The primary purpose of this presentation is to apply both model simulation and experimentation approaches to further expand the concept of the feasible stability region in gait, to explore the control of stability during recovery following a slip induced during walking, and to develop a motor training paradigm that can inoculate older adults against future falls.  A 7-link bipedal model with a dynamic optimization routine is employed to drive forward-dynamics simulation.  Such individualized human model was applied to determine the role of reactive control necessary to adjust the resultant moments (joint actuators) that must be made in individual joints of lower limbs in order to control the stability and to impede an unannounced slip during the single-stance phase.  Ten young adults’ resultant moments of 3 lower limb joints of both limbs, initially derived by an inverse-dynamics approach from empirical data, have been optimized to accurately reproduce the original motion before being applied as input to the control variables of their individualized forward-dynamic model.  Systematic alterations of the moments of each joint lead to corresponding changes in the displacement and velocity of the center of mass (COM) and of the base of support (BOS), and in the COM stability.  The model simulation results show that the knee flexors, followed by hip extensors, of the stance-limb have made the greatest impact in controlling the COM stability during the single-stance phase.  Finally, empirical evidence will be provided to demonstrate how this conceptual framework of the dynamic stability provides the theoretical basis for the establishment of a new and innovative motor training paradigm that employs repeated slips to induce adaptive control and resistance against falls among older adults.  Such approach might be cost effective in reducing fall-related financial cost and human suffering.

[This line of research is being supported by National Institute of Health (NIH) through grants RO1-AG029616 and 2RO1-AG016727.]