Use of the force-velocity test to determine the optimal braking force for a sprint exercise on a friction-loaded cycle ergometer

Abstract

A group of 15 untrained male subjects pedalled on a friction-loaded cycle ergometer as fast as possible for 5–7 s to reach the maximal velocity (V{immax}) against different braking forces (F _B). Power was averaged during a complete crank rotation by adding the power dissipated againstF _B to the power necessary to accelerate the flywheel. For each sprint, determinations were made of peak power output ($\dot W_{peak}$) power output attained atV _max ($\dot W_{vmax}$) calculated as the product ofV _max andF _B and the work performed to reachV _max expressed in mean power output ($\bar \dot W_{vmax}$). The relationships between these parameters andF _B were examined. A biopsy taken from the vastus lateralis muscle and tomodensitometric radiographs of both thighs were taken at rest to identify muscle metabolic and morphometric properties. The$\dot W_{peak}$ value was similar for allF _B. Therefore, the average of values was defined as corrected maximal power ($\dot W_{max}$). This value was 11 higher than the maximal power output uncorrected for the acceleration. Whereas the$\dot W_{max}$ determination did not require high loads, the highest$\bar \dot W_{vmax}$ value ($\bar \dot W_{max}$) was produced when loading was heavy, as evidenced by the$\bar \dot W_{vmax}$-F _B parabolic relationship. For each subject, the braking force ($F_{B,\bar \dot W_{max} }$) giving$\bar \dot W_{max}$ was defined as optimal. The$F_{B,\bar \dot W_{max} }$, equal to 0.844 (SD 0.108) N · kg⁻¹ bodymass, was related to thigh muscle area (r = 0.78,P < 0.05). The maximal velocity ($\upsilon _{m,\bar \dot W_{\max } }$) reached against this force seemed to be related more to intrinsic fibre properties (% fast twitch b fibre area and adenylate kinase activity). Thus, from the$\dot W_{max}$ determination, it is suggested that it should be possible to predict the conditions for optimal exercise on a cycle ergometer.