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Myriam Paquette, François Bieuzen and François Billaut

maximal incremental test on a canoe or kayak ergometer at the end of their competitive season to examine the relation between peak power output (PPO) and various physiological variables (cardiac output, VO 2 max, and muscle oxygenation). A subset of 21 participants (8 MK, 4 MC, 4 WK, and 5 WC) also

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Pablo Jodra, Raúl Domínguez, Antonio J. Sánchez-Oliver, Pablo Veiga-Herreros and Stephen J. Bailey

placebo condition. This improvement in variables related to acceleration and peak power output after BJ supplementation might be expected to translate into enhanced acceleration, rate of force development, and peak force development. Subsequently, these enhancements might be expected to improved

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Marco J. Konings, Jordan Parkinson, Inge Zijdewind and Florentina J. Hettinga

participants completed in a randomized order 1 of the 2 different experimental 4-km TT conditions (see Procedures). No verbal coaching or motivation was given to the subjects during any of the TTs. Before each TT condition, subjects performed a 5-minute warm-up at an intensity of 30% peak power output (PPO

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Sally P. Waterworth, Connor C. Spencer, Aaron L. Porter and James P. Morton

impaired during the morning training session. Indeed, we recently observed that stepwise reductions in preexercise muscle glycogen concentration ∼100 mmol/kg of dry weight (as achieved by the sleep-low model) impaired morning exercise capacity at 80% peak power output (PPO) by ∼20–50% ( Hearris et

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Gethin H. Evans, Phillip Watson, Susan M. Shirreffs and Ronald J. Maughan

Previous investigations have suggested that exercise at intensities greater than 70% maximal oxygen uptake (VO2max) reduces gastric emptying rate during exercise, but little is known about the effect of exercise intensity on gastric emptying in the postexercise period. To examine this, 8 healthy participants completed 3 experimental trials that included 30 min of rest (R), low-intensity (L; 33% of peak power output) exercise, or high-intensity (H; 10 × 1 min at peak power output followed by 2 min rest) exercise. Thirty minutes after completion of exercise, participants ingested 595 ml of a 5% glucose solution, and gastric emptying rate was assessed via the double-sampling gastric aspiration method for 60 min. No differences (p > .05) were observed in emptying characteristics for total stomach volume or test meal volume between the trials, and the quantity of glucose delivered to the intestine did not differ between trials (p > .05). Half-emptying times did not differ (p = .902) between trials and amounted to 22 ± 9, 22 ± 9, and 22 ± 7 min (M ± SD) during the R, L, and H trials, respectively. These results suggest that exercise has little effect on postexercise gastric emptying rate of a glucose solution.

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Veronique Labelle, Laurent Bosquet, Said Mekary, Thien Tuong Minh Vu, Mark Smilovitch and Louis Bherer

The purpose of this study was to assess the effects of exercise intensity, age, and fitness levels on executive and nonexecutive cognitive tasks during exercise. Participants completed a computerized modified-Stroop task (including denomination, inhibition, and switching conditions) while pedaling on a cycle ergometer at 40%, 60%, and 80% of peak power output (PPO). We showed that a bout of moderate-intensity (60% PPO) to high-intensity (80% PPO) exercise was associated with deleterious performance in the executive component of the computerized modified-Stroop task (i.e., switching condition), especially in lower-fit individuals (p < .01). Age did not have an effect on the relationship between acute cardiovascular exercise and cognition. Acute exercise can momentarily impair executive control equivalently in younger and older adults, but individual’s fitness level moderates this relation.

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Carl D. Paton

Purpose:

Aerobic economy is an important factor that affects the performance of competitive cyclists. It has been suggested that placing the foot more anteriorly on the bicycle pedals may improve economy over the traditional foot position by improving pedaling efficiency. The current study examines the effects of changing the anterior-posterior pedal foot position on the physiology and performance of well-trained cyclists.

Methods:

In a crossover study, 10 competitive cyclists completed two maximal incremental and two submaximal tests in either their preferred (control) or a forward (arch) foot position. Maximum oxygen consumption and peak power output were determined from the incremental tests for both foot positions. On two further occasions, cyclists also completed a two-part 60-min submaximal test that required them to maintain a constant power output (equivalent to 60% of their incremental peak power) for 30 min, during which respiratory and blood lactate samples were taken at predetermined intervals. Thereafter, subjects completed a 30-min self-paced maximal effort time trial.

Results:

Relative to the control, the mean changes (±90% confidence limits) in the arch condition were as follows: maximum oxygen consumption, -0.5% (±2.0%); incremental peak power output, -0.8% (±1.3%); steady-state oxygen consumption at 60%, -2.4% (±1.1%); steady-state heart rate 60%, 0.4% (±1.7%); lactate concentration 60%, 8.7% (±14.4%); and mean time trial power, -1.5% (±2.9%).

