Effects of body weight support on intermuscular coherence in triceps surae muscle during walking.

The triceps surae muscle plays an important role in walking. Previous studies using coherence analysis of surface electromyography (EMG) have indicated that each muscle pair in the triceps surae [i.e., the medial head of gastrocnemius (MG)-the lateral head of gastrocnemius (LG), MG-the soleus (SOL), and LG-SOL] receives common oscillatory input during walking. Although significant intermuscular coherence (IMC) in the triceps surae muscle during normal walking has been observed in the beta and low-gamma frequency bands, it remains unclear whether IMC in these frequency bands depends on the degree of the afferent input. This study aimed to investigate whether attenuating afferent input affects IMC in the triceps surae muscle during walking. Since load-related afferent input plays an important role in neuromuscular control during walking, we focused on walking under body weight support (BWS) to modulate load-related afferent input. Fourteen healthy young adults participated in this study. The four BWS conditions were used: 100 % (no unloading), 80 %, 60 %, and 40 % of individual body weight. IMC was calculated from surface EMG in the stance phase during walking in the following three pairs: MG-LG, MG-SOL, and LG-SOL. The results showed no significant changes in IMC levels with increasing BWS levels in any frequency bands in all muscle pairs. These results suggest that common oscillatory inputs to the triceps surae muscle during walking are robust to the attenuation of load-related afferent input. The present results will contribute to a better understanding of neuromuscular control in the triceps surae muscle during walking.