Recovery strategy from perturbations of the upper body during standing using mechanical energy analysis

A degree-of-freedom dynamic model of a standing human body, which includes the metatarsophalangeal (MP) joints, was derived using Kane method to study the relationship between the balance mode and the extent of a disturbance to the balance. Four health young subjects were recruited to test different size disturbances. Balance recovery strategies were analyzed by studying the mechanical energy generation and absorption at each joint during the recovery process. The results show that the stability of the human body after a perturbation deteriorates with increasing magnitude of the rotation momentum of the body relative to the MP joint. The tests also show that the balance recovery mode changes with the disturbance intensity. Recovery includes multiple-joint coordination, e.g. all joints contribute to balance recovery. MP joints and hip joints, however, dominate the contributions to the balance recovery from perturbations. The results will facilitate physical training of balance hypofunction patients and balance control of biped robots.