagues and by Linnarsson and Lindborg, and mixing-chamber measurement by Wilmore and colleagues. Challenges to both approaches soon emerged: e.g., the influence of mixing-chamber washout kinetics on mixed-expired gas concentration determination, and B × B alignment of gas-concentration signals with respired flow. The challenging algorithmic and technical refinements required for gas-exchange estimation at the alveolar level have also been extensively explored. In conclusion, while the technology (both hardware and software) underpinning real-time automated gas-exchange measurement has progressively advanced, there are still concerns regarding accuracy especially under the challenging conditions of changing metabolic rate.
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Affiliation(s)
- Susan A Ward
- Human Bio-Energetics Research Centre, Crickhowell, Wales, NP8 1AT, UK.
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Korzeniewski B. Regulation of oxidative phosphorylation is different in electrically- and cortically-stimulated skeletal muscle. PLoS One 2018; 13:e0195620. [PMID: 29698403 PMCID: PMC5919680 DOI: 10.1371/journal.pone.0195620] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 03/26/2018] [Indexed: 01/09/2023] Open
Abstract
A computer model of the skeletal muscle bioenergetic system was used to study the regulation of oxidative phosphorylation (OXPHOS) in electrically-stimulated and cortically-stimulated skeletal muscle. Two types of the dependence of the intensity of each-step activation (ESA) of OXPHOS complexes on ATP usage activity were tested: power-type dependence and saturating-type dependence. The dependence of muscle oxygen consumption ([Formula: see text]), phosphocreatine (PCr), cytosolic ADP, ATP, inorganic phosphate (Pi), pH and τp (characteristic transition time) of the principal component of the muscle [Formula: see text] on-kinetics on the ATP usage activity was simulated for both types of the ESA intensity-ATP usage activity dependence. Computer simulations involving the power-type dependence predict system properties that agree well with experimental data for electrically-stimulated muscle. On the other hand, model predictions for the saturating-type dependence in the presence of the 'additional' ATP usage (postulated previously to underlie the slow component of the VO2 on-kinetics) reproduce well system properties encountered in human skeletal muscle during voluntary exercise. It is postulated that the difference between the regulation and kinetic properties of the system in electrically- and cortically-stimulated muscle is mostly due to the different muscle fibers recruitment pattern. In the former, all fiber types are recruited in parallel already at low power output (PO) values, while in the latter type I fibers (with higher ESA intensity) are stimulated at low PO values, while type II fibers (especially type II b and IIx fibers) with low ESA intensity are recruited predominantly at high PO values.
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Affiliation(s)
- Bernard Korzeniewski
- Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland
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Ye L, Argha A, Yu H, Celler BG, Nguyen HT, Su S. Dynamic characteristics of oxygen consumption. Biomed Eng Online 2018; 17:44. [PMID: 29685173 PMCID: PMC5914074 DOI: 10.1186/s12938-018-0476-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 04/16/2018] [Indexed: 12/03/2022] Open
Abstract
Background Previous studies have indicated that oxygen uptake (\documentclass[12pt]{minimal}
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\begin{document}$$VO_2$$\end{document}VO2) is one of the most accurate indices for assessing the cardiorespiratory response to exercise. In most existing studies, the response of \documentclass[12pt]{minimal}
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\begin{document}$$VO_2$$\end{document}VO2 is often roughly modelled as a first-order system due to the inadequate stimulation and low signal to noise ratio. To overcome this difficulty, this paper proposes a novel nonparametric kernel-based method for the dynamic modelling of \documentclass[12pt]{minimal}
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\begin{document}$$VO_2$$\end{document}VO2 response to provide a more robust estimation. Methods Twenty healthy non-athlete participants conducted treadmill exercises with monotonous stimulation (e.g., single step function as input). During the exercise, \documentclass[12pt]{minimal}
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\begin{document}$$VO_2$$\end{document}VO2 was measured and recorded by a popular portable gas analyser (\documentclass[12pt]{minimal}
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\begin{document}$$K4b^2$$\end{document}K4b2, COSMED). Based on the recorded data, a kernel-based estimation method was proposed to perform the nonparametric modelling of \documentclass[12pt]{minimal}
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\begin{document}$$VO_2$$\end{document}VO2. For the proposed method, a properly selected kernel can represent the prior modelling information to reduce the dependence of comprehensive stimulations. Furthermore, due to the special elastic net formed by \documentclass[12pt]{minimal}
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\begin{document}$$\mathcal {L}_1$$\end{document}L1 norm and kernelised \documentclass[12pt]{minimal}
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\begin{document}$$\mathcal {L}_2$$\end{document}L2 norm, the estimations are smooth and concise. Additionally, the finite impulse response based nonparametric model which estimated by the proposed method can optimally select the order and fit better in terms of goodness-of-fit comparing to classical methods. Results Several kernels were introduced for the kernel-based \documentclass[12pt]{minimal}
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\begin{document}$$VO_2$$\end{document}VO2 modelling method. The results clearly indicated that the stable spline (SS) kernel has the best performance for \documentclass[12pt]{minimal}
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\begin{document}$$VO_2$$\end{document}VO2 modelling. Particularly, based on the experimental data from 20 participants, the estimated response from the proposed method with SS kernel was significantly better than the results from the benchmark method [i.e., prediction error method (PEM)] (\documentclass[12pt]{minimal}
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\begin{document}$$76.0\pm 5.72$$\end{document}76.0±5.72 vs \documentclass[12pt]{minimal}
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\begin{document}$$71.4\pm 7.24\%$$\end{document}71.4±7.24%). Conclusions The proposed nonparametric modelling method is an effective method for the estimation of the impulse response of VO2—Speed system. Furthermore, the identified average nonparametric model method can dynamically predict \documentclass[12pt]{minimal}
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\begin{document}$$VO_2$$\end{document}VO2 response with acceptable accuracy during treadmill exercise.
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Affiliation(s)
- Lin Ye
- School of Biomedical Engineering, University of Technology Sydney, 15 Broadway, Sydney, Australia
| | - Ahmadreza Argha
- School of Electrical Engineering, University of New South Wales, Sydney, Australia
| | - Hairong Yu
- School of Biomedical Engineering, University of Technology Sydney, 15 Broadway, Sydney, Australia
| | - Branko G Celler
- School of Electrical Engineering, University of New South Wales, Sydney, Australia
| | - Hung T Nguyen
- School of Biomedical Engineering, University of Technology Sydney, 15 Broadway, Sydney, Australia
| | - Steven Su
- School of Biomedical Engineering, University of Technology Sydney, 15 Broadway, Sydney, Australia.
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George MA, McLay KM, Doyle-Baker PK, Reimer RA, Murias JM. Fitness Level and Not Aging per se, Determines the Oxygen Uptake Kinetics Response. Front Physiol 2018; 9:277. [PMID: 29662455 PMCID: PMC5890239 DOI: 10.3389/fphys.2018.00277] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 03/08/2018] [Indexed: 11/16/2022] Open
Abstract
Although aging has been associated to slower V˙O2 kinetics, some evidence indicates that fitness status and not aging per se might modulate this response. The main goal of this study was to examine the V˙O2, deoxygenated hemoglobin+myoglobin (deoxy-[Hb+Mb]) kinetics, and the NIRS-derived vascular reperfusion responses in older compared to young men of different training levels (i.e., inactive, recreationally active, and endurance trained). Ten young inactive [YI; 26 ± 5 yrs.; peak V˙O2 (V˙O2peak), 2.96 ± 0.55 L·min−1], 10 young recreationally active (YR; 26 ± 6 yrs.; 3.92 ± 0.33 L·min−1), 10 young endurance trained (YT; 30 ± 4 yrs.; 4.42 ± 0.32 L·min−1), 7 older inactive (OI; 69 ± 4 yrs.; 2.50 ± 0.31 L·min−1), 10 older recreationally active (OR; 69 ± 5 yrs.; 2.71 ± 0.42 L·min−1), and 10 older endurance trained (OT; 66 ± 3 yrs.; 3.20 ± 0.35 L·min−1) men completed transitions of moderate intensity cycling exercise (MODS) to determine V˙O2 and deoxy-[Hb+Mb] kinetics, and the deoxy-[Hb+Mb]/V˙O2 ratio. The time constant of V˙O2 (τV˙O2) was greater in YI (38.8 ± 10.4 s) and OI (44.1 ± 10.8 s) compared with YR (26.8 ± 7.5 s) and OR (26.6 ± 6.5 s), as well as compared to YT (14.8 ± 3.4 s), and OT (17.7 ± 2.7 s) (p < 0.05). τV˙O2 was greater in YR and OR compared with YT and OT (p < 0.05). The deoxy-[Hb+Mb]/V˙O2 ratio was greater in YI (1.23 ± 0.05) and OI (1.29 ± 0.08) compared with YR (1.11 ± 0.03) and OR (1.13 ± 0.06), as well as compared to YT (1.01 ± 0.03), and OT (1.06 ± 0.03) (p < 0.05). Similarly, the deoxy-[Hb+Mb]/ V˙O2 ratio was greater in YR and OR compared with YT and OT (p < 0.05). There was a main effect of training (p = 0.033), whereby inactive (p = 0.018) and recreationally active men (p = 0.031) had significantly poorer vascular reperfusion than endurance trained men regardless of age. This study demonstrated not only that age-related slowing of V˙O2 kinetics can be eliminated in endurance trained individuals, but also that inactive lifestyle negatively impacts the V˙O2 kinetics response of young healthy individuals.
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Affiliation(s)
| | - Kaitlin M McLay
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
| | - Patricia K Doyle-Baker
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.,Faculty of Environmental Design, University of Calgary, Calgary, AB, Canada
| | - Raylene A Reimer
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.,Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Juan M Murias
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
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56
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Keir DA, Paterson DH, Kowalchuk JM, Murias JM. Using ramp-incremental V̇O 2 responses for constant-intensity exercise selection. Appl Physiol Nutr Metab 2018; 43:882-892. [PMID: 29570982 DOI: 10.1139/apnm-2017-0826] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Despite compelling evidence to the contrary, the view that oxygen uptake (V̇O2) increases linearly with exercise intensity (e.g., power output, speed) until reaching its maximum persists within the exercise physiology literature. This viewpoint implies that the V̇O2 response at any constant intensity is predictable from a ramp-incremental exercise test. However, the V̇O2 versus task-specific exercise intensity relationship constructed from ramp-incremental versus constant-intensity exercise are not equivalent preventing the use of V̇O2 responses from 1 domain to predict those of the other. Still, this "linear" translational framework continues to be adopted as the guiding principle for aerobic exercise prescription and there remains in the sport science literature a lack of understanding of how to interpret V̇O2 responses to ramp-incremental exercise and how to use those data to assign task-specific constant-intensity exercise. The objectives of this paper are to (i) review the factors that disassociate the V̇O2 versus exercise intensity relationship between ramp-incremental and constant-intensity exercise paradigms; (ii) identify when it is appropriate (or not) to use ramp V̇O2 responses to accurately assign constant-intensity exercise; and (iii) illustrate the technical and theoretical challenges with prescribing constant-intensity exercise solely on information acquired from ramp-incremental tests. Actual V̇O2 data collected during cycling exercise and V̇O2 kinetics modelling are presented to exemplify these concepts. Possible solutions to overcome these challenges are also presented to inform on appropriate intensity selection for individual-specific aerobic exercise prescription in both research and practical settings.
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Affiliation(s)
- Daniel A Keir
- a University Health Network, Department of Medicine, Toronto, Ontario, Canada.,b Canadian Centre for Activity and Aging, The University of Western Ontario, London, ON N6A 3K7, Canada.,c School of Kinesiology, The University of Western Ontario, London, ON N6A 3K7, Canada
| | - Donald H Paterson
- b Canadian Centre for Activity and Aging, The University of Western Ontario, London, ON N6A 3K7, Canada.,c School of Kinesiology, The University of Western Ontario, London, ON N6A 3K7, Canada
| | - John M Kowalchuk
- b Canadian Centre for Activity and Aging, The University of Western Ontario, London, ON N6A 3K7, Canada.,c School of Kinesiology, The University of Western Ontario, London, ON N6A 3K7, Canada.,d Department of Physiology and Pharmacology, The University of Western Ontario, London, ON N6A 3K7, Canada
| | - Juan M Murias
- e Faculty of Kinesiology, University of Calgary, Calgary, AB T2N 1N4, Canada
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do Nascimento Salvador PC, Souza KMD, De Lucas RD, Guglielmo LGA, Denadai BS. The effects of priming exercise on the V̇O 2 slow component and the time-course of muscle fatigue during very-heavy-intensity exercise in humans. Appl Physiol Nutr Metab 2018; 43:909-919. [PMID: 29566544 DOI: 10.1139/apnm-2017-0769] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We hypothesized that prior exercise would attenuate the muscle fatigue accompanied by oxygen uptake slow-component (V̇O2SC) behavior during a subsequent very-heavy (VH)-intensity cycling exercise. Thirteen healthy male subjects performed tests to determine the critical power (CP) and the fixed amount of work above CP ([Formula: see text]) and performed 6 square-wave bouts until 3 or 8 min, each at a work rate set to deplete 70% [Formula: see text] in 8 min, with a maximal isokinetic effort before and after the conditions without (VHCON) and with prior exercise (VHEXP), to measure the cycling peak torque decrement. The V̇O2SC magnitude at 3 min (VHCON = 0.280 ± 0.234, VHEXP = 0.116 ± 0.109 L·min-1; p = 0.04) and the V̇O2SC trajectory were significantly lower for VHEXP (VHCON = 0.108 ± 0.042, VHEXP = 0.063 ± 0.031 L·min-2; p < 0.01), leading to a V̇O2SC magnitude at the eighth minute that was significantly lower than VHCON (VHCON = 0.626 ± 0.296 L·min-1, VHEXP = 0.337 ± 0.179; p < 0.01). Conversely, peak torque progressively decreased from pre-exercise to 3 min (Δtorque = 21.5 ± 7.7 vs. 19.6 ± 9.2 Nm) and to 8 min (Δtorque = 29.4 ± 15.8 vs. 27.5 ± 12.0 Nm) at VHCON and VHEXP, respectively, without significant differences between conditions. Regardless of the condition, there was a significant relationship between Δtorque and the V̇O2SC (R2: VHCON = 0.23, VHEXP = 0.25; p = 0.01). Considering that "priming" effects on the V̇O2SC were not accompanied by the muscle force behavior, these findings do not support the hypothesis of a "causal" relationship between the time-course of muscle fatigue and V̇O2SC.
