Question

Why do our hands automatically move back and forth or swing while walking ?

Answer 1

Answer:

In the first one (1) a trio of specialists built a mechanical model to get an idea of the dynamics of arm-swinging and then recruited ten volunteers, who were asked to walk using four different types of arm swing: (a) normal, (b) bound, in which subjects’ arms were physically restrained from moving, (c) held, in which subjects held their own arms still and (d) anti-normal, where subjects actively swung their arms out of phase relative to normal. The energy expenditures were lowest in the normal condition and increased 7 per cent for bound, 12 per cent for held and 26 per cent for anti-normal.

In addition, the vertical ground reaction force was lowest during normal arm swinging, approximately 60 per cent higher during the bound and held modes and nearly 3-fold greater when arms were swung out of phase relative to normal. The vertical ground reaction force is the force exerted by the ground on a body in contact with it.

For example, a person standing motionless on the ground exerts a contact force on it (equal to the person's weight) and at the same time an equal and opposite ground reaction force is exerted by the ground on the person. Hence arm swinging is the least energy spending mode of locomotion.

Answer 2

hey mate...

here is your answer...

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.

hope it helps...