THE EFFECT OF ARM MOVEMENT ON THE BIOMECHANICS OF STANDING UP

The role of the arms and their relationship to the lower limbs in the action of standing up was evaluated. Six subjects were videotaped from the side as they stood up with their feet on a force plate. Subjects stood up, under three arm-movement conditions: with arms moving naturally, with arm movement restricted by holding a rod and with arm movement augmented by the requirement to point. The results indicated that arm movement occurs naturally during standing up. There was a close temporal synchrony between the onset of arm flexion and lower limb extension in both the preferred and the restricted conditions. When arm movement was augmented, however, this synchrony was not apparent. Augmenting arm movement increased the linear momentum of the body centre of gravity and force generation in the lower limbs. It appears, therefore, that arm movement does play a part in potentiating horizontal and vertical propulsion of the total body into the upright position. Clinical implications arising from this study are discussed.