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Marinari G, Iannetta D, Holash RJ, Trama R, Faricier R, Zagatto AM, Keir DA, Murias JM. A Ramp versus Step Transition to Constant Work Rate Exercise Decreases Steady-State Oxygen Uptake. Med Sci Sports Exerc 2024; 56:972-981. [PMID: 38181214 DOI: 10.1249/mss.0000000000003372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2024]
Abstract
PURPOSE This study aimed to investigate whether a ramp-to-constant WR (rCWR) transition compared with a square-wave-to-constant WR (CWR) transition within the heavy-intensity domain can reduce metabolic instability and decrease the oxygen cost of exercise. METHODS Fourteen individuals performed (i) a ramp-incremental test to task failure, (ii) a 21-min CWR within the heavy-intensity domain, and (iii) an rCWR to the same WR. Oxygen uptake (V̇O 2 ), lactate concentration ([La - ]), and muscle oxygen saturation (SmO 2 ) were measured. V̇O 2 and V̇O 2 gain (V̇O 2 -G) during the first 10-min steady-state V̇O 2 were analyzed. [La - ] before, at, and after steady-state V̇O 2 and SmO 2 during the entire 21-min steady-state exercise were also examined. RESULTS V̇O 2 and V̇O 2 -G during rCWR (2.49 ± 0.58 L·min -1 and 10.7 ± 0.2 mL·min -1 ·W -1 , respectively) were lower ( P < 0.001) than CWR (2.57 ± 0.60 L·min -1 and 11.3 ± 0.2 mL·min -1 ·W -1 , respectively). [La - ] before and at steady-state V̇O 2 during the rCWR condition (1.94 ± 0.60 and 3.52 ± 1.19 mM, respectively) was lower than the CWR condition (3.05 ± 0.82 and 4.15 ± 1.25 mM, respectively) ( P < 0.001). [La - ] dynamics after steady-state V̇O 2 were unstable for the rCWR ( P = 0.011). SmO 2 was unstable within the CWR condition from minutes 4 to 13 ( P < 0.05). CONCLUSIONS The metabolic disruption caused by the initial minutes of square-wave exercise transitions is a primary contributor to metabolic instability, leading to an increased V̇O 2 -G compared with the rCWR condition approach. The reduced early reliance on anaerobic energy sources during the rCWR condition may be responsible for the lower V̇O 2 -G.
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Affiliation(s)
| | - Danilo Iannetta
- Faculty of Kinesiology, University of Calgary, Calgary, CANADA
| | | | - Robin Trama
- Faculty of Kinesiology, University of Calgary, Calgary, CANADA
| | | | - Alessandro M Zagatto
- Laboratory of Physiology and Sport Performance (LAFIDE), Department of Physical Education, School of Sciences, São Paulo State University-UNESP, Bauru, BRAZIL
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Korzeniewski B. Sensitivity of V̇O2max, critical power and V̇O2 on-kinetics to O2 concentration/delivery and other factors in skeletal muscle. Respir Physiol Neurobiol 2023; 307:103977. [DOI: 10.1016/j.resp.2022.103977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 09/29/2022] [Accepted: 10/03/2022] [Indexed: 11/07/2022]
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Bar‐Yoseph R, Radom‐Aizik S, Coronato N, Moradinasab N, Barstow TJ, Stehli A, Brown D, Cooper DM. Heart rate and gas exchange dynamic responses to multiple brief exercise bouts (MBEB) in early- and late-pubertal boys and girls. Physiol Rep 2022; 10:e15397. [PMID: 35923083 PMCID: PMC9349595 DOI: 10.14814/phy2.15397] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 06/24/2022] [Accepted: 07/02/2022] [Indexed: 04/28/2023] Open
Abstract
Natural patterns of physical activity in youth are characterized by brief periods of exercise of varying intensity interspersed with rest. To better understand systemic physiologic response mechanisms in children and adolescents, we examined five responses [heart rate (HR), respiratory rate (RR), oxygen uptake (V̇O2 ), carbon dioxide production (V̇CO2 ), and minute ventilation (V̇E), measured breath-by-breath] to multiple brief exercise bouts (MBEB). Two groups of healthy participants (early pubertal: 17 female, 20 male; late-pubertal: 23 female, 21 male) performed five consecutive 2-min bouts of constant work rate cycle-ergometer exercise interspersed with 1-min of rest during separate sessions of low- or high-intensity (~40% or 80% peak work, respectively). For each 2-min on-transient and 1-min off-transient we calculated the average value of each cardiopulmonary exercise testing (CPET) variable (Y̅). There were significant MBEB changes in 67 of 80 on- and off-transients. Y̅ increased bout-to-bout for all CPET variables, and the magnitude of increase was greater in the high-intensity exercise. We measured the metabolic cost of MBEB, scaled to work performed, for the entire 15 min and found significantly higher V̇O2 , V̇CO2 , and V̇E costs in the early-pubertal participants for both low- and high-intensity MBEB. To reduce breath-by-breath variability in estimation of CPET variable kinetics, we time-interpolated (second-by-second), superimposed, and averaged responses. Reasonable estimates of τ (<20% coefficient of variation) were found only for on-transients of HR and V̇O2 . There was a remarkable reduction in τHR following the first exercise bout in all groups. Natural patterns of physical activity shape cardiorespiratory responses in healthy children and adolescents. Protocols that measure the effect of a previous bout on the kinetics of subsequent bouts may aid in the clinical utility of CPET.
