Effects of Normobaric Hypoxia on Matched-severe Exercise and Power-duration Relationship

2021 ◽  
Author(s):  
Ana Catarina Sousa ◽  
Gregoire P. Millet ◽  
João Viana ◽  
Jaime Milheiro ◽  
Vítor Reis
Keyword(s):  
Relative Intensity ◽  
Slow Component ◽  
Exponential Model ◽  
Normobaric Hypoxia ◽  
Time To Exhaustion ◽  
V̇o2 Kinetics ◽  
Severe Intensity ◽  
Lower Oxygen ◽  
Severe Exercise ◽  
Duration Relationship

AbstractWe investigated the effects of hypoxia on matched-severe intensity exercise and on the parameters of the power-duration relationship. Fifteen trained subjects performed in both normoxia and normobaric hypoxia (FiO2=0.13, ~3000 m) a maximal incremental test, a 3 min all-out test (3AOT) and a transition from rest to an exercise performed to exhaustion (Tlim) at the same relative intensity (80%∆). Respiratory and pulmonary gas-exchange variables were continuously measured (K5, Cosmed, Italy). Tlim test’s V̇O2 kinetics was calculated using a two-component exponential model. V̇O2max (44.1±5.1 vs. 58.7±6.4 ml.kg-1.min-1, p<0.001) was decreased in hypoxia. In Tlim, time-to-exhaustion sustained was similar (454±130 vs. 484±169 s) despite that V̇O2 kinetics was slower (τ1: 31.1±5.8 vs. 21.6±4.7 s, p<0.001) and the amplitude of the V̇O2 slow component lower (12.4±5.4 vs. 20.2±5.7 ml.kg-1.min-1, p<0.05) in hypoxia. CP was reduced (225±35 vs. 270±49 W, p<0.001) but W’ was unchanged (11.3±2.9 vs. 11.4±2.7 kJ) in hypoxia. The changes in CP/V̇O2max were positively correlated with changes in W’ (r = 0.58, p<0.05). The lower oxygen availability had an impact on aerobic related physiological parameters, but exercise tolerance is similar between hypoxia and normoxia when the relative intensity is matched despite a slower V̇O2 kinetics in hypoxia.

The Effect of Prior Moderate- and Heavy-Intensity Running on the VO2 Response to Exhaustive Severe-Intensity Running

2006 ◽  
Vol 1 (4) ◽  
pp. 361-374 ◽  
Author(s):  
Stephen B. Draper ◽  
Dan M. Wood ◽  
Jo Corbett ◽  
David V.B. James ◽  
Christopher R. Potter
Keyword(s):  
Oxygen Uptake ◽  
Slow Component ◽  
Maximum Oxygen Uptake ◽  
Moderate Intensity ◽  
Time To Exhaustion ◽  
Heavy Exercise ◽  
Square Wave ◽  
Severe Intensity ◽  
The Difference ◽  
Trained Runners

We tested the hypothesis that prior heavy-intensity exercise reduces the difference between asymptotic oxygen uptake (VO2) and maximum oxygen uptake (VO2max) during exhaustive severe-intensity running lasting ≍2 minutes. Ten trained runners each performed 2 ramp tests to determine peak VO2 (VO2peak) and speed at venti-latory threshold. They performed exhaustive square-wave runs lasting ≍2 minutes, preceded by either 6 minutes of moderate-intensity running and 6 minutes rest (SEVMOD) or 6 minutes of heavy-intensity running and 6 minutes rest (SEVHEAVY). Two transitions were completed in each condition. VO2 was determined breath by breath and averaged across the 2 repeats of each test; for the square-wave test, the averaged VO2 response was then modeled using a monoexponential function. The amplitude of the VO2 response to severe-intensity running was not different in the 2 conditions (SEVMOD vs SEVHEAVY; 3925 ± 442 vs 3997 ± 430 mL/min, P = .237), nor was the speed of the response (τ; 9.2 ± 2.1 vs 10.0 ± 2.1 seconds, P = .177). VO2peak from the square-wave tests was below that achieved in the ramp tests (91.0% ± 3.2% and 92.0% ± 3.9% VO2peak, P < .001). There was no difference in time to exhaustion between conditions (110.2 ± 9.7 vs 111.0 ± 15.2 seconds, P = .813). The results show that the primary VO2 response is unaffected by prior heavy exercise in running performed at intensities at which exhaustion will occur before a slow component emerges.

