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O'Malley BG, Robergs RA, Astorino TA. Increases in the incremental exercise mean response time across the steady state domain: Implications for exercise testing & prescription. SPORTS MEDICINE AND HEALTH SCIENCE 2024; 6:315-323. [PMID: 39309463 PMCID: PMC11411294 DOI: 10.1016/j.smhs.2024.02.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 01/27/2024] [Accepted: 02/07/2024] [Indexed: 09/25/2024] Open
Abstract
We hypothesized that slowed oxygen uptake (V ˙ O 2 ) kinetics for exercise transitions to higher power outputs (PO) within the steady state (SS) domain would increase the mean response time (MRT) with increasing exercise intensity during incremental exercise. Fourteen highly trained cyclists (mean ± standard deviation [SD]; age (39 ± 6) years [yr]; andV ˙ O 2 peak = (61 ± 9) mL/kg/min performed a maximal, ramp incremental cycling test and on separate days, four 6-min bouts of cycling at 30%, 45%, 65% & 75% of their incremental peak PO (Wpeak). SS trial data were used to calculate the MRT and verified by mono-exponential and linear curve fitting. When the ramp protocol attained the value from SS, the PO, in Watts (W), was converted to time (min) based on the ramp function W to quantify the incremental MRT (iMRT). Slope analyses for theV ˙ O 2 responses of the SS versus incremental exercise data below the gas exchange threshold (GET) revealed a significant difference (p = 0.003; [0.437 ± 0.08] vs. [0.382 ± 0.05] L⋅min-1). There was a significant difference between the 45% Wpeak steady stateV ˙ O 2 (ssV ˙ O 2 ) ([3.08 ± 0.30] L⋅min-1, respectively), and 30% Wpeak ssV ˙ O 2 (2.26 ± 0.24) (p < 0.0001; [3.61 ± 0.80] vs. [2.20 ± 0.39] L⋅min-1) and between the iMRT for 45% and 30% Wpeak ssV ˙ O 2 values ([50.58 ± 36.85] s vs. [32.20 ± 43.28] s). These data indicate there is no single iMRT, which is consistent with slowedV ˙ O 2 kinetics and an increasingV ˙ O 2 deficit for higher exercise intensities within the SS domain.
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Affiliation(s)
- Bridgette G.J. O'Malley
- Queensland University of Technology, Faculty of Health: School of Exercise and Nutrition Sciences, Brisbane, Australia
| | - Robert A. Robergs
- Queensland University of Technology, Faculty of Health: School of Exercise and Nutrition Sciences, Brisbane, Australia
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Behboodpour N, Halvorson B, Murias JM, Keir D, Belfry G. A Comparison of Methods to Identify the Mean Response Time of Ramp-Incremental Exercise for Exercise Prescription. RESEARCH QUARTERLY FOR EXERCISE AND SPORT 2024:1-9. [PMID: 38885203 DOI: 10.1080/02701367.2024.2346137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 03/13/2024] [Indexed: 06/20/2024]
Abstract
Introduction: The oxygen uptake (V ˙ O2) vs power output relationship from ramp incremental exercise is used to prescribe aerobic exercise. As power output increases, there is a delay in V ˙ O2 that contributes to a misalignment of V ˙ O2 from power output; the mean response time (MRT). If the MRT is not considered in exercise prescription, ramp incremental-identified power outputs will elicit V ˙ O2 values that are higher than intended. We compared three methods of determining MRT (exponential modeling (MRTEXP), linear modeling (MRTLIN), and the steady-state method (MRTSS)) and evaluated their accuracy at predicting the V ˙ O2 associated with power outputs approximating 75% and 85% of gas exchange threshold and 15% of the difference between gas exchange threshold and maximal V ˙ O2 (Δ15). Methods: Ten males performed a 30-W∙min-1 ramp incremental and three 30-min constant power output cycle ergometer trials with intensities at 75% gas exchange threshold, 85% gas exchange threshold, and ∆15. At each intensity, the measured steady-state V ˙ O2 during each 30-min test was compared to the V ˙ O2 predicted after adjustment by each of the three MRTs. Results: For all three MRT methods, predicted V ˙ O2 was not different (p = 1.000) from the measured V ˙ O2 at 75%GET (MRTEXP, 31 mL, MRTLIN, -35 mL, MRTSS 11 mL), 85%gas exchange threshold (MRTEXP -14 mL, MRTLIN -80 mL, MRTSS -32 mL). At Δ15, predicted V ˙ O2 based on MRTEXP was not different (p = .767) from the measured V ˙ O2, but was different for MRTLIN (p < .001) and MRTSS (p = .03). Conclusion: Given that the intensity is below gas exchange threshold, all model predictions implemented from the current study matched the exercise prescription.
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Mackie MZ, Iannetta D, Keir DA, Murias JM. Evaluation of the "Step-Ramp-Step" Protocol: Accurate Aerobic Exercise Prescription with Different Steps and Ramp Slopes. Med Sci Sports Exerc 2024; 56:990-998. [PMID: 38109201 DOI: 10.1249/mss.0000000000003362] [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: 12/20/2023]
Abstract
PURPOSE To assess whether: i) a lower amplitude constant-load MOD is appropriate to determine the mean response time (MRT); ii) the method accurately corrects the dissociation in the V̇O 2 -PO relationship during ramp compared with constant-load exercise when using different ramp slopes. METHODS Eighteen participants (7 females) performed three SRS tests including: i) step-transitions into MOD from 20 to 50 W (MOD 50 ) and 80 W (MOD 80 ); and ii) slopes of 15, 30, and 45 W·min -1 . The V̇O 2 and PO at the gas exchange threshold (GET) and the corrected respiratory compensation point (RCP CORR ) were determined. Two to three 30-min constant-load trials evaluated the V̇O 2 and PO at the maximal metabolic steady state (MMSS). RESULTS There were no differences in V̇O 2 at GET (1.97 ± 0.36, 1.99 ± 0.36, 1.95 ± 0.30 L·min -1 ), and RCP (2.81 ± 0.57, 2.86 ± 0.59, 2.84 ± 0.59) between 15, 30, and 45 W·min -1 ramps, respectively ( P > 0.05). The MRT in seconds was not affected by the amplitude of the MOD or the slope of the ramp (range 19 ± 10 s to 23 ± 20 s; P > 0.05). The mean PO at GET was not significantly affected by the amplitude of the MOD or the slope of the ramp (range 130 ± 30 W to 137 ± 30 W; P > 0.05). The PO at RCP CORR was similar for all conditions ((range 186 ± 43 W to 193 ± 47 W; P > 0.05). CONCLUSIONS The SRS protocol accounts for the V̇O 2 MRT when using smaller amplitude steps, and for the V̇O 2 slow component when using different ramp slopes, allowing for accurate partitioning of the exercise intensity domains in a single test.
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Affiliation(s)
- Mary Z Mackie
- Faculty of Kinesiology, University of Calgary, Calgary, AB, CANADA
| | - Danilo Iannetta
- Faculty of Kinesiology, University of Calgary, Calgary, AB, CANADA
| | - Daniel A Keir
- School of Kinesiology, Western University, London, ON, CANADA
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Iannetta D, Mackie MZ, Keir DA, Murias JM. A Single Test Protocol to Establish the Full Spectrum of Exercise Intensity Prescription. Med Sci Sports Exerc 2023; 55:2271-2280. [PMID: 37436932 DOI: 10.1249/mss.0000000000003249] [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: 07/14/2023]
Abstract
PURPOSE We aimed to test the extended capabilities of the SRS protocol by validating its capacity to predict the power outputs for targeted metabolic rates (V̇O 2 ) and time-to-task failure ( Tlim ) within the heavy- and severe-intensity domain, respectively. METHODS Fourteen young individuals completed (i) an SRS protocol from which the power outputs at GET and RCP (RCP CORR ), and the work accruable above RCP CORR , defined as W ' RAMP , were derived; (ii) one heavy-intensity bout at a power output predicted to elicit a targeted V̇O 2 equidistant from GET and RCP; and (iii) four severe-intensity trials at power outputs predicted to elicit targeted Tlim at minutes 2.5, 5, 10, and 13. These severe-intensity trials were also used to compute the constant-load-derived critical power and W ´ ( W ' CONSTANT ). RESULTS Targeted (2.41 ± 0.52 L·min -1 ) and measured (2.43 ± 0.52 L·min -1 ) V̇O 2 at the identified heavy-intensity power output (162 ± 43 W) were not different ( P = 0.71) and substantially concordant (CCC = 0.95). Likewise, targeted and measured Tlim for the four identified severe-intensity power outputs were not different ( P > 0.05), and the aggregated coefficient of variation was 10.7% ± 8.9%. The derived power outputs at RCP CORR (192 ± 53 W) and critical power (193 ± 53 W) were not different ( P = 0.65) and highly concordant (CCC = 0.99). There were also no differences between W ' RAMP and W ' CONSTANT ( P = 0.51). CONCLUSIONS The SRS protocol can accurately predict power outputs to elicit discrete metabolic rates and exercise durations, thus providing, with time efficiency, a high precision for the control of the metabolic stimulus during exercise.
