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This Article Full Text Full Text (PDF) All Versions of this Article: 294/3/R874    most recent 00678.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (3) Google Scholar Articles by Marcora, S. M. Articles by de Morree, H. M. PubMed PubMed Citation Articles by Marcora, S. M. Articles by de Morree, H. M.

NEUROHUMORAL CONTROL OF CARDIOVASCULAR FUNCTION

Locomotor muscle fatigue increases cardiorespiratory responses and reduces performance during intense cycling exercise independently from metabolic stress

¹School of Sport, Health and Exercise Sciences, Bangor University, Gwynedd, Wales, United Kingdom; and ²Faculty of Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands

Submitted 20 September 2007 ; accepted in final form 2 January 2008

Locomotor muscle fatigue, defined as an exercise-induced reduction in maximal voluntary force, occurs during prolonged exercise, but its effects on cardiorespiratory responses and exercise performance are unknown. In this investigation, a significant reduction in locomotor muscle force (–18%, P < 0.05) was isolated from the metabolic stress usually associated with fatiguing exercise using a 100-drop-jumps protocol consisting of one jump every 20 s from a 40-cm-high platform. The effect of this treatment on time to exhaustion during high-intensity constant-power cycling was measured in study 1 (n = 10). In study 2 (n = 14), test duration (871 ± 280 s) was matched between fatigue and control condition (rest). In study 1, locomotor muscle fatigue caused a significant curtailment in time to exhaustion (636 ± 278 s) compared with control (750 ± 281 s) (P = 0.003) and increased cardiac output. Breathing frequency was significantly higher in the fatigue condition in both studies despite similar oxygen consumption and blood lactate accumulation. In study 2, high-intensity cycling did not induce further fatigue to eccentrically-fatigued locomotor muscles. In both studies, there was a significant increase in heart rate in the fatigue condition, and perceived exertion was significantly increased in study 2 compared with control. These results suggest that locomotor muscle fatigue has a significant influence on cardiorespiratory responses and exercise performance during high-intensity cycling independently from metabolic stress. These effects seem to be mediated by the increased central motor command and perception of effort required to exercise with weaker locomotor muscles.

perception of effort; central motor command; cardiorespiratory regulation; motivation; endurance

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