To quantify the level of motor unit synchronization during slow anisometric contractions. To determine the association between training-induced improvements in steadiness and changes in the coefficient of variation of motor unit discharge. To establish the causative effect of changes in motor unit properties on the steadiness of isometric contractions. To assess the contralateral activity in a hand muscle during ipsilateral contractions. To compare the activation of a hand muscle during concentric and eccentric contractions performed at different movement speeds.
Older adults use a unique strategy to lift inertial loads with the elbow flexor muscles.
Steadiness is reduced and motor unit discharge is more variable in old adults. Limb immobilization alters muscle activation patterns during a fatiguing isometric contraction. Motor-unit synchronization is not responsible for larger motor unit forces in old adults. Motor unit synchronization increases EMG amplitude and decreases force steadiness in simulated contractions.