Abstract
Six adult males and thirteen adult females were used as subjects, and activities of thigh and leg muscles were recorded on electromyogram, while subjects performed horizontal sway (forward, backward, leftward or rightward) or rotation (left or right) and vertical postural change (half-rising, squatting or standing on tip-toe) and also they took weights (6kg x 2) by hands or were given horizontal push force on chest, on back or on a shoulder.
Human erect posture is maintained mainly by correcting small postural sways. This correction is made by activities of muscles, but two effects (1) restoration of the inclined body to erect position by increasing the opposing muscle activity, and (2) fixation of the erect posture by the joint fixation increasing the activities of both extensor and flexor, exist in the muscle activity patterns. Thus muscles or muscle activities acting on maintaining erect posture are better expressed by saying "anti-sway muscles" or "anti-sway activities" than by saying "anti-gravity muscles" or "anti-gravity activities".