Influence of repeated sprint training on pulmonary O2 uptake and muscle deoxygenation kinetics in humans

2009 ◽  
Vol 106 (6) ◽  
pp. 1875-1887 ◽  
Author(s):  
Stephen J. Bailey ◽  
Daryl P. Wilkerson ◽  
Fred J. DiMenna ◽  
Andrew M. Jones
Keyword(s):  
Slow Component ◽  
Moderate Intensity ◽  
Control Group ◽  
Sprint Training ◽  
Short Term ◽  
Muscle Deoxygenation ◽  
Severe Intensity ◽  
Exercise Transitions ◽  
Severe Exercise ◽  
Kinetics Of

We hypothesized that a short-term training program involving repeated all-out sprint training (RST) would be more effective than work-matched, low-intensity endurance training (ET) in enhancing the kinetics of oxygen uptake (V̇o2) and muscle deoxygenation {deoxyhemoglobin concentration ([HHb])} following the onset of exercise. Twenty-four recreationally active subjects (15 men, mean ± SD: age 21 ± 4 yr, height 173 ± 9 cm, body mass 71 ± 11 kg) were allocated to one of three groups: RST, which completed six sessions of four to seven 30-s RSTs; ET, which completed six sessions of work-matched, moderate-intensity cycling; and a control group (CON). All subjects completed moderate-intensity and severe-intensity “step” exercise transitions before (Pre) and after the 2-wk intervention period (Post). Following RST, [HHb] kinetics were speeded, and the amplitude of the [HHb] response was increased during both moderate and severe exercise ( P < 0.05); the phase II V̇o2 kinetics were accelerated for both moderate (Pre: 28 ± 8, Post: 21 ± 8 s; P < 0.01) and severe (Pre: 29 ± 5, Post: 23 ± 5 s; P < 0.05) exercise; the amplitude of the V̇o2 slow component was reduced (Pre: 0.52 ± 0.19, Post: 0.40 ± 0.17 l/min; P < 0.01); and exercise tolerance during severe exercise was improved by 53% (Pre: 700 ± 234, Post: 1,074 ± 431 s; P < 0.01). None of these parameters was significantly altered in the ET and CON groups. Six sessions of RST, but not ET, resulted in changes in [HHb] kinetics consistent with enhanced fractional muscle O2 extraction, faster V̇o2 kinetics, and an increased tolerance to high-intensity exercise.

scholarly journals O2 uptake kinetics during exercise at peak O2 uptake

2003 ◽  
Vol 95 (5) ◽  
pp. 2014-2022 ◽  
Author(s):  
Barry W. Scheuermann ◽  
Thomas J. Barstow
Keyword(s):  
Time Constant ◽  
Slow Component ◽  
Motor Units ◽  
Oxidative Capacity ◽  
Exponential Model ◽  
Primary Component ◽  
Moderate Intensity ◽  
O2 Uptake ◽  
Ergometer Exercise ◽  
Severe Intensity