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Affiliation(s)
- Danilo Iannetta
- Faculty of Kinesiology, University of Calgary, Calgary, AB, CANADA
| | - Mary Z Mackie
- Faculty of Kinesiology, University of Calgary, Calgary, AB, CANADA
| | - Daniel A Keir
- School of Kinesiology, Western University, London, ON, CANADA
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Sietsema KE, Rossiter HB. Exercise Physiology and Cardiopulmonary Exercise Testing. Semin Respir Crit Care Med 2023; 44:661-680. [PMID: 37429332 DOI: 10.1055/s-0043-1770362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/12/2023]
Abstract
Aerobic, or endurance, exercise is an energy requiring process supported primarily by energy from oxidative adenosine triphosphate synthesis. The consumption of oxygen and production of carbon dioxide in muscle cells are dynamically linked to oxygen uptake (V̇O2) and carbon dioxide output (V̇CO2) at the lung by integrated functions of cardiovascular, pulmonary, hematologic, and neurohumoral systems. Maximum oxygen uptake (V̇O2max) is the standard expression of aerobic capacity and a predictor of outcomes in diverse populations. While commonly limited in young fit individuals by the capacity to deliver oxygen to exercising muscle, (V̇O2max) may become limited by impairment within any of the multiple systems supporting cellular or atmospheric gas exchange. In the range of available power outputs, endurance exercise can be partitioned into different intensity domains representing distinct metabolic profiles and tolerances for sustained activity. Estimates of both V̇O2max and the lactate threshold, which marks the upper limit of moderate-intensity exercise, can be determined from measures of gas exchange from respired breath during whole-body exercise. Cardiopulmonary exercise testing (CPET) includes measurement of V̇O2 and V̇CO2 along with heart rate and other variables reflecting cardiac and pulmonary responses to exercise. Clinical CPET is conducted for persons with known medical conditions to quantify impairment, contribute to prognostic assessments, and help discriminate among proximal causes of symptoms or limitations for an individual. CPET is also conducted in persons without known disease as part of the diagnostic evaluation of unexplained symptoms. Although CPET quantifies a limited sample of the complex functions and interactions underlying exercise performance, both its specific and global findings are uniquely valuable. Some specific findings can aid in individualized diagnosis and treatment decisions. At the same time, CPET provides a holistic summary of an individual's exercise function, including effects not only of the primary diagnosis, but also of secondary and coexisting conditions.
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Affiliation(s)
- Kathy E Sietsema
- Division of Respiratory and Critical Care Physiology and Medicine, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, David Geffen School of Medicine at UCLA, Torrance, California
| | - Harry B Rossiter
- Division of Respiratory and Critical Care Physiology and Medicine, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, David Geffen School of Medicine at UCLA, Torrance, California
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Love LK, Hodgson MD, Keir DA, Kowalchuk JM. The effect of increasing work rate amplitudes from a common metabolic baseline on the kinetic response of V̇o 2p, blood flow, and muscle deoxygenation. J Appl Physiol (1985) 2023; 135:584-600. [PMID: 37439241 DOI: 10.1152/japplphysiol.00566.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 06/29/2023] [Accepted: 07/06/2023] [Indexed: 07/14/2023] Open
Abstract
A step-transition in external work rate (WR) increases pulmonary O2 uptake (V̇o2p) in a monoexponential fashion. Although the rate of this increase, quantified by the time constant (τ), has frequently been shown to be similar between multiple different WR amplitudes (ΔWR), the adjustment of O2 delivery to the muscle (via blood flow; BF), a potential regulator of V̇o2p kinetics, has not been extensively studied. To investigate the role of BF on V̇o2p kinetics, 10 participants performed step-transitions on a knee-extension ergometer from a common baseline WR (3 W) to: 24, 33, 45, 54, and 66 W. Each transition lasted 8 min and was repeated four to six times. Volume turbinometry and mass spectrometry, Doppler ultrasound, and near-infrared spectroscopy were used to measure V̇o2p, BF, and muscle deoxygenation (deoxy[Hb + Mb]), respectively. Similar transitions were ensemble-averaged, and phase II V̇o2p, BF, and deoxy[Hb + Mb] were fit with a monoexponential nonlinear least squares regression equation. With increasing ΔWR, τV̇o2p became larger at the higher ΔWRs (P < 0.05), while τBF did not change significantly, and the mean response time (MRT) of deoxy[Hb + Mb] became smaller. These findings that V̇o2p kinetics become slower with increasing ΔWR, while BF kinetics are not influenced by ΔWR, suggest that O2 delivery could not limit V̇o2p in this situation. However, the speeding of deoxy[Hb + Mb] kinetics with increasing ΔWR does imply that the O2 delivery-to-O2 utilization of the microvasculature decreases at higher ΔWRs. This suggests that the contribution of O2 delivery and O2 extraction to V̇O2 in the muscle changes with increasing ΔWR.NEW & NOTEWORTHY A step increase in work rate produces a monoexponential increase in V̇o2p and blood flow to a new steady-state. We found that step transitions from a common metabolic baseline to increasing work rate amplitudes produced a slowing of V̇o2p kinetics, no change in blood flow kinetics, and a speeding of muscle deoxygenation kinetics. As work rate amplitude increased, the ratio of blood flow to V̇o2p became smaller, while the amplitude of muscle deoxygenation became greater. The gain in vascular conductance became smaller, while kinetics tended to become slower at higher work rate amplitudes.
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Affiliation(s)
- Lorenzo 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 and Physical Education, Redeemer University, Ancaster, Ontario, Canada
| | - Michael D Hodgson
- 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
| | - Daniel A Keir
- 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
- Toronto General Research Institute, Toronto General Hospital, Toronto, Ontario, Canada
| | - John 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 Kinesiology and Physical Education, Redeemer University, Ancaster, Ontario, Canada
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Korzeniewski B. Mechanisms of slowed V̇O 2 on-kinetics in second step of two-step-incremental exercise in skeletal muscle. Respir Physiol Neurobiol 2023:104084. [PMID: 37230211 DOI: 10.1016/j.resp.2023.104084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 05/03/2023] [Accepted: 05/20/2023] [Indexed: 05/27/2023]
Abstract
Simulations using a computer model of the skeletal muscle bioenergetic system demonstrate that the slowed V̇O2 on-kinetics of the second step in two-step incremental exercise (exercise initiated from elevated baseline metabolic rate) can be accounted for by a decrease in the stimulation of oxidative phosphorylation (OXPHOS) and/or increase in the stimulation of glycolysis through each-step activation (ESA) in working skeletal muscle. This effect can be caused by either a recruitment of more glycolytic type IIa, IIx and IIb fibers or metabolic regulation in already recruited fibers, or both. The elevated-glycolysis-stimulation mechanism predicts that the end-second-step pH in two-step-incremental exercise is lower than the end-exercise pH in constant-power exercise with the same work intensity (power output). The lowered-OXPHOS-stimulation mechanism predicts higher end-exercise ADP and Pi, and lower PCr in the second step of two-step-incremental than in constant-power exercise. These predictions/mechanisms can be verified or falsified in the experimental way. DATA AVAILABILITY STATEMENT: There are no additional data available.
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Korzeniewski B. V̇O 2 (non-)linear increase in ramp-incremental exercise vs. V̇O 2 slow component in constant-power exercise: Underlying mechanisms. Respir Physiol Neurobiol 2023; 311:104023. [PMID: 36731708 DOI: 10.1016/j.resp.2023.104023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Revised: 12/31/2022] [Accepted: 01/28/2023] [Indexed: 02/01/2023]
Abstract
A computer model of the skeletal muscle bioenergetic system involving the Pi double-threshold mechanism of muscle fatigue was used to study the V̇O2 (non-)linear increase in time in ramp-incremental exercise as compared to the V̇O2 slow component in constant-power exercise. The Pi double-threshold mechanism applies to both constant-power and ramp-incremental exercise. The additional ATP usage is initiated at a significantly higher ATP usage activity (power output), determining the moderate/heavy exercise border, in ramp-incremental, than in constant-power exercise. A significantly lowered additional ATP usage activity or elevated glycolysis stimulation at the highest power outputs in ramp-incremental exercise in relation to constant-power exercise can additionally explain the much smaller (or zero) V̇O2 non-linearity in ramp-incremental exercise, than V̇O2 slow component in constant-power exercise. The V̇O2 (non-)linearity in ramp-incremental exercise and V̇O2 slow component in constant-power exercise is a derivative of a balance between the additional ATP usage and ATP production by anaerobic glycolysis.
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VAN Rassel CR, Ajayi OO, Sales KM, Azevedo RA, Murias JM, Macinnis MJ. A "Step-Ramp-Step" Protocol to Identify Running Speed and Power Associated with the Maximal Metabolic Steady State. Med Sci Sports Exerc 2023; 55:534-547. [PMID: 36251387 DOI: 10.1249/mss.0000000000003066] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
PURPOSE A previously established Step-Ramp-Step (SRS) exercise protocol was able to accurately predict the work rate associated with the maximal metabolic steady state (MMSS) in cyclists. The purpose of this study was to determine whether a modified SRS protocol could predict the running speed and power associated with the MMSS. METHODS Fifteen (8 male; 7 female) runners (V̇O 2max 54.5 [6.5] mL·kg -1 ·min -1 ) were recruited for this investigation composed of four to five visits. In the first visit, runners performed a moderate intensity step (MOD), an incremental exercise test, and a heavy intensity step (HVY), on a motorized treadmill. This SRS protocol was used to predict the running speed and power associated with the MMSS (i.e., the SRS-MMSS), where running power was assessed by a wearable device (Stryd) attached to each runner's shoe. Subsequent visits were used to confirm the maximal lactate steady state (MLSS) as a proxy measure of the MMSS (i.e., the MLSS-MMSS) and to validate the SRS-MMSS speed and power estimates. RESULTS The estimated SRS-MMSS running speed (7.2 [0.6] mph) was significantly lower than confirmed running speed at MLSS-MMSS (7.5 [0.8] mph; bias = 3.6%, P = 0.005); however, the estimated SRS-MMSS running power (241 [35] W) was not different than the MLSS-MMSS confirmed running power (240 [37] W; bias = -0.6%; P = 0.435). V̇O 2 at SRS-MMSS (3.22 [0.49] L·min -1 ) was not different than respiratory compensation point (3.26 [0.58] L·min -1 ; P = 0.430). Similarly, V̇O 2 at MLSS-MMSS (3.30 [0.54] L·min -1 ) was not different than respiratory compensation point ( P = 0.438). CONCLUSIONS The SRS protocol allows MMSS, as measured by MLSS, to be accurately determined using running power (Stryd), but not speed, in a single laboratory visit.
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Affiliation(s)
- Cody R VAN Rassel
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, CANADA
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Pleguezuelos E, Del Carmen A, Moreno E, Ortega P, Robles A, Serra-Prat M, Miravitlles M, Yebenes JC, Garnacho-Castaño MV. Impaired pulmonary and muscle function during moderate exercise in female patients recovered from SARS-CoV-2. Sci Rep 2022; 12:20943. [PMID: 36464697 PMCID: PMC9719894 DOI: 10.1038/s41598-022-24941-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 11/22/2022] [Indexed: 12/05/2022] Open
Abstract
This study aimed to assess pulmonary and muscle dysfunction by analyzing the slow component of oxygen uptake (VO2SC), and mechanical and ventilatory efficiency in adult women recovered from the severe acute respiratory syndrome coronavirus type II (SARS-CoV-2) during a constant load test. 32 women (N = 17 patients with SARS-CoV-2; N = 15 control group) performed two cardiopulmonary exercise tests (CPX) on a cycle ergometer. In the first test, the participants performed incremental CPX until extenuation. In the second test the participants performed a 10-min CPX at a constant load intensity (watts) corresponding to the first ventilatory threshold. There was a 48-72 h rest period between the two tests. There was a significant increase in the VO2SC in the patients recovered from SARS-CoV-2 (160.4 ± 60 mL min-1) in comparison with the healthy participants (59.6 ± 65 mL min-1) (P < 0.001). Mechanical efficiency significantly decreased in patients recovered from SARS-CoV-2 compared to the control group (P = 0.04). Ventilatory inefficiency significantly increased in the patients recovered from SARS-CoV-2 compared with the control group (P < 0.001). Adult women recovered from SARS-CoV-2 infection have important pulmonary and muscular dysfunction and fatigue which contributes to increasing the VO2SC and reducing mechanical and ventilatory efficiency during mild-moderate exercise at a constant load.
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Affiliation(s)
- Eulogio Pleguezuelos
- Physical Medicine and Rehabilitation Department, Hospital de Mataró, Barcelona, Spain
- Department of Experimental Science and Healthcare, Faculty of Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
| | - Amin Del Carmen
- Physical Medicine and Rehabilitation Department, Hospital de Mataró, Barcelona, Spain
| | - Eva Moreno
- Physical Medicine and Rehabilitation Department, Hospitalet General Hospital, L'Hospitalet de Llobregat, Barcelona, Spain
| | - Pilar Ortega
- Pneumology Department, Hospital de Mataró, Barcelona, Spain
| | | | - Mateo Serra-Prat
- Research Unit, Consorci Sanitari del Maresme, Mataró, Barcelona, Spain
| | - Marc Miravitlles
- Pneumology Department, Hospital Universitari Vall d'Hebron, Vall d'Hebron Institut de Recerca (VHIR), Barcelona Hospital Campus, CIBER de Enfermedades Respiratorias (CIBERES), Barcelona, Spain
| | | | - Manuel V Garnacho-Castaño
- Campus Docent Sant Joan de Déu, Fundación Privada, Universitat de Barcelona, Carrer de Miret i Sans, 10, 08034, Barcelona, Spain.
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Guluzade NA, Huggard JD, Keltz RR, Duffin J, Keir DA. Strategies to improve respiratory chemoreflex characterization by Duffin's rebreathing. Exp Physiol 2022; 107:1507-1520. [PMID: 36177675 DOI: 10.1113/ep090668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 09/21/2022] [Indexed: 12/14/2022]
Abstract
NEW FINDINGS What is the central question of this study? We assessed the test-retest variability of respiratory chemoreflex characterization by Duffin's modified rebreathing method and explored whether signal averaging of repeated trials improves confidence in parameter estimation. What is the main finding and its importance? Modified rebreathing is a reproducible method to characterize responses of central and peripheral respiratory chemoreflexes. Signal averaging of multiple repeated tests minimizes within- and between-test variability, improves the confidence of chemoreflex characterization and reduces the minimal change in parameters required to establish an effect. Future experiments that apply this method might benefit from signal averaging to improve its discriminatory effect. ABSTRACT We assessed the test-retest variability of central and peripheral respiratory chemoreflex characterization by Duffin's modified rebreathing method and explored whether signal averaging of repeated trials improves confidence in parameter estimation. Over four laboratory visits, 13 participants (mean ± SD age, 25 ± 5 years) performed six repetitions of modified rebreathing in isoxic-hypoxic conditions [end-tidal P O 2 ${P_{{{\rm{O}}_{\rm{2}}}}}$ ( P ET , O 2 ${P_{{\rm{ET,}}{{\rm{O}}_{\rm{2}}}}}$ ) = 50 mmHg] and isoxic-hyperoxic conditions ( P ET , O 2 ${P_{{\rm{ET,}}{{\rm{O}}_{\rm{2}}}}}$ = 150 mmHg). End-tidal P C O 2 ${P_{{\rm{C}}{{\rm{O}}_{\rm{2}}}}}$ ( P ET , C O 2 ${P_{{\rm{ET,C}}{{\rm{O}}_{\rm{2}}}}}$ ), P ET , O 2 ${P_{{\rm{ET,}}{{\rm{O}}_{\rm{2}}}}}$ and minute ventilation ( V ̇ $\dot {\rm V}$ E ) were measured breath-by-breath, by gas analyser and pneumotachograph. The V ̇ $\dot {\rm V}$ E versus P ET , C O 2 ${P_{{\rm{ET,C}}{{\rm{O}}_{\rm{2}}}}}$ relationships were fitted with a piecewise model to estimate the ventilatory recruitment threshold (VRT) and the slope above the VRT ( V ̇ $\dot {\rm V}$ E S). Breath-by-breath data from the three within- and between-day trials were averaged using two approaches [simple average (fit then average) and ensemble average (average then fit)] and compared with a single-trial fit. Variability was assessed by intraclass correlation (ICC) and coefficient of variance (CV), and the minimal detectable change was computed for each approach using two independent sets of three trials. Within days, the VRT and V ̇ $\dot {\rm V}$ E S exhibited excellent test-retest variability in both hyperoxic conditions (VRT: ICC = 0.965, CV = 2.3%; V ̇ $\dot {\rm V}$ E S: ICC = 0.932, CV = 15.5%) and hypoxic conditions (VRT: ICC = 0.970, CV = 2.9%; V ̇ $\dot {\rm V}$ E S: ICC = 0.891, CV = 17.2%). Between-day reproducibility was also excellent (hyperoxia, VRT: ICC = 0.930, CV = 2.2%; V ̇ $\dot {\rm V}$ E S: ICC = 0.918, CV = 14.2%; and hypoxia, VRT: ICC = 0.940, CV = 3.0%; V ̇ $\dot {\rm V}$ E S: ICC = 0.880, CV = 18.1%). Compared with a single-trial fit, there were no differences in VRT or V ̇ $\dot {\rm V}$ E S using the simple average or ensemble average approaches; however, ensemble averaging reduced the minimal detectable change for V ̇ $\dot {\rm V}$ E S from 2.95 to 1.39 L min-1 mmHg-1 (hyperoxia) and from 3.64 to 1.82 L min-1 mmHg-1 (hypoxia). Single trials of modified rebreathing are reproducible; however, signal averaging of repeated trials improves confidence in parameter estimation.
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Affiliation(s)
- Nasimi A Guluzade
- School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Joshua D Huggard
- School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Randi R Keltz
- School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - James Duffin
- Department of Anesthesiology and Pain Medicine, University of Toronto, Toronto, Ontario, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario, Canada.,Thornhill Research Inc., Toronto, Ontario, Canada
| | - Daniel A Keir
- School of Kinesiology, The University of Western Ontario, London, Ontario, Canada.,Toronto General Research Institute, Toronto General Hospital, Toronto, Ontario, Canada.,Lawson Health Research Institute, London, Ontario, Canada
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12
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Moreira-Reis A, Maté-Muñoz JL, Hernández-Lougedo J, García-Fernández P, Heredia-Elvar JR, Pleguezuelos E, Carbonell T, Alva N, Garnacho-Castaño MV. Similar Slow Component of Oxygen Uptake and Ventilatory Efficiency between an Aerobic Dance Session on an Air Dissipation Platform and a Constant-Load Treadmill Test in Healthy Women. BIOLOGY 2022; 11:biology11111646. [PMID: 36358347 PMCID: PMC9687828 DOI: 10.3390/biology11111646] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 10/29/2022] [Accepted: 10/30/2022] [Indexed: 11/12/2022]
Abstract
There is a lack of evidence about the slow component of oxygen consumption (V.O2sc) and ventilatory efficiency (slope VE·VCO2−1) during an aerobic dance (AD) session on an air dissipation platform (ADP) despite the key role played in endurance exercises. This research was designed to assess V.O2sc, ventilatory efficiency, and blood lactate concentration by comparing two exercise modes: AD session on an ADP versus treadmill test at a constant-load intensity of the first ventilatory threshold (VT1). In the first session, an incremental treadmill test was completed. In sessions 2 and 3, the participants were randomly assigned to the AD session on an ADP or to a treadmill constant-load test at VT1 intensity to determine their cardioventilatory responses. In addition, their blood lactate levels and ratings of perceived exertion (RPE, CR-10) were evaluated. No significant differences were found between the constant-load treadmill test and AD session on an ADP with respect to V.O2sc, VE VCO2−1 slope, and RPE (p > 0.05). Higher blood lactate concentrations were observed in an AD session on an ADP than in a constant-load treadmill test at 10 min (p = 0.003) and 20 min (p < 0.001). The two different exercise modalities showed similar V.O2sc and VE·VCO2−1 slope, even though the blood lactate concentrations were different.
