A STIFFNESS-VARYING MODEL OF HUMAN GAIT

We report on a conceptual two degrees of freedom (2 DOF) human gait mo del, which incorporates nonlinear joint stiffness as a stabilizing age nt. Specifically, muscle spring-like property provides inherent stabil ity during gait movement using a nonlinear angular spring and dash pot at each joint. The instability problem of the gait model in direct dy namic analysis is overcome by simulating the human co-contraction musc le function. By developing dynamic system stability requirements and h ypothesizing a minimum joint stiffness criterion, we determine time-va rying joint stiffness. Optimum joint stiffnesses are present for varyi ng gait pattern, stride lengths and cadences. We conclude that nonline ar joint stiffness can be incorporated into gait models to overcome st ability problems inherent in such linkage models. (C) 1997 IPEM. Publi shed by Elsevier Science Ltd.