Articles de revues : « VO2p kinetic »

1

Grassi, B., D. C. Poole, R. S. Richardson, D. R. Knight, B. K. Erickson et P. D. Wagner. « Muscle O2 uptake kinetics in humans : implications for metabolic control ». Journal of Applied Physiology 80, n^o 3 (1 mars 1996) : 988–98. http://dx.doi.org/10.1152/jappl.1996.80.3.988.

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Muscle O2 uptake (VO2) kinetics in response to an augmented energetic requirement (on-transition) has never been directly determined in humans. We have developed a constant-infusion thermodilution technique that allowed rapid measurements of leg blood flow (Qleg) and, in conjunction with frequent serial measurement of arteriovenous O2 content difference across the leg [(Ca - Cv)O2leg], permitted the determination of the VO2 of the leg (VO2leg) at 3- to 4-s time intervals. VO2leg kinetics during the on-transition was taken as a close approximation of muscle VO2 (VO2mus) kinetics. Alveolar VO2 (VO2A), Qleg, leg O2 delivery [(Q.CaO2leg)], (Ca - Cv)O2leg, and VO2leg kinetics were determined in six trained subjects [age 22.8 +/- 4.4 (SD) yr; maximal O2 uptake 59.1 +/- 5.3 ml.kg-1.min-1] during the transition from unloaded pedaling to a workload (loaded pedaling; LP) (183 +/- 20 W) well below the previously determined ventilatory threshold. For all variables, two distinct phases were recognized. During the first 10-15 s of loaded pedaling (phase I), VO2A, Qleg, and (Q.CaO2)leg increased rapidly, whereas VO2leg increased only slightly and (Ca - Cv)O2leg actually decreased. After phase I, all variables showed a monoexponential increase (phase II), with similar time courses [slightly faster for (Ca - CV)O2leg]. In a consideration of both phases, the half times of the responses among variables were not significantly different: 25.5 +/- 2.6 s for VO2A, 26.6 +/- 7.6 s for Qleg, 26.9 +/- 8.3 s for (Q.CaO2leg, 23.5 +/- 1.3 s for (Ca - Cv)O2leg, and 27.9 +/- 5.7 s for VO2leg. We conclude that during the on-transition the kinetics of VO2A and VO2leg, as measured by these methods, are similar. The analysis of the early phase (first 10-15 s) of the on-transition indicates that bulk delivery of O2 to the working muscles is not limiting VO2leg kinetics. However, the present results cannot discriminate between maldistribution of blood flow/VO2 vs. inertia the intracellular oxidative machinery as the limiting factor.

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Stathokostas, Liza, John M. Kowalchuk, Robert J. Petrella et Donald H. Paterson. « Moderate and heavy oxygen uptake kinetics in postmenopausal women ». Applied Physiology, Nutrition, and Metabolism 34, n^o 6 (décembre 2009) : 1065–72. http://dx.doi.org/10.1139/h09-107.

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The lack of estrogen in postmenopausal women not using hormone replacement therapy (HRT), compared with those using HRT, may reduce submaximal blood flow during exercise and result in an oxygen delivery limitation constraining oxygen uptake (VO2) kinetics. The adaptation of pulmonary VO2 (VO2p) during the transition to exercise in older women was examined in this study. Thirty-one healthy postmenopausal women (mean age, 61 ± 6 years), 15 not using HRT and 16 using HRT, performed repeated exercise transitions (6 min) on a cycle, to work rates corresponding to 80% of estimated ventilatory threshold (moderate-intensity exercise) and to Δ50 (heavy-intensity exercise). There was no difference in moderate-intensity τVO2p between non-HRT (40 ± 9 s) and HRT (41 ± 9 s) women. Similarly, there was no difference in heavy-intensity τVO2p between non-HRT (44 ± 8 s) and HRT (45 ± 8 s) women. Thus, HRT did not affect the slowing of VO2 kinetics of older women.

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Buekers, Joren, Jan Theunis, Alberto Peña Fernández, Emiel F. M. Wouters, Martijn A. Spruit, Patrick De Boever et Jean-Marie Aerts. « Box-Jenkins Transfer Function Modelling for Reliable Determination of VO2 Kinetics in Patients with COPD ». Applied Sciences 9, n^o 9 (1 mai 2019) : 1822. http://dx.doi.org/10.3390/app9091822.

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Oxygen uptake (VO2) kinetics provide information about the ability to respond to the increased physical load during a constant work rate test (CWRT). Box-Jenkins transfer function (BJ-TF) models can extract kinetic features from the phase II VO2 response during a CWRT, without being affected by unwanted noise contributions (e.g., phase I contribution or measurement noise). CWRT data of 18 COPD patients were used to compare model fits and kinetic feature values between BJ-TF models and three typically applied exponential modelling methods. Autocorrelation tests and normalised root-mean-squared error values (BJ-TF: 2.8 ± 1.3%; exponential methods A, B and C: 10.5 ± 5.8%, 11.3 ± 5.2% and 12.1 ± 7.0%; p < 0.05) showed that BJ-TF models, in contrast to exponential models, could account for the most important noise contributions. This led to more reliable kinetic feature values compared to methods A and B (e.g., mean response time (MRT), BJ-TF: 74 ± 20 s; methods A-B: 100 ± 56 s–88 ± 52 s; p < 0.05). Only exponential modelling method C provided kinetic feature values comparable to BJ-TF features values (e.g., MRT: 75 ± 20 s). Based on theoretical considerations, we recommend using BJ-TF models, rather than exponential models, for reliable determinations of VO2 kinetics.

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Larson, Rebecca D., Monica Barton, John W. Farrell III, Gregory S. Cantrell, David J. Lantis, Christopher D. Black et Carl J. Ade. « Evaluation of Oxygen Uptake Kinetic Asymmetries in Patients with Multiple Sclerosis : A Pilot Study ». International Journal of Kinesiology and Sports Science 6, n^o 4 (31 octobre 2018) : 21. http://dx.doi.org/10.7575/aiac.ijkss.v.6n.4p.21.

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Background of Study: Observations of limb to limb differences (bilateral asymmetry) in leg strength, power, peak oxygen uptake (VO2) and bone mineral density has been reported in individuals with Multiple Sclerosis (MS). Objetives: The purpose of this study was to quantify the magnitude of bilateral asymmetries in oxygen uptake (VO2) kinetics response to single leg cycling (SLC) in relapsing-remitting multiple sclerosis (MS) patients. Methods: Five MSpatients (2 men, 3 women; age 43±7 yrs) performed constant work rate SLC trials to determine VO2 kinetics in each leg. Asymmetry scores were used to quantify the magnitude of the bilateral asymmetries. Results: Significant asymmetries were seen in VO2 peak and parameters of VO2 kinetics. VO2peak asymmetry score was significantly different than 0% (p=0.015). Similarly,significant asymmetry for VO2 kinetic response to exercise as mean response time was observed (p=0.03). In addition the VO2 response to exercise resulted in a significant asymmetry in VO2 deficit between legs (p=0.03). No correlation between EDSS scores and any asymmetry scores existed. Conclusions: These findings provide insight into the potential differences in metabolic perturbation and limb specific symptomatic fatigue within the MS population.

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Cleland, Sarah Margaret, Juan Manuel Murias, John Michael Kowalchuk et Donald Hugh Paterson. « Effects of prior heavy-intensity exercise on oxygen uptake and muscle deoxygenation kinetics of a subsequent heavy-intensity cycling and knee-extension exercise ». Applied Physiology, Nutrition, and Metabolism 37, n^o 1 (février 2012) : 138–48. http://dx.doi.org/10.1139/h11-143.

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This study examined the effects of prior heavy-intensity exercise on the adjustment of pulmonary oxygen uptake (VO2p) and muscle deoxygenation Δ[HHb] during the transition to subsequent heavy-intensity cycling (CE) or knee-extension (KE) exercise. Nine young adults (aged 24 ± 5 years) performed 4 repetitions of repeated bouts of heavy-intensity exercise separated by light-intensity CE and KE, which included 6 min of baseline exercise, a 6-min step of heavy-intensity exercise (H1), 6-min recovery, and a 6-min step of heavy-intensity exercise (H2). Exercise was performed at 50 r·min–1 or contractions per minute per leg. Oxygen uptake (VO2) mean response time was ∼20% faster (p < 0.05) during H2 compared with H1 in both modalities. Phase 2 time constants (τ) were not different between heavy bouts of CE (H1, 29.6 ± 6.5 s; H2, 28.0 ± 4.6 s) or KE exercise (H1, 31.6 ± 6.7 s; H2, 29.8 ± 5.6 s). The VO2 slow component amplitude was lower (p < 0.05) in H2 in both modalities (CE, 0.19 ± 0.06 L·min–1; KE, 0.12 ± 0.07 L·min–1) compared with H1 (CE, 0.29 ± 0.09 L·min–1; KE, 0.18 ± 0.07 L·min–1), with the contribution of the slow component to the total VO2 response reduced (p < 0.05) in H2 during both exercise modes. The effective τHHb was similar between bouts for CE (H1, 18.2 ± 3.0 s; H2, 18.0 ± 3.6 s) and KE exercise (H1, 26.0 ± 7.0 s; H2, 24.0 ± 5.8 s). The ΔHHb slow component was reduced during H2 in both CE and KE (p < 0.05). In conclusion, phase 2 VO2p was unchanged with priming exercise; however, a faster mean response time of VO2p during the heavy-intensity exercise preceded by a priming heavy-intensity exercise was attributed to a smaller slow component and reduced muscle deoxygenation indicative of improved muscle O2 delivery during the second bout of exercise.

