Motor Unit Firing in the Human Anconeus During High Intensity Eccentric Contractions of Elbow Extensors
Abstract
PURPOSE: To track single motor units through both isometric and eccentric elbow extensor contractions, at near maximal contraction intensity, and compare firing rates between contraction modes at an absolute torque. METHODS: Bipolar fine-wire electrodes were inserted into the anconeus in order to record motor unit firing behaviour during sets of high torque isometric and eccentric contractions. Contractions were performed on an isokinetic dynamometer at a pre-determined speed of 10°/s, through 60° total range of elbow joint motion, and at 50, 75 or 100% MVC. RESULTS: Mean motor unit firing rates were lower during eccentric contractions across all intensities (p < 0.05), however surface EMG of the triceps brachii did not comprehensively follow the same pattern. CONCLUSION: Eccentric contraction is associated with an improvement in neuromechanical coupling in the anconeus, even at high torques. Previous studies have shown a similar effect but only at low to moderate contraction intensities.