Electromyographic evaluation of therapeutic massage effect using multi-finger robot hand

The multi-finger robot hand (IRA-Hand I) is specially designed for massage applications. Surface electromyographic (SEMG) evaluation of therapeutic massage effects using multi-finger robot hand are presented in this paper. After an isometric 50% MVC (maximum voluntary contraction) of human back muscles is performed for 90 seconds, SEMG signals of the subject show a muscular fatigue. A grasp-kneading massage by the robot hand is applied on the subject´s shoulder for recovering from muscular fatigue. To evaluate the therapeutic effects of massage, the SEMG signals measured from the trapezius muscles before and after the massage therapy are analyzed. Electrical activity (EA) and median frequency (MF) of the SEMG signals are calculated as indexes of the muscle physiological states. The experimental results show that EA increases from the occurrence of fatigue, while MF shifts towards lower frequency in the spectral distribution. After massage, a decrease in EA and an increase in MF are observed which demonstrate the effectiveness of recovery through the grasp-kneading massage by the robot hand. In addition, the joint analysis of EMG spectrum and amplitude (JASA), which considers the changes in time domain and in frequency domain simultaneously, verifies that the therapeutic massage recovers the trapezius muscle from fatigue effectively. For comparison, the experiments with a massage specialist performing the massage therapy are conducted with the same procedures. It is evidenced that the robot hand massage has even better effectiveness than the human hand in most cases.