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Effects of ageing on motor control

This study was designed to investigate the effects of ageing on motor control and to identify the adjustments within the nervous system during fatiguing tasks in the human dorsiflexor muscles.

The main results show that in advanced age, the loss of motor neurones usually observed is accompanied by an increase in the relative force of each motor unit and a decrease of their maximal discharge frequencies. Despite this profound remodelling of the motor system and reduced motor units discharge rate, the central neural command is still optimal for muscle activation and does not contribute to the observed reduction in muscle force and endurance during intermittent contractions. However, the slowing and decrease of the spinal and supraspinal reflex responses indicate that the balance of peripheral excitatory and inhibitory inputs into the motor neurones is modified with ageing. This observation further indicates that the sensory system is more affected than the motor system and consequently explains most of the degradation in skill performances during ageing.

Findings of this study have practical applications in fitness and rehabilitation programmes. They emphasis the need of regular physical activities, involving not only strength exercises but also proprioceptive ones, in order to maintain or improve the functional capacity of the sensory-motor system during senescence. The results can also contribute to optimise ergonomic designs for elderly adults to compensate for impairments in muscular force and endurance.

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Jacques DUCHATEAU, (Director of the Laboratory of Applied Biology Institute for Motor Sciences (ISM))
Tél.: +32-2-5553243
Fax: +32-2-6503966