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Morton, R. H. « Delayed or accelerated oxygen uptake kinetics in the transition from prior exercise ? » Journal of Applied Physiology 62, n^o 2 (1 février 1987) : 844–46. http://dx.doi.org/10.1152/jappl.1987.62.2.844.

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Reported experimental findings are at variance with each other on the question as to whether O2 uptake (VO2) kinetics are delayed, advanced, or remain unaltered in the transition from prior exercise. Critical examination of these studies tend to suggest that not a great deal of reliance can be placed on their evidence in attempting to resolve the question. They seem to display a disregard for the theoretical properties of the VO2 kinetic model used; in some cases incorrect statistical inferences appear to have been made; most are mathematically incomplete; and the experimental designs have not been appropriately chosen so as to examine the whole question of altered VO2 kinetics. These points are detailed and discussed so that future designed experiments obtain sufficient reliable evidence with which to resolve the question.

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Shoemaker, J. K., L. Hodge et R. L. Hughson. « Cardiorespiratory kinetics and femoral artery blood velocity during dynamic knee extension exercise ». Journal of Applied Physiology 77, n^o 6 (1 décembre 1994) : 2625–32. http://dx.doi.org/10.1152/jappl.1994.77.6.2625.

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The kinetics of femoral artery mean blood velocity (MBV; measured by pulsed Doppler) and whole body oxygen uptake (VO2; measured breath by breath) were assessed from the time constant during the on (tau on) and off (tau off) transients to step changes in work rate between complete rest and dynamic knee extension (KE) exercise. Six healthy men performed 5 min of seated KE exercise, with each leg alternately raising and lowering a weight (10% maximum voluntary contraction) over a 2-s duty cycle. Because kinetic analysis of VO2 kinetics during KE exercise is a new approach, the VO2 responses were also evaluated during the on and off transitions to the more familiar upright cycling exercise in which the magnitude of increase in VO2 and cardiac output was similar to that during KE exercise. During KE exercise, VO2 tau on [mean 72.2 +/- 11.2 (SE) s] was slower than VO2 tau off (33.3 +/- 1.8 s; P < 0.01). Cardiac output, measured with impedance cardiography, was not different for tau on (67.1 +/- 20.0 s) compared with that for tau off (52.9 +/- 7.6 s). Likewise, MBV tau on (34.5 +/- 3.9 s) was not different from tau off (35.3 +/- 3.2 s). During cycling, the VO2 tau on (18.0 +/- 2.4 s) and tau off (30.7 +/- 1.2 s) were both faster than KE VO2 tau on (P < 0.01). Even though the MBV kinetics indicated a rapid adaptation of blood flow during KE exercise, there was a slow adaptation of VO2. A transient hyperemia immediately on cessation of KE exercise, indicated by both MBV and calculated systemic vascular conductance responses, suggested that blood flow might have been inadequate and could have contributed to the delayed adaptation of VO2 at the onset of exercise, although other explanations are possible.

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Hughson, R. L., J. E. Cochrane et G. C. Butler. « Faster O2 uptake kinetics at onset of supine exercise with than without lower body negative pressure ». Journal of Applied Physiology 75, n^o 5 (1 novembre 1993) : 1962–67. http://dx.doi.org/10.1152/jappl.1993.75.5.1962.

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The kinetics of oxygen uptake (VO2) were observed at the onset of submaximal cycling exercise in seven men and one woman [mean age 22.6 +/- 0.9 (SE) yr] in the upright and supine positions and the supine position with -40 mmHg lower body negative pressure (LBNP). There was no significant difference for peak VO2 and ventilatory threshold between the supine (3,081 +/- 133 and 1,954 +/- 138 ml/min, respectively) and the supine + LBNP positions (3,062 +/- 152 and 1,973 +/- 122 ml/min); however, both were reduced compared with upright exercise (3,483 +/- 200 and 2,353 +/- 125 ml/min). Kinetic analysis applied to six repetitions by each subject indicated a slowing from a mean total lag time (time required to achieve 63% of the difference in VO2 between baseline and new steady state) of 36.3 +/- 2.7 s in upright exercise to 44.1 +/- 3.5 s in the supine position. However, total lag time for the supine + LBNP position (36.0 +/- 2.8 s) did not differ from upright exercise but was significantly faster than supine exercise. These data have been interpreted in support of an O2 transport limitation to VO2 kinetics at the onset of supine exercise that is countered by LBNP, likely through a more rapid increase in perfusion to the exercising muscle at these submaximal work rates.

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Xing, H. C., J. E. Cochrane, Y. Yamamoto et R. L. Hughson. « Frequency domain analysis of ventilation and gas exchange kinetics in hypoxic exercise ». Journal of Applied Physiology 71, n^o 6 (1 décembre 1991) : 2394–401. http://dx.doi.org/10.1152/jappl.1991.71.6.2394.

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The kinetics of O2 up-take (VO2), CO2 output (VCO2), ventilation (VE), and heart rate (HR) were studied during exercise in normoxia and hypoxia [inspired O2 fraction (FIO2) 0.14]. Eight male subjects each completed 6 on- and off-step transitions in work rate (WR) from low (25 W) to moderate (100–125 W) levels and a pseudorandom binary sequence (PRBS) exercise test in which WR was varied between the same WRs. Breath-by-breath data were linearly interpolated to yield 1-s values. After the first PRBS cycle had been omitted as a warm-up, five cycles were ensemble-averaged before frequency domain analysis by standard Fourier methods. The step data were fit by a two-component (three for HR) exponential model to estimate kinetic parameters. In the steady state of low and moderate WRs, each value of VO2, VCO2, VE, and HR was significantly greater during hypoxic than normoxic exercise (P less than 0.05) with the exception of VCO2 (low WR). Hypoxia slowed the kinetics of VO2 and HR in on- and off-step transitions and speeded up the kinetics of VCO2 and VE in the on-transition and of VE in the off-transition. Frequency domain analysis confined to the range of 0.003–0.019 Hz for the PRBS tests indicated reductions in amplitude and greater phase shifts in the hypoxic tests for VO2 and HR at specific frequencies, whereas amplitude tended to be greater with little change in phase shift for VCO2 and VE during hypoxic tests.(ABSTRACT TRUNCATED AT 250 WORDS)

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Lin, Xueyan, Wenyue Li, Xuan Pan, Shu Wang et Zhaoyang Fan. « Electrocatalytic and Conductive Vanadium Oxide on Carbonized Bacterial Cellulose Aerogel for the Sulfur Cathode in Li-S Batteries ». Batteries 9, n^o 1 (26 décembre 2022) : 14. http://dx.doi.org/10.3390/batteries9010014.

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Many transition-metal-oxide-based catalysts have been investigated to chemically bind soluble lithium polysulfides and accelerate their redox kinetics in lithium-sulfur (Li-S) battery chemistry. However, the intrinsic poor electrical conductivities of these oxides restrict their catalytic performance, consequently limiting the sulfur utilization and the rate performance of Li-S batteries. Herein, we report a freestanding electrocatalytic sulfur host consisting of hydrogen-treated VO2 nanoparticles (H-VO2) anchored on nitrogen-doped carbonized bacterial cellulose aerogels (N-CBC). The hydrogen treatment enables the formation and stabilization of the rutile VO2(R) phase with metallic conductivity at room temperature, significantly enhancing its catalytic capability compared to the as-synthesized insulative VO2(M) phase. Several measurements characterize the electrocatalytic performance of this unique H-VO2@N-CBC structure. In particular, the two kinetic barriers between S8, polysulfides, and Li2S are largely reduced by 28.2 and 43.3 kJ/mol, respectively. Accordingly, the Li-S battery performance, in terms of sulfur utilization and charge/discharge rate, is greatly improved. This work suggests an effective strategy to develop conductive catalysts based on a typical transition metal oxide (VO2) for Li-S batteries.

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Phillips, S. M., H. J. Green, M. J. MacDonald et R. L. Hughson. « Progressive effect of endurance training on VO2 kinetics at the onset of submaximal exercise ». Journal of Applied Physiology 79, n^o 6 (1 décembre 1995) : 1914–20. http://dx.doi.org/10.1152/jappl.1995.79.6.1914.

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The rates of increase in O2 uptake (VO2) after step changes in work rate from 25 W to 60% of pretraining peak VO2 (VO2 peak) were measured at various times during an endurance training program (2 h/day at 60% pretraining VO2 peak). Seven untrained males [23 +/- 1 (SE) yr] performed a series of repeated step changes in work rate before training (PRE) and after 4 days (4D), 9 days (9D), and 30 days (30D) of training. VO2 kinetic responses were determined from breath-by-breath data averaged across four repetitions and analyzed using a two-component exponential model. Mean response time (time taken to reach 63% of steady-state VO2) was faster (P < 0.01) than PRE (38.1 +/- 2.6 s) at both 4D (34.9 +/- 2.4 s) and 9D (32.5 +/- 1.8 s) and was faster (P < 0.01) at 30D than at all other times (28.3 +/- 1.0 s). Blood lactate concentrations (after 6 min of cycling) were also lower at 4D and 9D than PRE (P < 0.01) and were lower at 30D than at all other times (P < 0.01). VO2 peak was unchanged from PRE (3.52 +/- 0.20 l/min) at 8D (3.55 +/- 0.20 l/min) but was increased (P < 0.01) at 30D (3.89 +/- 0.18 l/min). Muscle oxidative capacity (maximal citrate synthase activity) was not significantly increased until 30D (P < 0.01). It is concluded that at least part of the acceleration of whole body VO2 kinetics with endurance training is a rapid phenomenon, occurring before changes in VO2 peak and/or muscle oxidative potential.

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Chilibeck, Philip D., Donald H. Paterson, Robert J. Petrella et David A. Cunningham. « The Influence of Age and Cardiorespiratory Fitness on Kinetics of Oxygen Uptake ». Canadian Journal of Applied Physiology 21, n^o 3 (1 juin 1996) : 185–96. http://dx.doi.org/10.1139/h96-015.

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The purpose of this study was to determine the influences of ageing and cardiorespiratory fitness on kinetics of VO2 during the transition to exercise of moderate intensity. Subjects performed three transitions to and from a 6-minute square wave constant load, at an intensity corresponding to 90% of ventilatory threshold (VET), to determine VO2 kinetics. The young group had a significantly faster time constant of VO2 (τVO2). τVO2 was significantly correlated with VO2max for both young and old groups; however, the slope of the τVO2 - VO2max regression equation was steeper for the old group, indicating that fit older subjects had VO2 kinetics that approached those of fit young. A multiple linear regression indicated that relative fitness was the strongest significant predictor of τVO2, followed by sex and age. Although VO2 kinetics are definitely slowed with age, relative levels of cardiorespiratory fitness also have a great influence on the dynamic response of VO2. Key words: VO2max, ventilatory threshold, heart rate kinetics

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Lai, Nicola, Melita M. Nasca, Marco A. Silva, Fatima T. Silva, Brian J. Whipp et Marco E. Cabrera. « Influence of exercise intensity on pulmonary oxygen uptake kinetics at the onset of exercise and recovery in male adolescents ». Applied Physiology, Nutrition, and Metabolism 33, n^o 1 (février 2008) : 107–17. http://dx.doi.org/10.1139/h07-154.

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The dynamics of the pulmonary oxygen uptake (VO2) responses to square-wave changes in work rate can provide insight into bioenergetic processes sustaining and limiting exercise performance. The dynamic responses at the onset of exercise and during recovery have been investigated systematically and are well characterized at all intensities in adults; however, they have not been investigated completely in adolescents. We investigated whether adolescents display a slow component in their VO2 on- and off-kinetic responses to heavy- and very heavy-intensity exercise, as demonstrated in adults. Healthy African American male adolescents (n = 9, 14–17 years old) performed square-wave transitions on a cycle ergometer (from and to a baseline work rate of 20 W) to work rates of moderate (M), heavy (H), and very heavy (VH) intensity. In all subjects, the VO2 on-kinetics were best described with a single exponential at moderate intensity (τ1, on = 36 ± 11 s) and a double exponential at heavy (τ1, on = 29 ± 9 s; τ2, on = 197 ± 92 s) and very heavy (τ1, on = 36 ± 9 s; τ2, on = 302 ± 14 s) intensities. In contrast, the VO2 off-kinetics were best described with a single exponential at moderate (τ1, off = 48 ± 9 s) and heavy (τ1, off = 53 ± 7 s) intensities and a double exponential at very heavy (τ1, off = 51 ± 3 s; τ2, off = 471 ± 54 s) intensity. In summary, adolescents consistently displayed a slow component during heavy exercise (on- but not off- transition) and very heavy exercise (on- and off-transitions). Although the overall response dynamics in adolescents were similar to those previously observed in adults, their specific characterizations were different, particularly the lack of symmetry between the on- and off-responses.

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di Prampero, P. E., P. B. Mahler, D. Giezendanner et P. Cerretelli. « Effects of priming exercise on VO2 kinetics and O2 deficit at the onset of stepping and cycling ». Journal of Applied Physiology 66, n^o 5 (1 mai 1989) : 2023–31. http://dx.doi.org/10.1152/jappl.1989.66.5.2023.

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Breath-by-breath O2 uptake (VO2) kinetics and increase of blood lactate concentration (delta Lab) were determined at the onset of square-wave stepping (S) or cycling (C) exercise on six male subjects during 1) transition from rest (R) to constant work load, 2) transition from lower to heavier work loads, wherein the baseline VO2 (VO2 s) was randomly chosen between 20 and 65% of the subjects' maximal O2 uptake (VO2 max), and 3) inverse transition from higher to lower work loads and/or to rest. VO2 differences between starting and arriving levels were 20–60% VO2 max. In C, the VO2 on-response became monotonically slower with increasing VO2 s, the half time (t1/2) increasing from approximately 22 s for VO2 s = R to approximately 63 s when VO2 s approximately equal to 50% VO2 max. In S, the fastest VO2 kinetics (t1/2 = 16 s) was attained from VO2 s = 15–30% VO2 max, the t1/2 being approximately 25 s when starting from R or from 50% VO2 max. The slower VO2 kinetics in C were associated with a much larger delta Lab. The VO2 kinetics in recovery were essentially the same in all cases and could be approximated by a double exponential with t1/2 of 21.3 +/- 6 and 93 +/- 45 s for the fast and slow components, respectively. It is concluded that the O2 deficit incurred is the sum of three terms: 1) O2 stores depletion, 2) O2 equivalent of early lactate production, and 3) O2 equivalent of phosphocreatine breakdown.(ABSTRACT TRUNCATED AT 250 WORDS)

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Gladden, L. B., M. C. Hogan, R. A. Meyer, S. Segal, R. L. Hughson, B. Grassi et B. J. Whipp. « MISCLE VO2 ON-KINETICS ». Medicine & ; Science in Sports & ; Exercise 31, Supplement (mai 1999) : S235. http://dx.doi.org/10.1097/00005768-199905001-01113.

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McNulty, C., et R. Robergs. « New method for processing and quantifying VO2 kinetics : Linear VO2 onset kinetics ». Journal of Science and Medicine in Sport 19 (décembre 2015) : e49. http://dx.doi.org/10.1016/j.jsams.2015.12.494.

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Reis, Victor M., Eduardo B. Neves, Nuno Garrido, Ana Sousa, André L. Carneiro, Carlo Baldari et Tiago Barbosa. « Oxygen Uptake On-Kinetics during Low-Intensity Resistance Exercise : Effect of Exercise Mode and Load ». International Journal of Environmental Research and Public Health 16, n^o 14 (15 juillet 2019) : 2524. http://dx.doi.org/10.3390/ijerph16142524.

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Oxygen uptake (VO2) kinetics has been analyzed through mathematical modeling of constant work-rate exercise, however, the exponential nature of the VO2 response in resistance exercise is currently unknown. The present work assessed the VO2 on-kinetics during two different sub maximal intensities in the inclined bench press and in the seated leg extension exercise. Twelve males (age: 27.2 ± 4.3 years, height: 177 ± 5 cm, body mass: 79.0 ± 10.6 kg and estimated body fat: 11.4 ± 4.1%) involved in recreational resistance exercise randomly performed 4-min transitions from rest to 12% and 24% of 1 repetition maximum each, of inclined bench press (45°) and leg extension exercises. During all testing, expired gases were collected breath-by-breath with a portable gas analyzer (K4b2, Cosmed, Italy) and VO2 on-kinetics were identified using a multi-exponential mathematical model. Leg extension exercise exhibited a higher R-square, compared with inclined bench press, but no differences were found in-between exercises for the VO2 kinetics parameters. VO2 on-kinetics seems to be more sensitive to muscle related parameters (upper vs. lower body exercise) and less to small load variations in the resistance exercise. The absence of a true slow component indicates that is possible to calculate low-intensity resistance exercise energy cost based solely on VO2 measurements.

