Force generation performance and motor unit recruitment strategy in muscles of contralateral limbs

The purpose of the present study was to determine whether the motor unit (M U) recruitment strategy of the agonist and antagonist muscles in the domina nt arm differs from that in the non-dominant arm, The median frequency (MF) of the power density spectrum (PDS) of the electromyogram (EMG) was used a s a tracking parameter to describe the MU recruitment. In 8 subjects the EM G was recorded from the biceps brachii and triceps brachii of each limb dur ing isometric elbow flexion performed in a ramp fashion, Force was increase d from 0 to 100% of the maximum voluntary contraction (MVC) in 3 s followin g a track displayed on an oscilloscope. When comparing the dominant versus non-dominant arm we found no statistical difference in the MU recruitment p attern of the biceps brachii and the triceps. Because the dominant arm was not always the better performing arm, we grouped the data according to the ability of the subjects to track the ramp signal. In this case we found a s tatistically significant difference between the better and worse performing arm in the full MU recruitment of the biceps. A more precise and accurate control of the increase in force was obtained when the central nervous syst em selected a slower and prolonged recruitment of MUs in the agonist muscle . (C) 1999 Published by Elsevier Science Ltd. All rights reserved.