Effect of Tissue Compression on the Hoffmann Reflex: Comparison Between the Ischial Tuberosity and Posterior Thigh

Abstract

This projected monitored nerve function during 9-minutes of compression at 210 mmHg and in the ensuing 10-minute recovery period. Compression was produced by a purpose-built plunger. A within-subjects design was used to compare the effects of tissue compression at two different locations: the middle posterior thigh, to replicate previous research, and the ischial tuberocities, to serve as control. Ten (5 men and 5 woman) apparently healthy adults (M = 22.44, SD = 3.13) were the participants in this study. Throughout testing, a 50% Hmax stimulus was administered during the onset of each minute. Thermography and oxygenation measures showed that total limb blood flow and oxygenation, respectively, did not change from baseline values throughout testing. Four 2 (Location) x 5 (Time) repeated measures ANOVAs, with alpha set at the .05 level, were conducted to investigate the influence of location and time on the H-wave amplitude, H-wave latency, two-point discrimination test, and subjective comfort. The times of interest were pre-compression, the ninth (i.e., final) minute of compression, and the first, fifth, and tenth minutes post-compression. A significant main effect for the time emerged for the H-wave amplitude indicating that the H-wave amplitude was significantly higher during the last minute of compression than at baseline and the first minute post-compression. Subjective comfort was significantly lower during the last minute of compression than during pre- and post-compression. This study demonstrated that tissue compression impacted the Hoffmann Reflex H-wave amplitude generated at the tibial nerve and recorded at the soleus. The findings suggest that compression in the absence of full limb ischemia may provide different effects on nerve function than a pneumatic cuff inflated around the circumference of the thigh. Future research should replicate these findings and identify the mechanisms responsible for producing the increase of H-wave amplitude responses, regardless of location, observed during compression.