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Affiliation(s)
| | - Kristopher Mendes de Souza
- a Physical effort Laboratory, Sports Center, Federal University of Santa Catarina, Florianópolis 88040-900, Brazil
| | - Ricardo Dantas De Lucas
- a Physical effort Laboratory, Sports Center, Federal University of Santa Catarina, Florianópolis 88040-900, Brazil
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Hirai DM, Craig JC, Colburn TD, Eshima H, Kano Y, Sexton WL, Musch TI, Poole DC. Skeletal muscle microvascular and interstitial PO2 from rest to contractions. J Physiol 2018; 596:869-883. [PMID: 29288568 DOI: 10.1113/jp275170] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 12/01/2017] [Indexed: 01/21/2023] Open
Abstract
KEY POINTS Oxygen pressure gradients across the microvascular walls are essential for oxygen diffusion from blood to tissue cells. At any given flux, the magnitude of these transmural gradients is proportional to the local resistance. The greatest resistance to oxygen transport into skeletal muscle is considered to reside in the short distance between red blood cells and myocytes. Although crucial to oxygen transport, little is known about transmural pressure gradients within skeletal muscle during contractions. We evaluated oxygen pressures within both the skeletal muscle microvascular and interstitial spaces to determine transmural gradients during the rest-contraction transient in anaesthetized rats. The significant transmural gradient observed at rest was sustained during submaximal muscle contractions. Our findings support that the blood-myocyte interface provides substantial resistance to oxygen diffusion at rest and during contractions and suggest that modulations in microvascular haemodynamics and red blood cell distribution constitute primary mechanisms driving increased transmural oxygen flux with contractions. ABSTRACT Oxygen pressure (PO2) gradients across the blood-myocyte interface are required for diffusive O2 transport, thereby supporting oxidative metabolism. The greatest resistance to O2 flux into skeletal muscle is considered to reside between the erythrocyte surface and adjacent sarcolemma, although this has not been measured during contractions. We tested the hypothesis that O2 gradients between skeletal muscle microvascular (PO2 mv ) and interstitial (PO2 is ) spaces would be present at rest and maintained or increased during contractions. PO2 mv and PO2 is were determined via phosphorescence quenching (Oxyphor probes G2 and G4, respectively) in the exposed rat spinotrapezius during the rest-contraction transient (1 Hz, 6 V; n = 8). PO2 mv was higher than PO2 is in all instances from rest (34.9 ± 6.0 versus 15.7 ± 6.4) to contractions (28.4 ± 5.3 versus 10.6 ± 5.2 mmHg, respectively) such that the mean PO2 gradient throughout the transient was 16.9 ± 6.6 mmHg (P < 0.05 for all). No differences in the amplitude of PO2 fall with contractions were observed between the microvasculature and interstitium (10.9 ± 2.3 versus 9.0 ± 3.5 mmHg, respectively; P > 0.05). However, the speed of the PO2 is fall during contractions was slower than that of PO2 mv (time constant: 12.8 ± 4.7 versus 9.0 ± 5.1 s, respectively; P < 0.05). Consistent with our hypothesis, a significant transmural gradient was sustained (but not increased) from rest to contractions. This supports that the blood-myocyte interface is the site of a substantial PO2 gradient driving O2 diffusion during metabolic transients. Based on Fick's law, elevated O2 flux with contractions must thus rely primarily on modulations in effective diffusing capacity (mainly erythrocyte haemodynamics and distribution) as the PO2 gradient is not increased.
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Affiliation(s)
- Daniel M Hirai
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Jesse C Craig
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Trenton D Colburn
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Hiroaki Eshima
- Department of Engineering Science, University of Electro-Communications, Tokyo, Japan
| | - Yutaka Kano
- Department of Engineering Science, University of Electro-Communications, Tokyo, Japan
| | - William L Sexton
- Department of Physiology, A.T. Still University of Health Sciences, Kirksville, MO, USA
| | - Timothy I Musch
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, KS, USA
| | - David C Poole
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, KS, USA
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Storniolo JL, Pavei G, Minetti AE. A "Wearable" Test for Maximum Aerobic Power: Real-Time Analysis of a 60-m Sprint Performance and Heart Rate Off-Kinetics. Front Physiol 2017; 8:868. [PMID: 29163210 PMCID: PMC5672015 DOI: 10.3389/fphys.2017.00868] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 10/17/2017] [Indexed: 11/13/2022] Open
Abstract
Maximum aerobic power (V˙O2peak) as an indicator of body fitness is today a very well-known concept not just for athletes but also for the layman. Unfortunately, the accurate measurement of that variable has remained a complex and exhaustive laboratory procedure, which makes it inaccessible to many active people. In this paper we propose a quick estimate of it, mainly based on the heart rate off-kinetics immediately after an all-out 60-m sprint run. The design of this test took into account the recent availability of wrist wearable, heart band free, multi-sensor smart devices, which could also inertially detect the different phases of the sprint and check the distance run. 25 subjects undertook the 60-m test outdoor and a V˙O2peak test on the laboratory treadmill. Running average speed, HR excursion during the sprint and the time constant (τ) of HR exponential decay in the off-kinetics were fed into a multiple regression, with measured V˙O2peak as the dependent variable. Statistics revealed that within the investigated range (25–55 ml O2/(kg min)), despite a tendency to overestimate low values and underestimate high values, the three predictors confidently estimate individual V˙O2peak (R2 = 0.65, p < 0.001). The same analysis has been performed on a 5-s averaged time course of the same measured HR off-kinetics, as these are the most time resolved data for HR provided by many modern smart watches. Results indicate that despite of the substantial reduction in sample size, predicted V˙O2peak still explain 59% of the variability of the measured V˙O2peak.
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Affiliation(s)
- Jorge L Storniolo
- Laboratory of Locomotion Physiomechanics, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Gaspare Pavei
- Laboratory of Locomotion Physiomechanics, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Alberto E Minetti
- Laboratory of Locomotion Physiomechanics, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
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Davies MJ, Benson AP, Cannon DT, Marwood S, Kemp GJ, Rossiter HB, Ferguson C. Dissociating external power from intramuscular exercise intensity during intermittent bilateral knee-extension in humans. J Physiol 2017; 595:6673-6686. [PMID: 28776675 PMCID: PMC5663836 DOI: 10.1113/jp274589] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 07/28/2017] [Indexed: 12/25/2022] Open
Abstract
Key points Continuous high‐intensity constant‐power exercise is unsustainable, with maximal oxygen uptake (V˙O2 max ) and the limit of tolerance attained after only a few minutes. Performing the same power intermittently reduces the O2 cost of exercise and increases tolerance. The extent to which this dissociation is reflected in the intramuscular bioenergetics is unknown. We used pulmonary gas exchange and 31P magnetic resonance spectroscopy to measure whole‐body V˙O2, quadriceps phosphate metabolism and pH during continuous and intermittent exercise of different work:recovery durations. Shortening the work:recovery durations (16:32 s vs. 32:64 s vs. 64:128 s vs. continuous) at a work rate estimated to require 110% peak aerobic power reduced V˙O2, muscle phosphocreatine breakdown and muscle acidification, eliminated the glycolytic‐associated contribution to ATP synthesis, and increased exercise tolerance. Exercise intensity (i.e. magnitude of intramuscular metabolic perturbations) can be dissociated from the external power using intermittent exercise with short work:recovery durations.
Abstract Compared with work‐matched high‐intensity continuous exercise, intermittent exercise dissociates pulmonary oxygen uptake (V˙O2) from the accumulated work. The extent to which this reflects differences in O2 storage fluctuations and/or contributions from oxidative and substrate‐level bioenergetics is unknown. Using pulmonary gas‐exchange and intramuscular 31P magnetic resonance spectroscopy, we tested the hypotheses that, at the same power: ATP synthesis rates are similar, whereas peak V˙O2 amplitude is lower in intermittent vs. continuous exercise. Thus, we expected that: intermittent exercise relies less upon anaerobic glycolysis for ATP provision than continuous exercise; shorter intervals would require relatively greater fluctuations in intramuscular bioenergetics than in V˙O2 compared to longer intervals. Six men performed bilateral knee‐extensor exercise (estimated to require 110% peak aerobic power) continuously and with three different intermittent work:recovery durations (16:32, 32:64 and 64:128 s). Target work duration (576 s) was achieved in all intermittent protocols; greater than continuous (252 ± 174 s; P < 0.05). Mean ATP turnover rate was not different between protocols (∼43 mm min−1 on average). However, the intramuscular phosphocreatine (PCr) component of ATP generation was greatest (∼30 mm min−1), and oxidative (∼10 mm min−1) and anaerobic glycolytic (∼1 mm min−1) components were lowest for 16:32 and 32:64 s intermittent protocols, compared to 64:128 s (18 ± 6, 21 ± 10 and 10 ± 4 mm min−1, respectively) and continuous protocols (8 ± 6, 20 ± 9 and 16 ± 14 mm min−1, respectively). As intermittent work duration increased towards continuous exercise, ATP production relied proportionally more upon anaerobic glycolysis and oxidative phosphorylation, and less upon PCr breakdown. However, performing the same high‐intensity power intermittently vs. continuously reduced the amplitude of fluctuations in V˙O2 and intramuscular metabolism, dissociating exercise intensity from the power output and work done. Continuous high‐intensity constant‐power exercise is unsustainable, with maximal oxygen uptake (V˙O2 max ) and the limit of tolerance attained after only a few minutes. Performing the same power intermittently reduces the O2 cost of exercise and increases tolerance. The extent to which this dissociation is reflected in the intramuscular bioenergetics is unknown. We used pulmonary gas exchange and 31P magnetic resonance spectroscopy to measure whole‐body V˙O2, quadriceps phosphate metabolism and pH during continuous and intermittent exercise of different work:recovery durations. Shortening the work:recovery durations (16:32 s vs. 32:64 s vs. 64:128 s vs. continuous) at a work rate estimated to require 110% peak aerobic power reduced V˙O2, muscle phosphocreatine breakdown and muscle acidification, eliminated the glycolytic‐associated contribution to ATP synthesis, and increased exercise tolerance. Exercise intensity (i.e. magnitude of intramuscular metabolic perturbations) can be dissociated from the external power using intermittent exercise with short work:recovery durations.
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Affiliation(s)
- Matthew J Davies
- School of Biomedical Sciences, Faculty of Biological Sciences & Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK
| | - Alan P Benson
- School of Biomedical Sciences, Faculty of Biological Sciences & Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK
| | - Daniel T Cannon
- School of Exercise & Nutritional Sciences, San Diego State University, San Diego, CA, USA
| | - Simon Marwood
- School of Health Sciences, Liverpool Hope University, Liverpool, UK
| | - Graham J Kemp
- Magnetic Resonance & Image Analysis Research Centre, University of Liverpool, Liverpool, UK.,Department of Musculoskeletal Biology, University of Liverpool, Liverpool, UK
| | - Harry B Rossiter
- School of Biomedical Sciences, Faculty of Biological Sciences & Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK.,Rehabilitation Clinical Trials Center, Division of Respiratory & Critical Care Physiology & Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA
| | - Carrie Ferguson
- School of Biomedical Sciences, Faculty of Biological Sciences & Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK
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Harris E, Rakobowchuk M, Birch KM. Interval exercise increases angiogenic cell function in postmenopausal women. BMJ Open Sport Exerc Med 2017; 3:e000248. [PMID: 29021911 PMCID: PMC5633736 DOI: 10.1136/bmjsem-2017-000248] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2017] [Indexed: 01/17/2023] Open
Abstract
INTRODUCTION Exercise can help to negate the increased cardiovascular disease risk observed in women after the menopausal transition. This study sought to determine whether interval or continuous exercise has differential effects on endothelial function and circulating angiogenic cell (CAC) number and function in postmenopausal women. METHODS Fifteen healthy postmenopausal women completed a 30 min acute moderate-intensity continuous (CON) and interval exercise (MOD-INT) session on a cycle ergometer on separate days. Nine participants completed a further single 30 min acute heavy-intensity interval (HEAVY-INT) exercise session. Brachial artery flow-mediated dilation (FMD) was assessed pre-exercise and 15 min post-exercise session. CAC number and colony-forming capacity in vitro were assessed post exercise and compared with resting levels. RESULTS FMD and CAC number did not change post exercise regardless of exercise type (p>0.05). However, the number (mean±SD) of colony-forming units (CFUs) increased from visit 1 (12±10 CFUs/well) to post MOD-INT (32±30 CFUs/well) and post HEAVY-INT (38±23 CFUs/well) but not post CON (13±14 CFUs/well). CONCLUSION A single session of interval exercise is more effective than a continuous exercise session for increasing the intercellular communication of CACs, regardless of exercise intensity. The enhanced ability of CACs to form colonies may reflect an increased number and/or function of angiogenic T-cells. The repeated exertions to higher work rates during interval exercise may explain this response. Repeated exercise sessions might be required to improve FMD in postmenopausal women.
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Affiliation(s)
- Emma Harris
- School of Human and Health Sciences, University of Huddersfield, Huddersfield, UK
| | - Mark Rakobowchuk
- Department of Biological Sciences, Faculty of Science, Thompson Rivers University, Kamloops, British Columbia, Canada
| | - Karen M Birch
- Multidisciplinary Cardiovascular Research Centre, Faculty of Biological Sciences, University of Leeds, Leeds, UK
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Mattioni Maturana F, Peyrard A, Temesi J, Millet GY, Murias JM. Faster V̇O 2 kinetics after priming exercises of different duration but same fatigue. J Sports Sci 2017; 36:1095-1102. [PMID: 28721747 DOI: 10.1080/02640414.2017.1356543] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
This study compared the responses of two priming exercises of similar fatigue on the adjustment of the oxygen uptake time constant (τV̇O2) in cycling. Ten healthy young adults (25 ± 3 yr) performed: three step transitions from a 20-W baseline to the power output (PO) below the gas exchange threshold (MOD, MODPRE); a 3-min bout (P3MIN) at 90% of peak PO (POpeak), followed by MOD (MOD3MIN); and a 6-min bout (P6MIN) at 80% of POpeak, followed by MOD (MOD6MIN). The O2 supply-to-O2 demand ([HHb]/V̇O2) ratio was calculated for MODPRE, MOD3MIN, and MOD6MIN. Neuromuscular fatigue was measured isometrically pre- and post-priming exercise. Reductions in maximal voluntary contraction (-29 ± 6 vs -34 ± 7%) and high-frequency doublet amplitude (-48 ± 13 vs -43 ± 11%) were not significantly different between P3MIN vs P6MIN, suggesting similar fatigue. τV̇O2 for MOD3MIN and MOD6MIN were similar, being ~25% smaller than MODPRE. The [HHb]/V̇O2 ratio was significantly greater in MODPRE (1.13 ± 0.12) compared to MOD3MIN (1.02 ± 0.04) and MOD6MIN (1.02 ± 0.04). This study showed that priming exercise of shorter duration and higher intensity, was sufficient to accelerate V̇O2 kinetics similarly to that observed subsequent to P6MIN when the muscle fatigue was similar.
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Affiliation(s)
- Felipe Mattioni Maturana
- a Human Performance Laboratory, Faculty of Kinesiology , University of Calgary , Calgary , Canada
| | - Arthur Peyrard
- a Human Performance Laboratory, Faculty of Kinesiology , University of Calgary , Calgary , Canada
| | - John Temesi
- a Human Performance Laboratory, Faculty of Kinesiology , University of Calgary , Calgary , Canada
| | - Guillaume Y Millet
- a Human Performance Laboratory, Faculty of Kinesiology , University of Calgary , Calgary , Canada
| | - Juan M Murias
- a Human Performance Laboratory, Faculty of Kinesiology , University of Calgary , Calgary , Canada
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63
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Benson AP, Bowen TS, Ferguson C, Murgatroyd SR, Rossiter HB. Data collection, handling, and fitting strategies to optimize accuracy and precision of oxygen uptake kinetics estimation from breath-by-breath measurements. J Appl Physiol (1985) 2017; 123:227-242. [PMID: 28450551 DOI: 10.1152/japplphysiol.00988.2016] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 03/20/2017] [Accepted: 04/19/2017] [Indexed: 11/22/2022] Open
Abstract
Phase 2 pulmonary oxygen uptake kinetics (ϕ2 τV̇o2P) reflect muscle oxygen consumption dynamics and are sensitive to changes in state of training or health. This study identified an unbiased method for data collection, handling, and fitting to optimize V̇o2P kinetics estimation. A validated computational model of V̇o2P kinetics and a Monte Carlo approach simulated 2 × 105 moderate-intensity transitions using a distribution of metabolic and circulatory parameters spanning normal health. Effects of averaging (interpolation, binning, stacking, or separate fitting of up to 10 transitions) and fitting procedures (biexponential fitting, or ϕ2 isolation by time removal, statistical, or derivative methods followed by monoexponential fitting) on accuracy and precision of V̇o2P kinetics estimation were assessed. The optimal strategy to maximize accuracy and precision of τV̇o2P estimation was 1-s interpolation of 4 bouts, ensemble averaged, with the first 20 s of exercise data removed. Contradictory to previous advice, we found optimal fitting procedures removed no more than 20 s of ϕ1 data. Averaging method was less critical: interpolation, binning, and stacking gave similar results, each with greater accuracy compared with analyzing repeated bouts separately. The optimal procedure resulted in ϕ2 τV̇o2P estimates for transitions from an unloaded or loaded baseline that averaged 1.97 ± 2.08 and 1.04 ± 2.30 s from true, but were within 2 s of true in only 47-62% of simulations. Optimized 95% confidence intervals for τV̇o2P ranged from 4.08 to 4.51 s, suggesting a minimally important difference of ~5 s to determine significant changes in τV̇o2P during interventional and comparative studies.NEW & NOTEWORTHY We identified an unbiased method to maximize accuracy and precision of oxygen uptake kinetics (τV̇o2P) estimation. The optimum number of bouts to average was four; interpolation, bin, and stacking averaging methods gave similar results. Contradictory to previous advice, we found that optimal fitting procedures removed no more than 20 s of phase 1 data. Our data suggest a minimally important difference of ~5 s to determine significant changes in τV̇o2P during interventional and comparative studies.