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Affiliation(s)
- Ronen Bar‐Yoseph
- Pediatric Exercise and Genomics Research CenterUniversity of California at IrvineIrvineCaliforniaUSA
- Pediatric Pulmonary DivisionRuth Children's Hospital, Rambam Health Care CenterHaifaIsrael
| | - Shlomit Radom‐Aizik
- Pediatric Exercise and Genomics Research CenterUniversity of California at IrvineIrvineCaliforniaUSA
| | - Nicholas Coronato
- University of VirginiaCharlottesvilleVirginiaUSA
- United States Military AcademyWest PointNew YorkUSA
| | | | | | - Annamarie Stehli
- Pediatric Exercise and Genomics Research CenterUniversity of California at IrvineIrvineCaliforniaUSA
| | - Don Brown
- University of VirginiaCharlottesvilleVirginiaUSA
| | - Dan M. Cooper
- Pediatric Exercise and Genomics Research CenterUniversity of California at IrvineIrvineCaliforniaUSA
- Department of Pediatrics, Institute for Clinical and Translational Science, and Pediatric Exercise and Genomics Research CenterUniversity of CaliforniaIrvineCaliforniaUSA
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MacDougall KB, Falconer TM, MacIntosh BR. Efficiency of cycling exercise: Quantification, mechanisms, and misunderstandings. Scand J Med Sci Sports 2022; 32:951-970. [PMID: 35253274 DOI: 10.1111/sms.14149] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 01/19/2022] [Accepted: 02/09/2022] [Indexed: 12/24/2022]
Abstract
The energetics of cycling represents a well-studied area of exercise science, yet there are still many questions that remain. Efficiency, broadly defined as the ratio of energy output to energy input, is one key metric that, despite its importance from both a scientific as well as performance perspective, is commonly misunderstood. There are many factors that may affect cycling efficiency, both intrinsic (e.g., muscle fiber type composition) and extrinsic (e.g., cycling cadence, prior exercise, and training), creating a complex interplay of many components. Due to its relative simplicity, the measurement of oxygen uptake continues to be the most common means of measuring the energy cost of exercise (and thus efficiency); however, it is limited to only a small proportion of the range of outputs humans are capable of, further limiting our understanding of the energetics of high-intensity exercise and any mechanistic bases therein. This review presents evidence that delta efficiency does not represent muscular efficiency and challenges the notion that the slow component of oxygen uptake represents decreasing efficiency. It is noted that gross efficiency increases as intensity of exercise increases in spite of the fact that fast-twitch fibers are recruited to achieve this high power output. Understanding the energetics of high-intensity exercise will require critical evaluation of the available data.
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Affiliation(s)
- Keenan B MacDougall
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Tara M Falconer
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Brian R MacIntosh
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
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Gløersen Ø, Colosio AL, Boone J, Dysthe DK, Malthe-Sørenssen A, Capelli C, Pogliaghi S. Modeling VO 2 on-kinetics based on intensity-dependent Delayed Adjustment and Loss of Efficiency (DALE). J Appl Physiol (1985) 2022; 132:1480-1488. [PMID: 35482330 DOI: 10.1152/japplphysiol.00570.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study presents and evaluates a new mathematical model of V̇O2 on-kinetics, with the following properties: (i) a progressively slower primary phase following the size-principle of motor unit recruitment, explaining the delayed V̇O2 steady state seen in the heavy exercise intensity domain, and (ii) a severe-domain slow component modelled as a time-dependent decrease in efficiency. Breath-by-breath V̇O2 measurements from eight subjects performing step cycling transitions, in the moderate, heavy and severe exercise domains, were fitted to the conventional 3-phase model and the new model. Model performance was evaluated with a residual analysis and by comparing Bayesian (BIC) and corrected Akaike (AICc) information criteria. The residual analysis showed no systematic deviations, except perhaps for the initial part of the primary phase. BIC favored the new model, being 9.3 (SD 7.1) lower than the conventional model while AICc was similar between models. Compared to the conventional 3-phase model, the proposed model distinguishes between the kinetic adaptations in the heavy and severe domains by predicting a delayed steady state V̇O2 in the heavy and no steady state V̇O2 in the severe domain. This allows to determine when stable oxygen costs of exercise are attainable and it also represents a first step in defining time-dependent oxygen costs when stable energy conversion efficiency is not attainable.
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Affiliation(s)
- Øyvind Gløersen
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway.,Department of Physics, University of Oslo, Oslo, Norway.,Smart Sensors and Microsystems, SINTEF Digital, Oslo, Norway
| | - Alessandro L Colosio
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.,Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Jan Boone
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | | | | | - Carlo Capelli
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Silvia Pogliaghi
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
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Salzmann K, Sanchez AMJ, Borrani F. Effects of Blood Flow Restriction on O 2 Muscle Extraction and O 2 Pulmonary Uptake Kinetics During Heavy Exercise. Front Physiol 2021; 12:722848. [PMID: 34539445 PMCID: PMC8441002 DOI: 10.3389/fphys.2021.722848] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 08/03/2021] [Indexed: 11/13/2022] Open
Abstract
This study aimed to determine the effects of three levels of blood flow restriction (BFR) on V˙O2 and O2 extraction kinetics during heavy cycling exercise transitions. Twelve healthy trained males completed two bouts of 10 min heavy intensity exercise without BFR (CON), with 40% or 50% BFR (BFR40 and BFR50, respectively). V˙O2 and tissue saturation index (TSI) were continuously measured and modelled using multiexponential functions. The time constant of the V˙O2 primary phase was significantly slowed in BFR40 (26.4 ± 2.0s; p < 0.001) and BFR50 (27.1 ± 2.1s; p = 0.001) compared to CON (19.0 ± 1.1s). The amplitude of the V˙O2 slow component was significantly increased (p < 0.001) with BFR in a pressure-dependent manner 3.6 ± 0.7, 6.7 ± 0.9 and 9.7 ± 1.0 ml·min−1·kg−1 for CON, BFR40, and BFR50, respectively. While no acceleration of the primary component of the TSI kinetics was observed, there was an increase (p < 0.001) of the phase 3 amplitude with BFR (CON −0.8 ± 0.3% VS BFR40 −2.9 ± 0.9%, CON VS BFR50 −2.8 ± 0.8%). It may be speculated that BFR applied during cycling exercise in the heavy intensity domain shifted the working muscles to an O2 dependent situation. The acceleration of the extraction kinetics could have reached a plateau, hence not permitting compensation for the slowdown of the blood flow kinetics, and slowing V˙O2 kinetics.
