The Effects of Psychosocial Stress on Surface Electromyography Signals of the Lower Leg During Isometric Contractions

Psychosocial stress has been shown to affect EMG activity in the upper body; however, no known studies have attempted similar research on the lower body. Accordingly, this study aimed to analyze the effects of psychosocial stress on surface EMG amplitude and frequency in the lower leg. The tibialis anterior (TA) and gastrocnemius medialis (GM) were tested on 13 healthy subjects. Two sets of isometric fatigue trials were performed by each muscle, separated by the Trier Social Stress Test. Wilcoxon signed-rank tests were performed (confidence interval (CI) of 95%), and no significant difference was found in mean amplitude (p ≈ 0.30), mean frequency (p ≈ 0.20), or rate of change before and after psychosocial stress. All pre- to post-stress comparisons were determined to be statistically equivalent using the two one-sided t-tests method at 5% significance using a 90% CI. The results imply that the effects of psychosocial stress observed in upper-body muscles may not generalize directly to the lower leg for the conditions of this study and should be evaluated in a muscle-specific and task-specific manner. While limited by a small cohort, these exploratory findings challenge the generalizability of upper-body stress models and establish critical baseline parameters for larger, muscle-specific lower-limb neuromusculoskeletal investigations.