A muscle action in which a muscle exerts a force while lengthening. Such actions are used to resist external forces, such as gravity. They also occur during the deceleration phases of locomotion. For example, the quadriceps produces an eccentric action when a person walks down a hill. During eccentric actions, muscle fibres move in the opposite direction to the change in joint angle and the mechanical work done is negative: W = F − D; where W = work; F = force; and D = distance. Compare concentric action.
Subjects: Sports and Exercise Medicine.