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Affiliation(s)
- Killian Salzmann
- Institute of Sport Sciences of University of Lausanne (ISSUL), University of Lausanne, Lausanne, Switzerland
| | - Anthony M J Sanchez
- University of Perpignan Via Domitia (UPVD), Faculty of Sports Sciences, Laboratoire Interdisciplinaire Performance Santé Environnement De Montagne (LIPSEM), Font-Romeu, France
| | - Fabio Borrani
- Institute of Sport Sciences of University of Lausanne (ISSUL), University of Lausanne, Lausanne, Switzerland
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Colosio AL, Caen K, Bourgois JG, Boone J, Pogliaghi S. Metabolic instability vs fibre recruitment contribution to the [Formula: see text] slow component in different exercise intensity domains. Pflugers Arch 2021; 473:873-882. [PMID: 34009455 PMCID: PMC8164613 DOI: 10.1007/s00424-021-02573-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 04/15/2021] [Accepted: 04/23/2021] [Indexed: 11/26/2022]
Abstract
This study focused on the steady-state phase of exercise to evaluate the relative contribution of metabolic instability (measured with NIRS and haematochemical markers) and muscle activation (measured with EMG) to the oxygen consumption (\documentclass[12pt]{minimal}
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\begin{document}$${\dot{V}O_2}$$\end{document}V˙O2) slow component (\documentclass[12pt]{minimal}
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\begin{document}$${\dot{V}O_2}{_s}{_c}$$\end{document}V˙O2sc) in different intensity domains. We hypothesized that (i) after the transient phase, \documentclass[12pt]{minimal}
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\begin{document}$${\dot{V}O_2}$$\end{document}V˙O2, metabolic instability and muscle activation tend to increase differently over time depending on the relative exercise intensity and (ii) the increase in \documentclass[12pt]{minimal}
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\begin{document}$${\dot{V}O_2}{_s}{_c}$$\end{document}V˙O2sc is explained by a combination of metabolic instability and muscle activation. Eight active men performed a constant work rate trial of 9 min in the moderate, heavy and severe intensity domains. \documentclass[12pt]{minimal}
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\begin{document}$${\dot{V}O_2}$$\end{document}V˙O2, root mean square by EMG (RMS), deoxyhaemoglobin by NIRS ([HHb]) and haematic markers of metabolic stability (i.e. [La−], pH, HCO3−) were measured. The physiological responses in different intensity domains were compared by two-way RM-ANOVA. The relationships between the increases of [HHb] and RMS with \documentclass[12pt]{minimal}
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\begin{document}$${\dot{V}O_2}$$\end{document}V˙O2 after the third min were compared by simple and multiple linear regressions. We found domain-dependent dynamics over time of \documentclass[12pt]{minimal}
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\begin{document}$${\dot{V}O_2}$$\end{document}V˙O2, [HHb], RMS and the haematic markers of metabolic instability. After the transient phase, the rises in [HHb] and RMS showed medium–high correlations with the rise in \documentclass[12pt]{minimal}
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\begin{document}$${\dot{V}O_2}$$\end{document}V˙O2 ([HHb] r = 0.68, p < 0.001; RMS r = 0.59, p = 0.002). Moreover, the multiple linear regression showed that both metabolic instability and muscle activation concurred to the \documentclass[12pt]{minimal}
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\begin{document}$${\dot{V}O_2}{_s}{_c}$$\end{document}V˙O2sc (r = 0.75, [HHb] p = 0.005, RMS p = 0.042) with metabolic instability possibly having about threefold the relative weight compared to recruitment. Seventy-five percent of the dynamics of the \documentclass[12pt]{minimal}
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\begin{document}$${\dot{V}O_2}{_s}{_c}$$\end{document}V˙O2sc was explained by [HHb] and RMS.
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Affiliation(s)
- Alessandro L Colosio
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Via Casorati 43, 37131, Verona, Italy
| | - Kevin Caen
- Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, Ghent, Belgium
| | - Jan G Bourgois
- Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, Ghent, Belgium
| | - Jan Boone
- Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, Ghent, Belgium
| | - Silvia Pogliaghi
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Via Casorati 43, 37131, Verona, Italy.
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Garnacho-Castaño MV, Albesa-Albiol L, Serra-Payá N, Gomis Bataller M, Pleguezuelos Cobo E, Guirao Cano L, Guodemar-Pérez J, Carbonell T, Domínguez R, Maté-Muñoz JL. Oxygen Uptake Slow Component and the Efficiency of Resistance Exercises. J Strength Cond Res 2021; 35:1014-1022. [PMID: 30335719 DOI: 10.1519/jsc.0000000000002905] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
ABSTRACT Garnacho-Castaño, MV, Albesa-Albiol, L, Serra-Payá, N, Gomis Bataller, M, Pleguezuelos Cobo, E, Guirao Cano, L, Guodemar-Pérez, J, Carbonell, T, Domínguez, R, and Maté-Muñoz, JL. Oxygen uptake slow component and the efficiency of resistance exercises. J Strength Cond Res 35(4): 1014-1022, 2021-This study aimed to evaluate oxygen uptake slow component (V̇o2sc) and mechanical economy/efficiency in half squat (HS) exercise during constant-load tests conducted at lactate threshold (LT) intensity. Nineteen healthy young men completed 3 HS exercise tests separated by 48-hour rest periods: 1 repetition maximum (1RM), incremental-load HS test to establish the %1RM corresponding to the LT, and constant-load HS test at the LT. During the last test, cardiorespiratory, lactate, and mechanical responses were monitored. Fatigue in the lower limbs was assessed before and after the constant-load test using a countermovement jump test. A slight and sustained increase of the V̇o2sc and energy expended (EE) was observed (p < 0.001). In blood lactate, no differences were observed between set 3 to set 21 (p > 0.05). A slight and sustained decrease of half squat efficiency and gross mechanical efficiency (GME) was detected (p < 0.001). Significant inverse correlations were observed between V̇o2 and GME (r = -0.93, p < 0.001). Inverse correlations were detected between EE and GME (r = -0.94, p < 0.001). Significant losses were observed in jump height ability and in mean power output (p < 0.001) in response to the constant-load HS test. In conclusion, V̇o2sc and EE tended to rise slowly during constant-load HS exercise testing. This slight increase was associated with lowered efficiency throughout constant-load test and a decrease in jump capacity after testing. These findings would allow to elucidate the underlying fatigue mechanisms produced by resistance exercises in a constant-load test at LT intensity.