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Affiliation(s)
- Alessandra Moreira-Reis
- Department of Cell Biology, Physiology and Immunology, Faculty of Biology, University of Barcelona, 08028 Barcelona, Spain
| | - José Luis Maté-Muñoz
- Department of Radiology, Rehabilitation and Physiotherapy, Complutense University of Madrid, 28040 Madrid, Spain
| | - Juan Hernández-Lougedo
- Department of Physiotherapy, Faculty of Health Sciences, Camilo José Cela University, 28692 Madrid, Spain
| | - Pablo García-Fernández
- Department of Radiology, Rehabilitation and Physiotherapy, Complutense University of Madrid, 28040 Madrid, Spain
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), 28040 Madrid, Spain
| | - Juan Ramón Heredia-Elvar
- Department of Physical Activity and Sports Science, Alfonso X El Sabio University, 28691 Madrid, Spain
| | - Eulogio Pleguezuelos
- Physical Medicine and Rehabilitation Department, Hospital de Mataró, 08304 Barcelona, Spain
| | - Teresa Carbonell
- Department of Cell Biology, Physiology and Immunology, Faculty of Biology, University of Barcelona, 08028 Barcelona, Spain
| | - Norma Alva
- Department of Cell Biology, Physiology and Immunology, Faculty of Biology, University of Barcelona, 08028 Barcelona, Spain
| | - Manuel Vicente Garnacho-Castaño
- Campus Docent Sant Joan de Déu, University of Barcelona, 08830 Sant Boi de Llobregat, Spain
- Correspondence: ; Tel.: +34-606-27-5392
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13
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Marini CF, Sisti D, Skinner JS, Sarzynski MA, Bouchard C, Amatori S, Rocchi MBL, Piccoli G, Stocchi V, Federici A, Lucertini F. Effect of individual characteristics and aerobic training on the %HRR-% V˙O 2R relationship. Eur J Sport Sci 2022:1-12. [PMID: 35960537 DOI: 10.1080/17461391.2022.2113441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
This study aimed to assess if, during incremental exercise, considering individual characteristics can make the relationship between the percentages of heart rate (HRR) and oxygen uptake (VO2R) reserve either 1:1 or more accurate. Cycle ergometer data of the maximal incremental exercise tests performed by 450 healthy and sedentary participants (17-66 years) of the HERITAGE Family Study, grouped for sex, ethnicity, age, body fat, resting HR, and VO2max, were used to calculate the individual linear regressions between %HRR and %VO2R. The mean slope and intercept of the individual linear regressions of each subgroup were compared with 1 and 0 (identity line), respectively, using Hotelling tests followed by post-hoc one-sample t-tests. Two multiple linear regressions were also performed, using either the slopes or intercepts of the individual linear regressions as dependent variables and sex, age, resting HR, and VO2max as independent variables. The mean %HRR-%VO2R relationships of all subgroups differed from the identity line. Moreover, individual linear regression intercepts (8.9±16.0) and slopes (0.971±0.190) changed (p<0.001) after 20 weeks of aerobic training (13.1±11.1 and 0.891±0.122). The multiple linear regressions could explain only 3.8% and 1.3% of the variance in the intercepts and slopes, whose variability remained high (standard error of estimate of 15.8 and 0.189). In conclusion, the %HRR-%VO2R relationship differs from the identity line regardless of individual characteristics and their difference increased after aerobic training. Moreover, due to the high interindividual variability, using a single equation for the whole population seems not suitable for representing the %HRR-%VO2R relationship of a given subject, even when several individual characteristics are considered.
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Affiliation(s)
- Carlo Ferri Marini
- Department of Biomolecular Sciences - Division of Exercise and Health Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - Davide Sisti
- Department of Biomolecular Sciences - Unit of Biostatistics, University of Urbino Carlo Bo, Urbino, Italy
| | - James S Skinner
- Department of Kinesiology, Indiana University, Bloomington (IN), USA
| | - Mark A Sarzynski
- Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Columbia (SC), USA
| | - Claude Bouchard
- Human Genomics Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge (LA), USA
| | - Stefano Amatori
- Department of Biomolecular Sciences - Unit of Biostatistics, University of Urbino Carlo Bo, Urbino, Italy
| | - Marco B L Rocchi
- Department of Biomolecular Sciences - Unit of Biostatistics, University of Urbino Carlo Bo, Urbino, Italy
| | - Giovanni Piccoli
- Department of Biomolecular Sciences - Division of Exercise and Health Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - Vilberto Stocchi
- Department of Human Sciences for the Promotion of Quality of Life, University San Raffaele Roma, Rome, Italy
| | - Ario Federici
- Department of Biomolecular Sciences - Division of Exercise and Health Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - Francesco Lucertini
- Department of Biomolecular Sciences - Division of Exercise and Health Sciences, University of Urbino Carlo Bo, Urbino, Italy
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14
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Keir DA, Iannetta D, Mattioni Maturana F, Kowalchuk JM, Murias JM. Identification of Non-Invasive Exercise Thresholds: Methods, Strategies, and an Online App. Sports Med 2021; 52:237-255. [PMID: 34694596 DOI: 10.1007/s40279-021-01581-z] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/03/2021] [Indexed: 10/20/2022]
Abstract
During incremental exercise, two thresholds may be identified from standard gas exchange and ventilatory measurements. The first signifies the onset of blood lactate accumulation (the lactate threshold, LT) and the second the onset of metabolic acidosis (the respiratory compensation point, RCP). The ability to explain why these thresholds occur and how they are identified, non-invasively, from pulmonary gas exchange and ventilatory variables is fundamental to the field of exercise physiology and requisite to the understanding of core concepts including exercise intensity, assessment, prescription, and performance. This review is intended as a unique and comprehensive theoretical and practical resource for instructors, clinicians, researchers, lab technicians, and students at both undergraduate and graduate levels to facilitate the teaching, comprehension, and proper non-invasive identification of exercise thresholds. Specific objectives are to: (1) explain the underlying physiology that produces the LT and RCP; (2) introduce the classic non-invasive measurements by which these thresholds are identified by connecting variable profiles to underlying physiological behaviour; (3) discuss common issues that can obscure threshold detection and strategies to identify and mitigate these challenges; and (4) introduce an online resource to facilitate learning and standard practices. Specific examples of exercise gas exchange and ventilatory data are provided throughout to illustrate these concepts and a novel online application tool designed specifically to identify the estimated LT (θLT) and RCP is introduced. This application is a unique platform for learners to practice skills on real exercise data and for anyone to analyze incremental exercise data for the purpose of identifying θLT and RCP.
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Affiliation(s)
- Daniel A Keir
- School of Kinesiology, The University of Western Ontario, AHB 3G18, 1151 Richmond Street, London, ON, N6A 3K7, Canada. .,Toronto General Research Institute, Toronto General Hospital, Toronto, ON, Canada.
| | - Danilo Iannetta
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
| | | | - John M Kowalchuk
- School of Kinesiology, The University of Western Ontario, AHB 3G18, 1151 Richmond Street, London, ON, N6A 3K7, Canada.,Department of Physiology and Pharmacology, The University of Western Ontario, London, ON, Canada
| | - Juan M Murias
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
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15
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Impact of supine versus upright exercise on muscle deoxygenation heterogeneity during ramp incremental cycling is site specific. Eur J Appl Physiol 2021; 121:1283-1296. [PMID: 33575912 PMCID: PMC8064998 DOI: 10.1007/s00421-021-04607-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 01/17/2021] [Indexed: 10/24/2022]
Abstract
PURPOSE We tested the hypothesis that incremental ramp cycling exercise performed in the supine position (S) would be associated with an increased reliance on muscle deoxygenation (deoxy[heme]) in the deep and superficial vastus lateralis (VLd and VLs, respectively) and the superficial rectus femoris (RFs) when compared to the upright position (U). METHODS 11 healthy men completed ramp incremental exercise tests in S and U. Pulmonary [Formula: see text]O2 was measured breath-by-breath; deoxy[heme] was determined via time-resolved near-infrared spectroscopy in the VLd, VLs and RFs. RESULTS Supine exercise increased the overall change in deoxy[heme] from baseline to maximal exercise in the VLs (S: 38 ± 23 vs. U: 26 ± 15 μM, P < 0.001) and RFs (S: 36 ± 21 vs. U: 25 ± 15 μM, P < 0.001), but not in the VLd (S: 32 ± 23 vs. U: 29 ± 26 μM, P > 0.05). CONCLUSIONS The present study supports that the impaired balance between O2 delivery and O2 utilization observed during supine exercise is a regional phenomenon within superficial muscles. Thus, deep muscle defended its O2 delivery/utilization balance against the supine-induced reductions in perfusion pressure. The differential responses of these muscle regions may be explained by a regional heterogeneity of vascular and metabolic control properties, perhaps related to fiber type composition.