Compared with moderate- and heavy-intensity exercise, the adjustment of O2 uptake (V̇o2) to exercise intensities that elicit peak V̇o2 has received relatively little attention. This study examined the V̇o2 response of 21 young, healthy subjects (25 ± 6 yr; mean ± SD) during cycle ergometer exercise to step transitions in work rate (WR) corresponding to 90, 100, and 110% of the peak WR achieved during a preliminary ramp protocol (15-30 W/min). Gas exchange was measured breath by breath and interpolated to 1-s values. V̇o2 kinetics were determined by use of a two- or three-component exponential model to isolate the time constant (τ2) as representative of V̇o2 kinetics and the amplitude (Amp) of the primary fast component independent of the appearance of any V̇o2 slow component. No difference in V̇o2 kinetics was observed between WRs (τ90 = 24.7 ± 9.0; τ100 = 22.8 ± 6.7; τ110 = 21.5 ± 9.2 s, where subscripts denote percent of peak WR; P > 0.05); nor in a subgroup of eight subjects was τ2 different from the value for moderate-intensity (<lactate threshold) exercise (τ2 = 25 ± 12 s, P > 0.05). As expected, the Amp increased with increasing WRs (Amp90 = 2,089 ± 548; Amp100 = 2,165 ± 517; Amp110 = 2,225 ± 559 ml/min; Amp90 vs. Amp110, P < 0.05). However, the gain (G) of the V̇o2 response (ΔV̇o2/ΔWR) decreased with increasing WRs (G90 = 8.5 ± 0.6; G100 = 7.9 ± 0.6; G110 = 7.3 ± 0.6 ml·min-1·W-1; P < 0.05). The Amp of the primary component approximated 85, 88, and 89% of peak V̇o2 during 90, 100, and 110% WR transitions, respectively. The results of the present study demonstrate that, compared with moderate- and heavy-intensity exercise, the gain of the V̇o2 response (as ΔV̇o2/ΔWR) is reduced for exercise transitions in the severe-intensity domain, but the approach to this gain is well described by a common time constant that is invariant across work intensities. The lower ΔV̇o2/ΔWR may be due to an insufficient adjustment of the cardiovascular and/or pulmonary systems that determine O2 delivery to the exercising muscles or due to recruitment of motor units with lower oxidative capacity, after the onset of exercise in the severe-intensity domain.

Determination of Critical Power by Pulmonary Gas Exchange

1999 ◽  
Vol 24 (1) ◽  
pp. 74-86 ◽  
Author(s):  
David W. Hill ◽  
Jimmy C. Smith
Keyword(s):  
Critical Power ◽  
Metabolic Response ◽  
Slow Component ◽  
Practice Effect ◽  
Time To Exhaustion ◽  
Good Precision ◽  
Severe Intensity ◽  
Text Response ◽  
Two Parameters ◽  
The Relationship

Although the physiological underpinnings of critical power (CP) have yet to be fully elucidated, it has been proposed that CP demarcates the heavy and severe exercise intensity domains and that each domain is associated with a different pattern of metabolic response and mechanism of fatigue. Severe intensity has been defined such that, during exercise at intensities above CP, the slow component of the [Formula: see text] response will drive [Formula: see text] to [Formula: see text] at the point of fatigue. In this Study, two parameters were derived for each of 8 participants: (a) CP, the asymptote of the relationship between power and time to exhaustion, and (b) a related parameter, CP′, the asymptote of the relationship between power and time to [Formula: see text] CP′ theoretically represents the threshold intensity above which [Formula: see text] will be elicited during exercise of sufficient duration. Participants performed two exhaustive tests at CP. There were three important findings: First, there was a practice effect on time to exhaustion at CP, and times increased 27% in the second test. Second, both CP and CP′ could be obtained with good precision. Third, and most important, CP was equal to CP′, thereby providing a physiological description of the mathematically derived CP parameter. It was concluded that [Formula: see text] cannot be elicited at intensities equal to or less than CP. Key words: cycle ergometry, endurance, exercise

Acute l-arginine supplementation reduces the O2 cost of moderate-intensity exercise and enhances high-intensity exercise tolerance

2010 ◽  
Vol 109 (5) ◽  
pp. 1394-1403 ◽  
Author(s):  
Stephen J. Bailey ◽  
Paul G. Winyard ◽  
Anni Vanhatalo ◽  
Jamie R. Blackwell ◽  
Fred J. DiMenna ◽  
...  
Keyword(s):  
Exercise Tolerance ◽  
Slow Component ◽  
Moderate Intensity ◽  
Time To Exhaustion ◽  
Moderate Intensity Exercise ◽  
Double Blind ◽  
Healthy Humans ◽  
Severe Intensity ◽  
Component Amplitude ◽  
Plasma Nitrite

