Muscle co-activation in neurological conditions

Authors: Busse, M.E.; Wiles, C.M.; van Deursen, R. W.M.

Source: Physical Therapy Reviews, Volume 10, Number 4, December 2005 , pp. 247-253(7)

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Abstract:

Co-activation of agonist and antagonist muscles in healthy people is considered a normal strategy that aids movement efficiency during the performance of functional activities. In some cases, however, it is an abnormal strategy that aids stability and/or precision but not efficiency of movement. Co-activation varies not only between agonist and antagonist pairs, but within a pair from time to time, and depending on a range of factors. Muscle co-activation strategies are used when uncertainty in relation to execution of a specific task occurs, during the learning of a new skill or as compensation. Movement dysfunction in neurological conditions may coincide with abnormal levels of co-activation. It is unclear at what level co-activation assists or impedes functional ability, and to what extent reduced agonist excitation and antagonist co-activation combine to cause significant weakness. A major limitation in understanding the mechanisms of co-activation in neurologically impaired individuals is the wide range of methods that are used to determine levels of antagonist activation and hence co-activation levels. The muscle action, joint position, contraction type and testing conditions may influence the antagonist EMG recorded. This review investigates the methods routinely used to quantify co-activation, and relevant findings, particularly with respect to neurologically impaired individuals. Inconsistencies in methods used limit comparison between studies, but it is clear that whilst co-activation may occur alongside clinical features in neurological conditions, it is often viewed as a task-related strategy used to cope with the complexity of a task. This review highlights whether the use of co-activation strategies should be considered useful contributions to successful rehabilitation.

Keywords: VOLUNTARY MOVEMENT; MUSCLE WEAKNESS; NEUROLOGY; CO-ACTIVATION; CO-CONTRACTION

Document Type: Research Article

DOI: http://dx.doi.org/10.1179/108331905X78915

Publication date: 2005-12-01

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