EFFECTS OF AEROBIC EXERCISE ON THE TORQUE-VELOCITY RELATIONSHIP IN CYCLING

The kinetics of the torque-velocity (T-omega) relationship after aerob ic exercise was studied to assess the effect of fatigue on the contrac tile properties of muscle. A group of 13 subjects exercised until fati gued on a cycle ergometer, at an intensity which corresponded to 60% o f their maximal aerobic power for 50 min (MAP60%); ten subjects exerci sed until fatigued at 80% of their maximal aerobic power for 15 min (M AP80%). Of the subjects 7 exercised at both intensities with al least a 1-week interval between sessions. Pedalling rate was set at 60 rpm. The T-omega relationship was determined from the velocity data collect ed during all-out sprints against a 19 N.m braking torque on the same ergometer, according to a method proposed previously. Maximal theoreti cal velocity (omega(0)) and maximal theoretical torque (T-0) were esti mated by extrapolation of the linear T-omega relationship. Maximal pow er (P-max) was calculated from the values of T-0 and omega(0) (P-max = 0.25 omega(0) T-0). The T-omega relationships were determined before, immediately after and 5 and 10 min after the aerobic exercise. The ki netics Of omega(0),T-0 and P-max was assumed to express the effects of fatigue on the muscle contractile properties (maximal shortening velo city, maximal muscle strength and maximal power). Immediately after ex ercise at MAP60% a 7.8% decrease in T-0 and 8.8% decrease in P-max was seen while the decrease in omega(0) was nonsignificant, which suggest ed that P-max decreased in the main because of a loss in maximal muscl e strength. In contrast, MAP80% induced a 8.1% decrease in omega(0) an d 12.8% decrease in P-max while the decrease in To was nonsignificant, which suggested that the main cause of the decrease in P-max was prob ably a slowing of maximal shortening velocity. The short recovery time of the T-omega relationship suggests that the causes of the decrease of torque and velocity are processes which recover rapidly.