It has recently been reported that dietary nitrate (NO3−) supplementation, which increases plasma nitrite (NO2−) concentration, a biomarker of nitric oxide (NO) availability, improves exercise efficiency and exercise tolerance in healthy humans. We hypothesized that dietary supplementation with l-arginine, the substrate for NO synthase (NOS), would elicit similar responses. In a double-blind, crossover study, nine healthy men (aged 19–38 yr) consumed 500 ml of a beverage containing 6 g of l-arginine (Arg) or a placebo beverage (PL) and completed a series of “step” moderate- and severe-intensity exercise bouts 1 h after ingestion of the beverage. Plasma NO2− concentration was significantly greater in the Arg than the PL group (331 ± 198 vs. 159 ± 102 nM, P < 0.05) and systolic blood pressure was significantly reduced (123 ± 3 vs. 131 ± 5 mmHg, P < 0.01). The steady-state O2 uptake (V̇o2) during moderate-intensity exercise was reduced by 7% in the Arg group (1.48 ± 0.12 vs. 1.59 ± 0.14 l/min, P < 0.05). During severe-intensity exercise, the V̇o2 slow component amplitude was reduced (0.58 ± 0.23 and 0.76 ± 0.29 l/min in Arg and PL, respectively, P < 0.05) and the time to exhaustion was extended (707 ± 232 and 562 ± 145 s in Arg and PL, respectively, P < 0.05) following consumption of Arg. In conclusion, similar to the effects of increased dietary NO3− intake, elevating NO bioavailability through dietary l-Arg supplementation reduced the O2 cost of moderate-intensity exercise and blunted the V̇o2 slow component and extended the time to exhaustion during severe-intensity exercise.

Effect of acute nitrate ingestion on V̇O2 response at different exercise intensity domains

2017 ◽  
Vol 42 (11) ◽  
pp. 1127-1134 ◽  
Author(s):  
Thaysa Ghiarone ◽  
Thays Ataide-Silva ◽  
Romulo Bertuzzi ◽  
Glenn Kevin McConell ◽  
Adriano Eduardo Lima-Silva
Keyword(s):  
Oxygen Uptake ◽  
Exercise Intensity ◽  
Slow Component ◽  
Peak Oxygen Uptake ◽  
Time To Exhaustion ◽  
Severe Exercise ◽  
Nitrate Supplementation ◽  
The Difference ◽  
Response To Exercise ◽  
Gas Exchange Threshold

While nitrate supplementation influences oxygen uptake (V̇O2) response to exercise, this effect may be intensity dependent. The purpose of this study was to investigate the effect of acute nitrate supplementation on V̇O2 response during different exercise intensity domains in humans. Eleven men ingested 10 mg·kg−1 body mass (8.76 ± 1.35 mmol) of sodium nitrate or sodium chloride (placebo) 2.5 h before cycling at moderate (90% of gas exchange threshold; GET), heavy (GET + 40% of the difference between GET and peak oxygen uptake (V̇O2peak), Δ 40) or severe (GET + 80% of the difference between GET and V̇O2peak, Δ 80) exercise intensities. Volunteers performed exercise for 10 min (moderate), 15 min (heavy) or until exhaustion (severe). Acute nitrate supplementation had no effect on any V̇O2 response parameters during moderate and severe exercise intensities. However, the V̇O2 slow amplitude (nitrate: 0.93 ± 0.36 L·min−1 vs. placebo: 1.13 ± 0.59 L·min−1, p = 0.04) and V̇O2 slow gain (nitrate: 5.81 ± 2.37 mL·min–1·W−1 vs. placebo: 7.09 ± 3.67 mL·min–1·W−1, p = 0.04) were significantly lower in nitrate than in placebo during the heavy exercise intensity. There was no effect of nitrate on plasma lactate during any exercise intensity (p > 0.05). Time to exhaustion during the severe exercise intensity was also not affected by nitrate (p > 0.05). In conclusion, acute nitrate supplementation reduced the slow component of V̇O2 only when performing heavy-intensity exercise, which might indicate an intensity-dependent effect of nitrate on V̇O2 response.