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Affiliation(s)
- Alan P Benson
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom; .,Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, United Kingdom
| | - T Scott Bowen
- Heart Centre, University of Leipzig, Leipzig, Germany
| | - Carrie Ferguson
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom.,Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, United Kingdom
| | - Scott R Murgatroyd
- Neurosciences Intensive Care Unit, Wessex Neurological Centre, University Hospital Southampton, Southampton, United Kingdom; and
| | - Harry B Rossiter
- Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California.,School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
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McLay KM, Murias JM, Paterson DH. Similar pattern of change in V̇o 2 kinetics, vascular function, and tissue oxygen provision following an endurance training stimulus in older and young adults. Am J Physiol Regul Integr Comp Physiol 2017; 312:R467-R476. [PMID: 28122720 DOI: 10.1152/ajpregu.00399.2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 01/23/2017] [Accepted: 01/23/2017] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to examine the time course of changes in the oxygen uptake (V̇o2) kinetics response subsequent to short-term exercise training (i.e., 24, 48, 72, and 120 h posttraining) and examine the relationship with the time course of changes in microvascular [deoxygenated hemoglobin concentration ([HHb])-to-V̇o2 ratio ([HHb])/V̇o2)] and macrovascular [flow-mediated dilation (FMD)] O2 delivery to the active tissues/limbs. Seven healthy older [OA; 74 ± 6 (SD) yr] and young men (YA; 25 ± 3 yr) completed three endurance cycling exercise training sessions at 70% V̇o2peak Moderate-intensity exercise on-transient V̇o2 (measured breath by breath) and [HHb] (measured by near-infrared spectroscopy) were modeled with a monoexponential and normalized (0-100% of response), and the [HHb])/V̇o2 was calculated. Ultrasound-derived FMD of the popliteal artery was assessed after 5 min of cuff occlusion. %FMD was calculated as the greatest percent change in diameter from baseline. Time constant of V̇o2 (τV̇o2) was significantly reduced in both OA (~18%) and YA (~23%) at 24 h (P < 0.001) posttraining and remained decreased at 48 h before returning toward pretraining (PRE) values. Both groups showed a significant decrease in the [HHb])/V̇o2 at 24, 48, and 72 h (P = 0.001, 0.01, and 0.03, respectively) posttraining before returning toward PRE values at 120 h. %FMD followed a similar time course to that of changes in the [HHb])/V̇o2, being significantly greater in both OA (by ~64%) and YA (by ~26%) at 24 h (P < 0.001), remaining increased at 48 and 72 h (P = 0.02 and 0.03, respectively), and returning toward PRE values at 120 h. These data suggest the rate of adjustment of V̇o2 may be constrained by O2 availability in the active tissues.
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Affiliation(s)
- Kaitlin M McLay
- Canadian Centre for Activity and Aging, London, Ontario, Canada.,School of Kinesiology, The University of Western Ontario, London, Ontario, Canada; and
| | - Juan M Murias
- School of Kinesiology, The University of Western Ontario, London, Ontario, Canada; and .,Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Donald H Paterson
- Canadian Centre for Activity and Aging, London, Ontario, Canada.,School of Kinesiology, The University of Western Ontario, London, Ontario, Canada; and
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65
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Muniz-Pumares D, Pedlar C, Godfrey R, Glaister M. A comparison of methods to estimate anaerobic capacity: Accumulated oxygen deficit and W' during constant and all-out work-rate profiles. J Sports Sci 2016; 35:2357-2364. [PMID: 28019724 DOI: 10.1080/02640414.2016.1267386] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
This study investigated (i) whether the accumulated oxygen deficit (AOD) and curvature constant of the power-duration relationship (W') are different during constant work-rate to exhaustion (CWR) and 3-min all-out (3MT) tests and (ii) the relationship between AOD and W' during CWR and 3MT. Twenty-one male cyclists (age: 40 ± 6 years; maximal oxygen uptake [V̇O2max]: 58 ± 7 ml · kg-1 · min-1) completed preliminary tests to determine the V̇O2-power output relationship and V̇O2max. Subsequently, AOD and W' were determined as the difference between oxygen demand and oxygen uptake and work completed above critical power, respectively, in CWR and 3MT. There were no differences between tests for duration, work, or average power output (P ≥ 0.05). AOD was greater in the CWR test (4.18 ± 0.95 vs. 3.68 ± 0.98 L; P = 0.004), whereas W' was greater in 3MT (9.55 ± 4.00 vs. 11.37 ± 3.84 kJ; P = 0.010). AOD and W' were significantly correlated in both CWR (P < 0.001, r = 0.654) and 3MT (P < 0.001, r = 0.654). In conclusion, despite positive correlations between AOD and W' in CWR and 3MT, between-test differences in the magnitude of AOD and W', suggest that both measures have different underpinning mechanisms.
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Affiliation(s)
- Daniel Muniz-Pumares
- a School of Sport, Health and Applied Science , St Mary's University , Twickenham , UK.,b Department of Psychology and Sport Science, School of Life and Medical Sciences , University of Hertfordshire , Hatfield , UK
| | - Charles Pedlar
- a School of Sport, Health and Applied Science , St Mary's University , Twickenham , UK
| | - Richard Godfrey
- c The Centre for Sports Medicine and Human Performance , Brunel University , Uxbridge , UK
| | - Mark Glaister
- a School of Sport, Health and Applied Science , St Mary's University , Twickenham , UK
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66
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Floriano LT, da Silva JF, Teixeira AS, Salvador PCDN, Dittrich N, Carminatti LJ, Nascimento LL, Guglielmo LGA. Physiological Responses During the Time Limit at 100% of the Peak Velocity in the Carminatti's Test in Futsal Players. J Hum Kinet 2016; 54:91-101. [PMID: 28031761 PMCID: PMC5187963 DOI: 10.1515/hukin-2016-0038] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The aim of this study was to investigate the physiological responses during the time limit at the intensity of the peak velocity of the Carminatti's test (T-CAR). Ten professional futsal players (age, 27.4 ± 5.8 years, body mass, 78.8 ± 8.5 kg, body height, 175.8 ± 6.8 cm, body fat mass, 14.1 ± 2.6%) took part in the study. The players performed three tests, with an interval of at least 48 hours, as follows: the T-CAR to determine the peak velocity and the maximal heart rate; an incremental treadmill protocol to determine the maximal physiological responses; and a time limit running test at the peak velocity reached in the T-CAR. During the last two tests, a portable gas analyzer was used for direct measurement of cardiorespiratory variables. It was shown that the peak velocity was not significantly different from the maximal aerobic speed achieved in the laboratory (p = 0.213). All athletes reached their maximum oxygen uptake during the time limit test. The maximum oxygen uptake achieved during the time limit test was not different from that observed in the laboratory condition (51.1 ± 4.7 vs. 49.6 ± 4.7 ml·kg-1·min-1, respectively, p = 0.100). In addition, Bland and Altman plots evidenced acceptable agreement between them. On average, athletes took ~140 s to achieve maximum oxygen uptake and maintained it for ~180 s. Therefore, the peak velocity intensity can be used as an indicator of maximal aerobic power of futsal athletes and the time limit can be used as a reference for training prescription.
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Affiliation(s)
- Leandro Teixeira Floriano
- Sports Center, Federal University of Santa Catarina, Physical Effort Laboratory, Florianópolis, Brazil
| | | | | | | | - Naiandra Dittrich
- Sports Center, Federal University of Santa Catarina, Physical Effort Laboratory, Florianópolis, Brazil
| | - Lorival José Carminatti
- Sports Center, Federal University of Santa Catarina, Physical Effort Laboratory, Florianópolis, Brazil
| | - Lucas Loyola Nascimento
- Sports Center, Federal University of Santa Catarina, Physical Effort Laboratory, Florianópolis, Brazil
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Black MI, Jones AM, Kelly JA, Bailey SJ, Vanhatalo A. The constant work rate critical power protocol overestimates ramp incremental exercise performance. Eur J Appl Physiol 2016; 116:2415-2422. [PMID: 27787608 PMCID: PMC5118414 DOI: 10.1007/s00421-016-3491-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 10/13/2016] [Indexed: 12/02/2022]
Abstract
Purpose The parameters of the power-duration relationship (i.e., the critical power, CP, and the curvature constant, W′) may theoretically predict maximal performance capability for exercise above the CP. The CP and Wʹ are associated with the parameters of oxygen uptake (\documentclass[12pt]{minimal}
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\begin{document}$${\dot{\text{V}}}$$\end{document}V˙O2) kinetics, which can be altered by manipulation of the work-rate forcing function. We tested the hypothesis that the CP and Wʹ derived from constant work-rate (CWR) prediction trials would overestimate ramp incremental exercise performance. Methods Thirty subjects (males, n = 28; females, n = 2) performed a ramp incremental test, and 3–5 CWR prediction trials for the determination of the CP and Wʹ. Multiple ramp incremental tests and corresponding CP and Wʹ estimates were available for some subjects such that in total 51 ramp test performances were predicted. Results The ramp incremental test performance (729 ± 113 s) was overestimated by the CP and Wʹ estimates derived from the best (751 ± 114 s, P < 0.05) and worst (749 ± 111 s, P < 0.05) individual fits of CWR prediction trial data. The error in the prediction was inversely correlated with the magnitude of the Wʹ for the best (r = −0.56, P < 0.05) and worst individual fits (r = −0.36, P < 0.05). Conclusions The overestimation of ramp incremental performance suggests that the CP and Wʹ derived from different work-rate forcing functions, thus resulting in different \documentclass[12pt]{minimal}
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\begin{document}$${\dot{\text{V}}}$$\end{document}V˙O2 kinetics, cannot be used interchangeably. The present findings highlight a potential source of error in performance prediction that is of importance to both researchers and applied practitioners.
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Affiliation(s)
- Matthew I Black
- Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, St. Luke's Campus, Heavitree Road, Exeter, EX1 2LU, UK
- School of Sport, Exercise and Health Sciences, Loughborough University, Epinal Way, LE11 3TU, UK
| | - Andrew M Jones
- Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, St. Luke's Campus, Heavitree Road, Exeter, EX1 2LU, UK
| | - James A Kelly
- Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, St. Luke's Campus, Heavitree Road, Exeter, EX1 2LU, UK
| | - Stephen J Bailey
- Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, St. Luke's Campus, Heavitree Road, Exeter, EX1 2LU, UK
- School of Sport, Exercise and Health Sciences, Loughborough University, Epinal Way, LE11 3TU, UK
| | - Anni Vanhatalo
- Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, St. Luke's Campus, Heavitree Road, Exeter, EX1 2LU, UK.
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68
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Lai N, Martis A, Belfiori A, Tolentino-Silva F, Nasca MM, Strainic J, Cabrera ME. Gender differences in V˙O2 and HR kinetics at the onset of moderate and heavy exercise intensity in adolescents. Physiol Rep 2016; 4:4/18/e12970. [PMID: 27655810 PMCID: PMC5037918 DOI: 10.14814/phy2.12970] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 08/22/2016] [Indexed: 11/24/2022] Open
Abstract
The majority of the studies on V˙O2 kinetics in pediatric populations investigated gender differences in prepubertal children during submaximal intensity exercise, but studies are lacking in adolescents. The purpose of this study was to test the hypothesis that gender differences exist in the V˙O2 and heart rate (HR) kinetic responses to moderate (M) and heavy (H) intensity exercise in adolescents. Twenty-one healthy African-American adolescents (9 males, 15.8 ± 1.1 year; 12 females, 15.7 ± 1 year) performed constant work load exercise on a cycle ergometer at M and H. The V˙O2 kinetics of the male group was previously analyzed (Lai et al., Appl. Physiol. Nutr. Metab. 33:107-117, 2008b). For both genders, V˙O2 and HR kinetics were described with a single exponential at M and a double exponential at H. The fundamental time constant (τ1) of V˙O2 was significantly higher in female than male at M (45 ± 7 vs. 36 ± 11 sec, P < 0.01) and H (41 ± 8 vs. 29 ± 9 sec, P < 0.01), respectively. The functional gain (G1) was not statistically different between gender at M and statistically higher in females than males at H: 9.7 ± 1.2 versus 10.9 ± 1.3 mL min-1 W-1, respectively. The amplitude of the slow component was not significantly different between genders. The HR kinetics were significantly (τ1, P < 0.01) slower in females than males at M (61 ± 16 sec vs. 45 ± 20 sec, P < 0.01) and H (42 ± 10 sec vs. 30 ± 8 sec, P = 0.03). The G1 of HR was higher in females than males at M: 0.53 ± 0.11 versus 0.98 ± 0.2 bpm W-1 and H: 0.40 ± 0.11 versus 0.73 ± 0.23 bpm W-1, respectively. Gender differences in the V˙O2 and HR kinetics suggest that oxygen delivery and utilization kinetics of female adolescents differ from those in male adolescents.
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Affiliation(s)
- Nicola Lai
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio Department of Pediatrics Cardiology, Case Western Reserve University, Cleveland, Ohio Center for Modeling Integrated Metabolic Systems, Cleveland, Ohio Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia Biomedical Engineering Institute, Old Dominion University, Norfolk, Virginia
| | - Alessandro Martis
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
| | - Alfredo Belfiori
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
| | | | - Melita M Nasca
- Department of Pediatrics Cardiology, Case Western Reserve University, Cleveland, Ohio Rainbow Babies and Children's Hospital, Cleveland, Ohio
| | - James Strainic
- Department of Pediatrics Cardiology, Case Western Reserve University, Cleveland, Ohio Rainbow Babies and Children's Hospital, Cleveland, Ohio
| | - Marco E Cabrera
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio Department of Pediatrics Cardiology, Case Western Reserve University, Cleveland, Ohio Center for Modeling Integrated Metabolic Systems, Cleveland, Ohio Rainbow Babies and Children's Hospital, Cleveland, Ohio
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69
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Turnes T, de Aguiar RA, de Oliveira Cruz RS, Lisbôa FD, Pereira KL, Caputo F. Short-term interval training at both lower and higher intensities in the severe exercise domain result in improvements in V̇O₂ on-kinetics. Eur J Appl Physiol 2016; 116:1975-84. [PMID: 27491618 DOI: 10.1007/s00421-016-3449-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 07/28/2016] [Indexed: 12/22/2022]
Abstract
PURPOSE Although high-intensity interval training (HIT) seems to promote greater improvements in aerobic parameters than continuous training, the influence of exercise intensity on [Formula: see text] on-kinetics remains under investigation. METHODS After an incremental test, twenty-one recreationally trained cyclists performed several time-to-exhaustion tests to determine critical power (CP), and the highest intensity (I HIGH), and the lowest exercise duration (T LOW) at which [Formula: see text] is attained during constant exercise. Subjects also completed a series of step transitions to moderate- and heavy-intensity work rates to determine pulmonary [Formula: see text] on-kinetics. Surface electromyography (EMG) of vastus lateralis muscle and blood lactate accumulation (∆BLC) was measured during heavy exercise. Subjects were assigned to one of two 4-week work-matched training groups: the lower [105 % CP: n = 11; 4 × 5 min at 105 % CP (218 ± 39 W), 1 min recovery] or the upper [I HIGH: n = 10; 8 × 100 % I HIGH (355 ± 60 W), 1:2 work:recovery ratio] intensity of the severe exercise domain. RESULTS The two interventions were similarly effective in reducing the phase II [Formula: see text] time constant during moderate (105 % CP: 34 ± 13 to 25 ± 8 s; I HIGH: 31 ± 9 to 23 ± 6 s) and heavy exercise (105 % CP: 25 ± 7 to 18 ± 5 s; I HIGH: 27 ± 7 to 16 ± 5 s) and in reducing the amplitude of [Formula: see text] slow component, EMG amplitude, and ∆BLC during heavy exercise. CONCLUSION In conclusion, the short-term adjustments in response to step transitions to moderate and heavy exercise were independent of training intensity within the severe exercise domain.
