The effects of passive joint movement on stretch reflex gain at the human ankle

Stretch reflex gain is known to decrease in the presence of ongoing passive movement. The objective of this work was to determine what properties of the movement were responsible for this decrease. Two types of stochastic position perturbations of constant amplitude and varying bandwidths were superimposed onto short duration reflex-evoking position pulses. The stretch reflex gain was found to decrease with an increase in the mean absolute velocity of the imposed joint movement. However, the attenuation of the stretch reflex was also influenced by the spectra and probability distribution functions of the imposed perturbations.