Different Temporal Structure of Muscle Synergy Between Sit-to-Walk and Sit-to-Stand Motions in Human Standing Leg

Humans do not only perform individual motion separately, but they transit motions from one to another. It has been widely known that human sit-to-stand and walking motions are composed of four and five muscle synergies, but it is not clarified how humans utilize these muscle synergies to generate sit-to-walk motion. This study conducted a measurement experiment to identify muscle synergy structure in standing leg during the sit-to-walk motion. Results showed that the same muscle synergy of sit-to-stand and walking could explain sit-to-walk motion. Three of four synergies in sit-to-stand was not significant different but the last synergy was adaptively changed in order to shorten the time of postural stabilization to initiate stepping motion.