A dynamic model for simulating a trip and fall during gait

The purpose of this study was to develop an analytical model to simulate a trip and fall during gait. The human body was modeled as a 12 degree-of-freedom linkage system. The kinematics of the lower extremity for one cycle of gait were obtained for a healthy subject using an optoelectronic three-dimensional data acquisition system. Inverse dynamics was used to compute the moments about the hip, knee and ankle joints of the lower extremity. These moments were then used as input actuators to the joints in to a forward dynamics model to simulate the swing phase of gait from toe-off to heel-strike. An optimization procedure to minimize errors associated with the computed experimental torque was applied to correct for mathematical instability. An experiment was performed to measure the three-dimensional foot--obstacle contact force for a healthy subject tripping on an obstacle during gait. The contact force was applied to the swing limb of the forward dynamics model for 0.09 s beginning at 0.04 s after toe-off. Tripping on an obstacle followed by a muscle-relaxed fall was simulated. The simulation results were visualized with animation software.