Analysis of velocity's influence on forces and muscular activity in the context of sit-to-stand motion assisted by an elderly care robot

The sit-to-stand movement is an apparently simple yet fundamental activity of daily life. Failure of performing this movement strongly impacts the quality of life of an increasing number of elderly people. Much research thus focuses on assisting this motion. The time necessary for rising up from a sit position is very short for healthy subjects, in the order of few seconds. Using similar speeds for the assisted motion would create safety concerns, hence slower speeds are usually employed. In this paper we experimentally investigate the effects of this speed reduction. We detail the relationship among robot's speed, forces acting on the robot's user and muscular activation. From the results of this analysis we derive indications on the speeds appropriate for assisting the sit-to-stand movement.