Effect of joint angle on mechanomyogram (MMG)

Abstract

This study was designed to examine the effects of length changes in ankle dorsiflexor, tibialis anterior, on the activation of the muscle, using the mechanomyogram (MMG) and force relationship during isometric ramp contractions. The relationships between the root mean squared amplitude (RMS) and mean power frequency (MPF) of the MMG and relative force (% MVC) in the dorsiflexed ankle and plantarflexed ankle were markedly different from those in the neutral positioned ankle. It is widely accepted now that the RMS and MPF of the MMG reflect the motor unit activation patterns. Therefore, these differences in MMG suggest that the changes in length of muscle probably influence the muscle activation pattern during isometric ramp contraction.