Perceptual and Motor Skill\, 2007, 104,287-297. O Perceptual and Motor Skills 2007 PRACTICE EVOKING THE FLEXOR CARPI RADIALIS H-REFLEX: A GUIDELINE FOR PROFICIENCY ' ' J. GREIG INGLIS, ANITA D. CIIRISTIE, DAVID A. GABRIEL Summavy.-The purpose of this research was to identify the number of sessions required for a new investigator to become proficient at evoking an 11-reflex in the flexor carpi radialis (FCR), in comparison to an experienccd investigator. 31 students from Brock University in the greater Niagara region (16 women ikf age=32.2, SD=8.9 yr.; 15 men iM age=27.8, SD=7.8 yr.) with no known neurological disorders volun- teered and completed two tcst sessions performed by either an experienced or a nov- ice investigator. In randomized order, both investigators stimulated each subject's me- dian nerve 10 times, once every 15 sec. Each session inclucled the nleasurement of the subject's flexor carpi radialis maximal M-wave amplitude and H-reflex amplitude and latency with surface electromyographic electrodes. The intraclass correlation coeffi- cients (ICC) indicated an adequate correlation between investigators for both M-wave maximal amplitude and H-reflex at 5 % of the M-wave maximal amplitude (.84 and .70, respectively). However, there was a low correlation 1.38) betureen the latency val- ues obtained by the two investigators. Thc peak-to-peak amplitudes of the H-reflex and M-wave do not appear to be influenced by experience of the tester. The latency of the response, however, appears to have an associated learning curve, improving in consistency with increasing practice of tester. The Hoffmann reflex (H-reflex) is an electrically evoked stretch reflex. It is elicited by applying a submaximal electrical impulse to a peripheral nerve supplying a surface muscle. Theoretically, the H-reflex can be success- fully recorded from any limb muscle with an accessible nerve (Bischoff, 2002). Recordings of the H-reflex are commonly used in clinical settings to assess motor neuron pool excitability and functionality of the peripheral nerves, as well as identifying pathologies and lesions. The characteristics of the H-reflex used to assess excitability and to make clinical diagnoses include both the peak-to-peak amplitude and the latency of the response. The mag- nitude of the H-reflex is generally measured by electromyography (EMG). The H-reflex can be evoked when a submaximal stimulus is applied to the nerve which innervates a specific motor unit. The Ia afferents subse- quently propagate the action potential towards the spinal cord (Christie, Lester, LaPierre, & Gabriel, 2004). From the spinal cord, the efferent nerves -- - 'Address correspondence to J. Grcig Inglis, M.A., Faculty of Applied Health Science, Brock piversity, 500 Glenridge Avenue, Brock University, St. Catharines, Ontario, Canada L2S 3A1. A grant from the Nat~~ral Sciences and Engineering Research Council of Canada was used to fund this study. DOT 10.2466/PMS.104.1.287 297