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Vianna, Jeferson M., Francisco Z. Werneck, Emerson F. Coelho, Vinicius O. Damasceno et Victor M. Reis. « Oxygen Uptake and Heart Rate Kinetics after Different Types of Resistance Exercise ». Journal of Human Kinetics 42, n^o 1 (1 octobre 2014) : 235–44. http://dx.doi.org/10.2478/hukin-2014-0077.

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Abstract Oxygen uptake (VO2) and heart rate (HR) kinetics after exercise are important indicators of fitness and cardiovascular health. However, these variables have been little investigated in resistance exercise (RE). The current study compared post-exercise kinetics of VO2 and the HR among different types of REs. The study included 14 males (age: 26.5±5.4 years, body mass: 80.1±11.4 kg, body height: 1.77±0.07 m, fat content: 11.3±4.6%) with RE experience. Dynamic muscle strength was measured using one repetition maximum (1RM) with regard to the half-squat, bench press, pull-down, and triceps pushdown exercises. The participants performed a maximum number of repetitions at 80% of 1RM for each exercise, separated by a recovery period of 60 minutes. VO2 was measured using ergospirometry. VO2 and HR kinetics were assessed using the time constant of the recovery curves, and excess oxygen consumption (EPOC) was calculated afterward. Significant differences were not observed across the exercises with regard to VO2 kinetics. However, the half-squat exercise elicited a greater EPOC than the bench press and triceps pushdown exercises (p<.05). HR kinetics was slower for the half-squat exercise than for the other exercises (p<.05). These findings confirm that the type of RE influences both the cardiac autonomic response post-exercise and EPOC, but not VO2 kinetics

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Poole, David C., Casey A. Kindig, Brad J. Behnke et Andrew M. Jones. « Oxygen uptake (VO2) kinetics in different species : a brief review ». Equine and Comparative Exercise Physiology 2, n^o 1 (février 2005) : 1–15. http://dx.doi.org/10.1079/ecp200445.

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AbstractWhen a human begins to move or locomote, the energetic demands of its skeletal muscles increase abruptly and the oxygen (O2) transport system responds to deliver increased amounts of O2 to the respiring mitochondria. It is intuitively reasonable that the rapidity with which O2 transport can be increased to and utilized by (VO2) the contracting muscles would be greater in those species with a higher maximal VO2 capacity (i.e., VO2max). This review explores the relationship between VO2max and VO2 dynamics or kinetics at across a range of species selected, in part, for their disparate VO2max capacities. In healthy humans there is compelling evidence that the speed of the VO2 kinetics at the onset of exercise is limited by an oxidative enzyme inertia within the exercising muscles rather than by VO2 delivery to those muscles. This appears true also for the horse and dog but possibly not for a certain species of frog. Whereas there is a significant correlation between VO2max and the speed of VO2 kinetics among different species, it is possible to identify species or individuals within a species that exhibit widely disparate mass-specific VO2max capacities but similar VO2 kinetics (i.e., superlative human athlete and horse).

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Zacca, Rodrigo, Rui Azevedo, Pedro Figueiredo, João Vilas-Boas, Flávio Castro, David Pyne et Ricardo Fernandes. « VO2FITTING : A Free and Open-Source Software for Modelling Oxygen Uptake Kinetics in Swimming and other Exercise Modalities ». Sports 7, n^o 2 (24 janvier 2019) : 31. http://dx.doi.org/10.3390/sports7020031.

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The assessment of oxygen uptake (VO2) kinetics is a valuable non-invasive way to evaluate cardiorespiratory and metabolic response to exercise. The aim of the study was to develop, describe and evaluate an online VO2 fitting tool (VO2FITTING) for dynamically editing, processing, filtering and modelling VO2 responses to exercise. VO2FITTING was developed in Shiny, a web application framework for R language. Validation VO2 datasets with both noisy and non-noisy data were developed and applied to widely-used models (n = 7) for describing different intensity transitions to verify concurrent validity. Subsequently, we then conducted an experiment with age-group swimmers as an example, illustrating how VO2FITTING can be used to model VO2 kinetics. Perfect fits were observed, and parameter estimates perfectly matched the known inputted values for all available models (standard error = 0; p < 0.001). The VO2FITTING is a valid, free and open-source software for characterizing VO2 kinetics in exercise, which was developed to help the research and performance analysis communities.

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Murias, Juan M., Matthew D. Spencer, Darren S. DeLorey, Brendon J. Gurd, John M. Kowalchuk et Donald H. Paterson. « Speeding of V̇o2 kinetics during moderate-intensity exercise subsequent to heavy-intensity exercise is associated with improved local O2 distribution ». Journal of Applied Physiology 111, n^o 5 (novembre 2011) : 1410–15. http://dx.doi.org/10.1152/japplphysiol.00607.2011.

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The relationship between the adjustment of muscle deoxygenation (Δ[HHb]) and phase II VO2p during moderate-intensity exercise was examined before (Mod 1) and after (Mod 2) a bout of heavy-intensity “priming” exercise. Moderate intensity VO2p and Δ[HHb] kinetics were determined in 18 young males (26 ± 3 yr). VO2p was measured breath-by-breath. Changes in Δ[HHb] of the vastus lateralis muscle were measured by near-infrared spectroscopy. VO2p and Δ[HHb] response profiles were fit using a monoexponential model, and scaled to a relative % of the response (0–100%). The Δ[HHb]/V̇o2 ratio for each individual (reflecting the local matching of O2 delivery to O2 utilization) was calculated as the average Δ[HHb]/V̇o2 response from 20 s to 120 s during the exercise on-transient. Phase II τVO2p was reduced in Mod 2 compared with Mod 1 ( P < 0.05). The effective τ′Δ[HHb] remained the same in Mod 1 and Mod 2 ( P > 0.05). During Mod 1, there was an “overshoot” in the Δ[HHb]/V̇o2 ratio (1.08; P < 0.05) that was not present during Mod 2 (1.01; P > 0.05). There was a positive correlation between the reduction in the Δ[HHb]/V̇o2 ratio and the smaller τVO2p from Mod 1 to Mod 2 ( r = 0.78; P < 0.05). This study showed that a smaller τVO2p during a moderate bout of exercise subsequent to a heavy-intensity priming exercise was associated with improved microvascular O2 delivery during the on-transient of exercise, as suggested by a smaller Δ[HHb]/V̇o2 ratio.

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Barstow, T. J., et P. A. Mole. « Simulation of pulmonary O2 uptake during exercise transients in humans ». Journal of Applied Physiology 63, n^o 6 (1 décembre 1987) : 2253–61. http://dx.doi.org/10.1152/jappl.1987.63.6.2253.

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Computer simulation of blood flow and O2 consumption (QO2) of leg muscles and of blood flow through other vascular compartments was made to estimate the potential effects of circulatory adjustments to moderate leg exercise on pulmonary O2 uptake (VO2) kinetics in humans. The model revealed a biphasic rise in pulmonary VO2 after the onset of constant-load exercise. The length of the first phase represented a circulatory transit time from the contracting muscles to the lung. The duration and magnitude of rise in VO2 during phase 1 were determined solely by the rate of rise in venous return and by the venous volume separating the muscle from the lung gas exchange sites. The second phase of VO2 represented increased muscle metabolism (QO2) of exercise. With the use of a single-exponential model for muscle QO2 and physiological estimates of other model parameters, phase 2 VO2 could be well described as a first-order exponential whose time constant was within 2 s of that for muscle QO2. The use of unphysiological estimates for certain parameters led to responses for VO2 during phase 2 that were qualitatively different from QO2. It is concluded that 1) the normal response of VO2 in humans to step increases in muscle work contains two components or phases, the first determined by cardiovascular phenomena and the second primarily reflecting muscle metabolism and 2) the kinetics of VO2 during phase 2 can be used to estimate the kinetics of muscle QO2. The simulation results are consistent with previously published profiles of VO2 kinetics for square-wave transients.

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Chilibeck, P. D., D. H. Paterson, W. D. Smith et D. A. Cunningham. « Cardiorespiratory kinetics during exercise of different muscle groups and mass in old and young ». Journal of Applied Physiology 81, n^o 3 (1 septembre 1996) : 1388–94. http://dx.doi.org/10.1152/jappl.1996.81.3.1388.

