Dépense énergétique et rendement au cours de la répétition de sprints sur bicyclette ergométrique : effet de la vitesse de pédalage

Abstract

During an all-out exercise, where the metabolic demand is considered as maximal, it has been demonstrated that cycling velocity influences largely mechanical power and work. This paper intends to show how during an all-out intermittent exercise, pedalling rate simultaneously influences the physiological response by modifying the metabolic power and/or the efficiency of the muscular contraction. Nine cyclists performed 2 series of 12 repeated 5-s sprints at a constant velocity interspersed by 45-s resting recovery : one series was performed at optimal velocity (Vopt, velocity at which maximal power is produced) and the second one at 50 % of Vopt ( 1/2Vopt), in a randomly selected order and separated by 48 hours. Activation level of the primary agonist muscle (vastus lateralis) and the rate of perceived exertion (Borg's scale) were similar during both conditions. Consecutively the cardiorespiratory adaptation period, mean values between the 7 th and 12 th sprint of power output, oxygen consumption and blood lactate accumulation were significantly higher at Vopt (944,5 ± 123 W; 2,55 ± 0,29 l.min -1 ; 3 mmol.l -1) than at 1/2Vopt (702 ± 88 W; 2,18 ± 0,28 l.min -1 ; 0,8mmol.l -1). The mechanical conditions of muscle contraction, notably contraction velocity, seem to act preferentially on metabolic power rather than on efficiency during supra-maximal intermittent exercise.