Anticipation of elbow joint perturbation shortens the onset time of the reflex EMG response in biceps brachii and triceps brachii.

This study aimed to investigate the influence of the anticipation of a perturbation torque applied to extend the elbow joint on the onset time of reflex electromyogram (EMG) responses. A perturbation torque generated by an electromagnetic torque motor system was applied to the forearm of eleven subjects during trials. The trials were divided into an anticipated (AN) condition - perturbation torque applied after the auditory signal - and an unanticipated (UAN) condition - suddenly applied perturbation. To detect the reflex EMG response in the biceps brachii (Bb) and triceps brachii (Tb) muscles, a new method involving the discrete wavelet transform and outlier tests was used. We found that the onset time of the reflex response in both the muscles in the AN condition was significantly shorter than that in the UAN condition. The angle of transition from flexion to extension, which was induced by the reflex response of Bb, was also significantly smaller in the AN condition than in the UAN condition. The results indicate that the anticipation of an applied perturbation torque decreases the onset time of the reflex response in the Bb and Tb.