USHERWOOD, J.R.; LARSON, S.G.; BERTRAM, J.E.A.: Mechanisms of force and power production in unsteady ricochetal brachiation

Force production and kinematics during ricochetal brachiation of white handed gibbons Hylabates lar were recorded. Both the mechanisms of force production, and power input, may be inferred for accelerating and decelerating brachiation by combining force data with kinematics. Examples of steady-state, accelerating, and decelerating ricochetal brachiation are highlighted. Gibbons are able to produce horizontal impulses by releasing early (resulting in a loss of potential energy, but an accelerating horizontal impulse) or delaying release (associated with an increase in potential energy and a decelerating horizontal impulse). Torque about the shoulder, leg-lifting (or dropping), and elbow flexing (or straightening) are discussed as potential mechanisms for controlling energy within the brachiating system. Of these possibilities, leg-lifting and arm-flexing were observed as mechanisms of adding mechanical energy. Net energy loss, and substantial torques about the shoulder were not observed.