The role of co-activation in strength and force modulation in the elbow of children with unilateral cerebral palsy

Abstract 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 con...

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Bibliographic Details
Published in:Journal of electromyography and kinesiology 2012-02, Vol.22 (1), p.137-144
Main Authors: Brændvik, Siri Merete, Roeleveld, Karin
Format: Article
Language:English
Subjects:
Adaptation, Physiological
Adolescent
Cerebral palsy
Cerebral Palsy - physiopathology
Child
Co-activation
Elbow Joint - physiopathology
Female
Force modulation
Humans
Male
Muscle Contraction
Muscle weakness
Muscle, Skeletal - physiopathology
Physical Endurance
Physical Medicine and Rehabilitation
Postural Balance
Spasticity
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Summary:Abstract 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.
ISSN:1050-6411
1873-5711
DOI:10.1016/j.jelekin.2011.10.002