The effect of cooling on muscle co-ordination in spasticity: assessment with the repetitive movement test.

Abstract

Cooling muscles might produce a temporary reduction of spasticity. This study investigated muscle co-ordination in spasticity under the influence of cooling. A repetitive movement (RM-) test of the ankle was used, while measuring the angle and surface-electromyography (EMG) of the m. tibialis anterior and m. triceps surae. Ensemble averaging provided quantified measures of muscle activation. Sixteen patients with spasticity in their lower extremity due to stroke or spinal cord injury participated in the study. Physical examination and the RM-test was done before and after cooling the m. triceps surae for 20 minutes by coldpacks. The results show that Achilles hyperreflexia and clonus were abolished in all, and all but one patient, respectively. The EMG of the m. triceps surae, acting as a prime mover, was increased (p = 0.028). However, this improved muscle co-ordination resulted in just a slightly increased active range of motion (less than 2 degrees at p = 0.049). Apparently, the increase in excitability of the alpha motoneuron pool in voluntary movements of patients with spasticity is not followed by an improvement in the ability to move.