Arm swing is ignored by most runners but shouldn’t be. A vertical arm swing — elbows and hands smoothly moving in a straight line, front to back, as you run — propels all your energy and momentum forward. But many of us swing cross-chest — elbows splaying out to the sides, hands swinging back and forth across the middle of the body — which sends your energy sideways and leaves you “rotating like a washing machine on every stride,” says Owen Anderson, author of “Running Form.” “That wastes energy, stresses your joints and causes you to run a slightly crooked line.” Tip: If you can see the back of your hands as you run, you are crossing your chest. Gently remind yourself to keep elbows in at your side, Anderson advises. Soon, it will become second nature. Also, balled-up hands create excessive muscular tension and contribute to a cross-chest swing. So relax the hands.
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