An estimation method of muscular tensions using functional effective muscle strength

Conventional estimation methods of muscular tensions, which utilizes gross joint torques caused by plural muscles, have not been accurate because of existence of bi-articular muscles that drive two joints at both ends. Kumamoto has been proposed the functional effective muscle strength of three antagonistic pairs of six muscles, which are a musculoskeletal model of human limbs in sagittal plane. The functional effective muscle shows relation between each muscle and corresponding joint torque for tip force. Estimation of muscular tensions by the functional effective muscle strength, however, is the maximum force, not the instantaneous force. This paper proposes an estimation method of instantaneous functional effective muscle strength by utilizing both a scaling using a magnitude of tip force and a muscle activity pattern for direction of tip force. Effectiveness of the method is confirmed by an exercise of hip and knee joints.