EFFECT OF FATIGUE ON MAXIMAL VELOCITY AND MAXIMAL TORQUE DURING SHORTEXHAUSTING CYCLING

A group of 24 subjects performed on a cycle ergometer a fatigue test c onsisting of four successive all-out sprints against the same braking torque. The subjects were not allowed time to recover between sprints and consequently the test duration was shorter than 30 s. The pedal ve locity was recorded every 10 ms from a disc fixed to the flywheel with 360 slots passing in front of a photo-electric cell linked to a micro computer which processed the data. Taking into account the variation o f kinetic energy of the ergometer flywheel, it was possible to determi ne the linear torque velocity relationship from data obtained during t he all-out cycling exercise by computing torque and velocity from zero velocity to peak velocity according to a method proposed previously. The maximal theoretical velocity (vol and the maximal theoretical torq ue (T-o) were estimated by extrapolation of each torque-velocity relat ionship. Maximal power (P-max) was calculated from the values of T-o a nd v(o) (P-max = 0.25 v(o) T-o). The kinetics of v(o), T-o and P-max w as assumed to express the effects of fatigue on the muscle contractile properties (maximal shortening velocity, maximal muscle strength and maximal power). Fatigue induced a parallel shift to the left of the to rque-velocity relationships. The v(o), T-o and P-max decreases were eq ual to 16.3%, 17.3% and 31%, respectively. The magnitude of the decrea se was similar for v(o) and T-o which suggested that P-max decreased b ecause of a slowing of maximal shortening velocity as well as a loss i n maximal muscle strength. However, the interpretation of a decrease i n cycling v(o) which has the dimension of a maximal cycling frequency is made difficult by the possible interactions between the agonistic a nd the antagonistic muscles and could also be explained by a slowing o f the muscle relaxation rate.