Time-lapse Changes in EEG-EMG Coherence during Weak Voluntary Contraction of the Tibialis Anterior Muscle

In this study, we investigated the relationship between EEG-EMG coherence and time-lapse changes during weak voluntary contraction of the tibialis anterior (TA) muscle. Eleven healthy men (21-29 years old) participated in the study. The subject was directed to contract his TA muscle for one minute at 10%, 15%, or 30% of maximum voluntary contraction by flexing his right tarsus. Each contraction was randomly performed and repeated five times. The relationships between each contraction level and the epoch number (1 epoch = 12 seconds) were analyzed. Peak coherence values increased significantly over time (p < 0.05). Moreover, the peak coherence value of the beta band changed significantly with time (p < 0.05). For contraction at 30%, the peak coherence appeared in the gamma band on the first and third epochs, while it was seen in the beta band on the second, fourth, and fifth epochs. A decrease in mean power frequency was observed over time. We observed significant differences in the voluntary contraction level (p < 0.05) in each epoch (p < 0.01). The fact that muscle fatigue and the maintenance of muscle contraction leads to synchronization of motor units suggests the activation of afferent feedback.