Biomechanical Analysis of the STS Movement and Impact of an Assistive Device on the Elderly and People with Displacement Difficulties

This study presents a biomechanical analysis of the performance of the STS (sit-to-stand) movement applied to elderly and people with difficulty of displacement comparing it with and without an assistive technology device. A biomechanical kinemetry method was used for the movement evaluation. A two-dimensional virtual human model was developedthrough segmented ergonomic video analysis and the data obtained were numerically simulated to measure the inertial forces and torques of the complete execution of the STS movement. The device allows a vertical elevation of 0 to 400 mm and an anterior slope of up to 25°. A prototype was used to compare the movement with and without the assistive device. As a result, the torques in the lower limbs’ joints and the vertical ground reaction forces were reduced by up to 60% and 23%, respectively. There was a reduction of up to 37° in the maximum trunk flexion angle during the cycle. The horizontal displacement of the center of mass was reduced by up to 70%.