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Affiliation(s)
- Manuel V Garnacho-Castaño
- GRI-AFIRS, Department of Physical Activity and Sports Science, School of Health Sciences, TecnoCampus, Pompeu Fabra University, Barcelona, Spain
| | - Lluis Albesa-Albiol
- GRI-AFIRS, Department of Physical Activity and Sports Science, School of Health Sciences, TecnoCampus, Pompeu Fabra University, Barcelona, Spain
| | - Noemí Serra-Payá
- GRI-AFIRS, Department of Physical Activity and Sports Science, School of Health Sciences, TecnoCampus, Pompeu Fabra University, Barcelona, Spain
| | - Manuel Gomis Bataller
- GRI-AFIRS, Department of Physical Activity and Sports Science, School of Health Sciences, TecnoCampus, Pompeu Fabra University, Barcelona, Spain
| | - Eulogio Pleguezuelos Cobo
- GRI-AFIRS, Department of Physical Activity and Sports Science, School of Health Sciences, TecnoCampus, Pompeu Fabra University, Barcelona, Spain
- Department of Physical and Rehabilitation Medicine, Mataró Hospital, Barcelona, Spain
| | - Lluis Guirao Cano
- GRI-AFIRS, Department of Physical Activity and Sports Science, School of Health Sciences, TecnoCampus, Pompeu Fabra University, Barcelona, Spain
- Department of Physical and Rehabilitation Medicine, Mataró Hospital, Barcelona, Spain
| | | | - Teresa Carbonell
- Department of Physiology, University of Barcelona, Barcelona, Spain ; and
| | - Raúl Domínguez
- Department of Physical Activity and Sports Science, Alfonso X El Sabio University, Madrid, Spain
| | - José Luis Maté-Muñoz
- Department of Physical Activity and Sports Science, Alfonso X El Sabio University, Madrid, Spain
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Bartlett MF, Fitzgerald LF, Kent JA. Rates of oxidative ATP synthesis are not augmented beyond the pH threshold in human vastus lateralis muscles during a stepwise contraction protocol. J Physiol 2021; 599:1997-2013. [PMID: 33576028 DOI: 10.1113/jp280851] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 02/05/2021] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The oxygen cost of high-intensity exercise at power outputs above an individual's lactate threshold (LT) is greater than would be predicted by the linear oxygen consumption-power relationship observed below the LT. However, whether these augmentations are caused by an increased ATP cost of force generation (ATPCOST ) or an increased oxygen cost of ATP synthesis is unclear. We used 31 P-MRS to measure changes in cytosolic [ADP] (intramyocellular marker of oxidative metabolism), oxidative ATP synthesis (ATPOX ) and ATPCOST during a 6-stage, stepwise knee extension protocol. ATPCOST was unchanged across stages. The relationship between [ADP] and muscle power output was augmented at workloads above the pH threshold (pHT ; proxy for LT), whereas increases in ATPOX were attenuated. These results suggest the greater oxygen cost of contractions at workloads beyond the pHT is not caused by mechanisms that increase ATPCOST , but rather mechanisms that alter intrinsic mitochondrial function or capacity. ABSTRACT Increases in skeletal muscle metabolism and oxygen consumption are linearly related to muscle power output for workloads below the lactate threshold (LT), but are augmented (i.e. greater rate of increase relative to workload) thereafter. Presently, it is unclear whether these metabolic augmentations are caused by increases in the ATP cost of force generation (ATPCOST ) or changes in the efficiency of mitochondrial oxygen consumption and oxidative ATP synthesis (ATPOX ). To partition these two hypotheses in vivo, we used 31 P-MRS to calculate slopes relating step-changes in muscle work to concurrent changes in cytosolic phosphates and ATPOX before and after the pH threshold (pHT ; used here as a proxy for LT) within the vastus lateralis muscle of eight young adults during a stepwise knee extension test. Changes in muscle phosphates and ATPOX were linearly related to workload below the pHT . However, slopes above the pHT were greater for muscle phosphates (P < 0.05) and lower for ATPOX (P < 0.05) than were the slopes observed below the pHT . The maximal capacity for ATPOX ( V ̇ max ) and ADP-specific ATPOX also declined beyond the pHT (P < 0.05), whereas ATPCOST was unchanged (P = 0.10). These results oppose the hypothesis that high-intensity contractions increase ATPCOST and suggest that greater oxidative metabolism at workloads beyond the pHT is caused by mechanisms that affect intrinsic mitochondrial function or capacity, such as alterations in substrate selection or electron entry into the electron transport chain, temperature-mediated changes in mitochondrial permeability to protons, or stimulation of mitochondrial uncoupling by reactive oxygen species generation.
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Affiliation(s)
- Miles F Bartlett
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts, Amherst, MA, 01003, USA
| | - Liam F Fitzgerald
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts, Amherst, MA, 01003, USA
| | - Jane A Kent
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts, Amherst, MA, 01003, USA
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Maximal Time Spent at VO 2max from Sprint to the Marathon. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17249250. [PMID: 33321958 PMCID: PMC7763525 DOI: 10.3390/ijerph17249250] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 12/01/2020] [Accepted: 12/08/2020] [Indexed: 12/30/2022]
Abstract
Until recently, it was thought that maximal oxygen uptake (VO2max) was elicited only in middle-distance events and not the sprint or marathon distances. We tested the hypothesis that VO2max can be elicited in both the sprint and marathon distances and that the fraction of time spent at VO2max is not significantly different between distances. Methods: Seventy-eight well-trained males (mean [SD] age: 32 [13]; weight: 73 [9] kg; height: 1.80 [0.8] m) performed the University of Montreal Track Test using a portable respiratory gas sampling system to measure a baseline VO2max. Each participant ran one or two different distances (100 m, 200 m, 800 m, 1500 m, 3000 m, 10 km or marathon) in which they are specialists. Results: VO2max was elicited and sustained in all distances tested. The time limit (Tlim) at VO2max on a relative scale of the total time (Tlim at VO2max%Ttot) during the sprint, middle-distance, and 1500 m was not significantly different (p > 0.05). The relevant time spent at VO2max was only a factor for performance in the 3000 m group, where the Tlim at VO2max%Ttot was the highest (51.4 [18.3], r = 0.86, p = 0.003). Conclusions: By focusing on the solicitation of VO2max, we demonstrated that the maintenance of VO2max is possible in the sprint, middle, and marathon distances.
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Colosio AL, Caen K, Bourgois JG, Boone J, Pogliaghi S. Bioenergetics of the VO 2 slow component between exercise intensity domains. Pflugers Arch 2020; 472:1447-1456. [PMID: 32666276 PMCID: PMC7476983 DOI: 10.1007/s00424-020-02437-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 05/28/2020] [Accepted: 07/07/2020] [Indexed: 01/28/2023]
Abstract
During heavy and severe constant-load exercise, VO2 displays a slow component (VO2sc) typically interpreted as a loss of efficiency of locomotion. In the ongoing debate on the underpinnings of the VO2sc, recent studies suggested that VO2sc could be attributed to a prolonged shift in energetic sources rather than loss of efficiency. We tested the hypothesis that the total cost of cycling, accounting for aerobic and anaerobic energy sources, is affected by time during metabolic transitions in different intensity domains. Eight active men performed 3 constant load trials of 3, 6, and 9 min in the moderate, heavy, and severe domains (i.e., respectively below, between, and above the two ventilatory thresholds). VO2, VO2 of ventilation and lactate accumulation ([La-]) were quantified to calculate the adjusted oxygen cost of exercise (AdjO2Eq, i.e., measured VO2 - VO2 of ventilation + VO2 equivalent of [La-]) for the 0-3, 3-6, and 6-9 time segments at each intensity, and compared by a two-way RM-ANOVA (time × intensity). After the transient phase, AdjO2Eq was unaffected by time in moderate (ml*3 min-1 at 0-3, 0-6, 0-9 min: 2126 ± 939 < 2687 ± 1036, 2731 ± 1035) and heavy (4278 ± 1074 < 5121 ± 1268, 5225 ± 1123) while a significant effect of time was detected in the severe only (5863 ± 1413 < 7061 ± 1516 < 7372 ± 1443). The emergence of the VO2sc was explained by a prolonged shift between aerobic and anaerobic energy sources in heavy (VO2 - VO2 of ventilation: ml*3 min-1 at 0-3, 0-6, 0-9 min: 3769 ± 1128 < 4938 ± 1256, 5091 ± 1123, [La-]: 452 ± 254 < 128 ± 169, 79 ± 135), while a prolonged metabolic shift and a true loss of efficiency explained the emergence of the VO2sc in severe.
