Three-dimensional lower limb kinematic and kinetic analysis based on a wireless sensor system

Although many wearable sensors have been developed or commercialized for gait analysis, ambulatory force sensors and motion sensors were rarely integrated to implement complete human dynamics analysis. Three dimensional (3D) lower limb kinematic and kinetic analysis based on ambulatory measurements is introduced in this paper. We developed a wireless sensor system composed of a mobile force plate system, 3D motion analysis units and a wireless data logger. 3D motions of body segment and triaxial ground reaction force (GRF) could be simultaneously measured using the system, and the data obtained from sensor units on thighs, shanks and feet could be transferred to a personal computer by wireless local area network (LAN). A stick-chain model was built to visually analyze lower limb postures and joint trajectories, and an inverse dynamics method was adopted to calculate triaxial joint moments. We conducted application experiments on volunteers to visualize and analyze 3D segment orientations and joint moments during successive gait for level ground walking, treadmill walking, and stair climbing. Experiment results showed that 3D segment orientations and joint trajectories could be shown and analyzed using the stick chain model, and that joint loads for different walking conditions could be compared in each gait cycle.