This article proposes a new muscle strength estimation method for upper limbs. It uses an inverse model of a musculo-skeletal model based on the muscle force applied on joints as well as the arrangement of the muscles. We did basic analyses of the parameters of the shape of a living body from magnetic resonance imaging (MRI) images and electromyography (EMG) in order to express isometric motion using the musculo-skeletal model. The model shows high reproducibility of a living body’s isometric motion. We propose two easy methods of estimating muscle strength without optimization calculations and using a model which is the inverse of the musculo-skeletal model: a method based on output force distribution and a method based on joint torque distribution. We have validated them via experiments.

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