EFFECT OF TISSUE COMPRESSION ON THE HOFFMANN REFLEX: POTENTIAL USE OF NERVE FUNCTION CHANGES AS AN OBJECTIVE METRIC OF SEAT COMFORT

Introduction: Monitoring nerve function during long duration sitting may provide a physiologically based objective metric of seat comfort. This study was conducted as a basic research effort evaluating the impact of tissue compression on nerve function in 10 healthy adults (22 +/- 3 years old). Methods: Nerve function was monitored prior to, during 9-minutes of compression at 210 mmHg, and throughout 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 the control. Throughout testing, a 50% H-max stimulus was administered each minute. Thermography and oxygenation measures showed that total limb blood flow and oxygenation, respectively, did not change from baseline values throughout testing. Repeated measures ANOVAs were conducted to investigate the influence of location and time on the H-wave amplitude and latency. Pearson correlation coefficients were determined for H-wave amplitude, H-wave latency, and subjective comfort, with alpha set at the .05 level for all analyses. Results: A significant main effect for time emerged for the H-wave amplitude indicating that the H-wave amplitude was higher during the last minute of compression than immediately prior to and immediately after compression. Discussion: These findings suggest that compression during normal lower limb perfusion provides effects on nerve function that could emerge as an objective metric of seat comfort. However, due to negligible change in reported subjective comfort, no relationship emerged between nerve function and subjective comfort. Future research should use longer compression durations to produce the seat discomfort reported by military aircrew associated with extended duration sitting.