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The purpose was to compare cardiorespiratory kinetics during exercise of different muscle groups (double-leg cycling vs treadmill walking and single-leg ankle plantar flexion) in old and young subjects. Oxygen uptake (VO2) during exercise transitions was measured breath by breath, and the phase 2 portion of the response was fit by a monoexponential for determination of the time constant (tau) of VO2. Two separate studies were performed: in study 1, 12 old (age 66.7 yr) and 16 young (aged 26.3 yr) subjects were compared during cycling and ankle plantar flexion exercise, and in the study 2, five old (aged 69.6 yr) and five young (24.4 yr) subjects were compared during cycling and treadmill walking. VO2 transients during square-wave cycling exercise were significantly slower in the old compared with the young groups. In contrast, VO2 kinetics did not differ between old and young groups during plantar flexion exercise. Heart rate (HR) kinetics followed the same pattern, with tau HR being significantly slower in the old vs young groups during transitions to cycling but not to plantar flexion. In study 2 tau VO2 and tau HR during on-transients to treadmill square-wave exercise were significantly slower in the old group compared with the young group, but tau VO2 was significantly faster during treadmill exercise than during cycling in the old group. The differences with aging between the modes of exercise may be related to the muscle mass involved and the circulatory demands. On the other hand, slowed VO2 kinetics with age appear to occur in a mode (cycling) in which the muscles are not accustomed to the activity, whereas in a mode of normal activity (walking) and with the muscle groups (plantar flexors) accustomed to the activity, VO2 kinetics are not slowed to the same degree with age.

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Gerbino, A., S. A. Ward et B. J. Whipp. « Effects of prior exercise on pulmonary gas-exchange kinetics during high-intensity exercise in humans ». Journal of Applied Physiology 80, n^o 1 (1 janvier 1996) : 99–107. http://dx.doi.org/10.1152/jappl.1996.80.1.99.

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The effects of prior exercise on O2 uptake (VO2) kinetics during supra-lactate threshold (LT) cycling were assessed in 11 subjects. Protocols consisted of two consecutive 6-min work bouts separated by 0 W (6 min) with 1) both bouts sub-LT, 2) both bouts supra-LT, 3) bout 1 sub-LT and bout 2 supra-LT, and 4) bout 1 supra-LT and bout 2 sub-LT. Sub-LT VO2 kinetics were similar whether the prior bout was supra- or sub-LT. The VO2 kinetics for supra-LT work preceded by a sub-LT “warm-up” were similar to those for supra-LT work that was not preceded by exercise (O-W warm-up): the “partial”: O2 deficit averaged 2.64 vs. 2.57 liters, and the “effective” VO2 time constant averaged 56 vs. 65 s. Exercise responses (i.e., the change between O W and minute 6 of exercise) were unaffected for lactate concentration (4.58 vs. 4.50 meq/l), pH (-0.08 vs. -0.10), and CO2 output (VCO2; 2.65 vs. 2.49 l/min). However, when the supra-LT work was preceded by a supra-LT warm-up, VO2 kinetics were appreciably faster (O2 deficit = 1.82 liters, VO2 time constant = 37 s) relative to 0-W warm-up; the lactate (0.69 meq/l), pH (-0.01), and VCO2 (2.08 l/min) responses were smaller; and the effective VCO2 time constant was longer (58 vs. 43 s). The mechanism(s) that underlie this speeding of the VO2 kinetics cannot be firmly established, but we suggest that an improved muscle perfusion during the exercise may be involved consequent to the residual metabolic acidemia from the high-intensity warm-up.

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Casaburi, R., T. J. Barstow, T. Robinson et K. Wasserman. « Influence of work rate on ventilatory and gas exchange kinetics ». Journal of Applied Physiology 67, n^o 2 (1 août 1989) : 547–55. http://dx.doi.org/10.1152/jappl.1989.67.2.547.

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A linear system has the property that the kinetics of response do not depend on the stimulus amplitude. We sought to determine whether the responses of O2 uptake (VO2), CO2 output (VCO2), and ventilation (VE) in the transition between loadless pedaling and higher work rates are linear in this respect. Four healthy subjects performed a total of 158 cycle ergometer tests in which 10 min of exercise followed unloaded pedaling. Each subject performed three to nine tests at each of seven work rates, spaced evenly below the maximum the subject could sustain. VO2, VCO2, and VE were measured breath by breath, and studies at the same work rate were time aligned and averaged. Computerized nonlinear regression techniques were used to fit a single exponential and two more complex expressions to each response time course. End-exercise blood lactate was determined at each work rate. Both VE and VO2 kinetics were markedly slower at work rates associated with sustained blood lactate elevations. A tendency was also detected for VO2 (but not VE) kinetics to be slower as work rate increased for exercise intensities not associated with lactic acidosis (P less than 0.01). VO2 kinetics at high work rates were well characterized by the addition of a slower exponential component to the faster component, which was seen at lower work rates. In contrast, VCO2 kinetics did not slow at the higher exercise intensities; this may be the result of the coincident influence of several sources of CO2 related to lactic acidosis. These findings provide guidance for interpretation of ventilatory and gas exchange kinetics.

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Kinker, J. R., A. S. Haffor, M. Stephan et T. L. Clanton. « Kinetics of CO uptake and diffusing capacity in transition from rest to steady-state exercise ». Journal of Applied Physiology 72, n^o 5 (1 mai 1992) : 1764–72. http://dx.doi.org/10.1152/jappl.1992.72.5.1764.

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In the transition from rest to steady-state exercise, O2 uptake from the lungs (VO2) depends on the product of pulmonary blood flow and pulmonary arteriovenous O2 content difference. The kinetics of pulmonary blood flow are believed to be somewhat faster than changes in pulmonary arteriovenous O2 content difference. We hypothesized that during CO breathing, the kinetics of CO uptake (VCO) and diffusing capacity for CO (DLCO) should be faster than VO2 because changes in pulmonary arteriovenous CO content difference should be relatively small. Six subjects went abruptly from rest to constant exercise (inspired CO fraction = 0.0005) at 40, 60, and 80% of their peak VO2, measured with an incremental test (VO2peak). At all exercise levels, DLCO and VCO rose faster than VO2 (P less than 0.001), and DLCO rose faster than VCO (P less than 0.001). For example, at 40% VO2peak, the time constant (tau) for DLCO in phase 2 was 19 +/- 5 (SD), 24 +/- 5 s for VCO, and 33 +/- 5 s for VO2. Both VCO and DLCO increased with exercise intensity but to a lesser degree than VO2 at all exercise intensities (P less than 0.001). In addition, no significant rise in DLCO was observed between 60 and 80% VO2peak. We conclude that the kinetics of VCO and DLCO are faster than VO2, suggesting that VCO and DLCO kinetics reflect, to a greater extent, changes in pulmonary blood flow and thus recruitment of alveolar-capillary surface area. However, other factors, such as the time course of ventilation, may also be involved.(ABSTRACT TRUNCATED AT 250 WORDS)

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Cooper, D. M., C. Berry, N. Lamarra et K. Wasserman. « Kinetics of oxygen uptake and heart rate at onset of exercise in children ». Journal of Applied Physiology 59, n^o 1 (1 juillet 1985) : 211–17. http://dx.doi.org/10.1152/jappl.1985.59.1.211.

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Requirements for cellular homeostasis appear to be unchanged between childhood and maturity. We hypothesized, therefore, that the kinetics of O2 uptake (VO2) in the transition from rest to exercise would be the same in young children as in teenagers. To test this, VO2 and heart rate kinetics from rest to constant work rate (75% of the subject's anaerobic threshold) in 10 children (5 boys and 5 girls) aged 7–10 yr were compared with values found in 10 teenagers (5 boys and 5 girls) aged 15–18 yr. Gas exchange was measured breath to breath, and phases I and II of the transition and phase III (steady-state exercise) were evaluated from multiple transitions in each child. Phase I (the VO2 at 20 s of exercise expressed as percent rest-to-steady-state exercise VO2) was not significantly correlated with age or weight [mean value 42.5 +/- 8.9% (SD)] nor was the phase II time constant for VO2 [mean 27.3 +/- 4.7 (SD) s]. The older girls had significantly slower kinetics than the other children but were also found to be less fit. When the teenagers exercised at work rates well below 75% of their anaerobic threshold, phase I VO2 represented a higher proportion of the overall response, but the phase II kinetics were unchanged. The temporal coupling between the cellular production of mechanical work at the onset of exercise and the uptake of environmental O2 appears to be controlled throughout growth in children.

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Li, Yang, Shida Yang, Yunhe Zhao, Nauman Mubarak, Mengyang Xu, Muhammad Ihsan-Ul-Haq, Tianshou Zhao, Qing Chen et Jang-Kyo Kim. « Deciphering the exceptional kinetics of hierarchical nitrogen-doped carbon electrodes for high-performance vanadium redox flow batteries ». Journal of Materials Chemistry A 10, n^o 10 (2022) : 5605–13. http://dx.doi.org/10.1039/d2ta00324d.