Conclusions:

We conclude that there was no substantial physiological or performance advantage in this group using an arch-cleat shoe position in comparison with a cyclist’s normal preferred condition.

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Andrew D. Williams, Isaac Selva Raj, Kristie L. Stucas, James W. Fell, Diana Dickenson and John R. Gregory

Objectives:

Uncoupled cycling cranks are designed to remove the ability of one leg to assist the other during the cycling action. It has been suggested that training with this type of crank can increase mechanical efficiency. However, whether these improvements can confer performance enhancement in already well-trained cyclists has not been reported.

Method:

Fourteen well-trained cyclists (13 males, 1 female; 32.4 ± 8.8 y; 74.5 ± 10.3 kg; Vo2max 60.6 ± 5.5 mL·kg−1·min−1; mean ± SD) participated in this study. Participants were randomized to training on a stationary bicycle using either an uncoupled (n = 7) or traditional crank (n = 7) system. Training involved 1-h sessions, 3 days per week for 6 weeks, and at a heart rate equivalent to 70% of peak power output (PPO) substituted into the training schedule in place of other training. Vo2max, lactate threshold, gross efficiency, and cycling performance were measured before and following the training intervention. Pre- and post testing was conducted using traditional cranks.

Results:

No differences were observed between the groups for changes in Vo2max, lactate threshold, gross efficiency, or average power maintained during a 30-minute time trial.

Conclusion:

Our results indicate that 6 weeks (18 sessions) of training using an uncoupled crank system does not result in changes in any physiological or performance measures in well-trained cyclists.

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Neil S. Maxwell, Richard W.A. Mackenzie and David Bishop

Purpose:

To examine the effect of hypohydration on physiological strain and intermittent sprint exercise performance in the heat (35.5 ± 0.6°C, 48.7 ± 3.4% relative humidity).

Methods:

Eight unacclimatized males (age 23.4 ± 6.2 y, height 1.78 ± 0.04 m, mass 76.8 ± 7.7 kg) undertook three trials, each over two days. On day 1, subjects performed 90 min of exercise/heat-induced dehydration on a cycle ergometer, before following one of three rehydration strategies. On day 2, subjects completed a 36-min cycling intermittent sprint test (IST) with a -0.62 ± 0.74% (euhydrated, EUH), -1.81 (0.99)% (hypohydrated1, HYPO1), or -3.88 ± 0.89% (hypohydrated2, HYPO2) body mass defcit.

Results:

No difference was observed in average total work (EUH, 3790 ± 556 kJ; HYPO1, 3785 ± 628 kJ; HYPO2, 3647 ± 339 kJ, P = 0.418), or average peak power (EUH, 1315 ± 129 W; HYPO1, 1304 ± 175 W; HYPO2, 1282 ± 128 W, P = 0.356) between conditions on day 2. Total work and peak power output in the sprint immediately following an intense repeated sprint bout during the IST were lower in the HYPO2 condition. Physiological strain index was greater in the HYPO2 vs. the EUH condition, but without changes in metabolic markers.

Conclusion:

A greater physiological strain was observed with the greatest degree of hypohydration; however, sprint performance only diminished in the most hypohydrated state near the end of the IST, following an intense bout of repeating sprinting.

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Jos J. de Koning, Dionne A. Noordhof, Tom P. Uitslag, Rianna E Galiart, Christopher Dodge and Carl Foster

Purpose:

Gross efficiency (GE) is coupling power production to propulsion and is an important performance-determining factor in endurance sports. Measuring GE normally requires measuring VO2 during submaximal exercise. In this study a method is proposed to estimating GE during high-intensity exercise.

Methods:

Nineteen subjects completed a maximal incremental test and 2 GE tests (1 experimental and 1 control test). The GE test consisted of 10 min cycling at 50% peak power output (PPO), 2 min at 25 W, followed by 4 min 100% PPO, 1 min at 25 W, and another 10 min at 50% PPO. GE was determined for the 50%-PPO sections and was, for the second 50%-PPO section, back-extrapolated, using linear regression, to the end of the 100%-PPO bout.

Results:

Back-extrapolation of the GE data resulted in a calculated GE of 15.8% ± 1.7% at the end of the 100%-PPO bout, in contrast to 18.3% ± 1.3% during the final 2 min of the first 10-min 50%-PPO bout.

Conclusion:

Back-extrapolation seems valuable in providing more insight in GE during high-intensity exercise.