MAXIMAL POWER AND TORQUE VELOCITY RELATIONSHIP ON A CYCLE ERGOMETER DURING THE ACCELERATION PHASE OF A SINGLE ALL OUT EXERCISE

Seven subjects pedalled on a Monark cycle ergometer as fast as possible for approximately 7 s against four different resistances which corresponded to braking torques (T-B) equal to 19, 38, 57 and 76 N.m at the crank level. Exercise periods were separated by 5-min recovery periods. Pedal velocity was recorded every 50 ms by means of a disc with 360 slots fixed on the flywheel, passing in front of a photo-electric cell linked to a microcomputer which processed the data. Every 50 ms, the time necessary to perform half a pedal revolution (t(1/2)) was computed by adding the 50-ms periods necessary to reach 669 slots (the number of slots corresponding to half a pedal revolution). To measure t(1/2) to an accuracy better than 50 ms, this time was computed by a linear interpolation of the time-slot number relationship. Power (P) was averaged during t(1/2) by adding the power dissipated against braking torque and the power necessary to accelerate the flywheel. The torque-velocity (T-v) relationship was studied during the acceleration phase of a sprint against a single T-B by computing every 50ms the relationship between v and T (N.m), equal to the sum of T-B and the torque necessary to accelerate the flywheel at the same time. The T-v relationships calculated from the acceleration phase of a single all-out exercise were linear and similar to the previously described relationships between peak velocity and braking force. These relationships can be expressed as follows: v = v(o,acc) (1 - T/T-o,T-acc) where v is pedal velocity, T the torque exerted on the crank and T-o,T-acc and V-o,V-acc have the dimensions of maximal torque and maximal velocity respectively. Based on this model, maximal power (P-max,P-acc) is calculated as 0.25 v(o,acc) T-o,T-acc. Maximal power P-max,P-acc measured with the acceleration method was independent of braking torque T-B slightly higher than P-max calculated from the relationship between peak velocity and T-B.