Influence of priming exercise on pulmonary O2 uptake kinetics during transitions to high-intensity exercise from an elevated baseline

2008 ◽  
Vol 105 (2) ◽  
pp. 538-546 ◽  
Author(s):  
Fred J. DiMenna ◽  
Daryl P. Wilkerson ◽  
Mark Burnley ◽  
Andrew M. Jones
Keyword(s):  
Gas Exchange ◽  
Metabolic Rate ◽  
Phase Ii ◽  
Slow Component ◽  
Vastus Lateralis ◽  
Moderate Intensity ◽  
Severe Intensity ◽  
Severe Exercise ◽  
Priming Exercise ◽  
The Difference

It has been suggested that the slower O2 uptake (V̇o2) kinetics observed when exercise is initiated from an elevated baseline metabolic rate are linked to an impairment of muscle O2 delivery. We hypothesized that “priming” exercise would significantly reduce the phase II time constant (τ) during subsequent severe-intensity cycle exercise initiated from an elevated baseline metabolic rate. Seven healthy men completed exercise transitions to 70% of the difference between gas exchange threshold (GET) and peak V̇o2 from a moderate-intensity baseline (90% GET) on three occasions in each of the “unprimed” and “primed” conditions. Pulmonary gas exchange, heart rate, and the electromyogram of m. vastus lateralis were measured during all tests. The phase II V̇o2 kinetics were slower when severe exercise was initiated from a baseline of moderate exercise compared with unloaded pedaling (mean ± SD τ, 42 ± 15 vs. 33 ± 8 s; P < 0.05), but were not accelerated by priming exercise (42 ± 17 s; P > 0.05). The amplitude of the V̇o2 slow component and the change in electromyogram from minutes 2 to 6 were both significantly reduced following priming exercise (V̇o2 slow component: from 0.47 ± 0.09 to 0.27 ± 0.13 l/min; change in integrated electromyogram between 2 and 6 min: from 51 ± 35 to 26±43% of baseline; P < 0.05 for both comparisons). These results indicate that the slower phase II V̇o2 kinetics observed during transitions to severe exercise from an elevated baseline are not altered by priming exercise, but that the reduced V̇o2 slow component may be linked to changes in muscle fiber activation.

scholarly journals Ergogenic effects of beetroot juice supplementation during severe-intensity exercise in obese adolescents

2018 ◽  
Vol 315 (3) ◽  
pp. R453-R460 ◽  
Author(s):  
Letizia Rasica ◽  
Simone Porcelli ◽  
Mauro Marzorati ◽  
Desy Salvadego ◽  
Alessandra Vezzoli ◽  
...  
Keyword(s):  
Exercise Tolerance ◽  
Healthy Subjects ◽  
Slow Component ◽  
Moderate Intensity ◽  
Time To Exhaustion ◽  
Beetroot Juice ◽  
Obese Adolescents ◽  
Physiological Variables ◽  
Severe Intensity ◽  
Ergogenic Effects

Previous studies showed a higher O2 cost of exercise, and therefore, a reduced exercise tolerance in patients with obesity during constant work rate (CWR) exercise compared with healthy subjects. Among the ergogenic effects of dietary nitrate ([Formula: see text]) supplementation in sedentary healthy subjects, a reduced O2 cost and enhanced exercise tolerance have often been demonstrated. The aim of this study was to evaluate the effects of beetroot juice (BR) supplementation, rich in [Formula: see text], on physiological variables associated with exercise tolerance in adolescents with obesity. In a double-blind, randomized crossover study, 10 adolescents with obesity (8 girls, 2 boys; age = 16 ± 1 yr; body mass index = 35.2 ± 5.0 kg/m2) were tested after 6 days of supplementation with BR (5 mmol [Formula: see text] per day) or placebo (PLA). Following each supplementation period, patients carried out two repetitions of 6-min moderate-intensity CWR exercise and one severe-intensity CWR exercise until exhaustion. Plasma [Formula: see text] concentration was significantly higher in BR versus PLA (108 ± 37 vs. 15 ± 5 μM, P < 0.0001). The O2 cost of moderate-intensity exercise was not different in BR versus PLA (13.3 ± 1.7 vs. 12.9 ± 1.1 ml·min−1·W−1, P = 0.517). During severe-intensity exercise, signs of a reduced amplitude of the O2 uptake slow component were observed in BR, in association with a significantly longer time to exhaustion (561 ± 198 s in BR vs. 457 ± 101 s in PLA, P = 0.0143). In obese adolescents, short-term dietary [Formula: see text] supplementation is effective in improving exercise tolerance during severe-intensity exercise. This may prove to be useful in counteracting early fatigue and reduced physical activity in this at-risk population.