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Affiliation(s)
- Tiago Turnes
- Human Performance Research Group, Center for Health and Sport Science (CEFID), Santa Catarina State University (UDESC), Pascoal Simone, 358, Coqueiros, Florianópolis, SC, CEP 88080-350, Brazil.
| | - Rafael Alves de Aguiar
- Human Performance Research Group, Center for Health and Sport Science (CEFID), Santa Catarina State University (UDESC), Pascoal Simone, 358, Coqueiros, Florianópolis, SC, CEP 88080-350, Brazil
| | - Rogério Santos de Oliveira Cruz
- Human Performance Research Group, Center for Health and Sport Science (CEFID), Santa Catarina State University (UDESC), Pascoal Simone, 358, Coqueiros, Florianópolis, SC, CEP 88080-350, Brazil
| | - Felipe Domingos Lisbôa
- Human Performance Research Group, Center for Health and Sport Science (CEFID), Santa Catarina State University (UDESC), Pascoal Simone, 358, Coqueiros, Florianópolis, SC, CEP 88080-350, Brazil
| | - Kayo Leonardo Pereira
- Human Performance Research Group, Center for Health and Sport Science (CEFID), Santa Catarina State University (UDESC), Pascoal Simone, 358, Coqueiros, Florianópolis, SC, CEP 88080-350, Brazil
| | - Fabrizio Caputo
- Human Performance Research Group, Center for Health and Sport Science (CEFID), Santa Catarina State University (UDESC), Pascoal Simone, 358, Coqueiros, Florianópolis, SC, CEP 88080-350, Brazil
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Zoladz JA, Majerczak J, Grassi B, Szkutnik Z, Korostyński M, Gołda S, Grandys M, Jarmuszkiewicz W, Kilarski W, Karasinski J, Korzeniewski B. Mechanisms of Attenuation of Pulmonary V'O2 Slow Component in Humans after Prolonged Endurance Training. PLoS One 2016; 11:e0154135. [PMID: 27104346 PMCID: PMC4841588 DOI: 10.1371/journal.pone.0154135] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 04/09/2016] [Indexed: 11/19/2022] Open
Abstract
In this study we have examined the effect of prolonged endurance training program on the pulmonary oxygen uptake (V'O2) kinetics during heavy-intensity cycling-exercise and its impact on maximal cycling and running performance. Twelve healthy, physically active men (mean±SD: age 22.33±1.44 years, V'O2peak 3198±458 mL ∙ min-1) performed an endurance training composed mainly of moderate-intensity cycling, lasting 20 weeks. Training resulted in a decrease (by ~5%, P = 0.027) in V'O2 during prior low-intensity exercise (20 W) and in shortening of τp of the V'O2 on-kinetics (30.1±5.9 s vs. 25.4±1.5 s, P = 0.007) during subsequent heavy-intensity cycling. This was accompanied by a decrease of the slow component of V'O2 on-kinetics by 49% (P = 0.001) and a decrease in the end-exercise V'O2 by ~5% (P = 0.005). An increase (P = 0.02) in the vascular endothelial growth factor receptor 2 mRNA level and a tendency (P = 0.06) to higher capillary-to-fiber ratio in the vastus lateralis muscle were found after training (n = 11). No significant effect of training on the V'O2peak was found (P = 0.12). However, the power output reached at the lactate threshold increased by 19% (P = 0.01). The power output obtained at the V'O2peak increased by 14% (P = 0.003) and the time of 1,500-m performance decreased by 5% (P = 0.001). Computer modeling of the skeletal muscle bioenergetic system suggests that the training-induced decrease in the slow component of V'O2 on-kinetics found in the present study is mainly caused by two factors: an intensification of the each-step activation (ESA) of oxidative phosphorylation (OXPHOS) complexes after training and decrease in the ''additional" ATP usage rising gradually during heavy-intensity exercise.
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Affiliation(s)
- Jerzy A. Zoladz
- Department of Muscle Physiology, Chair of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Krakow, Poland
| | - Joanna Majerczak
- Department of Muscle Physiology, Chair of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Krakow, Poland
| | - Bruno Grassi
- Dipartimento di Scienze Mediche e Biologiche, Università degli Studi di Udine, Udine, Italy
| | - Zbigniew Szkutnik
- Faculty of Applied Mathematics, AGH-University of Science and Technology, Krakow, Poland
| | - Michał Korostyński
- Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Sławomir Gołda
- Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Marcin Grandys
- Department of Muscle Physiology, Chair of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Krakow, Poland
| | - Wiesława Jarmuszkiewicz
- Department of Bioenergetics, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Poznan, Poland
| | - Wincenty Kilarski
- Department of Cell Biology and Imaging, Institute of Zoology, Jagiellonian University, Krakow, Poland
| | - Janusz Karasinski
- Department of Cell Biology and Imaging, Institute of Zoology, Jagiellonian University, Krakow, Poland
| | - Bernard Korzeniewski
- Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland
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Combes A, Dekerle J, Bougault V, Daussin FN. Effect of work:rest cycle duration on [Formula: see text] fluctuations during intermittent exercise. J Sports Sci 2016; 35:7-13. [PMID: 26943697 DOI: 10.1080/02640414.2016.1154591] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The succession of on-transient phases that induce a repetition of metabolic changes is a possible mechanism responsible for the greater response to intermittent training (IT). The objective of this study was to quantify [Formula: see text] fluctuations during intermittent exercise characterised by the same work:rest ratio, but different durations and identify which duration leads to the greatest fluctuations. Ten participants (24 ± 5 years; [Formula: see text]: 42 ± 7 mL·min-1·kg-1) performed (1) an incremental test to exhaustion to determine peak work rate (WRpeak) and oxygen uptake ([Formula: see text]), (2), and three 1 h intermittent exercises alternating work period at 70% WRpeak with passive recovery period of different 1:1 work:recovery duty cycles (30 s:30 s, 60 s:60 s, 120 s:120 s). [Formula: see text] response analysis revealed differences in the fluctuations across the intermittent conditions despite an identical total energy expenditure. The sum of the cycle's nadir-to-peak [Formula: see text] differences (ΣΔ[Formula: see text]) and the oxygen fluctuation index (OFI) were both greater in the 60 s:60 s condition (ΣΔ[Formula: see text]: +38% ± 13% and +19% ± 18% vs. 120 s:120 s and 30 s:30 s, P < 0.05; OFI: +41% ± 29% and +67% ± 62% vs. 120 s:120 s and 30:30 s, P < 0.05). [Formula: see text] fluctuation analysis was successful in identifying the intermittent condition associated with the greatest disturbances: the 60 s:60 s duty cycle induces more [Formula: see text] fluctuations. The present findings also demonstrate that the selection of the duty cycle duration for submaximal intermittent exercise (70% of WRpeak) prescription is of interest to produce high [Formula: see text] fluctuations.
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Affiliation(s)
- Adrien Combes
- a University of Lille, EA 7369 - URePSSS - Unité de Recherche Pluridisciplinaire Sport Santé Société , F-59000 Lille , France
| | - Jeanne Dekerle
- b Centre for Sport Exercise Science and Medicine (SESAME) , University of Brighton , Eastbourne , UK
| | - Valérie Bougault
- a University of Lille, EA 7369 - URePSSS - Unité de Recherche Pluridisciplinaire Sport Santé Société , F-59000 Lille , France
| | - Frédéric N Daussin
- a University of Lille, EA 7369 - URePSSS - Unité de Recherche Pluridisciplinaire Sport Santé Société , F-59000 Lille , France
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Ederer AK, Didier KD, Reiter LK, Brown M, Hardy R, Caldwell J, Black CD, Larson RD, Ade CJ. Influence of Adjuvant Therapy in Cancer Survivors on Endothelial Function and Skeletal Muscle Deoxygenation. PLoS One 2016; 11:e0147691. [PMID: 26807572 PMCID: PMC4726690 DOI: 10.1371/journal.pone.0147691] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 01/07/2016] [Indexed: 12/16/2022] Open
Abstract
The cardiotoxic effects of adjuvant cancer treatments (i.e., chemotherapy and radiation treatment) have been well documented, but the effects on peripheral cardiovascular function are still unclear. We hypothesized that cancer survivors i) would have decreased resting endothelial function; and ii) altered muscle deoxygenation response during moderate intensity cycling exercise compared to cancer-free controls. A total of 8 cancer survivors (~70 months post-treatment) and 9 healthy controls completed a brachial artery FMD test, an index of endothelial-dependent dilation, followed by an incremental exercise test up to the ventilatory threshold (VT) on a cycle ergometer during which pulmonary V˙O2 and changes in near-infrared spectroscopy (NIRS)-derived microvascular tissue oxygenation (TOI), total hemoglobin concentration ([Hb]total), and muscle deoxygenation ([HHb] ≈ fractional O2 extraction) were measured. There were no significant differences in age, height, weight, and resting blood pressure between cancer survivors and control participants. Brachial artery FMD was similar between groups (P = 0.98). During exercise at the VT, TOI was similar between groups, but [Hb]total and [HHb] were significantly decreased in cancer survivors compared to controls (P < 0.01) The rate of change for TOI (ΔTOIΔ/V˙O2) and [HHb] (Δ[HHb]/ΔV˙O2) relative to ΔV˙O2 were decreased in cancer survivors compared to controls (P = 0.02 and P = 0.03 respectively). In cancer survivors, a decreased skeletal muscle microvascular function was observed during moderate intensity cycling exercise. These data suggest that adjuvant cancer therapies have an effect on the integrated relationship between O2 extraction, V˙O2 and O2 delivery during exercise.
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Affiliation(s)
- Austin K. Ederer
- Department of Health and Exercise Science, The University of Oklahoma, Norman, OK, United States of America
| | - Kaylin D. Didier
- Department of Health and Exercise Science, The University of Oklahoma, Norman, OK, United States of America
| | - Landon K. Reiter
- Department of Health and Exercise Science, The University of Oklahoma, Norman, OK, United States of America
| | - Michael Brown
- Department of Health and Exercise Science, The University of Oklahoma, Norman, OK, United States of America
| | - Rachel Hardy
- Department of Health and Exercise Science, The University of Oklahoma, Norman, OK, United States of America
| | - Jacob Caldwell
- Department of Health and Exercise Science, The University of Oklahoma, Norman, OK, United States of America
| | - Christopher D. Black
- Department of Health and Exercise Science, The University of Oklahoma, Norman, OK, United States of America
| | - Rebecca D. Larson
- Department of Health and Exercise Science, The University of Oklahoma, Norman, OK, United States of America
| | - Carl J. Ade
- Department of Health and Exercise Science, The University of Oklahoma, Norman, OK, United States of America
- * E-mail:
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Sarcopenic obesity and the pathogenesis of exercise intolerance in heart failure with preserved ejection fraction. Curr Heart Fail Rep 2016; 12:205-14. [PMID: 25750186 DOI: 10.1007/s11897-015-0257-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Heart failure with preserved ejection fraction (HFpEF) is the most common form of heart failure (HF) in older adults. The primary chronic symptom in patients with HFpEF, even when well compensated, is severe exercise intolerance. Cardiac and peripheral functions contribute equally to exercise intolerance in HFpEF, though the latter has been the focus of fewer studies. Of note, multiple studies with exercise training have shown that exercise intolerance can improve significantly in the absence of improvements in exercise cardiac output, indicating a role of peripheral, noncardiac adaptations. In addition, clinical drug trials performed to date in HFpEF, all of which have focused on influencing cardiovascular function, have not been positive on primary clinical outcomes and most have not improved exercise capacity. Mounting evidence indicates that sarcopenic obesity, characterized by the coexistence of excess fat mass and decreased muscle mass, could contribute to the pathophysiology of exercise intolerance in older HFpEF patients and may provide avenues for novel treatments.
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Aerobic training enhances muscle deoxygenation in early post-myocardial infarction. Eur J Appl Physiol 2016; 116:673-85. [PMID: 26759155 PMCID: PMC4819748 DOI: 10.1007/s00421-016-3326-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 01/04/2016] [Indexed: 11/30/2022]
Abstract
Purpose Exercise-induced skeletal muscle deoxygenation is startling by its absence in early post-myocardial infarction (MI) patients. Exercise training early post-MI is associated with reduced cardiovascular risk and increased aerobic capacity. We therefore investigated whether aerobic training could enhance the muscle deoxygenation in early post-MI patients. Methods 21 ± 8 days after the first MI patients (n = 16) were divided into 12-week aerobic training (TR, n = 10) or non-training (CON, n = 6) groups. Before and after intervention, patients performed ramp bicycle exercise until exhaustion. Muscle deoxygenation was measured at vastus lateralis by near-infrared spectroscopy during exercise. Results Aerobic training significantly increased peak oxygen uptake (VO2) (18.1 ± 3.0 vs. 22.9 ± 2.8 mL/kg/min), decreased the change in muscle oxygen saturation from rest to submaximal and peak exercise (∆SmO2; 2.4 ± 5.7 vs. −7.0 ± 3.4 %), and increased the relative change in deoxygenated hemoglobin/myoglobin concentration from rest to submaximal (−1.5 ± 2.3 vs. 3.0 ± 3.6 μmol/L) and peak exercise (1.1 ± 4.5 vs. 8.2 ± 3.5 μmol/L). Change in total hemoglobin/myoglobin concentration in muscle was not significantly affected by training. In CON, no significant alterations were found after 12 weeks in either muscle deoxygenation or peak VO2 (18.6 ± 3.8 vs. 18.9 ± 4.6 mL/kg/min). An increase in peak VO2 was significantly negatively correlated with change in ∆SmO2 (r = −0.65) and positively associated with change in ∆deoxy-Hb/Mb at peak exercise (r = 0.64) in TR. Conclusions In early post-MI patients, aerobic training enhanced skeletal muscle deoxygenation, and the enhancement was related to increased aerobic capacity.
