Between-days reliability of H-reflexes in human flexor carpi radialis

OBJECTIVES: To assess between-day reliability of the latency and peak-to-peak amplitude of a technique to elicit the H-reflex and M response of the flexor carpi radialis (FCR) and the ratio of maximum H-reflex and M-response amplitude (Hmax/Mmax). DESIGN: Test-retest reliability study. SETTING: Electrophysiology laboratory at a university. PARTICIPANTS: Fifteen consecutively recruited healthy volunteers (8 men, 7 women; age range, 22-65y). INTERVENTION: Volunteers were tested on 2 separate days at the same time of day for H-reflex and M response by stimulating the median nerve in the cubital fossa in the presence of a standardized voluntary contraction of the FCR muscle. MAIN OUTCOME MEASURES: Onset latencies, peak-to-peak amplitudes, and Hmax/Mmax. RESULTS: Latency measurements of H-reflex and M response showed excellent reliability between days, as did the maximum amplitude of the M response. The maximum amplitudes of the H-reflex and Hmax/Mmax ratio were less reliable but still within acceptable limits. CONCLUSIONS: The H-reflex and M response can be reliably elicited in the FCR. This technique provides a useful clinical tool for diagnostic purposes during the course of neurologic disorders and in preclinical and postclinical intervention studies.