MUSCLE FUNCTION DURING BRIEF MAXIMAL EXERCISE - ACCURATE MEASUREMENTSON A FRICTION-LOADED CYCLE ERGOMETER

A friction loaded cycle ergometer was instrumented with a strain gauge and an incremental encoder to obtain accurate measurement of human me chanical work output during the acceleration phase of a cycling sprint . This device was used to characterise muscle function in a group of 1 5 well-trained male subjects, asked to perform six short maximal sprin ts on the cycle against a constant friction load. Friction loads were successively set at 0.25, 0.35, 0.45, 0.55, 0.65 and 0.75 N . kg(-1) b ody mass. Since the sprints were performed from a standing start, and since the acceleration was not restricted, the greatest attention was paid to the measurement of the acceleration balancing load due to flyw heel inertia. Instantaneous pedalling velocity (v) and power output (P ) were calculated each 5 ms and then averaged over each downstroke per iod so that each pedal downstroke provided a combination of v, force a nd P. Since an 8-s acceleration phase was composed of about 21 to 34 p edal downstrokes, this many v-P combinations were obtained amounting t o 137-180 v-P combinations for all six friction loads in one individua l, over the widest functional range of pedalling velocities (17-214 rp m). Thus, the individual's muscle function was characterised by the v- P relationships obtained during the six acceleration phases of the six sprints, An important finding of the present study was a strong linea r relationship between individual optimal velocity (v(opt)) and indivi dual maximal power output (P-max) (n=15, r=0.95, P <0.001) which has n ever been observed before. Since upsilon(opt) has been demonstrated to be related to human fibre type composition both v(opt), P-max and the ir inter-relationship could represent a major feature in characterisin g muscle function in maximal unrestricted exercise. It is suggested th at the present method is well suited to such analyses.