Locomotor muscle fatigue increases cardiorespiratory responses and reduces performance during intense cycling exercise independently from metabolic stress
Tóm tắt
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.
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Tài liệu tham khảo
Amann M, Dempsey JA.Peripheral muscle fatigue from hyperoxia to moderate hypoxia–a carefully regulated variable?Physiology News66: 28–29, 2007.
Amann M, Hopkins WG, Marcora SM.Similar sensitivity of time to exhaustion and time trial time to changes in endurance.Med Sci Sports Exerc.In press.
Borg GA.Borg's Perceived Exertion and Pain Scales. Champaign, IL: Human Kinetics, 1998.
Dempsey JA, Miller JD, Romer LM.The respiratory system. In:ACSM's Advanced Exercise Physiology, edited by Tipton CM. Philadelphia, PA: Lippincott Williams Wilkins, 2006, p. 246–299.
Edwards R.Biochemical basis of fatigue in exercise performance: catastrophe theory of muscular fatigue. In:Biochemistry of Exercise, edited by Knuttgen H. Champaign, IL: Human Kinetics, 1983, p. 3–28.
Fitts RH.The muscular system: fatigue processes. In:ACSM's Advanced Exercise Physiology, edited by Tipton CM. Philadelphia: Lippincott Williams Wilkins, 2006, p. 178–196.
Holm S.A simple sequentially rejective multiple test procedure.Scand J Stat6: 65–70, 1979.
Noble BJ, Robertson RJ.Perceived Exertion.Champaign, IL: Human Kinetics, 1996.
Wright RA.Brehm's theory of motivation as a model of effort and cardiovascular response. In:The Psychology of Action: Linking Cognition and Motivation to Behavior, edited by Gollwitzer PM and Bargh JA. New York: Guilford, 1996, p. 424–453.