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16
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Iannetta D, Inglis EC, Pogliaghi S, Murias JM, Keir DA. A "Step-Ramp-Step" Protocol to Identify the Maximal Metabolic Steady State. Med Sci Sports Exerc 2021; 52:2011-2019. [PMID: 32205678 DOI: 10.1249/mss.0000000000002343] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The oxygen uptake (V[Combining Dot Above]O2) at the respiratory compensation point (RCP) closely identifies with the maximal metabolic steady state. However, the power output (PO) at RCP cannot be determined from contemporary ramp-incremental exercise protocols. PURPOSE This study aimed to test the efficacy of a "step-ramp-step" (SRS) cycling protocol for estimating the PO at RCP and the validity of RCP as a maximal metabolic steady-state surrogate. METHODS Ten heathy volunteers (5 women; age: 30 ± 7 yr; V[Combining Dot Above]O2max: 54 ± 6 mL·kg·min) performed in the following series: a moderate step transition to 100 W (MOD), ramp (30 W·min), and after 30 min of recovery, step transition to ~50% POpeak (HVY). Ventilatory and gas exchange data from the ramp were used to identify the V[Combining Dot Above]O2 at lactate threshold (LT) and RCP. The PO at LT was determined by the linear regression of the V[Combining Dot Above]O2 versus PO relationship after adjusting ramp data by the difference between the ramp PO at the steady-state V[Combining Dot Above]O2 from MOD and 100 W. Linear regression between the V[Combining Dot Above]O2-PO values associated with LT and HVY provided, by extrapolation, the PO at RCP. Participants then performed 30-min constant-power tests at the SRS-estimated RCP and 5% above this PO. RESULTS All participants completed 30 min of constant-power exercise at the SRS-estimated RCP achieving steady-state V[Combining Dot Above]O2 of 3176 ± 595 mL·min that was not different (P = 0.80) from the ramp-identified RCP (3095 ± 570 mL·min) and highly consistent within participants (bias = -26 mL·min, r = 0.97, coefficient of variation = 2.3% ± 2.8%). At 5% above the SRS-estimated RCP, four participants could not complete 30 min and all, but two exhibited non-steady-state responses in blood lactate and V[Combining Dot Above]O2. CONCLUSIONS In healthy individuals cycling at their preferred cadence, the SRS protocol and the RCP are capable of accurately predicting the PO associated with maximal metabolic steady state.
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Affiliation(s)
- Danilo Iannetta
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, CANADA
| | | | - Silvia Pogliaghi
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, ITALY
| | - Juan M Murias
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, CANADA
| | - Daniel A Keir
- University Health Network, Department of Medicine, Toronto, Ontario, CANADA
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17
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Dutra YM, Claus GM, Malta EDS, Seda DMDF, Zago AS, Campos EZ, Ferraresi C, Zagatto AM. Photobiomodulation 30 min or 6 h Prior to Cycling Does Not Alter Resting Blood Flow Velocity, Exercise-Induced Physiological Responses or Time to Exhaustion in Healthy Men. Front Physiol 2021; 11:607302. [PMID: 33519511 PMCID: PMC7844325 DOI: 10.3389/fphys.2020.607302] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 12/02/2020] [Indexed: 11/13/2022] Open
Abstract
Purpose The aim of the current study was to investigate the effects of photobiomodulation therapy (PBMT) applied 30 min or 6 h prior to cycling on blood flow velocity and plasma nitrite concentrations at rest, time to exhaustion, cardiorespiratory responses, blood acid-base balance, and K+ and lactate concentrations during exercise. Methods In a randomized, crossover design, 13 healthy untrained men randomly completed four cycling bouts until exhaustion at the severe-intensity domain (i.e., above respiratory compensation point). Thirty minutes or 6 h prior to the cycling trials, participants were treated with PBMT on the quadriceps, hamstrings, and gastrocnemius muscles of both limbs using a multi-diode array (11 cm × 30 cm with 264 diodes) at doses of 152 J or a sham irradiation (with device turned off, placebo). Blood samples were collected before and 30 min or 6 h after treatments to measure plasmatic nitrite concentrations. Doppler ultrasound exams of the femoral artery were also performed at the same time points. Cardiorespiratory responses, blood acid-base balance, and K+ and lactate concentrations were monitored during exercise sessions. Results PBMT did not improve the time to exhaustion (p = 0.30). At rest, no differences were found in the peak systolic velocity (p = 0.97) or pulsatility index (p = 0.83) in the femoral artery, and in plasma nitrite concentrations (p = 0.47). During exercise, there were no differences for any cardiorespiratory response monitored (heart rate, p = 0.15; oxygen uptake, p = 0.15; pulmonary ventilation, p = 0.67; carbon dioxide output, p = 0.93; and respiratory exchange ratio, p = 0.32), any blood acid-base balance indicator (pH, p = 0.74; base excess, p = 0.33; bicarbonate concentration, p = 0.54), or K+ (p = 0.22) and lactate (p = 0.55) concentrations. Conclusions PBMT at 152 J applied 30 min or 6 h before cycling at severe-intensity did not alter resting plasma nitrite and blood flow velocity in the femoral artery, exercise-induced physiological responses, or time to exhaustion in healthy untrained men.
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Affiliation(s)
- Yago Medeiros Dutra
- Post-Graduate Program in Movement Sciences, Laboratory of Physiology and Sport Performance (LAFIDE), Department of Physical Education, School of Sciences, São Paulo State University - UNESP, Bauru, Brazil
| | - Gabriel Machado Claus
- Post-Graduate Program in Movement Sciences, Laboratory of Physiology and Sport Performance (LAFIDE), Department of Physical Education, School of Sciences, São Paulo State University - UNESP, Bauru, Brazil
| | - Elvis de Souza Malta
- Post-Graduate Program in Movement Sciences, Laboratory of Physiology and Sport Performance (LAFIDE), Department of Physical Education, School of Sciences, São Paulo State University - UNESP, Bauru, Brazil
| | - Daniela Moraes de Franco Seda
- Post-Graduate Program in Movement Sciences, Laboratory of Physiology and Sport Performance (LAFIDE), Department of Physical Education, School of Sciences, São Paulo State University - UNESP, Bauru, Brazil
| | - Anderson Saranz Zago
- Post-Graduate Program in Movement Sciences, Department of Physical Education, School of Sciences, São Paulo State University - UNESP, Bauru, Brazil
| | | | - Cleber Ferraresi
- Physical Therapy Department, Federal University of Sao Carlos (UFSCar), São Paulo, Brazil
| | - Alessandro Moura Zagatto
- Post-Graduate Program in Movement Sciences, Laboratory of Physiology and Sport Performance (LAFIDE), Department of Physical Education, School of Sciences, São Paulo State University - UNESP, Bauru, Brazil.,Department of Physical Education, Federal University of Pernambuco, Recife, Brazil
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18
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Hedge ET, Hughson RL. Frequency domain analysis to extract dynamic response characteristics for oxygen uptake during transitions to moderate- and heavy-intensity exercises. J Appl Physiol (1985) 2020; 129:1422-1430. [PMID: 33054659 DOI: 10.1152/japplphysiol.00503.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
At the onset of an exercise transition, exponential modeling to calculate a time constant (τ) is the conventional method to analyze pulmonary oxygen uptake (V̇O2p) kinetics for moderate and heavy exercises. A new frequency domain analysis technique, mean normalized gain (MNG), has been used to analyze V̇O2p kinetics during moderate exercise, but has not been evaluated for its ability to detect differences in kinetics between moderate and heavy exercises. This study tested the hypothesis that MNG would detect smaller amplitude V̇O2p responses in the heavy-exercise domain compared with moderate-exercise domain. Eight young healthy adults (3 female; age: 27 ± 6 yr; peak V̇O2p: 43 ± 6 mL·min-1·kg-1; means ± SD) performed three bouts of pseudorandom binary sequence (PRBS) exercise for frequency analysis, with the work rate (WR) changing between 25 W and 90% ventilatory threshold (VT; L → MPRBS), 25 W and 50% of the difference between VT and peak V̇O2p (Δ50%; L → HPRBS), and VT to Δ50% (VT → HPRBS). Step exercise tests with equivalent changes in WR to the PRBS tests were performed to facilitate the comparison between MNG and τ. MNG was the highest for L → MPRBS (59 ± 7%), then L → HPRBS (52 ± 6%), and the lowest for VT → HPRBS (38 ± 7%, F(2,14) = 129.755, P < 0.001) exercise conditions indicating slower kinetics with increasing exercise intensity that correlated strongly in repeated measures with τ from step transitions (rrm = -0.893). These results indicate that frequency domain analysis and MNG reliably detect differences in V̇O2p kinetics observed across exercise intensity domains.NEW & NOTEWORTHY Mean normalized gain is able to detect differences in V̇O2p kinetics between moderate-, heavy-, and heavy-intensity exercises from a raised WR within the same individuals. This new method of kinetic analysis may be advantageous compared with conventional V̇O2p curve fitting, as it is less sensitive to breath-by-breath noise, it can provide useful information from a single exercise testing session, and it can be applied to nonconstant work rate exercise situations.
