<P> Arm swing in human bipedal walking is a natural motion wherein each arm swings with the motion of the opposing leg . Swinging arms in an opposing direction with respect to the lower limb reduces the angular momentum of the body, balancing the rotational motion produced during walking . Although such pendulum - like motion of arms is not essential for walking, recent studies point that arm swing improves the stability and energy efficiency in human locomotion . Those positive effects of arm swing have been utilized in sports, especially in racewalking and sprinting . </P> <P> Studies on the role of arm swing consist mainly of analysis of bipedal walking models and treadmill experiments on human subjects . Bipedal walking models of various complexity levels provided an explanation for the effects of arm swing on human locomotion . On the course of bipedal walking, the leg swing results in an angular momentum that is balanced by the ground reaction moments on the stance foot . Swinging arms create an angular momentum in the opposing direction of lower limb rotation, reducing the total angular momentum of the body . Lower angular momentum of the body results in a decline on the ground reaction moment on the stance foot . </P>

Why do we wave our arms when we walk