A dynamic analysis of the joint forces and torques during rising from a chair

A method of calculating the net forces and torques on human joints using inverse dynamics and an 11 segment model of the human body is presented. This method was used to analyze 20 chair-rise trials performed by ten normal adult subjects. Representative force and torque curves are given, and a quantitative comparison of the relative importance of segmental dynamics on joint loads is presented. The results of this study suggest that the effects of segmental dynamics can be neglected for the ankle and knee joints, as they contribute to less than 1% of the total ankle and knee forces and torques. The segmental dynamic contributions to hip forces and torques were less than 10%, which may or may not be acceptable, depending on the need for accuracy in a particular study. For the back and neck joints, segmental dynamics should not be neglected as they were responsible for more than 15% of the total forces and torques on these joints. The effect of ascent speed on segmental dynamics is also addressed by comparing three slow chair-rise trials with three fast chair-rise trials, all performed by one normal adult subject