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Affiliation(s)
- Eric T Hedge
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, Ontario, Canada.,Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada
| | - Richard L Hughson
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, Ontario, Canada.,Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada
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20
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de Lima LAP, Achiche S, de Lucas RD, Raison M. Second-order simultaneous components model for the overshoot and "slow component" in V̇O 2 kinetics. Respir Physiol Neurobiol 2020; 280:103479. [PMID: 32593589 DOI: 10.1016/j.resp.2020.103479] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 06/05/2020] [Accepted: 06/11/2020] [Indexed: 10/24/2022]
Abstract
The human oxygen uptake responses to exercise step on-transients present different shapes depending on the overshoot and/or the "slow component" manifestations. The conventional First-Order Multi-Exponential (FOME) model incorporates delayed add-on terms to comprise these phenomena, increasing parameter quantity, requiring a delayed recruitment of type II fibers to explain the "slow component," and not offering a unified structure for different individuals and intensity domains. We hypothesized that a model composed of two Second-Order Simultaneous Components (SOSC) would present a better overall fitting performance than the FOME. Fourteen well-trained male cyclists performed repeated step on-transitions to moderate, heavy, and severe cycling intensities, whose responses were fitted with FOME and SOSC models. The SOSC presented significantly smaller (p < 0.05) root mean squared errors for moderate, supra-moderate, and all intensities combined. Along with conceptual analyses, these findings suggest the SOSC as a comprehensive alternative to the FOME model, explaining all oxygen uptake step responses with as many parameters and without delayed add-on components.
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Affiliation(s)
- Luis Antonio Pereira de Lima
- Mechanical Engineering Department of Polytechnique Montréal, 2500, Chemin de Polytechnique, H3T1J4, Montréal, QC, Canada.
| | - Sofiane Achiche
- Mechanical Engineering Department of Polytechnique Montréal, 2500, Chemin de Polytechnique, H3T1J4, Montréal, QC, Canada.
| | - Ricardo Dantas de Lucas
- Sports Centre, Federal University of Santa Catarina, Brazil Campus Universitário, 88040900, Florianópolis, SC, Brazil.
| | - Maxime Raison
- Mechanical Engineering Department of Polytechnique Montréal, 2500, Chemin de Polytechnique, H3T1J4, Montréal, QC, Canada.
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21
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Inglis EC, Iannetta D, Keir DA, Murias JM. Training-Induced Changes in the Respiratory Compensation Point, Deoxyhemoglobin Break Point, and Maximal Lactate Steady State: Evidence of Equivalence. Int J Sports Physiol Perform 2020; 15:119-125. [PMID: 31034305 DOI: 10.1123/ijspp.2019-0046] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 04/10/2019] [Accepted: 04/17/2019] [Indexed: 11/18/2022]
Abstract
PURPOSE To evaluate whether the coherence in the oxygen uptake (V˙O2) associated with the respiratory compensation point (RCP), near-infrared spectroscopy-derived muscle deoxyhemoglobin ([HHb]) break point ([HHb]BP), and maximal lactate steady state (MLSS) would persist at the midpoint and endpoint of a 7-month training and racing season. METHODS Eight amateur male cyclists were tested in 3 separate phases over the course of a cycling season (PRE, MID, and POST). Testing at each phase included a ramp-incremental test to exhaustion to determine RCP and [HHb]BP. The PRE and POST phases also included constant power output rides to determine MLSS. RESULTS Compared with PRE, V˙O2 at both RCP and [HHb]BP was greater at MID (delta: RCP 0.23 [0.14] L·min-1, [HHb]BP 0.33 [0.17] L·min-1) and POST (delta: RCP 0.21 [0.12], [HHb]BP 0.30 [0.14] L·min-1) (P < .05). V˙O2 at MLSS also increased from PRE to POST (delta: 0.17 [12] L·min-1) (P < .05). V˙O2 was not different at RCP, [HHb]BP, and MLSS at PRE (3.74 [0.34], 3.64 [0.40], 3.78 [0.23] L·min-1) or POST (3.96 [0.25], 3.95 [0.32], 3.94 [0.18] L·min-1) respectively, and RCP (3.98 [0.33] L·min-1) and [HHb]BP (3.97 [0.34] L·min-1) were not different at MID (P > .05). PRE-MID and PRE-POST changes in V˙O2 associated with RCP, [HHb]BP, and MLSS were strongly correlated (range: r = .85-.90) and demonstrated low mean bias (range = -.09 to .12 L·min-1). CONCLUSIONS At all measured time points, V˙O2 at RCP, [HHb]BP, and MLSS were not different. Irrespective of phase comparison, direction, or magnitude of V˙O2 changes, intraindividual changes between each index were strongly related, indicating that interindividual differences were reflected in the group mean response and that their interrelationships are beyond coincidental.
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Iannetta D, Passfield L, Qahtani A, MacInnis MJ, Murias JM. Interlimb differences in parameters of aerobic function and local profiles of deoxygenation during double-leg and counterweighted single-leg cycling. Am J Physiol Regul Integr Comp Physiol 2019; 317:R840-R851. [PMID: 31617749 DOI: 10.1152/ajpregu.00164.2019] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
It is typically assumed that in the context of double-leg cycling, dominant (DOMLEG) and nondominant legs (NDOMLEG) have similar aerobic capacity and both contribute equally to the whole body physiological responses. However, there is a paucity of studies that have systematically investigated maximal and submaximal aerobic performance and characterized the profiles of local muscle deoxygenation in relation to leg dominance. Using counterweighted single-leg cycling, this study explored whether peak O2 consumption (V̇o2peak), maximal lactate steady-state (MLSSp), and profiles of local deoxygenation [HHb] would be different in the DOMLEG compared with the NDOMLEG. Twelve participants performed a series of double-leg and counterweighted single-leg DOMLEG and NDOMLEG ramp-exercise tests and 30-min constant-load trials. V̇o2peak was greater in the DOMLEG than in the NDOMLEG (2.87 ± 0.42 vs. 2.70 ± 0.39 L/min, P < 0.05). The difference in V̇o2peak persisted even after accounting for lean mass (P < 0.05). Similarly, MLSSp was greater in the DOMLEG than in the NDOMLEG (118 ± 31 vs. 109 ± 31 W; P < 0.05). Furthermore, the amplitude of the [HHb] signal during ramp exercise was larger in the DOMLEG than in the NDOMLEG during both double-leg (26.0 ± 8.4 vs. 20.2 ± 8.8 µM, P < 0.05) and counterweighted single-leg cycling (18.5 ± 7.9 vs. 14.9 ± 7.5 µM, P < 0.05). Additionally, the amplitudes of the [HHb] signal were highly to moderately correlated with the mode-specific V̇o2peak values (ranging from 0.91 to 0.54). These findings showed in a group of young men that maximal and submaximal aerobic capacities were greater in the DOMLEG than in the NDOMLEG and that superior peripheral adaptations of the DOMLEG may underpin these differences.NEW & NOTEWORTHY It is typically assumed that the dominant and nondominant legs contribute equally to the whole physiological responses. In this study, we found that the dominant leg achieved greater peak O2 uptake values, sustained greater power output while preserving whole body metabolic stability, and showed larger amplitudes of deoxygenation responses. These findings highlight heterogeneous aerobic capacities of the lower limbs, which have important implications when whole body physiological responses are examined.
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Affiliation(s)
- Danilo Iannetta
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Louis Passfield
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,School of Sport and Exercise Sciences, University of Kent, Canterbury, United Kingdom
| | - Ahmad Qahtani
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Martin J MacInnis
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Juan M Murias
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
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Iannetta D, de Almeida Azevedo R, Keir DA, Murias JM. Establishing the V̇o 2 versus constant-work-rate relationship from ramp-incremental exercise: simple strategies for an unsolved problem. J Appl Physiol (1985) 2019; 127:1519-1527. [PMID: 31580218 DOI: 10.1152/japplphysiol.00508.2019] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The dissociation between constant work rate of O2 uptake (V̇o2) and ramp V̇o2 at a given work rate might be mitigated during slowly increasing ramp protocols. This study characterized the V̇o2 dynamics in response to five different ramp protocols and constant-work-rate trials at the maximal metabolic steady state (MMSS) to characterize 1) the V̇o2 gain (G) in the moderate, heavy, and severe domains, 2) the mean response time of V̇o2 (MRT), and 3) the work rates at lactate threshold (LT) and respiratory compensation point (RCP). Eleven young individuals performed five ramp tests (5, 10, 15, 25, and 30 W/min), four to five time-to-exhaustions for critical power estimation, and two to three constant-work-rate trials for confirmation of the work rate at MMSS. G was greatest during the slowest ramp and progressively decreased with increasing ramp slopes (from ~12 to ~8 ml·min-1·W-1, P < 0.05). The MRT was smallest during the slowest ramp slopes and progressively increased with faster ramp slopes (1 ± 1, 2 ± 1, 5 ± 3, and 10 ± 4, 15 ± 6 W, P < 0.05). After "left shifting" the ramp V̇o2 by the MRT, the work rate at LT was constant regardless of the ramp slope (~150 W, P > 0.05). The work rate at MMSS was 215 ± 55 W and was similar and highly correlated with the work rate at RCP during the 5 W/min ramp (P > 0.05, r = 0.99; Lin's concordance coefficient = 0.99; bias = -3 W; root mean square error = 6 W). Findings showed that the dynamics of V̇o2 (i.e., G) during ramp exercise explain the apparent dichotomy existing with constant-work-rate exercise. When these dynamics are appropriately "resolved", LT is constant regardless of the ramp slope of choice, and RCP and MMSS display minimal variations between each other.NEW & NOTEWORTHY This study demonstrates that the dynamics of V̇o2 during ramp-incremental exercise are dependent on the characteristics of the increments in work rate, such that during slow-incrementing ramp protocols the magnitude of the dissociation between ramp V̇o2 and constant V̇o2 at a given work rate is reduced. Accurately accounting for these dynamics ensures correct characterizations of the V̇o2 kinetics at ramp onset and allows appropriate comparisons between ramp and constant-work-rate exercise-derived indexes of exercise intensity.