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Affiliation(s)
- Shun Takagi
- Faculty of Sport Sciences, Waseda University
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76
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Keir DA, Benson AP, Love LK, Robertson TC, Rossiter HB, Kowalchuk JM. Influence of muscle metabolic heterogeneity in determining the V̇o2p kinetic response to ramp-incremental exercise. J Appl Physiol (1985) 2015; 120:503-13. [PMID: 26679614 DOI: 10.1152/japplphysiol.00804.2015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 12/15/2015] [Indexed: 10/22/2022] Open
Abstract
The pulmonary O2 uptake (V̇o2p) response to ramp-incremental (RI) exercise increases linearly with work rate (WR) after an early exponential phase, implying that a single time constant (τ) and gain (G) describe the response. However, variability in τ and G of V̇o2p kinetics to different step increments in WR is documented. We hypothesized that the "linear" V̇o2p-WR relationship during RI exercise results from the conflation between WR-dependent changes in τ and G. Nine men performed three or four repeats of RI exercise (30 W/min) and two step-incremental protocols consisting of four 60-W increments beginning from 20 W or 50 W. During testing, breath-by-breath V̇o2p was measured by mass spectrometry and volume turbine. For each individual, the V̇o2p RI response was characterized with exponential functions containing either constant or variable τ and G values. A relationship between τ and G vs. WR was determined from the step-incremental protocols to derive the variable model parameters. τ and G increased from 21 ± 5 to 98 ± 20 s and from 8.7 ± 0.6 to 12.0 ± 1.9 ml·min(-1)·W(-1) for WRs of 20-230 W, respectively, and were best described by a second-order (τ) and a first-order (G) polynomial function of WR (lowest Akaike information criterion score). The sum of squared residuals was not different (P > 0.05) when the V̇o2p RI response was characterized with either the constant or variable models, indicating that they described the response equally well. Results suggest that τ and G increase progressively with WR during RI exercise. Importantly, these relationships may conflate to produce a linear V̇o2p-WR response, emphasizing the influence of metabolic heterogeneity in determining the apparent V̇o2p-WR relationship during RI exercise.
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Affiliation(s)
- Daniel A Keir
- Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada; School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Alan P Benson
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Lorenzo K Love
- Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada; School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Taylor C Robertson
- Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada; School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Harry B Rossiter
- Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California; and School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - John M Kowalchuk
- Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada; School of Kinesiology, The University of Western Ontario, London, Ontario, Canada; Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada;
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Korzeniewski B, Rossiter HB. Each-step activation of oxidative phosphorylation is necessary to explain muscle metabolic kinetic responses to exercise and recovery in humans. J Physiol 2015; 593:5255-68. [PMID: 26503399 PMCID: PMC4704516 DOI: 10.1113/jp271299] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 10/22/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The basic control mechanisms of oxidative phosphorylation (OXPHOS) and glycolysis during work transitions in human skeletal muscle are still a matter of debate. We used simulations of skeletal muscle bioenergetics to identify key system features that contribute to this debate, by comparing kinetic model outputs with experimental human data, including phosphocreatine, pH, pulmonary oxygen uptake and fluxes of ATP production by OXPHOS (vOX), anaerobic glycolysis and creatine kinase in moderate and severe intensity exercise transitions. We found that each-step activation of particular OXPHOS complexes, NADH supply and glycolysis, and strong (third-order) glycolytic inhibition by protons was required to reproduce observed phosphocreatine, pH and vOX kinetics during exercise. A slow decay of each-step activation during recovery, which was slowed further following severe exercise, was necessary to reproduce the experimental findings. Well-tested computer models offer new insight in the control of the human skeletal muscle bioenergetic system during physical exercise. ABSTRACT To better understand muscle bioenergetic regulation, a previously-developed model of the skeletal muscle cell bioenergetic system was used to simulate the influence of: (1) each-step activation (ESA) of NADH supply (including glycolysis) and oxidative phosphorylation (OXPHOS) complexes and (2) glycolytic inhibition by protons on the kinetics of ATP synthesis from OXPHOS, anaerobic glycolysis and creatine kinase. Simulations were fitted to previously published experimental data of ATP production fluxes and metabolite concentrations during moderate and severe intensity exercise transitions in bilateral knee extension in humans. Overall, the computer simulations agreed well with experimental results. Specifically, a large (>5-fold) direct activation of all OXPHOS complexes was required to simulate measured phosphocreatine and OXPHOS responses to both moderate and severe intensity exercise. In addition, slow decay of ESA was required to fit phosphocreatine recovery kinetics, and the time constant of ESA decay was slower following severe (180 s) than moderate (90 s) exercise. Additionally, a strong inhibition of (anaerobic) glycolysis by protons (glycolytic rate inversely proportional to the cube of proton concentration) provided the best fit to the experimental pH kinetics, and may contribute to the progressive increase in oxidative ATP supply during acidifying contractions. During severe-intensity exercise, an 'additional' ATP usage (a 27% increase at 8 min, above the initial ATP supply) was necessary to explain the observed V̇O2 slow component. Thus, parallel activation of ATP usage and ATP supply (ESA), and a strong inhibition of ATP supply by anaerobic glycolysis, were necessary to simulate the kinetics of muscle bioenergetics observed in humans.
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Affiliation(s)
- Bernard Korzeniewski
- Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland
| | - Harry B Rossiter
- Rehabilitation Clinical Trials Centre, Division of Respiratory & Critical Care Physiology & Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Centre, Torrance, CA, USA
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK
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Hirai DM, Musch TI, Poole DC. Exercise training in chronic heart failure: improving skeletal muscle O2 transport and utilization. Am J Physiol Heart Circ Physiol 2015; 309:H1419-39. [PMID: 26320036 DOI: 10.1152/ajpheart.00469.2015] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 08/23/2015] [Indexed: 01/13/2023]
Abstract
Chronic heart failure (CHF) impairs critical structural and functional components of the O2 transport pathway resulting in exercise intolerance and, consequently, reduced quality of life. In contrast, exercise training is capable of combating many of the CHF-induced impairments and enhancing the matching between skeletal muscle O2 delivery and utilization (Q̇mO2 and V̇mO2 , respectively). The Q̇mO2 /V̇mO2 ratio determines the microvascular O2 partial pressure (PmvO2 ), which represents the ultimate force driving blood-myocyte O2 flux (see Fig. 1). Improvements in perfusive and diffusive O2 conductances are essential to support faster rates of oxidative phosphorylation (reflected as faster V̇mO2 kinetics during transitions in metabolic demand) and reduce the reliance on anaerobic glycolysis and utilization of finite energy sources (thus lowering the magnitude of the O2 deficit) in trained CHF muscle. These adaptations contribute to attenuated muscle metabolic perturbations (e.g., changes in [PCr], [Cr], [ADP], and pH) and improved physical capacity (i.e., elevated critical power and maximal V̇mO2 ). Preservation of such plasticity in response to exercise training is crucial considering the dominant role of skeletal muscle dysfunction in the pathophysiology and increased morbidity/mortality of the CHF patient. This brief review focuses on the mechanistic bases for improved Q̇mO2 /V̇mO2 matching (and enhanced PmvO2 ) with exercise training in CHF with both preserved and reduced ejection fraction (HFpEF and HFrEF, respectively). Specifically, O2 convection within the skeletal muscle microcirculation, O2 diffusion from the red blood cell to the mitochondria, and muscle metabolic control are particularly susceptive to exercise training adaptations in CHF. Alternatives to traditional whole body endurance exercise training programs such as small muscle mass and inspiratory muscle training, pharmacological treatment (e.g., sildenafil and pentoxifylline), and dietary nitrate supplementation are also presented in light of their therapeutic potential. Adaptations within the skeletal muscle O2 transport and utilization system underlie improvements in physical capacity and quality of life in CHF and thus take center stage in the therapeutic management of these patients.
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Affiliation(s)
- Daniel M Hirai
- Department of Medicine, Queen's University, Kingston, Ontario, Canada; Department of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, São Paulo, Brazil; and
| | - Timothy I Musch
- Departments of Anatomy and Physiology and Kinesiology, Kansas State University, Manhattan, Kansas
| | - David C Poole
- Departments of Anatomy and Physiology and Kinesiology, Kansas State University, Manhattan, Kansas
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Fullagar HHK, Skorski S, Duffield R, Hammes D, Coutts AJ, Meyer T. Sleep and athletic performance: the effects of sleep loss on exercise performance, and physiological and cognitive responses to exercise. Sports Med 2015; 45:161-86. [PMID: 25315456 DOI: 10.1007/s40279-014-0260-0] [Citation(s) in RCA: 410] [Impact Index Per Article: 45.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Although its true function remains unclear, sleep is considered critical to human physiological and cognitive function. Equally, since sleep loss is a common occurrence prior to competition in athletes, this could significantly impact upon their athletic performance. Much of the previous research has reported that exercise performance is negatively affected following sleep loss; however, conflicting findings mean that the extent, influence, and mechanisms of sleep loss affecting exercise performance remain uncertain. For instance, research indicates some maximal physical efforts and gross motor performances can be maintained. In comparison, the few published studies investigating the effect of sleep loss on performance in athletes report a reduction in sport-specific performance. The effects of sleep loss on physiological responses to exercise also remain equivocal; however, it appears a reduction in sleep quality and quantity could result in an autonomic nervous system imbalance, simulating symptoms of the overtraining syndrome. Additionally, increases in pro-inflammatory cytokines following sleep loss could promote immune system dysfunction. Of further concern, numerous studies investigating the effects of sleep loss on cognitive function report slower and less accurate cognitive performance. Based on this context, this review aims to evaluate the importance and prevalence of sleep in athletes and summarises the effects of sleep loss (restriction and deprivation) on exercise performance, and physiological and cognitive responses to exercise. Given the equivocal understanding of sleep and athletic performance outcomes, further research and consideration is required to obtain a greater knowledge of the interaction between sleep and performance.
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Affiliation(s)
- Hugh H K Fullagar
- Institute of Sport and Preventive Medicine, Saarland University, GEB. B82, 66123, Saarbrucken, Germany,
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Fukuoka Y, Poole DC, Barstow TJ, Kondo N, Nishiwaki M, Okushima D, Koga S. Reduction of V̇O2 slow component by priming exercise: novel mechanistic insights from time-resolved near-infrared spectroscopy. Physiol Rep 2015; 3:3/6/e12432. [PMID: 26109190 PMCID: PMC4510633 DOI: 10.14814/phy2.12432] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Novel time-resolved near-infrared spectroscopy (TR-NIRS), with adipose tissue thickness correction, was used to test the hypotheses that heavy priming exercise reduces the V̇O2 slow component (V̇O2SC) (1) by elevating microvascular [Hb] volume at multiple sites within the quadriceps femoris (2) rather than reducing the heterogeneity of muscle deoxygenation kinetics. Twelve subjects completed two 6-min bouts of heavy work rate exercise, separated by 6 min of unloaded cycling. Priming exercise induced faster overall V̇O2 kinetics consequent to a substantial reduction in the V̇O2SC (0.27 ± 0.12 vs. 0.11 ± 0.09 L·min−1, P < 0.05) with an unchanged primary V̇O2 time constant. An increased baseline for the primed bout [total (Hb + Mb)] (197.5 ± 21.6 vs. 210.7 ± 22.5 μmol L−1, P < 0.01), reflecting increased microvascular [Hb] volume, correlated significantly with the V̇O2SC reduction. At multiple sites within the quadriceps femoris, priming exercise reduced the baseline and slowed the increase in [deoxy (Hb + Mb)]. Changes in the intersite coefficient of variation in the time delay and time constant of [deoxy (Hb + Mb)] during the second bout were not correlated with the V̇O2SC reduction. These results support a mechanistic link between priming exercise-induced increase in muscle [Hb] volume and the reduced V̇O2SC that serves to speed overall V̇O2 kinetics. However, reduction in the heterogeneity of muscle deoxygenation kinetics does not appear to be an obligatory feature of the priming response.
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Affiliation(s)
- Yoshiyuki Fukuoka
- Environmental Physiology Laboratory, Prefectural University of Kumamoto, Kumamoto, Japan Graduate School of Health and Sports Science, Doshisha University, Kyoto, Japan
| | - David C Poole
- Departments of Anatomy and Physiology and Kinesiology, Kansas State University, Manhattan, Kansas
| | - Thomas J Barstow
- Departments of Anatomy and Physiology and Kinesiology, Kansas State University, Manhattan, Kansas
| | - Narihiko Kondo
- Graduate School of Cultural Studies and Human Science, Kobe University, Kobe, Japan
| | - Masato Nishiwaki
- Faculty of Engineering, Osaka Institute of Technology, Osaka, Japan
| | - Dai Okushima
- Applied Physiology Laboratory, Kobe Design University, Kobe, Japan
| | - Shunsaku Koga
- Applied Physiology Laboratory, Kobe Design University, Kobe, Japan
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81
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de Jesus K, Sousa A, de Jesus K, Ribeiro J, Machado L, Rodríguez F, Keskinen K, Vilas-Boas JP, Fernandes RJ. The effects of intensity on V̇O2 kinetics during incremental free swimming. Appl Physiol Nutr Metab 2015; 40:918-23. [PMID: 26300011 DOI: 10.1139/apnm-2015-0029] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Swimming and training are carried out with wide variability in distances and intensities. However, oxygen uptake kinetics for the intensities seen in swimming has not been reported. The purpose of this study was to assess and compare the oxygen uptake kinetics throughout low-moderate to severe intensities during incremental swimming exercise. We hypothesized that the oxygen uptake kinetic parameters would be affected by swimming intensity. Twenty male trained swimmers completed an incremental protocol of seven 200-m crawl swims to exhaustion (0.05 m·s(-1) increments and 30-s intervals). Oxygen uptake was continuously measured by a portable gas analyzer connected to a respiratory snorkel and valve system. Oxygen uptake kinetics was assessed using a double exponential regression model that yielded both fast and slow components of the response of oxygen uptake to exercise. From low-moderate to severe swimming intensities changes occurred for the first and second oxygen uptake amplitudes (P ≤ 0.04), time constants (P = 0.01), and time delays (P ≤ 0.02). At the heavy and severe intensities, a notable oxygen uptake slow component (>255 mL·min(-1)) occurred in all swimmers. Oxygen uptake kinetics whilst swimming at different intensities offers relevant information regarding cardiorespiratory and metabolic stress that might be useful for appropriate performance diagnosis and training prescription.
