Stand up from a chair with lesser body load: Biomechanical simulation and visual supplement

The natural standing-up movements of unimpaired people are often thought to be models to follow in rehabilitation, although it is not known whether these movements place a minimum body load. We aim to determine the angular trajectories of the ankle, knee, and hip joints when standing up from a chair without unnecessary body load. The minimized body load was quantified by an index value that has a strong negative correlation with the chair height. Decreasing the value of this index by changing the movement during sit-to-stand transfer could reduce the impact on the body, which is the same amount of load placed on the body while standing up from a higher chair height. We have also developed a novel integrated system that visualizes the differences between a patient´s current movement and a load minimized movement with the associated kinematic and kinetic data. The visual supplement system could be used to help users see how much force and moment are placed on lower limb joints, and provide personalized optimum movements for rehabilitation with reduced body load on patients. An example minimization of an index value, accumulated moment of force at knee and hip, when standing up from a 45-cm-height chair is described here. If the system is properly developed, people in need could be able to repetitively exercise at any time without requiring human instructors to preserve their remaining function and improve their performance by quantitatively evaluated suggestions.