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Affiliation(s)
- Danilo Iannetta
- Faculty of Kinesiology, University of Calgary, Calgary, Canada
| | | | - Daniel A Keir
- Department of Medicine, University Health Network, Toronto, Canada
| | - Juan M Murias
- Faculty of Kinesiology, University of Calgary, Calgary, Canada
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Niemeyer M, Leithaeuser R, Beneke R. Oxygen uptake plateau occurrence depends on oxygen kinetics and oxygen deficit accumulation. Scand J Med Sci Sports 2019; 29:1466-1472. [PMID: 31166042 DOI: 10.1111/sms.13493] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Accepted: 05/26/2019] [Indexed: 11/29/2022]
Abstract
We tested the hypothesis that participants with an oxygen uptake ( V ˙ O 2 ) plateau during incremental exercise exhibit a lower VO2 -deficit (VO2DEF )-accumulation in the submaximal intensity domain due to faster ramp and square wave O2 -kinetics. Twenty-six male participants performed a standard ramp test (increment: 30 W·min-1 ), a ramp test with an individualized ramp slope and a two-step (moderate and severe) square wave exercise followed by a V ˙ O 2 m a x -verification bout. VO2DEF was calculated by the difference between individualized ramp test V ˙ O2 and V ˙ O2 -demand estimated from steady-state V ˙ O2 -kinetics. Twenty-four participants verified their V ˙ O2max in the verification test. Ten of them showed a plateau in the individualized ramp test. VO2DEF at the end of this ramp test (4.34 ± 0.60 vs 4.54 ± 0.43 L) was not different between the plateau and the non-plateau group (P > 0.05). The plateau group had a significantly (P < 0.05) lower VO2DEF 2 minutes before termination of the individualized ramp test (2.24 ± 0.40 vs 2.78 ± 0.33 L). This coincided with a shorter mean response time (43 ± 9 vs 53 ± 7 seconds), a higher increase in V ˙ O2 per W (10.1 ± 0.2 vs 9.2 ± 0.5 mL·min-1 ·W-1 ) at the individualized ramp test as well as shorter time constants of moderate (36 ± 6 vs 48 ± 7 seconds) and severe (62 ± 9 vs 86 ± 10 seconds) square wave kinetics (all P < 0.05). We conclude that the V ˙ O2 -plateau occurrence requires a fast V ˙ O2 -kinetics and a low VO2DEF -accumulation at intensities below V ˙ O2max .
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Affiliation(s)
- Max Niemeyer
- Institute of Sports Science and Motology, Philipps-University Marburg, Marburg, Germany
| | - Renate Leithaeuser
- Institute of Sports Science and Motology, Philipps-University Marburg, Marburg, Germany
| | - Ralph Beneke
- Institute of Sports Science and Motology, Philipps-University Marburg, Marburg, Germany
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25
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IANNETTA DANILO, MURIAS JUANM, KEIR DANIELA. A Simple Method to Quantify the V˙O2 Mean Response Time of Ramp-Incremental Exercise. Med Sci Sports Exerc 2019; 51:1080-1086. [DOI: 10.1249/mss.0000000000001880] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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26
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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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KEIR DANIELA, POGLIAGHI SILVIA, MURIAS JUANM. The Respiratory Compensation Point and the Deoxygenation Break Point Are Valid Surrogates for Critical Power and Maximum Lactate Steady State. Med Sci Sports Exerc 2018; 50:2375-2378. [DOI: 10.1249/mss.0000000000001698] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Korzeniewski B, Rossiter HB, Zoladz JA. Mechanisms underlying extremely fast muscle V˙O 2 on-kinetics in humans. Physiol Rep 2018; 6:e13808. [PMID: 30156055 PMCID: PMC6113137 DOI: 10.14814/phy2.13808] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 07/02/2018] [Indexed: 01/31/2023] Open
Abstract
The time constant of the primary phase of pulmonary V˙O2 on-kinetics (τp ), which reflects muscle V˙O2 kinetics during moderate-intensity exercise, is about 30 s in young healthy untrained individuals, while it can be as low as 8 s in endurance-trained athletes. We aimed to determine the intramuscular factors that enable very low values of t0.63 to be achieved (analogous to τp , t0.63 is the time to reach 63% of the V˙O2 amplitude). A computer model of oxidative phosphorylation (OXPHOS) in skeletal muscle was used. Muscle t0.63 was near-linearly proportional to the difference in phosphocreatine (PCr) concentration between rest and work (ΔPCr). Of the two main factors that determine t0.63 , a huge increase in either OXPHOS activity (six- to eightfold) or each-step activation (ESA) of OXPHOS intensity (>3-fold) was needed to reduce muscle t0.63 from the reference value of 29 s (selected to represent young untrained subjects) to below 10 s (observed in athletes) when altered separately. On the other hand, the effect of a simultaneous increase of both OXPHOS activity and ESA intensity required only a twofold elevation of each to decrease t0.63 below 10 s. Of note, the dependence of t0.63 on OXPHOS activity and ESA intensity is hyperbolic, meaning that in trained individuals a large increase in OXPHOS activity and ESA intensity are required to elicit a small reduction in τp . In summary, we postulate that the synergistic action of elevated OXPHOS activity and ESA intensity is responsible for extremely low τp (t0.63 ) observed in highly endurance-trained athletes.
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Affiliation(s)
| | - Harry B. Rossiter
- Rehabilitation Clinical Trials CenterDivision of Pulmonary Critical Care Physiology and MedicineLos Angeles Biomedical Research Institute at Harbor‐UCLA Medical CenterTorranceCalifornia
- Faculty of Biological SciencesUniversity of LeedsLeedsUnited Kingdom
| | - Jerzy A. Zoladz
- Department of Muscle PhysiologyChair of Physiology and BiochemistryFaculty of RehabilitationUniversity School of Physical EducationKrakówPoland
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de Lima LAP, Raison M, Achiche S, de Lucas RD. Second order modeling for the pulmonary oxygen uptake on-kinetics: a comprehensive solution for overshooting and non-overshooting responses to exercise. J Appl Physiol (1985) 2018; 125:1315-1328. [PMID: 29901434 DOI: 10.1152/japplphysiol.00147.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The human oxygen uptake (VO2) response to step-like increases in work rate is currently modeled by a First Order System Multi-Exponential (FOME) arrangement. Due to their first order nature, none of FOME model's exponentials is able to model an overshoot in the oxygen uptake kinetics (OVO2K). Nevertheless, OVO2K phenomena are observed in the fundamental component of trained individuals' step responses. We hypothesized that a Mixed Multi-Exponential (MiME) model, where the fundamental component is modeled with a second instead of a first order system, would present a better overall performance than that of the traditional FOME model in fitting VO2 on-kinetics at all work rates, either presenting or not OVO2K. Fourteen well-trained male cyclists performed three step on-transitions at each of three work rates below their individual lactate thresholds' work rate (WRLT), and two step on-transitions at each of two exercise intensities above WRLT. Averaged responses for each WR were fitted with MiME and FOME models. Root mean standard errors were used for comparisons between fitting performances. Additionally, a methodology for detecting and quantifying OVO2K phenomena is proposed. Second order solutions performed better (p<0.000) than the first order exponential when the OVO2K was present, and did not differ statistically (p=0.973) in its absence. OVO2K occurrences were observed below and, for the first time, above WRLT (88 and 7%, respectively). We concluded that the MiME model is more adequate and comprehensive than the FOME model in explaining VO2 step on-transient responses, considering cases with or without OVO2K altogether.
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Affiliation(s)
| | - Maxime Raison
- Mechanical Engineering, Polytechinque Montreal, Canada
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30
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Iannetta D, Fontana FY, Maturana FM, Inglis EC, Pogliaghi S, Keir DA, Murias JM. An equation to predict the maximal lactate steady state from ramp-incremental exercise test data in cycling. J Sci Med Sport 2018; 21:1274-1280. [PMID: 29803737 DOI: 10.1016/j.jsams.2018.05.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 03/07/2018] [Accepted: 05/08/2018] [Indexed: 11/24/2022]
Abstract
OBJECTIVES The maximal lactate steady state (MLSS) represents the highest exercise intensity at which an elevated blood lactate concentration ([Lac]b) is stabilized above resting values. MLSS quantifies the boundary between the heavy-to-very-heavy intensity domains but its determination is not widely performed due to the number of trials required. DESIGN This study aimed to: (i) develop a mathematical equation capable of predicting MLSS using variables measured during a single ramp-incremental cycling test and (ii) test the accuracy of the optimized mathematical equation. METHODS The predictive MLSS equation was determined by stepwise backward regression analysis of twelve independent variables measured in sixty individuals who had previously performed ramp-incremental exercise and in whom MLSS was known (MLSSobs). Next, twenty-nine different individuals were prospectively recruited to test the accuracy of the equation. These participants performed ramp-incremental exercise to exhaustion and two-to-three 30-min constant-power output cycling bouts with [Lac]b sampled at regular intervals for determination of MLSSobs. Predicted MLSS (MLSSpred) and MLSSobs in both phases of the study were compared by paired t-test, major-axis regression and Bland-Altman analysis. RESULTS The predictor variables of MLSS were: respiratory compensation point (Wkg-1), peak oxygen uptake (V˙O2peak) (mlkg-1min-1) and body mass (kg). MLSSpred was highly correlated with MLSSobs (r=0.93; p<0.01). When this equation was tested on the independent group, MLSSpred was not different from MLSSobs (234±43 vs. 234±44W; SEE 4.8W; r=0.99; p<0.01). CONCLUSIONS These data support the validity of the predictive MLSS equation. We advocate its use as a time-efficient alternative to traditional MLSS testing in cycling.
