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The presence of corticomuscular coherence during unipedal stance

Objective To elucidate cortical involvement in postural control during unipedal stance by observing corticomuscular coherence (CMC) between the sensorimotor cortex and ankle joint muscles. Methods Twenty-one participants performed three tasks: bipedal stance, unipedal stance, and isometric contraction. We measured the maximal peak of CMC (CMCmax) between electroencephalograms overlying the foot representation area and surface electromyograms from the tibialis anterior (TA), medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (SOL), respectively, for each task. We measured the center of pressure (COP) during both stance tasks. Results Although there was no significant CMC during bipedal stance, significant CMC was observed for all muscles during unipedal stance, with larger COP fluctuation. The results revealed significant differences in CMCmax between unipedal and bipedal stance tasks (TA, p = 0.002; MG, p = 0.016; LG, p = 0.003; SOL, p = 0.009). Additionally, CMCmax was obtained in higher frequency bands during the unipedal stance task than during the isometric contraction task. Conclusions Significant CMC indicates direct involvement of the sensorimotor cortex in postural control during unipedal stance. Significance Greater postural demands due to narrow base-of-support during unipedal stance requires voluntary control of muscle activity by the sensorimotor cortex. Highlights Corticomuscular coherence (CMC) was measured in ankle muscles during bipedal stance, unipedal stance and isometric contraction. Significant CMC was observed during unipedal stance but not during bipedal stance. The peak frequency of CMC was higher during unipedal stance than during isometric contraction.