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Affiliation(s)
- Kelly de Jesus
- a Centre of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal
| | - Ana Sousa
- a Centre of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal
| | - Karla de Jesus
- a Centre of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal
| | - João Ribeiro
- a Centre of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal
| | - Leandro Machado
- a Centre of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal.,b Porto Biomechanics Laboratory, University of Porto, Porto, Portugal
| | - Ferran Rodríguez
- c National Institute for Physical Education of Catalonia, University of Barcelona, Barcelona, Spain
| | - Kari Keskinen
- d Finnish Society of Sport Sciences, Helsinki, Finland
| | - João Paulo Vilas-Boas
- a Centre of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal.,b Porto Biomechanics Laboratory, University of Porto, Porto, Portugal
| | - Ricardo J Fernandes
- a Centre of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal.,b Porto Biomechanics Laboratory, University of Porto, Porto, Portugal
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82
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Fleg JL, Cooper LS, Borlaug BA, Haykowsky MJ, Kraus WE, Levine BD, Pfeffer MA, Piña IL, Poole DC, Reeves GR, Whellan DJ, Kitzman DW. Exercise training as therapy for heart failure: current status and future directions. Circ Heart Fail 2015; 8:209-20. [PMID: 25605639 DOI: 10.1161/circheartfailure.113.001420] [Citation(s) in RCA: 120] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Jerome L Fleg
- From the Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, MD (J.L.F., L.S.C.); Division of Cardiovascular Disease, Mayo Clinic, Rochester, MN (B.A.B.); Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada (M.J.H.); Division of Cardiology, Duke University School of Medicine, Durham, NC (W.E.K.); Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center, Dallas (B.D.L.); Cardiovascular Division, Brigham and Women's Hospital, Boston, MA (M.A.P.); Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY (I.L.P.); Department of Kinesiology (D.C.P.) and Department of Anatomy and Physiology (D.C.P.), Kansas State University, Manhattan; Division of Cardiology, Jefferson Medical College, Philadelphia, PA (G.R.R., D.J.W.); and Sections on Cardiology and Geriatrics, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (D.W.K.).
| | - Lawton S Cooper
- From the Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, MD (J.L.F., L.S.C.); Division of Cardiovascular Disease, Mayo Clinic, Rochester, MN (B.A.B.); Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada (M.J.H.); Division of Cardiology, Duke University School of Medicine, Durham, NC (W.E.K.); Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center, Dallas (B.D.L.); Cardiovascular Division, Brigham and Women's Hospital, Boston, MA (M.A.P.); Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY (I.L.P.); Department of Kinesiology (D.C.P.) and Department of Anatomy and Physiology (D.C.P.), Kansas State University, Manhattan; Division of Cardiology, Jefferson Medical College, Philadelphia, PA (G.R.R., D.J.W.); and Sections on Cardiology and Geriatrics, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (D.W.K.)
| | - Barry A Borlaug
- From the Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, MD (J.L.F., L.S.C.); Division of Cardiovascular Disease, Mayo Clinic, Rochester, MN (B.A.B.); Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada (M.J.H.); Division of Cardiology, Duke University School of Medicine, Durham, NC (W.E.K.); Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center, Dallas (B.D.L.); Cardiovascular Division, Brigham and Women's Hospital, Boston, MA (M.A.P.); Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY (I.L.P.); Department of Kinesiology (D.C.P.) and Department of Anatomy and Physiology (D.C.P.), Kansas State University, Manhattan; Division of Cardiology, Jefferson Medical College, Philadelphia, PA (G.R.R., D.J.W.); and Sections on Cardiology and Geriatrics, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (D.W.K.)
| | - Mark J Haykowsky
- From the Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, MD (J.L.F., L.S.C.); Division of Cardiovascular Disease, Mayo Clinic, Rochester, MN (B.A.B.); Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada (M.J.H.); Division of Cardiology, Duke University School of Medicine, Durham, NC (W.E.K.); Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center, Dallas (B.D.L.); Cardiovascular Division, Brigham and Women's Hospital, Boston, MA (M.A.P.); Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY (I.L.P.); Department of Kinesiology (D.C.P.) and Department of Anatomy and Physiology (D.C.P.), Kansas State University, Manhattan; Division of Cardiology, Jefferson Medical College, Philadelphia, PA (G.R.R., D.J.W.); and Sections on Cardiology and Geriatrics, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (D.W.K.)
| | - William E Kraus
- From the Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, MD (J.L.F., L.S.C.); Division of Cardiovascular Disease, Mayo Clinic, Rochester, MN (B.A.B.); Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada (M.J.H.); Division of Cardiology, Duke University School of Medicine, Durham, NC (W.E.K.); Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center, Dallas (B.D.L.); Cardiovascular Division, Brigham and Women's Hospital, Boston, MA (M.A.P.); Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY (I.L.P.); Department of Kinesiology (D.C.P.) and Department of Anatomy and Physiology (D.C.P.), Kansas State University, Manhattan; Division of Cardiology, Jefferson Medical College, Philadelphia, PA (G.R.R., D.J.W.); and Sections on Cardiology and Geriatrics, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (D.W.K.)
| | - Benjamin D Levine
- From the Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, MD (J.L.F., L.S.C.); Division of Cardiovascular Disease, Mayo Clinic, Rochester, MN (B.A.B.); Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada (M.J.H.); Division of Cardiology, Duke University School of Medicine, Durham, NC (W.E.K.); Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center, Dallas (B.D.L.); Cardiovascular Division, Brigham and Women's Hospital, Boston, MA (M.A.P.); Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY (I.L.P.); Department of Kinesiology (D.C.P.) and Department of Anatomy and Physiology (D.C.P.), Kansas State University, Manhattan; Division of Cardiology, Jefferson Medical College, Philadelphia, PA (G.R.R., D.J.W.); and Sections on Cardiology and Geriatrics, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (D.W.K.)
| | - Marc A Pfeffer
- From the Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, MD (J.L.F., L.S.C.); Division of Cardiovascular Disease, Mayo Clinic, Rochester, MN (B.A.B.); Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada (M.J.H.); Division of Cardiology, Duke University School of Medicine, Durham, NC (W.E.K.); Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center, Dallas (B.D.L.); Cardiovascular Division, Brigham and Women's Hospital, Boston, MA (M.A.P.); Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY (I.L.P.); Department of Kinesiology (D.C.P.) and Department of Anatomy and Physiology (D.C.P.), Kansas State University, Manhattan; Division of Cardiology, Jefferson Medical College, Philadelphia, PA (G.R.R., D.J.W.); and Sections on Cardiology and Geriatrics, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (D.W.K.)
| | - Ileana L Piña
- From the Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, MD (J.L.F., L.S.C.); Division of Cardiovascular Disease, Mayo Clinic, Rochester, MN (B.A.B.); Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada (M.J.H.); Division of Cardiology, Duke University School of Medicine, Durham, NC (W.E.K.); Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center, Dallas (B.D.L.); Cardiovascular Division, Brigham and Women's Hospital, Boston, MA (M.A.P.); Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY (I.L.P.); Department of Kinesiology (D.C.P.) and Department of Anatomy and Physiology (D.C.P.), Kansas State University, Manhattan; Division of Cardiology, Jefferson Medical College, Philadelphia, PA (G.R.R., D.J.W.); and Sections on Cardiology and Geriatrics, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (D.W.K.)
| | - David C Poole
- From the Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, MD (J.L.F., L.S.C.); Division of Cardiovascular Disease, Mayo Clinic, Rochester, MN (B.A.B.); Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada (M.J.H.); Division of Cardiology, Duke University School of Medicine, Durham, NC (W.E.K.); Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center, Dallas (B.D.L.); Cardiovascular Division, Brigham and Women's Hospital, Boston, MA (M.A.P.); Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY (I.L.P.); Department of Kinesiology (D.C.P.) and Department of Anatomy and Physiology (D.C.P.), Kansas State University, Manhattan; Division of Cardiology, Jefferson Medical College, Philadelphia, PA (G.R.R., D.J.W.); and Sections on Cardiology and Geriatrics, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (D.W.K.)
| | - Gordon R Reeves
- From the Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, MD (J.L.F., L.S.C.); Division of Cardiovascular Disease, Mayo Clinic, Rochester, MN (B.A.B.); Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada (M.J.H.); Division of Cardiology, Duke University School of Medicine, Durham, NC (W.E.K.); Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center, Dallas (B.D.L.); Cardiovascular Division, Brigham and Women's Hospital, Boston, MA (M.A.P.); Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY (I.L.P.); Department of Kinesiology (D.C.P.) and Department of Anatomy and Physiology (D.C.P.), Kansas State University, Manhattan; Division of Cardiology, Jefferson Medical College, Philadelphia, PA (G.R.R., D.J.W.); and Sections on Cardiology and Geriatrics, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (D.W.K.)
| | - David J Whellan
- From the Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, MD (J.L.F., L.S.C.); Division of Cardiovascular Disease, Mayo Clinic, Rochester, MN (B.A.B.); Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada (M.J.H.); Division of Cardiology, Duke University School of Medicine, Durham, NC (W.E.K.); Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center, Dallas (B.D.L.); Cardiovascular Division, Brigham and Women's Hospital, Boston, MA (M.A.P.); Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY (I.L.P.); Department of Kinesiology (D.C.P.) and Department of Anatomy and Physiology (D.C.P.), Kansas State University, Manhattan; Division of Cardiology, Jefferson Medical College, Philadelphia, PA (G.R.R., D.J.W.); and Sections on Cardiology and Geriatrics, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (D.W.K.)
| | - Dalane W Kitzman
- From the Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, MD (J.L.F., L.S.C.); Division of Cardiovascular Disease, Mayo Clinic, Rochester, MN (B.A.B.); Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada (M.J.H.); Division of Cardiology, Duke University School of Medicine, Durham, NC (W.E.K.); Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center, Dallas (B.D.L.); Cardiovascular Division, Brigham and Women's Hospital, Boston, MA (M.A.P.); Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY (I.L.P.); Department of Kinesiology (D.C.P.) and Department of Anatomy and Physiology (D.C.P.), Kansas State University, Manhattan; Division of Cardiology, Jefferson Medical College, Philadelphia, PA (G.R.R., D.J.W.); and Sections on Cardiology and Geriatrics, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (D.W.K.)
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83
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Upadhya B, Taffet GE, Cheng CP, Kitzman DW. Heart failure with preserved ejection fraction in the elderly: scope of the problem. J Mol Cell Cardiol 2015; 83:73-87. [PMID: 25754674 DOI: 10.1016/j.yjmcc.2015.02.025] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 02/25/2015] [Accepted: 02/26/2015] [Indexed: 12/13/2022]
Abstract
Heart failure with preserved ejection fraction (HFpEF) is the most common form of heart failure (HF) in older adults, particularly women, and is increasing in prevalence as the population ages. With morbidity and mortality on par with HF with reduced ejection fraction, it remains a most challenging clinical syndrome for the practicing clinician and basic research scientist. Originally considered to be predominantly caused by diastolic dysfunction, more recent insights indicate that HFpEF in older persons is typified by a broad range of cardiac and non-cardiac abnormalities and reduced reserve capacity in multiple organ systems. The globally reduced reserve capacity is driven by: 1) inherent age-related changes; 2) multiple, concomitant co-morbidities; 3) HFpEF itself, which is likely a systemic disorder. These insights help explain why: 1) co-morbidities are among the strongest predictors of outcomes; 2) approximately 50% of clinical events in HFpEF patients are non-cardiovascular; 3) clinical drug trials in HFpEF have been negative on their primary outcomes. Embracing HFpEF as a true geriatric syndrome, with complex, multi-factorial pathophysiology and clinical heterogeneity could provide new mechanistic insights and opportunities for progress in management. This article is part of a Special Issue entitled CV Aging.
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Affiliation(s)
- Bharathi Upadhya
- Cardiology Section, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - George E Taffet
- Geriatrics and Cardiovascular Sciences, Baylor College of Medicine, Houston Methodist Hospital, Houston, TX, USA
| | - Che Ping Cheng
- Cardiology Section, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Dalane W Kitzman
- Cardiology Section, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA.
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84
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Cannon DT, Bimson WE, Hampson SA, Bowen TS, Murgatroyd SR, Marwood S, Kemp GJ, Rossiter HB. Skeletal muscle ATP turnover by 31P magnetic resonance spectroscopy during moderate and heavy bilateral knee extension. J Physiol 2014; 592:5287-300. [PMID: 25281731 DOI: 10.1113/jphysiol.2014.279174] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
During constant-power high-intensity exercise, the expected increase in oxygen uptake (V̇O2) is supplemented by a V̇O2 slow component (V̇O2 sc ), reflecting reduced work efficiency, predominantly within the locomotor muscles. The intracellular source of inefficiency is postulated to be an increase in the ATP cost of power production (an increase in P/W). To test this hypothesis, we measured intramuscular ATP turnover with (31)P magnetic resonance spectroscopy (MRS) and whole-body V̇O2 during moderate (MOD) and heavy (HVY) bilateral knee-extension exercise in healthy participants (n = 14). Unlocalized (31)P spectra were collected from the quadriceps throughout using a dual-tuned ((1)H and (31)P) surface coil with a simple pulse-and-acquire sequence. Total ATP turnover rate (ATPtot) was estimated at exercise cessation from direct measurements of the dynamics of phosphocreatine (PCr) and proton handling. Between 3 and 8 min during MOD, there was no discernable V̇O2 sc (mean ± SD, 0.06 ± 0.12 l min(-1)) or change in [PCr] (30 ± 8 vs. 32 ± 7 mm) or ATPtot (24 ± 14 vs. 17 ± 14 mm min(-1); each P = n.s.). During HVY, the V̇O2 sc was 0.37 ± 0.16 l min(-1) (22 ± 8%), [PCr] decreased (19 ± 7 vs. 18 ± 7 mm, or 12 ± 15%; P < 0.05) and ATPtot increased (38 ± 16 vs. 44 ± 14 mm min(-1), or 26 ± 30%; P < 0.05) between 3 and 8 min. However, the increase in ATPtot (ΔATPtot) was not correlated with the V̇O2 sc during HVY (r(2) = 0.06; P = n.s.). This lack of relationship between ΔATPtot and V̇O2 sc , together with a steepening of the [PCr]-V̇O2 relationship in HVY, suggests that reduced work efficiency during heavy exercise arises from both contractile (P/W) and mitochondrial sources (the O2 cost of ATP resynthesis; P/O).
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Affiliation(s)
- Daniel T Cannon
- Rehabilitation Clinical Trials Center, Division of Respiratory & Critical Care Physiology & Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - William E Bimson
- Magnetic Resonance & Image Analysis Research Centre, University of Liverpool, Liverpool, UK
| | - Sophie A Hampson
- School of Health Sciences, Liverpool Hope University, Liverpool, UK
| | - T Scott Bowen
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK Department of Internal Medicine and Cardiology, University of Leipzig - Heart Center, Leipzig, DE
| | - Scott R Murgatroyd
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Simon Marwood
- School of Health Sciences, Liverpool Hope University, Liverpool, UK
| | - Graham J Kemp
- Magnetic Resonance & Image Analysis Research Centre, University of Liverpool, Liverpool, UK Department of Musculoskeletal Biology, University of Liverpool, Liverpool, UK
| | - Harry B Rossiter
- Rehabilitation Clinical Trials Center, Division of Respiratory & Critical Care Physiology & Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK
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85
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Raper JA, Love LK, Paterson DH, Peters SJ, Heigenhauser GJF, Kowalchuk JM. Effect of high-fat and high-carbohydrate diets on pulmonary O2 uptake kinetics during the transition to moderate-intensity exercise. J Appl Physiol (1985) 2014; 117:1371-9. [PMID: 25277736 DOI: 10.1152/japplphysiol.00456.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mitochondrial pyruvate dehydrogenase (PDH) regulates the delivery of carbohydrate-derived substrate to the mitochondrial tricarboxylic acid cycle and electron transport chain. PDH activity at rest and its activation during exercise is attenuated following high-fat (HFAT) compared with high-carbohydrate (HCHO) diets. Given the reliance on carbohydrate-derived substrate early in transitions to exercise, this study examined the effects of HFAT and HCHO on phase II pulmonary O2 uptake (V̇o2 p) kinetics during transitions into the moderate-intensity (MOD) exercise domain. Eight active adult men underwent dietary manipulations consisting of 6 days of HFAT (73% fat, 22% protein, 5% carbohydrate) followed immediately by 6 days of HCHO (10% fat, 10% protein, 80% carbohydrate); each dietary phase was preceded by a glycogen depletion protocol. Participants performed three MOD transitions from a 20 W cycling baseline to work rate equivalent to 80% of estimated lactate threshold on days 5 and 6 of each diet. Steady-state V̇o2 p was greater (P < 0.05), and respiratory exchange ratio and carbohydrate oxidation rates were lower (P < 0.05) during HFAT. The phase II V̇o2 p time constant (τV̇o2 p) [HFAT 40 ± 16, HCHO 32 ± 19 s (mean ± SD)] and V̇o2 p gain (HFAT 10.3 ± 0.8, HCHO 9.4 ± 0.7 ml·min(-1·)W(-1)) were greater (P < 0.05) in HFAT. The overall adjustment (effective time constant) of muscle deoxygenation (Δ[HHb]) was not different between diets (HFAT 24 ± 4 s, HCHO 23 ± 4 s), which coupled with a slower τV̇o2 p, indicates a slowed microvascular blood flow response. These results suggest that the slower V̇o2 p kinetics associated with HFAT are consistent with inhibition and slower activation of PDH, a lower rate of pyruvate production, and/or attenuated microvascular blood flow and O2 delivery.