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Patti, Alessandro, Daniel Neunhaeuserer, Sara Ortolan, Fausto Roman, Andrea Gasperetti, Francesca Battista, Caterina Di Bella et al. « A clinical evaluation of VO2 kinetics in kidney transplant recipients ». European Journal of Applied Physiology 121, n^o 7 (3 avril 2021) : 2005–13. http://dx.doi.org/10.1007/s00421-021-04672-x.

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Abstract Purpose Aerobic exercise capacity is reduced in patients with chronic kidney disease, partly due to alterations at the muscular and microvascular level. This study evaluated oxygen uptake (VO2) kinetics as indicator of muscular oxidative metabolism in a population of Kidney Transplant Recipients (KTRs). Methods Two groups of KTRs enrolled 3 (n = 21) and 12 months (n = 14) after transplantation and a control group of healthy young adults (n = 16) underwent cardiopulmonary exercise testing on cycle-ergometer. The protocol consisted in two subsequent constant, moderate-load exercise phases with a final incremental test until exhaustion. Results The time constant of VO2 kinetics was slower in KTRs at 3 and 12 months after transplantation compared to controls (50.4 ± 13.1 s and 43.8 ± 11.6 s vs 28.9 ± 8.4 s, respectively; P < 0.01). Peak VO2 was lower in KTRs evaluated 3 months after transplantation compared to patients evaluated after 1 year (21.3 ± 4.3 and 26.4 ± 8.0 mL/kg/min; P = 0.04). Blood haemoglobin (Hb) concentration was higher in KTRs evaluated at 12 months (12.8 ± 1.7 vs 14.6 ± 1.7 g/dL; P < 0.01). Among KTRs, τ showed a moderate negative correlation with Peak VO2 (ρ = − 0.52) and Oxygen uptake efficiency slope (OUES) (r = − 0.57) while no significant correlation with Hb and peak heart rate. Conclusions KTRs show slower VO2 kinetics compared to healthy controls. Hb and peak VO2 seem to improve during the first year after transplantation. VO2 kinetics were significantly associated with indices of cardiorespiratory fitness, but less with central determinants of aerobic capacity, thus suggesting a potential usefulness of adding this index of muscular oxidative metabolism to functional evaluation in KTRs.

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Antunes, André, Christophe Domingos, Luísa Diniz, Cristina P. Monteiro, Mário C. Espada, Francisco B. Alves et Joana F. Reis. « The Relationship between VO2 and Muscle Deoxygenation Kinetics and Upper Body Repeated Sprint Performance in Trained Judokas and Healthy Individuals ». International Journal of Environmental Research and Public Health 19, n^o 2 (13 janvier 2022) : 861. http://dx.doi.org/10.3390/ijerph19020861.

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The present study sought to investigate if faster upper body oxygen uptake (VO2) and hemoglobin/myoglobin deoxygenation ([HHb]) kinetics during heavy intensity exercise were associated with a greater upper body repeated-sprint ability (RSA) performance in a group of judokas and in a group of individuals of heterogenous fitness level. Eight judokas (JT) and seven untrained healthy participants (UT) completed an incremental step test, two heavy intensity square-wave transitions and an upper body RSA test consisting of four 15 s sprints, with 45 s rest, from which the experimental data were obtained. In the JT group, VO2 kinetics, [HHb] kinetics and the parameters determined in the incremental test were not associated with RSA. However, when the two groups were combined, the amplitude of the primary phase VO2 and [HHb] were positively associated with the accumulated work in the four sprints (ΣWork). Additionally, maximal aerobic power (MAP), peak VO2 and the first ventilatory threshold (VT1) showed a positive correlation with ΣWork and an inverse correlation with the decrease in peak power output (Dec-PPO) between the first and fourth sprints. Faster VO2 and [HHb] kinetics do not seem to be associated with an increased upper body RSA in JT. However, other variables of aerobic fitness seem to be associated with an increased upper body RSA performance in a group of individuals with heterogeneous fitness level.

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Jones, Andrew M., et Mark Burnley. « Oxygen Uptake Kinetics : An Underappreciated Determinant of Exercise Performance ». International Journal of Sports Physiology and Performance 4, n^o 4 (décembre 2009) : 524–32. http://dx.doi.org/10.1123/ijspp.4.4.524.

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The rate at which VO2 adjusts to the new energy demand following the onset of exercise strongly influences the magnitude of the “O2 defcit” incurred and thus the extent to which muscle and systemic homeostasis is perturbed. Moreover, during continuous high-intensity exercise, there is a progressive loss of muscle contractile efficiency, which is reflected in a “slow component” increase in VO2. The factors that dictate the characteristics of these fast and slow phases of the dynamic response of VO2 following a step change in energy turnover remain obscure. However, it is clear that these features of the VO2 kinetics have the potential to influence the rate of muscle fatigue development and, therefore, to affect sports performance. This commentary outlines the present state of knowledge on the characteristics of, and mechanistic bases to, the VO2 response to exercise of different intensities. Several interventions have been reported to speed the early VO2 kinetics and/or reduce the magnitude of the subsequent VO2 slow component, and the possibility that these might enhance exercise performance is discussed.

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BARKER, Glenn A., Simon GREEN, Anita A. GREEN et Philip J. WALKER. « Walking performance, oxygen uptake kinetics and resting muscle pyruvate dehydrogenase complex activity in peripheral arterial disease ». Clinical Science 106, n^o 3 (1 mars 2004) : 241–49. http://dx.doi.org/10.1042/cs20030244.

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In the present study, we tested the hypothesis that walking intolerance in intermittent claudication (IC) is related to both slowed whole body oxygen uptake (VO2) kinetics and altered activity of the active fraction of the pyruvate dehydrogenase complex (PDCa) in skeletal muscle. Ten patients with IC and peripheral arterial disease [ankle/brachial index (ABI)=0.73±0.13] and eight healthy controls (ABI=1.17±0.13) completed three maximal walking tests. From these tests, averaged estimates of walking time, peak VO2 and the time constant of VO2 (τ) during submaximal walking were obtained. A muscle sample was taken from the gastrocnemius medialis muscle at rest and analysed for PDCa and several other biochemical variables. Walking time and peak VO2 were approx. 50% lower in patients with IC than controls, and τ was 2-fold higher (P<0.05). τ was significantly correlated with walking time (r=-0.72) and peak VO2 (r=-0.66) in patients with IC, but not in controls. PDCa was not significantly lower in patients with IC than controls; however, PDCa tended to be correlated with τ (r=-0.56, P=0.09) in patients with IC, but not in controls (r=-0.14). A similar correlation was observed between resting ABI and τ (r=-0.63, P=0.05) in patients with IC. These data suggest that the impaired VO2 kinetics contributes to walking intolerance in IC and that, within a group of patients with IC, differences in VO2 kinetics might be partly linked to differences in muscle carbohydrate oxidation.

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Haouzi, P., Y. Fukuba, R. Casaburi, W. Stringer et K. Wasserman. « O2 uptake kinetics above and below the lactic acidosis threshold during sinusoidal exercise ». Journal of Applied Physiology 75, n^o 4 (1 octobre 1993) : 1683–90. http://dx.doi.org/10.1152/jappl.1993.75.4.1683.

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O2 uptake (VO2) kinetics at the onset of a constant work rate exercise are difficult to describe for work rates above the lactic acidosis threshold (LAT), because the steady-state level of VO2 response can usually not be identified. To describe the ability of the O2 transport system to deliver and the cells to utilize O2 above the LAT relative to that below the LAT, we applied a fluctuating (sinusoidal) variation of work rate. After 4 min of constant work at the midpoint of the sinusoidal work rate, a fluctuating work rate, at a period of 4 min, was applied below the LAT for the next 16 min. This was repeated in a range of work rates above the LAT with the same sine-wave amplitude. VO2 response appeared to follow a sinusoidal pattern similar to that of work rate for below- and above-LAT exercise. However, the amplitude of the VO2 response was significantly reduced (5.4 +/- 2.6 vs. 7.6 +/- 1.9 ml.min-1 x W-1, P < 0.01), and the phase lag increased above- compared with below-LAT work rate. VO2/heart rate fluctuations were dramatically reduced, whereas heart rate amplitude decreased and phase lag increased, for above-LAT sinusoidal work rate changes. These results suggest that VO2 kinetics are slowed in the work rate domain above the LAT relative to that below the LAT and that VO2 kinetics could be limited by the O2 transport mechanisms to the exercising muscle.

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Samaja, M., L. Brenna, S. Allibardi et P. Cerretelli. « Human red blood cell aging at 5,050-m altitude : a role during adaptation to hypoxia ». Journal of Applied Physiology 75, n^o 4 (1 octobre 1993) : 1696–701. http://dx.doi.org/10.1152/jappl.1993.75.4.1696.

