Modeling the Role of the Foot, Toes, and Vestibular System in Human Balance

The study of human balance and gait is a complex area that involves a large number of biological systems, including the musculoskeletal, somatosensory, vestibular, visual, and central nervous systems. In contrast, computational models used for simulating motion of the human body tend to be relatively simple, especially with respect to the feet. Clinical research, however, has begun to more closely examine the mechanical and sensory contributions of the feet in balance and gait, leading to a disparity between the state of clinical research and models used for simulation. A model with a more complex foot would aid in the clinical diagnosis and treatment of motor control disorders, improvement of prostheses, and development of functional electrical stimulation for recovery of lost motor function. This dissertation presents a computational model of a human with a more complex foot, which uses four rigid and connected segments to represent the heel, forefoot, and toes. Derivation of physical parameters, equations of motion, actuation based on human musculature, and control based on proprioception, i.e. body segment positions and velocities, will be discussed. Computation of ground reaction forces under the heel, forefoot, and toes will also be addressed. Simulations focusing on the role of the toes and toe muscles in static balance, forward leaning, and tip-toe stading will be presented. Contributions by the vestibular system will also be considered.