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Affiliation(s)
- Alessandro L Colosio
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Via Casorati 43, 37131, Verona, Italy
| | - Kevin Caen
- Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, Ghent, Belgium
| | - Jan G Bourgois
- Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, Ghent, Belgium
| | - Jan Boone
- Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, Ghent, Belgium
| | - Silvia Pogliaghi
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Via Casorati 43, 37131, Verona, Italy.
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12
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Goulding RP, Wüst RCI. Uncoupling mitochondrial uncoupling from alternative substrate utilization: implications for heavy intensity exercise. J Physiol 2020; 598:3787-3788. [PMID: 32530050 PMCID: PMC7496970 DOI: 10.1113/jp280129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Richie P Goulding
- Applied Physiology Laboratory, Kobe Design University, Kobe, Japan.,Japan Society for Promotion of Sciences, Tokyo, Japan
| | - Rob C I Wüst
- Laboratory for Myology, Faculty of Behavioural and Movement Sciences, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
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13
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Bartlett MF, Fitzgerald LF, Nagarajan R, Kent JA. Reply from Miles F. Bartlett, Liam F. Fitzgerald, Rajakumar Nagarajan and Jane A. Kent. J Physiol 2020; 598:3789. [PMID: 32530069 DOI: 10.1113/jp280190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Miles F Bartlett
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Liam F Fitzgerald
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Rajakumar Nagarajan
- Human Magnetic Resonance Center, Institute for Applied Life Sciences (IALS), University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Jane A Kent
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts Amherst, Amherst, MA, 01003, USA
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14
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Korzeniewski B, Rossiter HB. Exceeding a "critical" muscle P i: implications for [Formula: see text] and metabolite slow components, muscle fatigue and the power-duration relationship. Eur J Appl Physiol 2020; 120:1609-1619. [PMID: 32435984 DOI: 10.1007/s00421-020-04388-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 05/02/2020] [Indexed: 12/21/2022]
Abstract
PURPOSE The consequences of the assumption that the additional ATP usage, underlying the slow component of oxygen consumption ([Formula: see text]) and metabolite on-kinetics, starts when cytosolic inorganic phosphate (Pi) exceeds a certain "critical" Pi concentration, and muscle work terminates because of fatigue when Pi exceeds a certain, higher, "peak" Pi concentration are investigated. METHODS A previously developed computer model of the myocyte bioenergetic system is used. RESULTS Simulated time courses of muscle [Formula: see text], cytosolic ADP, pH, PCr and Pi at various ATP usage activities agreed well with experimental data. Computer simulations resulted in a hyperbolic power-duration relationship, with critical power (CP) as an asymptote. CP was increased, and phase II [Formula: see text] on-kinetics was accelerated, by progressive increase in oxygen tension (hyperoxia). CONCLUSIONS Pi is a major factor responsible for the slow component of the [Formula: see text] and metabolite on-kinetics, fatigue-related muscle work termination and hyperbolic power-duration relationship. The successful generation of experimental system properties suggests that the additional ATP usage, underlying the slow component, indeed starts when cytosolic Pi exceeds a "critical" Pi concentration, and muscle work terminates when Pi exceeds a "peak" Pi concentration. The contribution of other factors, such as cytosolic acidification, or glycogen depletion and central fatigue should not be excluded. Thus, a detailed quantitative unifying mechanism underlying various phenomena related to skeletal muscle fatigue and exercise tolerance is offered that was absent in the literature. This mechanism is driven by reciprocal stimulation of Pi increase and additional ATP usage when "critical" Pi is exceeded.
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Affiliation(s)
| | - Harry B Rossiter
- Rehabilitation Clinical Trials Center, Division of Pulmonary and Critical Care Physiology and Medicine, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA, USA.,Faculty of Biological Sciences, University of Leeds, Leeds, UK
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15
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Gajanand T, Conde Alonso S, Ramos JS, Antonietti JP, Borrani F. Alterations to neuromuscular properties of skeletal muscle are temporally dissociated from the oxygen uptake slow component. Sci Rep 2020; 10:7728. [PMID: 32382067 PMCID: PMC7206089 DOI: 10.1038/s41598-020-64395-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 04/13/2020] [Indexed: 11/09/2022] Open
Abstract
To assess if the alteration of neuromuscular properties of knee extensors muscles during heavy exercise co-vary with the SCV ([Formula: see text] slow component), eleven healthy male participants completed an incremental ramp test to exhaustion and five constant heavy intensity cycling bouts of 2, 6, 10, 20 and 30 minutes. Neuromuscular testing of the knee extensor muscles were completed before and after exercise. Results showed a significant decline in maximal voluntary contraction (MVC) torque only after 30 minutes of exercise (-17.01% ± 13.09%; p < 0.05) while single twitch (PT), 10 Hz (P10), and 100 Hz (P100) doublet peak torque amplitudes were reduced after 20 and 30 minutes (p < 0.05). Voluntary activation (VA) and M-wave were not affected by exercise, but significant correlation was found between the SCV and PT, MVC, VA, P10, P100, and P10/P100 ratio, respectively (p < 0.015). Therefore, because the development of the SCV occurred mainly between 2-10 minutes, during which neuromuscular properties were relatively stable, and because PT, P10 and P100 were significantly reduced only after 20-30 minutes of exercise while SCV is stable, a temporal relationship between them does not appear to exist. These results suggest that the development of fatigue due to alterations of neuromuscular properties is not an essential requirement to elicit the SCV.
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Affiliation(s)
- Trishan Gajanand
- Department of Exercise Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand.,School of Human Movement and Nutrition Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Sonia Conde Alonso
- Institute of Sport Sciences of University of Lausanne (ISSUL), Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
| | - Joyce S Ramos
- SHAPE Research Centre, Exercise Science and Clinical Exercise Physiology, College of Nursing and Health Sciences, Flinders University, Bedford Park, South Australia, 5042, Australia
| | | | - Fabio Borrani
- Institute of Sport Sciences of University of Lausanne (ISSUL), Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
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16
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Bartlett MF, Fitzgerald LF, Nagarajan R, Hiroi Y, Kent JA. Oxidative ATP synthesis in human quadriceps declines during 4 minutes of maximal contractions. J Physiol 2020; 598:1847-1863. [PMID: 32045011 DOI: 10.1113/jp279339] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 01/30/2020] [Indexed: 12/16/2022] Open
Abstract
KEY POINTS During maximal exercise, skeletal muscle metabolism and oxygen consumption remain elevated despite precipitous declines in power. Presently, it is unclear whether these responses are caused by an increased ATP cost of force generation (ATPCOST ) or mitochondrial uncoupling; a process that reduces the efficiency of oxidative ATP synthesis (ATPOX ). To address this gap, we used 31-phosphorus magnetic resonance spectroscopy to measure changes in ATPCOST and ATPOX in human quadriceps during repeated trials of maximal intensity knee extensions lasting up to 4 min. ATPCOST remained unchanged. In contrast, ATPOX plateaued by ∼2 min and then declined (∼15%) over the final 2 min. The maximal capacity for ATPOX (Vmax ), as well as ADP-specific rates of ATPOX , were also significantly diminished. Collectively, these results suggest that mitochondrial uncoupling, and not increased ATPCOST , is responsible for altering the regulation of skeletal muscle metabolism and oxygen consumption during maximal exercise. ABSTRACT The relationship between skeletal muscle oxygen consumption and power output is augmented during exercise at workloads above the lactate threshold. Potential mechanisms for this response have been hypothesized, including increased ATP cost of force generation (ATPCOST ) and mitochondrial uncoupling, a process that reduces the efficiency of oxidative ATP synthesis (ATPOX ). To test these hypotheses, we used phosphorus magnetic resonance spectroscopy to non-invasively measure changes in phosphate concentrations and pH in the vastus lateralis muscle of nine young adults during repeated trials of maximal, all-out dynamic knee extensions (120°s-1 , 1 every 2 s) lasting 24, 60, 120, and 240 s. ATPOX was measured at each time point from the initial velocity of PCr resynthesis, and ATPCOST was calculated as the sum of ATP synthesized by the creatine and adenylate kinase reactions, non-oxidative glycolysis, ATPOX and net changes in [ATP]. Power output declined in a reproducible manner for all four trials. ATPCOST did not change over time (main effect P = 0.45). ATPOX plateaued from 60 to 120 s and then decreased over the final 120 s (main effect P = 0.001). The maximal capacity for oxidative ATP synthesis (Vmax ), as well as ADP-specific rates of ATPOX , also decreased over time (main effect P = 0.001, both). Collectively, these results demonstrate that prolonged maximal contraction protocols impair oxidative energetics and implicate mitochondrial uncoupling as the mechanism for this response. The causes of mitochondrial uncoupling are presently unknown but may offer a potential explanation for the dissociation between skeletal muscle power output and oxygen consumption during maximal, all-out exercise protocols.
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Affiliation(s)
- Miles F Bartlett
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts, 01003.,Department of Kinesiology, University of Texas, Arlington, Texas, 76019
| | - Liam F Fitzgerald
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts, 01003
| | - Rajakumar Nagarajan
- Human Magnetic Resonance Center, Institute for Applied Life Sciences (IALS), University of Massachusetts, Amherst, Massachusetts, 01003
| | - Yeun Hiroi
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts, 01003
| | - Jane A Kent
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts, 01003
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17
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Garnacho-Castaño MV, Albesa-Albiol L, Serra-Payá N, Gomis Bataller M, Felíu-Ruano R, Guirao Cano L, Pleguezuelos Cobo E, Maté-Muñoz JL. The Slow Component of Oxygen Uptake and Efficiency in Resistance Exercises: A Comparison With Endurance Exercises. Front Physiol 2019; 10:357. [PMID: 31019469 PMCID: PMC6458438 DOI: 10.3389/fphys.2019.00357] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 03/14/2019] [Indexed: 11/13/2022] Open
Abstract
Introduction There is a lack of information regarding the slow component of oxygen uptake (VO2sc) and efficiency/economy in resistance exercises despite the crucial role played in endurance performance. Purpose this study aimed to compare the VO2sc, efficiency/economy, metabolic, cardiorespiratory responses, rating of perceived effort and mechanical fatigue between cycling and half-squat (HS) exercises during a constant-load test at lactate threshold (LT1) intensity. Methods Twenty-one healthy men were randomly assigned in a crossover design to perform cycle-ergometer or HS tests. The order of the two cycle ergometer tests was an incremental test for determining load-intensity in watts (W) at LT1, followed by a constant-load test at the LT1 intensity. For the three HS tests, the order was a 1RM test to determine the load (kg) corresponding to the 1RM percentages to be used during the second test, incremental HS exercise to establish the load (kg) at the LT1 intensity, and finally, a constant-load HS test at the LT1 intensity. A rest period of 48 h between each test was established. During the HS and cycle-ergometer constant-load tests, cardiorespiratory and metabolic responses were recorded. Lower limbs fatigue was determined by a jump test before and after the constant-load tests. Results A significant exercise mode × time interaction effect was detected in VO2, heart rate, energy expenditure (EE), gross efficiency (GE), and economy (p < 0.05). A significant and sustained VO2 raise was confirmed in HS exercise (p < 0.05) and a steady-state VO2 was revealed in cycle-ergometer. A higher GE and economy were obtained in HS test than in cycle-ergometer exercise (p < 0.001). In both exercises, a non-significant decrease was observed in GE and economy (p > 0.05). Lower limbs fatigue was only detected after constant-load HS test. Conclusion Although the VO2, heart rate and EE responses were higher in cycling exercise, the constant-load HS test induced a greater VO2sc and EE raise than the cycling test in a predominantly aerobic metabolism. These results could explain a decrease observed in jump performance only after HS test. GE and economy could benefit from the eccentric phase of the HS exercise.
