Figure 1. Forces acting on the body of a climbing animal. (a) Galago. Weight of the centre of mass (black arrow) tends to accelerate the animal downward. Grasping the vertical support stops the fall, but the animal is still in jeopardy of tipping backwards (due to the tipping moment that results from force of the body weight and the distance from the support). Crouching close to the surface reduces this moment, but does not eliminate it. The animal must also apply balancing forces via the hands and feet. (b) and (c) The same balancing forces are produced by the feet and specialized tail feathers of the woodpecker and by the rope sling and spurs of a human pole climber.

Figure 2. Tracings of the swing path of a ricochetally brachiating gibbon. The key factor in effective brachiation is matching the path of the swing and flight phases of the step (when the hand is in contact and not in contact with the support). If this is the case, then energy loss at the transition is minimized and the support simply acts to redirect the animal's movement path. This is more similar to the motion of a stone skipping on the surface of a smooth pond than the swinging of a traditional pendulum. In this diagram the previous ballistic path is indicated by the solid line. Grasping the overhead branch diverts the path of the body along the short dashed line. The gibbon releases the grip to allow the second ballistic path, indicated by the long dashed line.