Peroneal motoneuron excitability increases immediately following application of a semirigid ankle brace.

Abstract

Within-session, within-subject comparison of 2 conditions. To determine the influence of application of a semirigid ankle brace on the excitability of the peroneus longus muscle motoneuron pool as measured by the H-reflex. The literature suggests that cutaneous mechanoreceptors can contribute to proprioception, especially during conditions in which skin experiences displacement. Further, skin displacement and stimulation of cutaneous mechanoreptors have been shown to increase motoneuron excitability. H-reflexes and M-waves of the peroneus longus muscle were acquired by stimulating the common peroneal nerve of 11 uninjured subjects during 2 randomly ordered conditions, with and without application of an Aircast Air-Stirrup. Five reflexes were collected at each of 12 stimulation voltages. The peak-to-peak amplitudes of the M-wave and H-reflex from each subject's ensemble-averaged data at each stimulation voltage was used to generate H-reflex and M-wave recruitment curves. The H-reflex amplitude was subsequently expressed as a percentage of the maximum M-wave amplitude. The normalized H-reflex amplitude increased by approximately 10% during the braced condition compared to the nonbraced condition. The peroneus longus H-reflex latency and M-wave amplitude were not affected by the bracing condition. Application of the ankle brace excited afferents possibly arising from a number of candidate mechanoreceptors, 1 of which is likely cutaneous. The findings raise questions as to whether the increased motorneuron excitability can be used for the purposes of rehabilitation from ankle injury.