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Affiliation(s)
| | - Federico Y Fontana
- Department of Neurological and Movement Sciences, University of Verona, Italy; Pro Motus, Italy
| | | | | | - Silvia Pogliaghi
- Department of Neurological and Movement Sciences, University of Verona, Italy
| | - Daniel A Keir
- University Health Network, Department of Medicine, Canada
| | - Juan M Murias
- Faculty of Kinesiology, University of Calgary, Canada.
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31
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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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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: 66] [Impact Index Per Article: 11.0] [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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Affiliation(s)
- Jeffrey A Leo
- Menzies Health Institute Queensland Griffith University Gold Coast, Queensland, AUSTRALIA Menzies Health Institute Queensland Griffith University Gold Coast, Queensland, AUSTRALIA Division of Cardiovascular Diseases Mayo Clinic, Rochester, MN
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34
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Mattioni Maturana F, Keir DA, McLay KM, Murias JM. Critical power testing or self-selected cycling: Which one is the best predictor of maximal metabolic steady-state? J Sci Med Sport 2017; 20:795-799. [DOI: 10.1016/j.jsams.2016.11.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 10/05/2016] [Accepted: 11/06/2016] [Indexed: 10/20/2022]
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35
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LEO JEFFREYA, SABAPATHY SURENDRAN, SIMMONDS MICHAELJ, CROSS TROYJ. The Respiratory Compensation Point is Not a Valid Surrogate for Critical Power. Med Sci Sports Exerc 2017; 49:1452-1460. [DOI: 10.1249/mss.0000000000001226] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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36
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McCrudden MC, Keir DA, Belfry GR. The effects of short work vs. longer work periods within intermittent exercise on V̇o 2p kinetics, muscle deoxygenation, and energy system contribution. J Appl Physiol (1985) 2017; 122:1435-1444. [PMID: 28336535 DOI: 10.1152/japplphysiol.00514.2016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 02/21/2017] [Accepted: 03/16/2017] [Indexed: 11/22/2022] Open
Abstract
We examined the effects of inserting 3-s recovery periods during high-intensity cycling exercise at 25-s and 10-s intervals on pulmonary oxygen uptake (V̇o2p), muscle deoxygenation [deoxyhemoglobin (HHb)], their associated kinetics (τ), and energy system contributions. Eleven men (24 ± 3 yr) completed two trials of three cycling protocols: an 8-min continuous protocol (CONT) and two 8-min intermittent exercise protocols with work-to-rest periods of 25 s to 3 s (25INT) and 10 s to 3 s (10INT). Each protocol began with a step-transition from a 20-W baseline to a power output (PO) of 60% between lactate threshold and maximal V̇o2p (Δ60). This PO was maintained for 8 min in CONT, whereas 3-s periods of 20-W cycling were inserted every 10 s and 25 s after the transition to Δ60 in 10INT and 25INT, respectively. Breath-by-breath gas exchange measured by mass spectrometry and turbine and vastus lateralis [HHb] measured by near-infrared spectroscopy were recorded throughout. Arterialized-capillary lactate concentration ([Lac-]) was obtained before and 2 min postexercise. The τV̇o2p was lowest (P < 0.05) for 10INT (24 ± 4 s) and 25INT (23 ± 5 s) compared with CONT (28 ± 4 s), whereas HHb kinetics did not differ (P > 0.05) between conditions. Postexercise [Lac-] was lowest (P < 0.05) for 10INT (7.0 ± 1.7 mM), was higher for 25INT (10.3 ± 1.9 mM), and was greatest in CONT (14.3 ± 3.1 mM). Inserting 3-s recovery periods during heavy-intensity exercise speeded V̇o2p kinetics and reduced overall V̇o2p, suggesting an increased reliance on PCr-derived phosphorylation during the work period of INT compared with an identical PO performed continuously.NEW & NOTEWORTHY We report novel observations on the effects of differing heavy-intensity work durations between 3-s recovery periods on pulmonary oxygen uptake (V̇o2p) kinetics, muscle deoxygenation, and energy system contributions. Relative to continuous exercise, V̇o2p kinetics are faster in intermittent exercise, and increased frequency of 3-s recovery periods improves microvascular O2 delivery and reduces V̇o2p and arterialized-capillary lactate concentration. The metabolic burden of identical intensity work is altered when performed intermittently vs. continuously.
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Affiliation(s)
- Michael C McCrudden
- School of Kinesiology, Canadian Center for Activity and Aging, University of Western Ontario, London, Ontario, Canada
| | - Daniel A Keir
- School of Kinesiology, Canadian Center for Activity and Aging, University of Western Ontario, London, Ontario, Canada
| | - Glen R Belfry
- School of Kinesiology, Canadian Center for Activity and Aging, University of Western Ontario, London, Ontario, Canada
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Roman MA, Rossiter HB, Casaburi R. Exercise, ageing and the lung. Eur Respir J 2016; 48:1471-1486. [PMID: 27799391 DOI: 10.1183/13993003.00347-2016] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 06/27/2016] [Indexed: 02/07/2023]
Abstract
This review provides a pulmonary-focused description of the age-associated changes in the integrative physiology of exercise, including how declining lung function plays a role in promoting multimorbidity in the elderly through limitation of physical function. We outline the ageing of physiological systems supporting endurance activity: 1) coupling of muscle metabolism to mechanical power output; 2) gas transport between muscle capillary and mitochondria; 3) matching of muscle blood flow to its requirement; 4) oxygen and carbon dioxide carrying capacity of the blood; 5) cardiac output; 6) pulmonary vascular function; 7) pulmonary oxygen transport; 8) control of ventilation; and 9) pulmonary mechanics and respiratory muscle function. Deterioration in function occurs in many of these systems in healthy ageing. Between the ages of 25 and 80 years pulmonary function and aerobic capacity each decline by ∼40%. While the predominant factor limiting exercise in the elderly likely resides within the function of the muscles of ambulation, muscle function is (at least partially) rescued by exercise training. The age-associated decline in pulmonary function, however, is not recovered by training. Thus, loss in pulmonary function may lead to ventilatory limitation in exercise in the active elderly, limiting the ability to accrue the health benefits of physical activity into senescence.
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Affiliation(s)
- Michael A Roman
- Division of Respiratory Medicine, Rockyview Hospital, University of Calgary, Calgary, AB, Canada
| | - Harry B Rossiter
- Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, Los Angeles Biomedical Research Institute, Torrance, CA, USA.,Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Richard Casaburi
- Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, Los Angeles Biomedical Research Institute, Torrance, CA, USA
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Nederveen JP, Keir DA, Love LK, Rossiter HB, Kowalchuk JM. Effect of heavy-intensity 'priming' exercise on oxygen uptake and muscle deoxygenation kinetics during moderate-intensity step-transitions initiated from an elevated work rate. Respir Physiol Neurobiol 2016; 235:62-70. [PMID: 27693390 DOI: 10.1016/j.resp.2016.09.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 08/26/2016] [Accepted: 09/26/2016] [Indexed: 10/20/2022]
Abstract
We examined the effect of heavy-intensity 'priming' exercise on the rate of adjustment of pulmonary O2 uptake (τV˙O2p) initiated from elevated intensities. Fourteen men (separated into two groups: τV˙O2p≤25s [Fast] or τV˙O2p>25s [Slow]) completed step-transitions from 20W to 45% lactate threshold (LT; lower-step, LS) and 45% to 90%LT (upper-step, US) performed (i) without; and (ii) with US preceded by heavy-intensity exercise (HUS). Breath-by-breath V˙O2p and near-infrared spectroscopy-derived muscle deoxygenation ([HHb+Mb]) were measured. Compared to LS, τV˙O2p was greater (p<0.05) in US in both Fast (LS, 19±4s; US, 30±4s) and Slow (LS, 25±5s; US, 40±11s) with τV˙O2p in US being lower (p<0.05) in Fast. In HUS, τV˙O2p in Slow was reduced (28±8s, p<0.05) and was not different (p>0.05) from LS or Fast group US. In Slow, τ[HHb+Mb] increased (p<0.05) in US relative to HUS; this finding coupled with a reduced τV˙O2p indicates a priming-induced improvement in matching of muscle O2 delivery-to-O2 utilization during transitions from elevated intensities in those with Slow but not Fast V˙O2p kinetics.
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Affiliation(s)
- Joshua P Nederveen
- Canadian Centre for Activity and Aging, London, ON, Canada; School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | - Daniel A Keir
- Canadian Centre for Activity and Aging, London, ON, Canada; School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | - Lorenzo K Love
- Canadian Centre for Activity and Aging, London, ON, Canada; School of Kinesiology, The University of Western Ontario, London, ON, 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, CA, USA; Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - John M Kowalchuk
- Canadian Centre for Activity and Aging, London, ON, Canada; School of Kinesiology, The University of Western Ontario, London, ON, Canada; Department of Physiology and Pharmacology, The University of Western Ontario, London, ON, Canada.
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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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