Article

To study the role of coactivation in strength and force modulation in the elbow
joint of children and adolescents with cerebral palsy (CP),
we investigated the
affected and contralateral arm of 21 persons (age 8-18) with spastic unilateral
CP in three tasks: maximal voluntary isokinetic concentric contraction and
passive isokinetic movement during elbow flexion and extension, and sub-maximal
isometric force tracing during elbow flexion. Elbow flexion-extension torque and
surface electromyography (EMG) of the biceps brachii (BB) and triceps brachii
(TB) muscles were recorded. During the maximal contractions, the affected arm was
weaker, had decreased agonist and similar antagonist EMG amplitudes, and thus
increased antagonist co-activation (% of maximal activity as agonist) during both
elbow flexion and extension, with higher coactivation levels of the TB than the
BB. During passive elbow extension, the BB of the affected arm showed increased
resistance torque and indication of reflex, and thus spastic, activity. No
difference between the two arms was found in the ability to modulate force,
despite increased TB coactivation in the affected arm. The results indicate that
coactivation plays a minor role in muscle weakness in CP, and does not limit
force modulation. Moreover, spasticity seems particularly to increase
coactivation in the muscle antagonistic to the spastic one, possibly in order to
increase stability.
CI - Copyright (c) 2011 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS