Electromyographic analysis of movement following a maximal isometric contraction

A post-contraction sensory discharge effect following an isometric contraction is commonly cited as the explanation for perception of movement or distortion of limb proprioception during post-contraction movements. The purpose of this study was to compare motor output of agonist neuromuscular activity between a control positioning movement and a post-contraction movement. Terminal positioning accuracy and electromyographic (EMG) data of the triceps brachii during rapid elbow extension were recorded during normal movements and during movements following a maximal isometric contraction. Separate t-tests revealed the post-contraction positioning resulted in significant undershooting of the target position, and also the integrated EMG (IEMG) for the post-contraction conditions was significantly less than the control condition. No difference was observed in mean peak frequencies between the control and post-contraction conditions. Apparently, the post-contraction target undershooting is a result of less total motor output rather than a change in neuromuscular frequency firing rates.