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

Study Design: Within-session, within-subject comparison of 2 conditions. Objectives: 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. Background: The literature suggests that cutaneous mechanoreceptors can con tribute to proprioception, especially during conditions in which skin exper iences displacement. Further, skin displacement and stimulation of cutaneou s mechanoreptors have been shown to increase motoneuron excitability. Methods and Measures: H-reflexes and M-waves of the peroneus longus muscle were acquired by stimulating the common peroneal nerve of 11 uninjured subj ects during 2 randomly ordered conditions, with and without application of an Aircast Air-Stirrup. Five reflexes were collected at each of 12 stimulat ion voltages. The peak-to-peak amplitudes of the M-wave and H-reflex from e ach subject's ensemble-averaged data at each stimulation voltage was used t o generate H-reflex and M-wave recruitment curves. The H-reflex amplitude w as subsequently expressed as a percentage of the maximum M-wave amplitude. Results: The normalized H-reflex amplitude increased by approximately 10% d uring the braced condition compared to the nonbraced condition. The peroneu s longus H-reflex latency and M-wave amplitude were not affected by the bra cing condition. Conclusions: Application of the ankle brace excited afferents possibly aris ing from a number of candidate mechanoreceptors, 1 of which is likely cutan eous. The findings raise questions as to whether the increased motorneuron excitability can be used for the purposes of rehabilitation from ankle inju ry.