The presence of corticomuscular coherence during unipedal stance

Standing in unipedal stance requires higher effort to maintain posture balance within narrow base-of-support. Although changes in cortical activity are known to occur as standing task difficulty increased, it is unclear whether it indicates a change in cortical control of muscle activity. To elucidate this point, this study examined corticomuscular coherence (CMC) between the sensorimotor cortex and ankle joint muscles during three tasks such as bipedal stance, unipedal stance, and isometric contraction tasks. For twenty-one healthy participants, 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 also measured the center of pressure (COP) during both stance tasks. Although there was no significant CMC during bipedal stance in all participants, most participants (n = 14) showed significant CMC for all muscles during unipedal stance with larger COP fluctuation in most participants. Indeed, there was significant difference in CMCmax between unipedal and bipedal stance tasks. The greater CMC would indicate increased cortical control of muscle activity to compensate for postural instability during unipedal stance.