Why do runners swing their arms?
Show answer & explanation
Answer: Balances rotational momentum
Balances rotational momentum ✓ — Correct! Angular momentum balance! Running: legs drive body forward. Each leg swing creates rotational torque on torso (Newton's 3rd law—action/reaction). Without arm swing: torso would rotate excessively—unstable, inefficient. Arms swing opposite to legs: right arm forward with left leg, vice versa. Angular momentum cancels out—torso stays stable. More efficient biomechanics. Faster running = more vigorous arm swing (greater momentum to balance). Tying arms behind back makes running very difficult—research shows ~10% more energy!
Increases oxygen to muscles — Wrong. Arm position doesn't affect oxygen delivery. Arms balance rotational momentum from leg swing—prevents torso rotation.
Makes running feel easier — Wrong. Proper arm swing does make running more efficient, but mechanism is balancing angular momentum—not psychological.