scholarly journals The Effects of 15 or 30 s SIT in Normobaric Hypoxia on Aerobic, Anaerobic Performance and Critical Power

2021 ◽  
Vol 18 (8) ◽  
pp. 3976
Author(s):  
Hakan Karabiyik ◽  
Mustafa Can Eser ◽  
Ozkan Guler ◽  
Burak Caglar Yasli ◽  
Goktug Ertetik ◽  
...  
Keyword(s):  
Critical Power ◽  
Interval Training ◽  
Normobaric Hypoxia ◽  
Time To Exhaustion ◽  
Anaerobic Performance ◽  
Sprint Interval Training ◽  
Mean Power ◽  
Training Adaptations ◽  
Post Test

Sprint interval training (SIT) is a concept that has been shown to enhance aerobic-anaerobic training adaptations and induce larger effects in hypoxia. The purpose of this study was to examine the effects of 4 weeks of SIT with 15 or 30 s in hypoxia on aerobic, anaerobic performance and critical power (CP). A total of 32 male team players were divided into four groups: SIT with 15 s at FiO2: 0.209 (15 N); FiO2: 0.135 (15 H); SIT with 30 s at FiO2: 0.209 (30 N); and FiO2: 0.135 (30 H). VO2max did not significantly increase, however time-to-exhaustion (TTE) was found to be significantly longer in the post test compared to pre test (p = 0.001) with no difference between groups (p = 0.86). Mean power (MPw.kg) after repeated wingate tests was significantly higher compared to pre training in all groups (p = 0.001) with no difference between groups (p = 0.66). Similarly, CP was increased in all groups with 4 weeks of SIT (p = 0.001) with no difference between groups (p = 0.82). This study showed that 4 weeks of SIT with 15 and 30 s sprint bouts in normoxia or hypoxia did not increased VO2max in trained athletes. However, anerobic performance and CP can be increased with 4 weeks of SIT both in normoxia or hypoxia with 15 or 30 s of sprint durations.

Longitudinal changes in the kinetic response to heavy-intensity exercise in children

2004 ◽  
Vol 97 (2) ◽  
pp. 460-466 ◽  
Author(s):  
Samantha G. Fawkner ◽  
Neil Armstrong
Keyword(s):  
Slow Component ◽  
Phase 1 ◽  
Exponential Model ◽  
Cycle Ergometer ◽  
Primary Component ◽  
Total Change ◽  
Exercise Tests ◽  
Longitudinal Changes ◽  
Dependent Change ◽  
The Difference

The purpose of this study was to investigate longitudinal changes with age in the kinetic response to cycling at heavy-intensity exercise in boys and girls. Twenty-two prepubertal children (13 male, 9 female) carried out a series of exercise tests on two test occasions with a 2-yr interval. On each test occasion, the subject completed multiple transitions from baseline to 40% of the difference between their previously determined V-slope and peak O2 uptake (V̇o2) for 9 min on an electronically braked cycle ergometer. Each subject's breath-by-breath responses were interpolated to 1-s intervals, time aligned, and averaged. The data after phase 1 were fit with 1) a double exponential model and 2) a single exponential model within a fitting window that was previously identified to exclude the slow component. There were no significant differences in the parameters of the primary component between each model. Subsequent analysis was carried out using model 2. The V̇o2 slow component was computed as the difference between the amplitude of the primary component and the end-exercise V̇o2 and was expressed as the percent contribution to the total change in V̇o2. Over the 2-yr period, the primary time constant (boys 16.8 ± 5.3 and 21.7 ± 5.3 s, girls 21.1 ± 8.1 and 26.4 ± 8.4 s, first and second occasion, respectively) and the relative amplitude of the slow component (boys 9.4 ± 4.6 and 13.8 ± 5.3%, girls 10.3 ± 2.4 and 15.5 ± 2.8%, first and second occasion, respectively) significantly increased with no sex differences. The data demonstrate that children do display a slow-component response to exercise and are consistent with an age-dependent change in the muscles' potential for O2 utilization.

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