Energy based criterion for dynamic balance of human body

An energy-based criterion for dynamic balance of human body is presented. As an example, two-segment model of human body, an inverted pendulum model, is employed to map the anterior and posterior boundaries of stability region with optimization algorithm, then the energy relationship between the dynamic characteristic of body and dynamic stability region is examined. It can be employed to predict the dynamic stability of human locomotion when a large displacement or velocity of mass center has occurred. In addition, the influence of reduction of muscle strength on the stability margin has been analyzed by computer simulation. The results show that the reduction of ankle muscle strength results in apparent decrease of stability region. And also, more reductions have been found on anterior boundary of stability region than posterior boundary. For example, someone subject to a reduction of ankle muscle strength who prefers to take forward step to keep balance than the normal. The results agree well with the clinical observation of balance pattern of the older, who prefer to take steps to keep balance than the young even on a small disturbance.