OPTIMAL VELOCITY FOR MAXIMAL POWER PRODUCTION IN NONISOKINETIC CYCLING IS RELATED TO MUSCLE-FIBER TYPE COMPOSITION

To determine whether power-velocity relationships obtained on a noniso kinetic cycle ergometer could be related to muscle fibre type composit ion, ten healthy specifically trained subjects (eight men and two wome n) performed brief periods of maximal cycling on a friction loaded cyc le ergometer. Frictional force and flywheel velocity were recorded al a sampling frequency of 200 Hz. Power output was computed as the produ ct of velocity and inertial plus frictional forces. Force, velocity an d power were averaged over each down stroke. Muscle fibre content was determined by biopsy of the vastus lateralis muscle. Maximal down stro ke power [14.36 (SD 2.37)W . kg(-1)] and velocity at maximal power [12 0 (SD 8) rpm] were in accordance with previous results obtained on an isokinetic cycle ergometer. The proportion of fast twitch fibres expre ssed in terms of cross sectional area was related to optimal velocity (r=0.88, P <0.001), to squat jump performance (r=0.78, P <0.01) and te nded to be related to maximal power expressed per kilogram of body mas s (r=0.60, P=0.06). Squat jump performance was also related to cycling maximal power expressed per kilogram of body mass (r=0.87, P <0.01) a nd to optimal velocity (r=0.86, P <0.01). All these data suggest that the nonisokinetic cycle ergometer is a good tool with which to evaluat e the relative contribution of type II fibres to maximal power output. Furthermore, the strong correlation obtained demonstrated that optima l velocity, when related to training status, would appear to be the mo st accurate parameter to explore the fibre composition of the knee ext ensor muscle.