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Affiliation(s)
- J A Raper
- Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada; School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada
| | - L K Love
- Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada; School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada; Department of Kinesiology, Centre for Bone and Muscle Health, Brock University, St. Catharines, Ontario, Canada
| | - D H Paterson
- Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada; School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada
| | - S J Peters
- Department of Kinesiology, Centre for Bone and Muscle Health, Brock University, St. Catharines, Ontario, Canada
| | - G J F Heigenhauser
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada; and
| | - J M Kowalchuk
- Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada; School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada; Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada;
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86
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Kitzman DW, Nicklas B, Kraus WE, Lyles MF, Eggebeen J, Morgan TM, Haykowsky M. Skeletal muscle abnormalities and exercise intolerance in older patients with heart failure and preserved ejection fraction. Am J Physiol Heart Circ Physiol 2014; 306:H1364-70. [PMID: 24658015 DOI: 10.1152/ajpheart.00004.2014] [Citation(s) in RCA: 219] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Heart failure (HF) with preserved ejection fraction (HFPEF) is the most common form of HF in older persons. The primary chronic symptom in HFPEF is severe exercise intolerance, and its pathophysiology is poorly understood. To determine whether skeletal muscle abnormalities contribute to their severely reduced peak exercise O2 consumption (Vo2), we examined 22 older HFPEF patients (70 ± 7 yr) compared with 43 age-matched healthy control (HC) subjects using needle biopsy of the vastus lateralis muscle and cardiopulmonary exercise testing to assess muscle fiber type distribution and capillarity and peak Vo2. In HFPEF versus HC patients, peak Vo2 (14.7 ± 2.1 vs. 22.9 ± 6.6 ml·kg(-1)·min(-1), P < 0.001) and 6-min walk distance (454 ± 72 vs. 573 ± 71 m, P < 0.001) were reduced. In HFPEF versus HC patients, the percentage of type I fibers (39.0 ± 11.4% vs. 53.7 ± 12.4%, P < 0.001), type I-to-type II fiber ratio (0.72 ± 0.39 vs. 1.36 ± 0.85, P = 0.001), and capillary-to-fiber ratio (1.35 ± 0.32 vs. 2.53 ± 1.37, P = 0.006) were reduced, whereas the percentage of type II fibers was greater (61 ± 11.4% vs. 46.3 ± 12.4%, P < 0.001). In univariate analyses, the percentage of type I fibers (r = 0.39, P = 0.003), type I-to-type II fiber ratio (r = 0.33, P = 0.02), and capillary-to-fiber ratio (r = 0.59, P < 0.0001) were positively related to peak Vo2. In multivariate analyses, type I fibers and the capillary-to-fiber ratio remained significantly related to peak Vo2. We conclude that older HFPEF patients have significant abnormalities in skeletal muscle, characterized by a shift in muscle fiber type distribution with reduced type I oxidative muscle fibers and a reduced capillary-to-fiber ratio, and these may contribute to their severe exercise intolerance. This suggests potential new therapeutic targets in this difficult to treat disorder.
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Affiliation(s)
- Dalane W Kitzman
- Cardiology Section, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
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87
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A single-session testing protocol to determine critical power and W′. Eur J Appl Physiol 2014; 114:1153-61. [DOI: 10.1007/s00421-014-2827-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 01/18/2014] [Indexed: 10/25/2022]
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88
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Clanton TL, Hogan MC, Gladden LB. Regulation of cellular gas exchange, oxygen sensing, and metabolic control. Compr Physiol 2013; 3:1135-90. [PMID: 23897683 DOI: 10.1002/cphy.c120030] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cells must continuously monitor and couple their metabolic requirements for ATP utilization with their ability to take up O2 for mitochondrial respiration. When O2 uptake and delivery move out of homeostasis, cells have elaborate and diverse sensing and response systems to compensate. In this review, we explore the biophysics of O2 and gas diffusion in the cell, how intracellular O2 is regulated, how intracellular O2 levels are sensed and how sensing systems impact mitochondrial respiration and shifts in metabolic pathways. Particular attention is paid to how O2 affects the redox state of the cell, as well as the NO, H2S, and CO concentrations. We also explore how these agents can affect various aspects of gas exchange and activate acute signaling pathways that promote survival. Two kinds of challenges to gas exchange are also discussed in detail: when insufficient O2 is available for respiration (hypoxia) and when metabolic requirements test the limits of gas exchange (exercising skeletal muscle). This review also focuses on responses to acute hypoxia in the context of the original "unifying theory of hypoxia tolerance" as expressed by Hochachka and colleagues. It includes discourse on the regulation of mitochondrial electron transport, metabolic suppression, shifts in metabolic pathways, and recruitment of cell survival pathways preventing collapse of membrane potential and nuclear apoptosis. Regarding exercise, the issues discussed relate to the O2 sensitivity of metabolic rate, O2 kinetics in exercise, and influences of available O2 on glycolysis and lactate production.
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Affiliation(s)
- T L Clanton
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, USA.
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89
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Ferguson C, Wilson J, Birch KM, Kemi OJ. Application of the speed-duration relationship to normalize the intensity of high-intensity interval training. PLoS One 2013; 8:e76420. [PMID: 24244266 PMCID: PMC3828304 DOI: 10.1371/journal.pone.0076420] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 08/27/2013] [Indexed: 01/18/2023] Open
Abstract
The tolerable duration of continuous high-intensity exercise is determined by the hyperbolic Speed-tolerable duration (S-tLIM) relationship. However, application of the S-tLIM relationship to normalize the intensity of High-Intensity Interval Training (HIIT) has yet to be considered, with this the aim of present study. Subjects completed a ramp-incremental test, and series of 4 constant-speed tests to determine the S-tLIM relationship. A sub-group of subjects (n = 8) then repeated 4 min bouts of exercise at the speeds predicted to induce intolerance at 4 min (WR4), 6 min (WR6) and 8 min (WR8), interspersed with bouts of 4 min recovery, to the point of exercise intolerance (fixed WR HIIT) on different days, with the aim of establishing the work rate that could be sustained for 960 s (i.e. 4×4 min). A sub-group of subjects (n = 6) also completed 4 bouts of exercise interspersed with 4 min recovery, with each bout continued to the point of exercise intolerance (maximal HIIT) to determine the appropriate protocol for maximizing the amount of high-intensity work that can be completed during 4×4 min HIIT. For fixed WR HIIT tLIM of HIIT sessions was 399±81 s for WR4, 892±181 s for WR6 and 1517±346 s for WR8, with total exercise durations all significantly different from each other (P<0.050). For maximal HIIT, there was no difference in tLIM of each of the 4 bouts (Bout 1: 229±27 s; Bout 2: 262±37 s; Bout 3: 235±49 s; Bout 4: 235±53 s; P>0.050). However, there was significantly less high-intensity work completed during bouts 2 (153.5±40. 9 m), 3 (136.9±38.9 m), and 4 (136.7±39.3 m), compared with bout 1 (264.9±58.7 m; P>0.050). These data establish that WR6 provides the appropriate work rate to normalize the intensity of HIIT between subjects. Maximal HIIT provides a protocol which allows the relative contribution of the work rate profile to physiological adaptations to be considered during alternative intensity-matched HIIT protocols.
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Affiliation(s)
- Carrie Ferguson
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- * E-mail:
| | - John Wilson
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Karen M. Birch
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Ole J. Kemi
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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90
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Williams AM, Paterson DH, Kowalchuk JM. High-intensity interval training speeds the adjustment of pulmonary O2 uptake, but not muscle deoxygenation, during moderate-intensity exercise transitions initiated from low and elevated baseline metabolic rates. J Appl Physiol (1985) 2013; 114:1550-62. [PMID: 23519229 DOI: 10.1152/japplphysiol.00575.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
During step transitions in work rate (WR) within the moderate-intensity (MOD) exercise domain, pulmonary O2 uptake (Vo2p) kinetics are slowed, and Vo2p gain (ΔVo2p/ΔWR) is greater when exercise is initiated from an elevated metabolic rate. High-intensity interval training (HIT) has been shown to speed Vo2p kinetics when step transitions to MOD exercise are initiated from light-intensity baseline metabolic rates. The effects of HIT on step transitions initiated from elevated metabolic rates have not been established. Therefore, this study investigated the effects of HIT on Vo2p kinetics during transitions from low and elevated metabolic rates, within the MOD domain. Eight young, untrained men completed 12 sessions of HIT (spanning 4 wk). HIT consisted of 8-12 1-min intervals, cycling at a WR corresponding to 110% of pretraining maximal WR (WRmax). Pre-, mid- and posttraining, subjects completed a ramp-incremental test to determine maximum O2 uptake, WRmax, and estimated lactate threshold (θL). Participants additionally completed double-step constant-load tests, consisting of step transitions from 20 W → Δ45% θL [lower step (LS)] and Δ45 → 90% θL [upper step (US)]. HIT led to increases in maximum O2 uptake (P < 0.05) and WRmax (P < 0.01), and τVo2p of both lower and upper MOD step transitions were reduced by ∼40% (LS: 24 s → 15 s; US: 45 s → 25 s) (P < 0.01). However, the time course of adjustment of local muscle deoxygenation was unchanged in the LS and US. These results suggest that speeding of Vo2p kinetics in both the LS and US may be due, in part, to an improved matching of muscle O2 utilization to microvascular O2 delivery within the working muscle following 12 sessions of HIT, although muscle metabolic adaptations cannot be discounted.
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Affiliation(s)
- Alexandra M Williams
- Canadian Centre for Activity and Aging and School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
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91
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Hoffmann U, Drescher U, Benson AP, Rossiter HB, Essfeld D. Skeletal muscle VO₂ kinetics from cardio-pulmonary measurements: assessing distortions through O₂ transport by means of stochastic work-rate signals and circulatory modelling. Eur J Appl Physiol 2013; 113:1745-54. [PMID: 23412541 DOI: 10.1007/s00421-013-2598-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 01/21/2013] [Indexed: 11/27/2022]
Abstract
During non-steady-state exercise, dynamic changes in pulmonary oxygen uptake (VO₂pulm) are dissociated from skeletal muscle VO₂ (VO₂musc) by changes in lung and venous O₂ concentrations (CvO₂), and the dynamics and distribution of cardiac output (CO) between active muscle and remaining tissues (Qrem). Algorithms can compensate for fluctuations in lung O₂ stores, but the influences of CO and CvO₂ kinetics complicate estimation of VO₂musc from cardio-pulmonary measurements. We developed an algorithm to estimate VO₂musc kinetics from VO₂pulm and heart rate (HR) during exercise. 17 healthy volunteers (28 ± 7 years; 71 ± 12 kg; 7 females) performed incremental exercise using recumbent cycle ergometry (VO₂peak 52 ± 8 ml min(-1) kg(-1)). Participants completed a pseudo-random binary sequence (PRBS) test between 30 and 80 W. VO₂pulm and HR were measured, and CO was estimated from HR changes and steady-state stroke volume. VO₂musc was derived from a circulatory model and time series analyses, by solving for the unique combination of venous volume and the perfusion of non-exercising tissues that provided close to mono-exponential VO₂musc kinetics. Independent simulations showed that this approach recovered the VO₂musc time constant (τ) to within 7% (R(2) = 0.976). Estimates during PRBS were venous volume 2.96 ± 0.54 L; Qrem 3.63 ± 1.61 L min(-1); τHR 27 ± 11 s; τVO₂musc 33 ± 8 s; τVO₂pulm 43 ± 14 s; VO₂pulm time delay 19 ± 8 s. The combination of stochastic test signals, time series analyses, and a circulatory model permitted non-invasive estimates of VO₂musc kinetics. Large kinetic dissociations exist between muscular and pulmonary VO₂ during rapid exercise transients.
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Affiliation(s)
- U Hoffmann
- Institute of Physiology and Anatomy, German Sport University, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany.
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92
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McNarry MA, Kingsley MIC, Lewis MJ. Relationship between changes in pulmonary V̇O₂ kinetics and autonomic regulation of blood flow. Scand J Med Sci Sports 2013; 24:613-21. [PMID: 23347008 DOI: 10.1111/sms.12041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/01/2012] [Indexed: 11/27/2022]
Abstract
Various regulatory mechanisms of pulmonary oxygen uptake (V̇O2) kinetics have been postulated. The purpose of this study was to investigate the relationship between vagal withdrawal, measured using RMSSDRR, the root mean square of successive differences in cardiac interval (RR) kinetics, a mediator of oxygen delivery, and V̇O2 kinetics. Forty-nine healthy adults (23 ± 3 years; 72 ± 13 kg; 1.80 ± 0.08 m) performed multiple repeat transitions to moderate- and heavy-intensity exercise. Electrocardiography, impedance cardiography, and pulmonary gas exchange parameters were measured throughout; time domain measures of heart rate variability were subsequently derived. The parameters describing the dynamic response of V̇O2, cardiac output (Q) and RMSSDRR were determined using a mono-exponential model. During heavy-intensity exercise, the phase II τ of V̇O2 was significantly correlated with the τ of RR (r = 0.36, P < 0.05), Q (r = 0.67, P < 0.05), and RMSSDRR (r = 0.38, P < 0.05). The τ describing the rise in Q explained 47% of the variation in V̇O2 τ, with 30% of the rate of this rise in Q explained by the τ of RR and RMSSDRR. No relationship was evident between V̇O2 kinetics and those of Q, RR, or RMSSDRR during moderate exercise. Vagal withdrawal kinetics support the concept of a centrally mediated oxygen delivery limitation partly regulating V̇O2 kinetics during heavy-, but not moderate-, intensity exercise.
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Affiliation(s)
- M A McNarry
- College of Engineering, Swansea University, Wales, UK
| | - M I C Kingsley
- College of Engineering, Swansea University, Wales, UK.,Faculty of Health Sciences, La Trobe University, Melbourne, Victoria, Australia
| | - M J Lewis
- College of Engineering, Swansea University, Wales, UK
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93
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Wüst RCI, van der Laarse WJ, Rossiter HB. On-off asymmetries in oxygen consumption kinetics of single Xenopus laevis skeletal muscle fibres suggest higher-order control. J Physiol 2012; 591:731-44. [PMID: 23165768 DOI: 10.1113/jphysiol.2012.241992] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The mechanisms controlling skeletal muscle oxygen consumption (V(o)₂) during exercise are not well understood. We determined whether first-order control could explain V(o)₂kinetics at contractions onset (V(o)₂(on)) and cessation (V(o)₂off)) in single skeletal muscle fibres differing in oxdidative capacity, and across stimulation intensities up to V(o)₂(max). Xenopus laevis fibres (n = 21) were suspended in a sealed chamber with a fast response P(o)₂ electrode to measure V(o)₂ every second before, during and after stimulated isometric contractions. A first-order model did not well characterize on-transient V(o)₂ kinetics. Including a time delay (TD) in the model provided a significantly improved characterization than a first-order fit without TD (F-ratio; P < 0.05), and revealed separate 'activation' and 'exponential' phases in 15/21 fibres contracting at V(o)₂(max) (mean ± SD TD: 14 ± 3s). On-transient kinetics (τV(o)₂(on)) was weakly and linearly related to V(o)₂(max) (R² = 0.271, P = 0.015). Off-transient kinetics, however, were first-order, and τV(o)₂(off) was greater in low-oxidative (V(o)₂max < 0.05 nmol mm⁻³s⁻¹ than high-oxidative fibres (V(o)₂(max > 0.10 nmol mm ⁻³ s⁻¹; 170 ± 70 vs. 29 ± 6 s, P < 0.001). 1/ τV(o)₂(off) was proportional to V(o)₂(max) (R² = 0.727, P < 0.001), unlike in the on-transient. The calculated oxygen deficit was larger (P < 0.05) than the post-contraction volume of consumed oxygen at all intensities except V(o)₂(max). These data show a clear dissociation between the kinetic control of V(o)₂at the onset and cessation of contractions and across stimulation intensities. More complex models are therefore required to understand the activation of mitochondrial respiration in skeletal muscle at the start of exercise.
