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"They act as counter balances for the legs and help to maintain an steady posture while walking. If you don't move your arms, the shifting of weight as you walk will cause more movement of the head and subsequently the balance region of the ear. It is also wasteful of energy, as the weight then has to be moved back. By using your arms, this is minimised.

It is natural to try to reduce movement of the head, this is why you swing your left arm in time with the right leg, and vice-versa. These movements are handled by the cerebellum, a specialised area of the brain. To do otherwise, that is, to square-gait, seems awkward because your head moves from side to side."

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