scholarly journals Effect of a 15% Increase in Preferred Pedal Rate on Time to Exhaustion During Heavy Exercise

2004 ◽  
Vol 29 (2) ◽  
pp. 146-156 ◽  
Author(s):  
Xavier Nesi ◽  
Laurent Bosquet ◽  
Serge Berthoin ◽  
Jeanne Dekerle ◽  
Patrick Pelayo
Keyword(s):  
Exercise Tolerance ◽  
Ventilatory Threshold ◽  
Slow Component ◽  
Time To Exhaustion ◽  
Heavy Exercise ◽  
Pedal Rate ◽  
Competitive Cyclists ◽  
Text Response ◽  
Specific Formula ◽  
The Difference

The aim of this study was to evaluate the effect of a 15% increase in preferred pedal rate (PPR) on both time to exhaustion and pulmonary O2 uptake [Formula: see text] response during heavy exercise. Seven competitive cyclists underwent two constant-power tests (CPT) at a power output that theoretically requires 50% of the difference in [Formula: see text] between the second ventilatory threshold and [Formula: see text]max (PΔ50). Each cyclist cycled a CPT at PPR (CPTPPR) and a CPT at +15% of PPR (CPT+15%) in a randomized order. The average PPR value was 94 ± 4 rpm, and time to exhaustion was significantly longer in CPTPPR compared with CPT+15% (465 ± 139 vs. 303 ± 42 s, respectively; p = 0.01). A significant decrease in [Formula: see text] values in the first minutes of exercise and a significant increase in [Formula: see text] slow component was reported in CPT+15% compared with CPTPPR. These data indicate that the increase of 15% PPR was associated with a decrease in exercise tolerance and a specific [Formula: see text] response, presumably due to an increase of negative muscular work, internal work, and an altering of motor unit recruitment patterns. Key words: aerobic demand, cadence, cyclists, exercise tolerance, pedaling frequency

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.

scholarly journals Effect of pedal rate on primary and slow-component oxygen uptake responses during heavy-cycle exercise

2003 ◽  
Vol 94 (4) ◽  
pp. 1501-1507 ◽  
Author(s):  
Jamie S. M. Pringle ◽  
Jonathan H. Doust ◽  
Helen Carter ◽  
Keith Tolfrey ◽  
Andrew M. Jones
Keyword(s):  
Power Output ◽  
Ventilatory Threshold ◽  
Slow Component ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Motor Units ◽  
Primary Component ◽  
Heavy Exercise ◽  
Cycle Exercise ◽  
Pedal Rate

We hypothesized that a higher pedal rate (assumed to result in a greater proportional contribution of type II motor units) would be associated with an increased amplitude of the O2 uptake (V˙o 2) slow component during heavy-cycle exercise. Ten subjects (mean ± SD, age 26 ± 4 yr, body mass 71.5 ± 7.9 kg) completed a series of square-wave transitions to heavy exercise at pedal rates of 35, 75, and 115 rpm. The exercise power output was set at 50% of the difference between the pedal rate-specific ventilatory threshold and peakV˙o 2, and the baseline power output was adjusted to account for differences in the O2 cost of unloaded pedaling. The gain of the V˙o 2primary component was significantly higher at 35 rpm compared with 75 and 115 rpm (mean ± SE, 10.6 ± 0.3, 9.5 ± 0.2, and 8.9 ± 0.4 ml · min−1 · W−1, respectively; P < 0.05). The amplitude of theV˙o 2 slow component was significantly greater at 115 rpm (328 ± 29 ml/min) compared with 35 rpm (109 ± 30 ml/min) and 75 rpm (202 ± 38 ml/min) ( P < 0.05). There were no significant differences in the time constants or time delays associated with the primary and slow components across the pedal rates. The change in blood lactate concentration was significantly greater at 115 rpm (3.7 ± 0.2 mM) and 75 rpm (2.8 ± 0.3 mM) compared with 35 rpm (1.7 ± 0.4 mM) ( P < 0.05). These data indicate that pedal rate influences V˙o 2 kinetics during heavy exercise at the same relative intensity, presumably by altering motor unit recruitment patterns.