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Affiliation(s)
| | - Lluis Albesa-Albiol
- GRI-AFIRS, School of Health Sciences, TecnoCampus-Pompeu Fabra University, Mataró, Spain
| | - Noemí Serra-Payá
- GRI-AFIRS, School of Health Sciences, TecnoCampus-Pompeu Fabra University, Mataró, Spain
| | - Manuel Gomis Bataller
- GRI-AFIRS, School of Health Sciences, TecnoCampus-Pompeu Fabra University, Mataró, Spain
| | - Raquel Felíu-Ruano
- GRI-AFIRS, School of Health Sciences, TecnoCampus-Pompeu Fabra University, Mataró, Spain
| | - Lluis Guirao Cano
- GRI-AFIRS, School of Health Sciences, TecnoCampus-Pompeu Fabra University, Mataró, Spain.,Department of Rehabilitation, Hospital Asepeyo, Barcelona, Spain
| | - Eulogio Pleguezuelos Cobo
- GRI-AFIRS, School of Health Sciences, TecnoCampus-Pompeu Fabra University, Mataró, Spain.,Department of Physical and Rehabilitation Medicine, Hospital de Mataró, Mataró, Spain
| | - José Luis Maté-Muñoz
- Department of Physical Activity and Sports Science, Alfonso X El Sabio University, Madrid, Spain
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18
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Korzeniewski B. Muscle V˙O2-power output nonlinearity in constant-power, step-incremental, and ramp-incremental exercise: magnitude and underlying mechanisms. Physiol Rep 2018. [PMCID: PMC6234149 DOI: 10.14814/phy2.13915] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
A computer model of the skeletal muscle bioenergetic system was used to simulate time courses of muscle oxygen consumption (V˙O2), cytosolic metabolite (ADP, PCr, Pi, and ATP) concentrations, and pH during whole‐body constant‐power exercise (CPE) (6 min), step‐incremental exercise (SIE) (30 W/3 min), and slow (10 W/min), medium (30 W/min), and fast (50 W/min) ramp‐incremental exercise (RIE). Different ESA (each‐step activation) of oxidative phosphorylation (OXPHOS) intensity‐ATP usage activity relationships, representing different muscle fibers recruitment patterns, gave best agreement with experimental data for CPE, and for SIE and RIE. It was assumed that the muscle V˙O2‐power output (PO) nonlinearity is related to a time‐ and PO‐dependent increase in the additional ATP usage underlying the slow component of the V˙O2 on‐kinetics minus the increase in ATP supply by anaerobic glycolysis leading to a decrease in V˙O2. The muscle V˙O2‐PO relationship deviated upward (+) or downward (−) from linearity above critical power (CP), and the nonlinearity equaled +16% (CPE),+12% (SIE), +8% (slow RIE), +1% (moderate RIE), and −2% (fast RIE) at the end of exercise, in agreement with experimental data. During SIE and RIE, changes in PCr and Pi accelerated moderately above CP, while changes in ADP and pH accelerated significantly with time and PO. It is postulated that the intensity of the additional ATP usage minus ATP supply by anaerobic glycolysis determines the size of the muscle V˙O2‐PO nonlinearity. It is proposed that the extent of the additional ATP usage is proportional to the time integral of PO ‐ CP above CP.
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19
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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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20
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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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21
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Sousa A, Borrani F, Rodríguez FA, Millet GP. Oxygen Uptake Kinetics Is Slower in Swimming Than Arm Cranking and Cycling during Heavy Intensity. Front Physiol 2017; 8:639. [PMID: 28919863 PMCID: PMC5585224 DOI: 10.3389/fphys.2017.00639] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 08/15/2017] [Indexed: 11/17/2022] Open
Abstract
Oxygen uptake (V·O2) kinetics has been reported to be influenced by the activity mode. However, only few studies have compared V·O2 kinetics between activities in the same subjects in which they were equally trained. Therefore, this study compared the V·O2 kinetics response to swimming, arm cranking, and cycling within the same group of subjects within the heavy exercise intensity domain. Ten trained male triathletes (age 23.2 ± 4.5 years; height 180.8 ± 8.3 cm; weight 72.3 ± 6.6 kg) completed an incremental test to exhaustion and a 6-min heavy constant-load test in the three exercise modes in random order. Gas exchange was measured by a breath-by-breath analyzer and the on-transient V·O2 kinetics was modeled using bi-exponential functions. V·O2peak was higher in cycling (65.6 ± 4.0 ml·kg−1·min−1) than in arm cranking or swimming (48.7 ± 8.0 and 53.0 ± 6.7 ml·kg−1·min−1; P < 0.01), but the V·O2 kinetics were slower in swimming (τ1 = 31.7 ± 6.2 s) than in arm cranking (19.3 ± 4.2 s; P = 0.001) and cycling (12.4 ± 3.7 s; P = 0.001). The amplitude of the primary component was lower in both arm cranking and swimming (21.9 ± 4.7 and 28.4 ± 5.1 ml·kg−1·min−1) compared with cycling (39.4 ± 4.1 ml·kg−1·min−1; P = 0.001). Although the gain of the primary component was higher in arm cranking compared with cycling (15.3 ± 4.2 and 10.7 ± 1.3 ml·min−1·W−1; P = 0.02), the slow component amplitude, in both absolute and relative terms, did not differ between exercise modes. The slower V·O2 kinetics during heavy-intensity swimming is exercise-mode dependent. Besides differences in muscle mass and greater type II muscle fibers recruitment, the horizontal position adopted and the involvement of trunk and lower-body stabilizing muscles could be additional mechanisms that explain the differences between exercise modalities.