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Affiliation(s)
- Rob C I Wüst
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK
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94
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Rakobowchuk M, Harris E, Taylor A, Cubbon RM, Birch KM. Moderate and heavy metabolic stress interval training improve arterial stiffness and heart rate dynamics in humans. Eur J Appl Physiol 2012; 113:839-49. [PMID: 22983616 PMCID: PMC3599166 DOI: 10.1007/s00421-012-2486-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 08/29/2012] [Indexed: 11/25/2022]
Abstract
Traditional continuous aerobic exercise training attenuates age-related increases of arterial stiffness, however, training studies have not determined whether metabolic stress impacts these favourable effects. Twenty untrained healthy participants (n = 11 heavy metabolic stress interval training, n = 9 moderate metabolic stress interval training) completed 6 weeks of moderate or heavy intensity interval training matched for total work and exercise duration. Carotid artery stiffness, blood pressure contour analysis, and linear and non-linear heart rate variability were assessed before and following training. Overall, carotid arterial stiffness was reduced (p < 0.01), but metabolic stress-specific alterations were not apparent. There was a trend for increased absolute high-frequency (HF) power (p = 0.10) whereas both absolute low-frequency (LF) power (p = 0.05) and overall power (p = 0.02) were increased to a similar degree following both training programmes. Non-linear heart rate dynamics such as detrended fluctuation analysis \documentclass[12pt]{minimal}
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\begin{document}$$({| {1 - \alpha_{1} }|})$$\end{document} also improved (p > 0.05). This study demonstrates the effectiveness of interval training at improving arterial stiffness and autonomic function, however, the metabolic stress was not a mediator of this effect. In addition, these changes were also independent of improvements in aerobic capacity, which were only induced by training that involved a high metabolic stress.
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Affiliation(s)
- Mark Rakobowchuk
- Health, Exercise and Active Life Research Unit, Sport and Exercise Sciences, Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK.
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95
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Gravelle BMR, Murias JM, Spencer MD, Paterson DH, Kowalchuk JM. Adjustments of pulmonary O2 uptake and muscle deoxygenation during ramp incremental exercise and constant-load moderate-intensity exercise in young and older adults. J Appl Physiol (1985) 2012; 113:1466-75. [PMID: 22961268 DOI: 10.1152/japplphysiol.00884.2011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The matching of muscle O(2) delivery to O(2) utilization can be inferred from the adjustments in muscle deoxygenation (Δ[HHb]) and pulmonary O(2) uptake (Vo(2p)). This study examined the adjustments of Vo(2p) and Δ[HHb] during ramp incremental (RI) and constant-load (CL) exercise in adult males. Ten young adults (YA; age: 25 ± 5 yr) and nine older adults (OA; age: 70 ± 3 yr) completed two RI tests and six CL step transitions to a work rate (WR) corresponding to 1) 80% of the estimated lactate threshold (same relative WR) and 2) 50 W (same absolute WR). Vo(2p) was measured breath by breath, and Δ[HHb] of the vastus lateralis was measured using near-infrared spectroscopy. Δ[HHb]-WR profiles were normalized from baseline (0%) to peak Δ[HHb] (100%) and fit using a sigmoid function. The sigmoid slope (d) was greater (P < 0.05) in OA (0.027 ± 0.01%/W) compared with YA (0.017 ± 0.01%/W), and the c/d value (a value corresponding to 50% of the amplitude) was smaller (P < 0.05) for OA (133 ± 40 W) than for YA (195 ± 51 W). No age-related differences in the sigmoid parameters were reported when WR was expressed as a percentage of peak WR. Vo(2p) kinetics compared with Δ[HHb] kinetics for the 50-W transition were similar between YA and OA; however, Δ[HHb] kinetics during the transition to 80% of the lactate threshold were faster than Vo(2p) kinetics in both groups. The greater reliance on O(2) extraction displayed in OA during RI exercise suggests a lower O(2) delivery-to-O(2) utilization relationship at a given absolute WR compared with YA.
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Affiliation(s)
- Braden M R Gravelle
- Canadian Centre for Activity and Aging, The University of Western Ontario, London, Ontario, Canada
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96
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Zoladz JA, Szkutnik Z, Majerczak J, Grandys M, Duda K, Grassi B. Isometric strength training lowers the O2 cost of cycling during moderate-intensity exercise. Eur J Appl Physiol 2012; 112:4151-61. [PMID: 22526253 DOI: 10.1007/s00421-012-2405-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 04/06/2012] [Indexed: 12/21/2022]
Abstract
The effect of maximal voluntary isometric strength training of knee extensor muscles on pulmonary V'O(2) on-kinetics, the O(2) cost of cycling and peak oxygen uptake (V'O(2peak)) in humans was studied. Seven healthy males (mean ± SD, age 22.3 ± 2.0 years, body weight 75.0 ± 9.2 kg, V'O(2peak) 49.5 ± 3.8 ml kg(-1) min(-1)) performed maximal isometric strength training lasting 7 weeks (4 sessions per week). Force during maximal voluntary contraction (MVC) increased by 15 % (P < 0.001) after 1 week of training, and by 19 % (P < 0.001) after 7 weeks of training. This increase in MVC was accompanied by no significant changes in the time constant of the V'O(2) on-kinetics during 6 min of moderate and heavy cycling intensities. Strength training resulted in a significant decrease (by ~7 %; P < 0.02) in the amplitude of the fundamental component of the V'O(2) on-kinetics, and therefore in a lower O(2) cost of cycling during moderate cycling intensity. The amplitude of the slow component of V'O(2) on-kinetics during heavy cycling intensity did not change with training. Training had no effect on the V'O(2peak), whereas the maximal power output reached at V'O(2peak) was slightly but significantly increased (P < 0.05). Isometric strength training rapidly (i.e., after 1 week) decreases the O(2) cost of cycling during moderate-intensity exercise, whereas it does not affect the amplitude of the slow component of the V'O(2) on-kinetics during heavy-intensity exercise. Isometric strength training can have beneficial effects on performance during endurance events.
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Affiliation(s)
- Jerzy A Zoladz
- Department of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, AWF-Kraków, Al. Jana Pawla II 78, Kraków, Poland.
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97
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Poole DC, Hirai DM, Copp SW, Musch TI. Muscle oxygen transport and utilization in heart failure: implications for exercise (in)tolerance. Am J Physiol Heart Circ Physiol 2012; 302:H1050-63. [PMID: 22101528 PMCID: PMC3311454 DOI: 10.1152/ajpheart.00943.2011] [Citation(s) in RCA: 206] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Accepted: 11/17/2011] [Indexed: 01/01/2023]
Abstract
The defining characteristic of chronic heart failure (CHF) is an exercise intolerance that is inextricably linked to structural and functional aberrations in the O(2) transport pathway. CHF reduces muscle O(2) supply while simultaneously increasing O(2) demands. CHF severity varies from moderate to severe and is assessed commonly in terms of the maximum O(2) uptake, which relates closely to patient morbidity and mortality in CHF and forms the basis for Weber and colleagues' (167) classifications of heart failure, speed of the O(2) uptake kinetics following exercise onset and during recovery, and the capacity to perform submaximal exercise. As the heart fails, cardiovascular regulation shifts from controlling cardiac output as a means for supplying the oxidative energetic needs of exercising skeletal muscle and other organs to preventing catastrophic swings in blood pressure. This shift is mediated by a complex array of events that include altered reflex and humoral control of the circulation, required to prevent the skeletal muscle "sleeping giant" from outstripping the pathologically limited cardiac output and secondarily impacts lung (and respiratory muscle), vascular, and locomotory muscle function. Recently, interest has also focused on the dysregulation of inflammatory mediators including tumor necrosis factor-α and interleukin-1β as well as reactive oxygen species as mediators of systemic and muscle dysfunction. This brief review focuses on skeletal muscle to address the mechanistic bases for the reduced maximum O(2) uptake, slowed O(2) uptake kinetics, and exercise intolerance in CHF. Experimental evidence in humans and animal models of CHF unveils the microvascular cause(s) and consequences of the O(2) supply (decreased)/O(2) demand (increased) imbalance emblematic of CHF. Therapeutic strategies to improve muscle microvascular and oxidative function (e.g., exercise training and anti-inflammatory, antioxidant strategies, in particular) and hence patient exercise tolerance and quality of life are presented within their appropriate context of the O(2) transport pathway.
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Affiliation(s)
- David C Poole
- Departments of Anatomy and Physiology, and Kinesiology, Kansas State University, Manhattan, KS 66506-5802, USA.
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98
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Rakobowchuk M, Harris E, Taylor A, Baliga V, Cubbon RM, Rossiter HB, Birch KM. Heavy and moderate interval exercise training alters low-flow-mediated constriction but does not increase circulating progenitor cells in healthy humans. Exp Physiol 2011; 97:375-85. [PMID: 22179420 PMCID: PMC3505374 DOI: 10.1113/expphysiol.2011.062836] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Moderate-intensity endurance exercise training improves vascular endothelial vasomotor function; however, the impact of high-intensity exercise training has been equivocal. Thus, the effect of the physiological stress of the exercise remains poorly understood. Furthermore, enhanced vascular repair mediated by circulating progenitor cells may also be improved. To address whether the physiological stress of exercise training is an important factor contributing to these adaptations, 20 healthy participants trained for 6 weeks. Training involved either moderate (MSIT; n = 9) or heavy metabolic stress (HSIT; n = 11) interval exercise training programmes matched for total work and duration of exercise. Before and after training, flow-mediated dilatation, low-flow-mediated constriction and total vessel reactivity were measured at the brachial artery using Doppler ultrasound. Circulating progenitor cells (CD34(+), CD133(+) and CD309/KDR(+)) were measured by flow cytometry (means ± SD). Relative (MSIT pre- 5.5 ± 3.4 versus post-training 6.6 ± 2.5%; HSIT pre- 6.6 ± 4.1 versus post-training 7.0 ± 3.4%, P = 0.33) and normalized (P = 0.16) flow-mediated dilatation did not increase with either training programme. However, low-flow-mediated constriction was greater after training in both groups (MSIT pre- -0.5 ± 3.2 versus post-training -1.9 ± 3.1%; HSIT pre- -1.0 ± 1.7 versus post-training -2.9 ± 3.0%, P = 0.04) and contributed to greater total vessel reactivity (MSIT pre- 7.4 ± 3.3 versus post-training 10.1 ± 3.7%; HSIT pre- 10.9 ± 5.9 versus post-training 12.7 ± 6.2%, P = 0.01). Peak reactive hyperaemia and the area under the shear rate curve were not different between groups, either before or after training. Although circulating progenitor cell numbers increased following heavy-intensity interval exercise training, variability was great amongst participants [MSIT pre- 16 ± 18 versus post-training 14 ± 12 cells (ml whole blood)(-1); HSIT pre- 8 ± 6 versus post-training 19 ± 23 cells (ml whole blood)(-1), P = 0.50]. Overall, vasoconstrictor function may be augmented by moderate- and heavy-intensity interval exercise training in young adults. However, circulating progenitor cell numbers were not increased, suggesting that these cells are not likely to be upregulated as a result of training.
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Affiliation(s)
- Mark Rakobowchuk
- Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK
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Bowen TS, Cannon DT, Murgatroyd SR, Birch KM, Witte KK, Rossiter HB. The intramuscular contribution to the slow oxygen uptake kinetics during exercise in chronic heart failure is related to the severity of the condition. J Appl Physiol (1985) 2011; 112:378-87. [PMID: 22033530 DOI: 10.1152/japplphysiol.00779.2011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mechanism for slow pulmonary O(2) uptake (Vo(2)) kinetics in patients with chronic heart failure (CHF) is unclear but may be due to limitations in the intramuscular control of O(2) utilization or O(2) delivery. Recent evidence of a transient overshoot in microvascular deoxygenation supports the latter. Prior (or warm-up) exercise can increase O(2) delivery in healthy individuals. We therefore aimed to determine whether prior exercise could increase muscle oxygenation and speed Vo(2) kinetics during exercise in CHF. Fifteen men with CHF (New York Heart Association I-III) due to left ventricular systolic dysfunction performed two 6-min moderate-intensity exercise transitions (bouts 1 and 2, separated by 6 min of rest) from rest to 90% of lactate threshold on a cycle ergometer. Vo(2) was measured using a turbine and a mass spectrometer, and muscle tissue oxygenation index (TOI) was determined by near-infrared spectroscopy. Prior exercise increased resting TOI by 5.3 ± 2.4% (P = 0.001), attenuated the deoxygenation overshoot (-3.9 ± 3.6 vs. -2.0 ± 1.4%, P = 0.011), and speeded the Vo(2) time constant (τVo(2); 49 ± 19 vs. 41 ± 16 s, P = 0.003). Resting TOI was correlated to τVo(2) before (R(2) = 0.51, P = 0.014) and after (R(2) = 0.36, P = 0.051) warm-up exercise. However, the mean response time of TOI was speeded between bouts in half of the patients (26 ± 8 vs. 20 ± 8 s) and slowed in the remainder (32 ± 11 vs. 44 ± 16 s), the latter group having worse New York Heart Association scores (P = 0.042) and slower Vo(2) kinetics (P = 0.001). These data indicate that prior moderate-intensity exercise improves muscle oxygenation and speeds Vo(2) kinetics in CHF. The most severely limited patients, however, appear to have an intramuscular pathology that limits Vo(2) kinetics during moderate exercise.
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Affiliation(s)
- T Scott Bowen
- Institute of Membrane and Systems Biology, University of Leeds, Leeds, UK
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Kano Y, Poole DC, Sudo M, Hirachi T, Miura S, Ezaki O. Control of microvascular PO₂ kinetics following onset of muscle contractions: role for AMPK. Am J Physiol Regul Integr Comp Physiol 2011; 301:R1350-7. [PMID: 21849631 DOI: 10.1152/ajpregu.00294.2011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The microvascular partial pressure of oxygen (Pmv(o(2))) kinetics following the onset of exercise reflects the relationship between muscle O(2) delivery and uptake (Vo(2)). Although AMP-activated protein kinase (AMPK) is known as a regulator of mitochondria and nitric oxide metabolism, it is unclear whether the dynamic balance of O(2) delivery and Vo(2) at exercise onset is dependent on AMPK activation level. We used transgenic mice with muscle-specific AMPK dominant-negative (AMPK-DN) to investigate a role for skeletal muscle AMPK on Pmv(o(2)) kinetics following onset of muscle contractions. Phosphorescence quenching techniques were used to measure Pmv(o(2)) at rest and across the transition to twitch (1 Hz) and tetanic (100 Hz, 3-5 V, 4-ms pulse duration, stimulus duration of 100 ms every 1 s for 1 min) contractions in gastrocnemius muscles (each group n = 6) of AMPK-DN mice and wild-type littermates (WT) under isoflurane anesthesia with 100% inspired O(2) to avoid hypoxemia. Baseline Pmv(o(2)) before contractions was not different between groups (P > 0.05). Both muscle contraction conditions exhibited a delay followed by an exponential decrease in Pmv(o(2)). However, compared with WT, AMPK-DN demonstrated 1) prolongation of the time delay before Pmv(o(2)) began to decline (1 Hz: WT, 3.2 ± 0.5 s; AMPK-DN, 6.5 ± 0.4 s; 100 Hz: WT, 4.4 ± 1.0 s; AMPK-DN, 6.5 ± 1.4 s; P < 0.05), 2) a faster response time (i.e., time constant; 1 Hz: WT, 19.4 ± 3.9 s; AMPK-DN, 12.4 ± 2.6 s; 100 Hz: WT, 15.1 ± 2.2 s; AMPK-DN, 9.0 ± 1.7 s; P < 0.05). These findings are consistent with the presence of substantial mitochondrial and microvascular dysfunction in AMPK-DN mice, which likely slows O(2) consumption kinetics (i.e., oxidative phosphorylation response) and impairs the hyperemic response at the onset of contractions thereby sowing the seeds for exercise intolerance.
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Affiliation(s)
- Yutaka Kano
- Dept. of Engineering Science, Bioscience and Technology Program, Univ. of Electro-Communications, Chofu,Tokyo, 1828585, Japan.
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