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O2 uptake (VO2) kinetics at the onset of a constant work rate exercise are difficult to describe for work rates above the lactic acidosis threshold (LAT), because the steady-state level of VO2 response can usually not be identified. To describe the ability of the O2 transport system to deliver and the cells to utilize O2 above the LAT relative to that below the LAT, we applied a fluctuating (sinusoidal) variation of work rate. After 4 min of constant work at the midpoint of the sinusoidal work rate, a fluctuating work rate, at a period of 4 min, was applied below the LAT for the next 16 min. This was repeated in a range of work rates above the LAT with the same sine-wave amplitude. VO2 response appeared to follow a sinusoidal pattern similar to that of work rate for below- and above-LAT exercise. However, the amplitude of the VO2 response was significantly reduced (5.4 +/- 2.6 vs. 7.6 +/- 1.9 ml.min-1 x W-1, P < 0.01), and the phase lag increased above- compared with below-LAT work rate. VO2/heart rate fluctuations were dramatically reduced, whereas heart rate amplitude decreased and phase lag increased, for above-LAT sinusoidal work rate changes. These results suggest that VO2 kinetics are slowed in the work rate domain above the LAT relative to that below the LAT and that VO2 kinetics could be limited by the O2 transport mechanisms to the exercising muscle.

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Noack, Jens, Nataliya Roznyatovskaya, Jessica Kunzendorf, Maria Skyllas-Kazacos, Chris Menictas et Jens Tübke. « The Influence of Electrochemical Treatment on Electrode Reactions for Vanadium Flow Batteries ». ECS Meeting Abstracts MA2022-01, n^o 3 (7 juillet 2022) : 461. http://dx.doi.org/10.1149/ma2022-013461mtgabs.

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The motivation for this work was to obtain an overview of the electrochemical behaviour of vanadium reactions on electrochemically treated glassy carbon electrodes in order to be able to make reproducible statements about changes with the treatment. In addition, optimal conditions for the reactions should be found in order to create a basis for targeted pre-treatment of the electrodes and, if applicable, a possibility for in situ treatments. Furthermore, if possible, causes should be determined by the behavior. A glassy carbon electrode was first polished and then treated in 2 M H2SO4 at different potentials. In a separate measurement setup, linear sweep voltammograms were then recorded instead of cyclic voltammograms in order to change the electrode as little as possible and to calculate kinetic values from the obtained data. In addition, roughness values were determined at selected treatment potentials using confocal microscopy and the surface composition was analyzed using XPS. The reaction rates increased significantly in all reactions compared to polished electrodes and had an optimum treatment potential of approx. 1600 mV vs. Hg/Hg2SO4, although the oxidation reaction of V2+ and the reduction reactions of V3+ and VO2+ had opposite tendencies to oxidation of VO2+ and the reduction of VO2 + in the area of low treatment potentials. In the former, the kinetics increased and in the latter, they decreased. No correlation was found to the roughness or size of the stretched surfaces, although these changed significantly as a result of the treatment. XPS measurements gave indications of a dependence on oxygen functional groups for the different reactions. Figure 1

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Molina, Renato, et Benedito Sérgio Denadai. « Muscle damage slows oxygen uptake kinetics during moderate-intensity exercise performed at high pedal rate ». Applied Physiology, Nutrition, and Metabolism 36, n^o 6 (décembre 2011) : 848–55. http://dx.doi.org/10.1139/h11-109.

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This study aimed to investigate the dependence of oxygen uptake (VO2) kinetics on pedal cadence during moderate-intensity exercise following exercise-induced muscle damage (EIMD). Twenty untrained males were randomly assigned to a 50 revolution per minute (rpm) (age, 23.3 ± 1.8 years; VO2max, 38.9 ± 2.8 mL·kg–1·min–1) or 100 rpm group (age, 24.4 ± 3.5 years, VO2max, 42.9 ± 4.3 mL·kg–1·min–1). Participants completed “step” tests to moderate-intensity exercise from an unloaded baseline on a cycle ergometer before (baseline) and at 24 and 48 h after muscle-damaging exercise (10 sets of 10 eccentric contractions performed on an isokinetic dynamometer with a 2-min rest between each set). Pedal cadence was kept constant throughout each cycling trial (50 or 100 rpm). There were no changes in phase II pulmonary VO2 kinetics following EIMD for the 50 rpm group (baseline = 35 ± 4 s; 24 h = 35 ± 7 s; and 48 h = 36 ± 9 s). However, the phase II VO2 was significantly greater at 24 h (59 ± 27 s) compared with baseline (39 ± 6 s) and 48 h (40 ± 9 s) for the 100 rpm group. It is concluded that the effects of EIMD on phase II VO2 kinetics during moderate-intensity cycling exercise is dependent on pedal cadence. The slower VO2 kinetics after muscle damage suggests that type II fibers are involved during transition to moderate-intensity exercise at high pedal cadence.

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McCreary, C. R., P. D. Chilibeck, G. D. Marsh, D. H. Paterson, D. A. Cunningham et R. T. Thompson. « Kinetics of pulmonary oxygen uptake and muscle phosphates during moderate-intensity calf exercise ». Journal of Applied Physiology 81, n^o 3 (1 septembre 1996) : 1331–38. http://dx.doi.org/10.1152/jappl.1996.81.3.1331.

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The purpose of this study is to directly compare the dynamic responses of phosphocreatine (PCr) and P(i) to those oxygen uptake (VO2) measured at the lung during transitions to and from moderate-intensity exercise. Changes in PCr and P(i) were measured by 31P-nuclear magnetic resonance spectroscopy, and changes in VO2 were measured breath by breath by mass spectroscopy during transitions to and from moderate-intensity square-wave ankle plantar flexion exercise in 11 subjects (7 men and 4 women; mean age 27 yr). Three repeated transitions were averaged for improvement in signal-to-noise ratio of phosphate data, and 12 transitions were averaged for VO2 measurements. Averaged transitions were fit with a monoexponential curve for determination of the time constant (tau) of the responses. Mean tau values for on transients of PCr, P(i), and phrase 2 VO2 were 47.0, 57.7, and 44.5 s, respectively, whereas means tau values for off transients were 44.8, 42.1, and 33.4 s, respectively. There were no significant differences between tau values for phosphate- and VO2-measured transients or on and off transients. The similarity of on and off kinetics supports linear first-order respiratory control models. Measurement of phase 2 pulmonary VO2 kinetics to and from moderate-intensity small-muscle-mass exercise reflect muscle phosphate kinetics (and muscle oxygen consumption).

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Hogan, Michael C. « VO2 On-Kinetics in Isolated Myocytes ». Medicine & ; Science in Sports & ; Exercise 41 (mai 2009) : 2. http://dx.doi.org/10.1249/01.mss.0000352590.15853.0f.

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Kowalchuk, John M. « VO2 On-Kinetics in Intact Humans ». Medicine & ; Science in Sports & ; Exercise 41 (mai 2009) : 2. http://dx.doi.org/10.1249/01.mss.0000352592.00606.0b.

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Biswas, R. K., et M. G. K. Mondal. « Kinetics of VO2+ extraction by D2EHPA ». Hydrometallurgy 69, n^o 1-3 (avril 2003) : 117–33. http://dx.doi.org/10.1016/s0304-386x(02)00208-6.

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Paterson, D. H., D. A. Cunningham, J. G. Pickering, M. A. Babcock et D. R. Boughner. « Oxygen uptake kinetics in cardiac transplant recipients ». Journal of Applied Physiology 77, n^o 4 (1 octobre 1994) : 1935–40. http://dx.doi.org/10.1152/jappl.1994.77.4.1935.

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Our purpose was to examine the gas exchange response to exercise in heart transplant (HT) patients and to characterize the O2 uptake kinetics (tau VO2) during successive square-wave on-transients from loadless cycling to moderate exercise. We hypothesized that with a slow heart rate response (and O2 transport limitation) O2 kinetics would be slowed but that with a repeated exercise initiated while the heart rate remained elevated the tau VO2 would be faster. Six male HT patients performed two ramp-function tests to determine peak O2 uptake (1.32 +/- 0.23 l/min) and ventilation threshold (1.02 +/- 0.16 l/min). Patients subsequently completed two repeats of a square-wave forcing function and repeated this on 2 days. Alveolar gas exchange was measured breath by breath. A monoexponential fit of signal-averaged data of the first exercise on-transient (between days) yielded a significantly slower tau VO2 in HT subjects than in healthy men (mean age 47 yr; n = 8) (77 +/- 26 vs. 45 +/- 4 s). With successive exercise (2nd transition) initiated while HR remained elevated the tau VO2 of HT patients was 46 +/- 17 s. The faster O2 kinetics of the second transition suggests that O2 delivery was enhanced and therefore that the tau VO2 may reflect bioenergetic processes controlling the rate of oxidative metabolism.

