The instantaneous torque-angular velocity relation in plantar flexion during jumping

Abstract

Torques, angular velocities, and power of the ankle joint during plantar flexion were measured in jumping experiments in order to achieve insight into shape and magnitude of the instantaneous torque-angular velocity relation in a complex movement. Twelve trained subjects performed maximal vertical jumps from a semi-squatting position with 100 degrees of flexion in the knee joint. Ground reaction force measurements and film analyses were used to calculate instantaneous torques, angular velocities, and power outputs during plantar flexion. The shape of the instantaneous torque-angular velocity was different from the well-known hyperbolic force-velocity relation for isolated muscles. Maximal power output (2499 +/- 751 [SD] W) occurred at 60% of the mean maximal torque (301 +/- 62 N X m) and 80% of the mean maximal angular velocity (970 degrees/s). The maximal power output was six times larger than the power output reported in the literature for maximal isokinetic (monoarticular) plantar flexions. Influences like storage of energy in the series elastic component of Hill's muscle model and the role of polyarticular muscles in transporting energy from knee to ankle are discussed. It is concluded that many more selective studies will be necessary before it is possible to relate intrinsic muscle properties to the performance of muscles in poly-articular complex movements.