Fig. 5. Swimming velocity and the forward velocity of the third toe of (A) an asynchronous and (B) a powerful synchronous kick. Note the difference in magnitude of body velocity. In the synchronous kick, the foot is moving backwards relative to the water throughout nearly the entire acceleration phase of the kick, while in the asynchronous kick the body starts to decelerate when the foot is still moving backwards relative to the water. The inserted images illustrate the posture of the frog at the time indicated by the position of the waist of the frog.