Comparison of human triceps surae H-reflexes obtained from mid and distal recording sites

The purpose of this study was to determine whether a distal triceps surae recording site produced H-reflex responses similar to those obtained from the conventional soleus location in 10 healthy subjects at rest. H-reflex and M-response recruitment profiles were generated and the peak-to-peak amplitudes were measured from the two sites simultaneously. Following this, an H-reflex control signal was determined (peak-to-peak amplitude approximately equal to 30% Mmax) and 4 series of 10 trials were recorded at 5 minute intervals. A paired t-test showed non-significant (p greater than 0.05) differences in Hmax, Mmax, and Hmax: Mmax values recorded from the two sites. Linear regression analyses of recruitment profile H-reflexes and M-responses, obtained simultaneously from the two recording sites showed strong correlations (r greater than 0.90, p less than 0.001). To assess the stability of the reflex over time, intraclass correlation coefficients (ICC) were computed for each recording site (R = 0.99 in both instances). Thus the distal recording site, just proximal to the flare of the medial malleolus, is an acceptable alternative to the conventional recording location. This permits recording H-reflex amplitude changes, resulting from the application of a therapeutic intervention to the calf muscles, without having to remove and reposition the recording electrodes.