Control engineering and electromyographic kinesiology analyses of normal human gait

In this study, we analyzed the electrical activity patterns of the antagonistic bi-articular and mono-articular muscles of both legs during normal gait cycles, in terms of electromyographic (EMG) kinesiology and control engineering. For control engineering analyses, we utilized a mechanical two-joint link model equipped with antagonistic pairs of bi-articular and mono-articular muscles. It was confirmed that the coordinated activity pattern, in which the bi-articular muscles of the rectus femoris (Rf) and the medial hamstrings (Mh) showed criss-cross EMG patterns, and the mono-articular muscles of the gluteus maximus and the vastus medialis showed sustained activities during the early stance phase in the gait cycle, contributed to the output force control and the output force direction control. Reversal of Rf and Mh activities was responsible for changes in the output force direction during the heel contact period. The results obtained here strongly highlight the importance of and necessity for control engineering evaluation of coordinated muscle activities of bi-articular and mono-articular antagonistic muscles for analyses not only of gait but also of sports injuries.