Rate of torque development scaled to maximum torque available is velocity dependent.

Abstract

The influence of angular velocity on rate of torque development (RTD) is unknown, despite the inverse, curvilinear torque-velocity relationship for angle- and velocity-specific maximum available torque (T_max) being well-established. This study investigated the relationship between angular velocity and RTD scaled to T_max. In 17 participants, tetanic contractions (100-Hz) of the knee extensors were evoked as the knee was passively extended at different iso-velocities between 0° s^-1 and 200° s^-1. Each condition consisted of evoking 0.25-s contractions without pre-activation (for measuring RTD) commencing as the knee passed 95° of extension, and 1.25-s contractions with pre-activation (for measuring T_max), commencing 1 s prior to the knee reaching 95°. Torque at 100 ms after torque onset (T₁₀₀) and peak RTD (RTD_peak) in the contractions without pre-activation were normalised to T_max. The torque-velocity relationship for T₁₀₀ was flat in comparison to an inverse, curvilinear relationship for T_max, resulting in linear increases in normalised T₁₀₀ and RTD_peak with increased velocity. Results also showed normalised T₁₀₀ and RTD_peak were likely overestimated due to shortening-induced force depression (FD) which would be greater in contractions with- than without- pre-activation. However, these effects of FD cannot explain the faster normalised RTD with increased velocity, as the relative difference in work done (a proxy for FD) between contractions with and without pre-activation decreased - and thus the overestimation of normalised RTD metrics likely decreased - with increased velocity. In conclusion, RTD scaled to T_max increases with increased velocity, which appears to be an intrinsic contractile property independent of the effects of force depression.