Gas exchange kinetics in obese adolescents. Inferences on exercise tolerance and prescription

2010 ◽  
Vol 299 (5) ◽  
pp. R1298-R1305 ◽  
Author(s):  
Desy Salvadego ◽  
Stefano Lazzer ◽  
Carlo Busti ◽  
Raffaela Galli ◽  
Fiorenza Agosti ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Gas Exchange ◽  
Oxidative Metabolism ◽  
Exercise Tolerance ◽  
Slow Component ◽  
Control Group ◽  
Time To Exhaustion ◽  
Functional Evaluation ◽  
Obese Adolescents ◽  
Fundamental Component

A functional evaluation of skeletal muscle oxidative metabolism was performed in a group of obese adolescents (OB). The various components of pulmonary O2 uptake (V̇o2) kinetics were evaluated during 10-min constant-load exercises (CLE) on a cycloergometer at different percentages of V̇o2max. The relationships of these components with the gas exchange threshold (GET) were determined. Fourteen male OB [age 16.5 ± 1.0 (SD) yr, body mass index 34.5 ± 3.1 kg·m−2] and 13 normal-weight, age-matched nonathletic male volunteers (control group) were studied. The time-constant (τf) of the fundamental component and the presence, pattern, and relative amplitude of the slow component of V̇o2 kinetics were determined at 40, 60, and 80% of V̇o2max, previously estimated during an incremental test. V̇o2max (l/min) was similar in the two groups. GET was lower in OB (55.7 ± 6.7% of V̇o2max) than in control (65.1 ± 5.2%) groups. The τf was higher in OB subjects, indicating a slower fundamental component. At CLE 60% (above GET in OB subjects, below GET in control subjects) a slow component was observed in nine out of fourteen OB subjects, but none in the control group. All subjects developed a slow component at CLE 80% (above GET in both OB and control). Twelve OB subjects did not complete the 10-min CLE 80% due to voluntary exhaustion. In nine OB subjects, the slow component was characterized by a linear increase in V̇o2 as a function of time. The slope of this increase was inversely related to the time to exhaustion. The above findings should negatively affect exercise tolerance in obese adolescents and suggest an impairment of skeletal muscle oxidative metabolism. Also in obese adolescents, exercise evaluation and prescription at submaximal loads should be done with respect to GET and not at a given percentage of V̇o2max.

Cardiovascular and Oxygen Uptake Kinetics During Sequential Heavy Cycling Exercises

2003 ◽  
Vol 28 (2) ◽  
pp. 283-298 ◽  
Author(s):  
Stéphane Perrey ◽  
Jodie Scott ◽  
Laurent Mourot ◽  
Jean-Denis Rouillon
Keyword(s):  
Cardiac Output ◽  
Oxygen Uptake ◽  
Time Constant ◽  
Impedance Cardiography ◽  
Ventilatory Threshold ◽  
Slow Component ◽  
Oxygen Uptake Kinetics ◽  
Cycle Ergometer ◽  
Fast Component ◽  
Heavy Exercise

The purpose of the present study was to assess the relationship between the rapidity of increased oxygen uptake [Formula: see text] and increased cardiac output (CO) during heavy exercise. Six subjects performed repeated bouts on a cycle ergometer above the ventilatory threshold (∼80% of peak [Formula: see text]) separated by 10-min recovery cycling at 35% peak [Formula: see text]. [Formula: see text] was determined breath-by-breath and CO was determined continuously by impedance cardiography. CO and [Formula: see text] values were significantly higher during the 2-min period preceding the second bout. The overall responses for [Formula: see text] and CO were significantly related and were faster during the second bout. Prior heavy exercise resulted in a significant increase in the amplitude of the fast component of [Formula: see text] with no change in the time constant and a decrease in the slow component. Under these circumstances, the amplitude of the fast component was more sensitive to prior heavy exercise than was the associated time constant. Key words: impedance cardiography, exercise transitions, cardiac output, prior exercise

Letters to the Editor

1998 ◽  
Vol 85 (4) ◽  
pp. 1593-1600
Author(s):  
Guido Ferretti
Keyword(s):  
Slow Component ◽  
Oxygen Uptake Kinetics ◽  
Work Rate ◽  
Hot Water ◽  
Muscle Temperature ◽  
Appreciable Effect ◽  
Heavy Exercise ◽  
Letters To The Editor ◽  
Heavy Work ◽  
The Difference

The following is the abstract of the article discussed in the subsequent letter: Koga, Shunsaku, Tomoyuki Shiojiri, Narihiko Kondo, and Thomas J. Barstow. Effect of increased muscle temperature on oxygen uptake kinetics during exercise. J. Appl. Physiol. 83(4): 1333–1338, 1997.—To test whether increased muscle temperature (Tm) would improve O2 uptake (V˙o 2) kinetics, seven men performed transitions from rest to a moderate work rate [below the estimated lactate threshold (LTest)] and a heavy work rate (V˙o 2 = 50% of the difference between LTest and peakV˙o 2) under conditions of normal Tm (N) and increased Tm (H), produced by wearing hot water-perfused pants before exercise. Quadriceps Tm was significantly higher in H, but rectal temperature was similar for the two conditions. There were no significant differences in the amplitudes of the fast component ofV˙o 2 or in the time constants of the on and off transients for moderate and heavy exercise between the two conditions. The increment inV˙o 2 between the 3rd and 6th min of heavy exercise was slightly but significantly smaller for H than for N. These data suggest that elevated Tm before exercise onset, which would have been expected to increase O2delivery and off-loading to the muscle, had no appreciable effect on the fast exponential component ofV˙o 2 kinetics (invariant time constant). These data further suggest that elevated Tm does not contribute to the slow component ofV˙o 2 during heavy exercise.

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.

scholarly journals Effect of muscle mass on V˙o 2kinetics at the onset of work

2001 ◽  
Vol 90 (2) ◽  
pp. 461-468 ◽  
Author(s):  
Shunsaku Koga ◽  
Thomas J. Barstow ◽  
Tomoyuki Shiojiri ◽  
Tetsuo Takaishi ◽  
Yoshiyuki Fukuba ◽  
...  
Keyword(s):  
Muscle Mass ◽  
Ventilatory Threshold ◽  
Slow Component ◽  
Cycle Ergometer ◽  
Muscle Recruitment ◽  
Heavy Exercise ◽  
Mean Response Time ◽  
Heavy Work ◽  
Exercise Transitions ◽  
Recruitment Patterns

The dependence of O2 uptake (V˙o 2) kinetics on the muscle mass recruited under conditions when fiber and muscle recruitment patterns are similar following the onset of exercise has not been determined. We developed a motorized cycle ergometer that facilitated one-leg (1L) cycling in which the electromyographic (EMG) profile of the active muscles was not discernibly altered from that during two-leg (2L) cycling. Six subjects performed 1L and 2L exercise transitions from unloaded cycling to moderate [<ventilatory threshold (VT)] and heavy (>VT) exercise. The 1L condition yielded kinetics that was unchanged from the 2L condition [the phase 2 time constants (τ1, in s) for <VT were as follows: 1L = 16.8±8.4 (SD), 2L = 18.4 ± 8.1, P > 0.05; for >VT: 1L = 26.8 ± 12.0; 2L = 27.8 ± 16.1, P > 0.05]. The overall V˙o 2 kinetics (mean response time) was not significantly different for the two exercise conditions. However, the gain of the fast component (the amplitude/work rate) during the 1L exercise was significantly higher than that for the 2L exercise for both moderate and heavy work rates. The slow-component responses evident for heavy exercise were temporally and quantitatively unaffected by the 1L condition. These data demonstrate that, when leg muscle recruitment patterns are unchanged as assessed by EMG analysis, on-transient V˙o 2 kinetics for both moderate and heavy exercise are not dependent on the muscle mass recruited.

scholarly journals Oxygen uptake kinetics during treadmill running in boys and men

2001 ◽  
Vol 90 (5) ◽  
pp. 1700-1706 ◽  
Author(s):  
Craig A. Williams ◽  
Helen Carter ◽  
Andrew M. Jones ◽  
Jonathan H. Doust
Keyword(s):  
Oxygen Uptake ◽  
Time Constant ◽  
Slow Component ◽  
Oxygen Uptake Kinetics ◽  
Primary Response ◽  
Treadmill Running ◽  
Initial Increase ◽  
Moderate Exercise ◽  
Heavy Exercise ◽  
The Difference

The purpose of this study was to compare the kinetics of the oxygen uptake (V˙o 2) response of boys to men during treadmill running using a three-phase exponential modeling procedure. Eight boys (11–12 yr) and eight men (21–36 yr) completed an incremental treadmill test to determine lactate threshold (LT) and maximum V˙o 2. Subsequently, the subjects exercised for 6 min at two different running speeds corresponding to 80% of V˙o 2 at LT (moderate exercise) and 50% of the difference betweenV˙o 2 at LT and maximumV˙o 2 (heavy exercise). For moderate exercise, the time constant for the primary response was not significantly different between boys [10.2 ± 1.0 (SE) s] and men (14.7 ± 2.8 s). The gain of the primary response was significantly greater in boys than men (239.1 ± 7.5 vs. 167.7 ± 5.4 ml · kg−1 · km−1; P < 0.05). For heavy exercise, theV˙o 2 on-kinetics were significantly faster in boys than men (primary response time constant = 14.9 ± 1.1 vs. 19.0 ± 1.6 s; P < 0.05), and the primary gain was significantly greater in boys than men (209.8 ± 4.3 vs. 167.2 ± 4.6 ml · kg−1 · km−1; P < 0.05). The amplitude of theV˙o 2 slow component was significantly smaller in boys than men (19 ± 19 vs. 289 ± 40 ml/min; P < 0.05). The V˙o 2responses at the onset of moderate and heavy treadmill exercise are different between boys and men, with a tendency for boys to have faster on-kinetics and a greater initial increase inV˙o 2 for a given increase in running speed.

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