Lower Limb Musculoskeletal Stiffness Analysis during Swing phase as a Cable-Driven Serial Chain System

To execute a lower limb movement task, the central nervous system (CNS) in human makes continuous adjustment through musculoskeletal system to generate suitable joint stability. Primarily, this is achieved by modulating the multi-joint stiffness values through adjustments in limb posture and muscle contraction level. This ability of CNS plays a significant role during a robotic gait rehabilitation training, where external forces are used to assist the leg training. A lower limb musculoskeletal model to study the stiffness variations during a movement task can be useful in designing better human-robot interaction paradigm. In this work, we model the lower limb musculoskeletal system as a cable-driven serial chain system during the swing phase of walking. Multijoint stiffness matrix is formulated for the serial chain system considering different number of muscles. Various joint stiffness parameters are formulated to study the role of dominant swing phase muscles in altering the multi-joint stiffness values.