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) being well-established. This study investigated the relationship between angular velocity and RTD scaled to T. 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 and 200° s. 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), commencing 1 s prior to the knee reaching 95°. Torque at 100 ms after torque onset (T) and peak RTD (RTD) in the contractions without pre-activation were normalised to T. The torque-velocity relationship for T was flat in comparison to an inverse, curvilinear relationship for T, resulting in linear increases in normalised T and RTD with increased velocity. Results also showed normalised T and RTD 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 increases with increased velocity, which appears to be an intrinsic contractile property independent of the effects of force depression.
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http://dx.doi.org/10.1016/j.jbiomech.2020.110144 | DOI Listing |
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