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Inbar, Omri, Marcello Faina, Sabrina Demarie et Brian J. Whipp. « VO2 Kinetics during Moderate Effort in Muscles of Different Masses and Training Level ». ISRN Physiology 2013 (31 décembre 2013) : 1–9. http://dx.doi.org/10.1155/2013/101565.

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Purpose. To examine the relative importance of central or peripheral factors in the on-transient VO2 response dynamics to exercise with “trained” and relatively “untrained” muscles. Methods. Seven professional road cyclists and seven elite kayak paddlers volunteered to participate in this study. Each completed two bouts of constant-load “square-wave” rest-to-exercise transition cycling and arm-cranking exercise at a power output 50–60% of the mode-specific VO2peak presented in a randomized order. Results. In the cyclists, the mean response time (MRT) as well as the phase II VO2 time constant () was significantly slower in the untrained compared with the trained muscles. The opposite was the case in the kayakers. With respect to the relatively untrained muscle groups, while both demonstrated faster VO2 kinetics than normal (moderately fit) subjects, the kayakers evidenced faster VO2 kinetics than the cyclists. This suggests that there is a greater stabilizing-counterforce involvement of the legs in the task of kayaking than of the arms for cycling. Conclusions. The results of the present study provide no support for the “transfer” of a training effect onto the VO2 on-transient response for moderate exercise, but rather support earlier reports demonstrating that peripheral effects may be important in dictating this kinetics.

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Rampinini, Ermanno, Aldo Sassi, Andrea Morelli, Stefano Mazzoni, Maurizio Fanchini et Aaron J. Coutts. « Repeated-sprint ability in professional and amateur soccer players ». Applied Physiology, Nutrition, and Metabolism 34, n^o 6 (décembre 2009) : 1048–54. http://dx.doi.org/10.1139/h09-111.

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This study investigated the repeated-sprint ability (RSA) physiological responses to a standardized, high-intensity, intermittent running test (HIT), maximal oxygen uptake (VO2 max), and oxygen uptake (VO2) kinetics in male soccer players (professional (N = 12) and amateur (N = 11)) of different playing standards. The relationships between each of these factors and RSA performance were determined. Mean RSA time (RSAmean) and RSA decrement were related to the physiological responses to HIT (blood lactate concentration ([La–]), r = 0.66 and 0.77; blood bicarbonate concentration ([HCO3–]), r = –0.71 and –0.75; and blood hydrogen ion concentration ([H+]),r = 0.61 and 0.73; all p < 0.05), VO2 max (r = –0.45 and –0.65, p < 0.05), and time constant (τ) in VO2 kinetics (r = 0.62 and 0.62, p < 0.05). VO2 max was not different between playing standards (58.5 ± 4.0 vs. 56.3 ± 4.5 mL·kg–1·min–1; p = 0.227); however, the professional players demonstrated better RSAmean (7.17 ± 0.09 vs. 7.41 ± 0.19 s; p = 0.001), lower [La–] (5.7 ± 1.5 vs. 8.2 ± 2.2 mmol·L–1; p = 0.004), lower [H+] (46.5 ± 5.3 vs. 52.2 ± 3.4 mmol·L–1; p = 0.007), and higher [HCO3–] (20.1 ± 2.1 vs. 17.7 ± 1.7 mmol·L–1; p = 0.006) after the HIT, and a shorter τ in VO2 kinetics (27.2 ± 3.5 vs. 32.3 ± 6.0 s; p = 0.019). These results show that RSA performance, the physiological response to the HIT, and τ differentiate between professional- and amateur-standard soccer players. Our results also show that RSA performance is related to VO2 max, τ, and selected physiological responses to a standardized, high-intensity, intermittent exercise.

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Wilkerson, Daryl P., Katrien Koppo et Andrew M. Jones. « Pulmonary Vo2 On-kinetic Response To Step Exercise ». Medicine & ; Science in Sports & ; Exercise 37, Supplement (mai 2005) : S362—S363. http://dx.doi.org/10.1249/00005768-200505001-01896.

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Wilkerson, Daryl P., Katrien Koppo et Andrew M. Jones. « Pulmonary Vo2 On-kinetic Response To Step Exercise ». Medicine & ; Science in Sports & ; Exercise 37, Supplement (mai 2005) : S362???S363. http://dx.doi.org/10.1097/00005768-200505001-01896.

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Palange, P., P. Galassetti, E. T. Mannix, M. O. Farber, F. Manfredi, P. Serra et S. Carlone. « Oxygen effect on O2 deficit and VO2 kinetics during exercise in obstructive pulmonary disease ». Journal of Applied Physiology 78, n^o 6 (1 juin 1995) : 2228–34. http://dx.doi.org/10.1152/jappl.1995.78.6.2228.

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We evaluated the effect of supplemental O2 on energy metabolism of hypoxemic humans by measuring O2 uptake (VO2) kinetics and other cardiorespiratory parameters in nine male chronic obstructive pulmonary disease (COPD) patients and seven age-matched control subjects (on air and on 30% O2) at rest and during moderate cycle ergometer exercise. Heart rate, ventilation, VO2, CO2 output, respiratory exchange ratio, O2 cost of work, and work efficiency were measured with a computerized metabolic cart; O2 deficit and VO2 time courses were calculated. In COPD patients, 30% O2 breathing resulted in 1) reduction of O2 deficit (from 488 +/- 34 ml in air to 398 +/- 27 ml in O2; P < 0.05) and phase 2 VO2 time constant (from 116 +/- 13 s in air to 74 +/- 12 s in O2; P < 0.05); 2) a smaller steady-state increment in CO2 output than in room air (315 +/- 17 ml/min in O2 vs. 358 +/- 27 ml/min in air; P < 0.02), which resulted in a lower exercise respiratory exchange ratio (0.75 +/- 0.02 in O2 vs. 0.80 +/- 0.02 in air; P < 0.02); and 3) reduced steady-state ventilation (22.6 +/- 1.0 l/min in O2 vs. 25.4 +/- 1.1 l/min in air; P < 0.05). In conclusion, 30% O2 breathing accelerated exercise VO2 kinetics in mildly hypoxemic COPD patients. The observed VO2 kinetics improvement with O2 supplementation is consistent with an enhancement of aerobic metabolism in skeletal muscles during moderate exercise.

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Broster, Annika, et Ralph Beneke. « No Acceleration In VO2 Onset Kinetics During Exercise Above VO2 peak ». Medicine & ; Science in Sports & ; Exercise 43, Suppl 1 (mai 2011) : 387. http://dx.doi.org/10.1249/01.mss.0000401068.01813.07.

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Sietsema, K. E., J. A. Daly et K. Wasserman. « Early dynamics of O2 uptake and heart rate as affected by exercise work rate ». Journal of Applied Physiology 67, n^o 6 (1 décembre 1989) : 2535–41. http://dx.doi.org/10.1152/jappl.1989.67.6.2535.

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The kinetics of O2 uptake (Vo2) and heart rate (HR) in response to constant work rate exercise have been characterized as two phases, an immediate response as the result largely of abrupt hemodynamic changes and a slower response as the result of increases in both blood flow and arteriovenous O2 difference (avDo2). There are few data reported concerning Vo2 and HR during phase I or the relationship between their kinetics and work rate or intensity. Because phase I responses depend on abrupt cardiovascular adjustments, it was hypothesized that phase I increases in Vo2 and HR would be greater the more “fit” the subject and would be relatively independent of work rate. To test this, 10 normal subjects exercised from rest to each of five work rates ranging from unloaded cycling to 150 W. The phase I increases of Vo2, HR, and Vo2/HR had small but significant correlations with work rate but not with fitness. At very low work rates (unloaded cycling and 25 W), Vo2 and HR often exceeded their steady-state levels in phase I. There was therefore no phase II increase for Vo2 or HR at these work rates, the entire O2 requirement having been met by phase I circulatory adjustments. For all other work rates, mean response times for Vo2 and HR were related to fitness and were slower than those for Vo2/HR, suggesting that avDo2 reached a steady state before cardiac output did.

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Grassi, B., M. C. Hogan, K. M. Kelley, J. J. Hamann, W. G. Aschenbach, S. Rampichini et L. B. Gladden. « PERIPHERAL O2DIFFUSION AND VO2 ON-KINETICS IN CANINE MUSCLE AT PEAK VO2 ». Medicine & ; Science in Sports & ; Exercise 33, n^o 5 (mai 2001) : S329. http://dx.doi.org/10.1097/00005768-200105001-01846.

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Gladden, L. Bruce. « VO2 On-Kinetics in Isolated Whole Muscle ». Medicine & ; Science in Sports & ; Exercise 41 (mai 2009) : 2. http://dx.doi.org/10.1249/01.mss.0000352591.92981.b8.

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