It is the first step for estimating the physical load of movements such as energy expenditure or load on joints to understand muscle strength induced by each movement. It is therefore necessary to analyze the motion from the viewpoint of dynamics, and "joint moment" calculation is one of the useful methods for that purpose. "Joint moment" is the muscle strength around the joint which provokes a rotation of lower extremity, and is applicable to quantitative estimation of muscle strength to some

more »

... xtent. In order to know the joint moment during walking, it is also necessary to understand "ground reaction force" in stance phase, and "inertia force" in swing phase . In this review, the concepts of "joint moment", "ground reaction force" and "inertia force" were plainly introduced to explain the implications of the measurement of movement .