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Affiliation(s)
- Ana Sousa
- Research Center for Sports, Exercise and Human Development, University of Trás-os-Montes and Alto DouroVila Real, Portugal
| | - Fabio Borrani
- Faculty of Biology and Medicine, ISSUL, Institute of Sport Sciences, University of LausanneLausanne, Switzerland
| | - Ferran A Rodríguez
- INEFC-Barcelona Sport Sciences Research Group, Institut Nacional d'Educació Física de Catalunya, University of BarcelonaBarcelona, Spain
| | - Grégoire P Millet
- Faculty of Biology and Medicine, ISSUL, Institute of Sport Sciences, University of LausanneLausanne, Switzerland
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22
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O'Connell JM, Weir JM, MacIntosh BR. Blood lactate accumulation decreases during the slow component of oxygen uptake without a decrease in muscular efficiency. Pflugers Arch 2017; 469:1257-1265. [PMID: 28550471 DOI: 10.1007/s00424-017-1986-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 04/10/2017] [Accepted: 04/23/2017] [Indexed: 11/26/2022]
Abstract
Pulmonary oxygen uptake ([Formula: see text]) slowly increases during exercise above the anaerobic threshold, and this increase is called the slow component of [Formula: see text]. The mechanism of the increase in [Formula: see text] is assumed to be due to increasing energy cost associated with increasingly inefficient muscle contraction. We hypothesized that the increase in [Formula: see text] would be accompanied by a constant or increasing rate of accumulation of blood lactate, indicating sustained anaerobic metabolism while [Formula: see text] increased. Ten male subjects performed cycle ergometry for 3, 6, and 9 min at a power output representing 60% of the difference between lactate threshold and maximal [Formula: see text] while [Formula: see text] and blood lactate accumulation were measured. Blood lactate accumulation decreased over time, providing the energy equivalent of (mean ± SD) 1586 ± 265, 855 ± 287, and 431 ± 392 ml of [Formula: see text] during 0-3, 3-6, and 6-9 min of exercise, respectively. As duration progressed, [Formula: see text] supplied 86.3 ± 2.0, 93.6 ± 1.9, and 96.8 ± 2.9% of total energy from 0 to 3, 3 to 6, and 6 to 9 min, respectively, while anaerobic contribution decreased. There was no change in total energy cost after 3 min, except that required by ventilatory muscles for the progressive increase in ventilation. The slow component of [Formula: see text] is accompanied by decreasing anaerobic energy contribution beyond 3 min during heavy exercise.
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Affiliation(s)
- J M O'Connell
- Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada
| | - J M Weir
- Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada
| | - B R MacIntosh
- Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada.
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Regulation of oxidative phosphorylation through each-step activation (ESA): Evidences from computer modeling. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 125:1-23. [DOI: 10.1016/j.pbiomolbio.2016.12.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 12/06/2016] [Indexed: 01/20/2023]
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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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Keir DA, Copithorne DB, Hodgson MD, Pogliaghi S, Rice CL, Kowalchuk JM. The slow component of pulmonary O2 uptake accompanies peripheral muscle fatigue during high-intensity exercise. J Appl Physiol (1985) 2016; 121:493-502. [DOI: 10.1152/japplphysiol.00249.2016] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 06/21/2016] [Indexed: 11/22/2022] Open
Abstract
During constant-power output (PO) exercise above lactate threshold (LT), pulmonary O2 uptake (V̇o2p) features a developing slow component (V̇o2pSC). This progressive increase in O2 cost of exercise is suggested to be related to the effects of muscle fatigue development. We hypothesized that peripheral muscle fatigue as assessed by contractile impairment would be associated with the V̇o2pSC. Eleven healthy men were recruited to perform four constant-PO tests at an intensity corresponding to ∼Δ60 (very heavy, VH) where Δ is 60% of the difference between LT and peak V̇o2p. The VH exercise was completed for each of 3, 8, 13, and 18 min (i.e., VH3, VH8, VH13, VH18) with each preceded by 3 min of cycling at 20 W. Peripheral muscle fatigue was assessed via pre- vs. postexercise measurements of quadriceps torque in response to brief trains of electrical stimulation delivered at low (10 Hz) and high (50 Hz) frequencies. During exercise, breath-by-breath V̇o2p was measured by mass spectrometry and volume turbine. The magnitude of V̇o2pSC increased ( P < 0.05) from 224 ± 81 ml/min at VH3 to 520 ± 119, 625 ± 134, and 678 ± 156 ml/min at VH8, VH13, and VH18, respectively. The ratio of the low-to-high frequency (10/50 Hz) response was reduced ( P < 0.05) at VH3 (−12 ± 9%) and further reduced ( P < 0.05) at VH8 (−25 ± 11%), VH13 (−42 ± 19%), and VH18 (−46 ± 16%), mirroring the temporal pattern of V̇o2pSC development. The reduction in 10/50 Hz ratio was correlated ( P < 0.001, r2 = 0.69) with V̇o2pSC amplitude. The temporal and quantitative association of decrements in muscle torque production and V̇o2pSC suggest a common physiological mechanism between skeletal muscle fatigue and loss of muscle efficiency.
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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
| | - David B. Copithorne
- 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
| | - Michael D. Hodgson
- 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
| | - Silvia Pogliaghi
- Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Italy
| | - Charles L. Rice
- 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 Anatomy and Cell Biology, The University of Western Ontario, London, Ontario, Canada; and
| | - 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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Lactate recovery kinetics in response to high-intensity exercises. Eur J Appl Physiol 2016; 116:1455-65. [PMID: 27364321 DOI: 10.1007/s00421-016-3420-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 06/22/2016] [Indexed: 10/21/2022]
Abstract
PURPOSE The aim of this study was to investigate lactate recovery kinetics after high-intensity exercises. METHODS Six competitive middle-distance runners performed 500-, 1000-, and 1500-m trials at 90 % of their current maximal speed over 1500 m. Each event was followed by a passive recovery to obtain blood lactate recovery curves (BLRC). BLRC were fitted by the bi-exponential time function: La(t) = La(0) + A 1(1-e (-γ1t) ) + A 2(1-e (-γ2t) ), where La(0) is the blood lactate concentration at exercise completion, and γ 1 and γ 2 enlighten the lactate exchange ability between the previously active muscles and the blood and the overall lactate removal ability, respectively. Applications of the model provided parameters related to lactate release, removal and accumulation rates at exercise completion, and net amount of lactate released during recovery. RESULTS The increase of running distance was accompanied by (1) a continuous decrease in γ 1 (p < 0.05), (2) a primary decrease (p < 0.05) and then a stabilization of γ 2, and (3) a constant increase in blood concentrations (p < 0.05) and whole body accumulation of lactate (p < 0.05). Estimated net lactate release, removal and accumulation rates at exercise completion, as well as the net amount of lactate released during recovery were not significantly altered by distance. CONCLUSION Alterations of lactate exchange and removal abilities have presumably been compensated by an increase in muscle-to-blood lactate gradient and blood lactate concentrations, respectively, so that estimated lactate release, removal and accumulation rates remained almost stable as distance increased.
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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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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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Korzeniewski B. Effects of OXPHOS complex deficiencies and ESA dysfunction in working intact skeletal muscle: implications for mitochondrial myopathies. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1847:1310-9. [DOI: 10.1016/j.bbabio.2015.07.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 07/14/2015] [Accepted: 07/15/2015] [Indexed: 10/23/2022]
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