– Why do our arms move the way they do, when we run fast?


We swing our arms while sprinting and it feels odd not to do it. Does it help with anything?

In: 6

It helps to maintain balance and to help with forward momentum. Try running with your arms at your sides or straight forward. You’ll find you’ll run slower and have to concentrate much more just to maintain your balance.

Your legs are heavy, they are also off-centre on your body. When walking or running, at any given moment you are swinging one leg forward and one leg back. This asymmetrical movement of your legs causes your body to rotate as a result of conservation of angular momentum.

Having your body constantly rotate from side to side as you walk or run would be supremely irritating, and would put a lot of stress on your knees, hips and spine. So you need to swing another mass in the other direction to counter your legs. The other off-centre mass that is conveniently mobile is your arms.

So you swing your legs on way and your arms the other, and your body doesn’t need to swing at all which is handy for looking forwards.

When we walk we are (subconsciously) always rebalancing out body weight so we don’t fall over like big dolls. Just pick an action figure or barbie doll and try to make it stand on its own. Its a surprising amount of calculating.

You don’t notice this cause you have been doing it for years since you started to walk every day. People who lost a leg and got a prosthetic report that they had to genuinely learn how to walk again as s full adult cause all their instincts are based on a foot/leg that can shift miniscule amounts of weight all the time.

Now when you run you essentially exponentially up the difficulty of this by moving through positions much faster and more rapidly. So your body does the same thing it does when balancing on a wire: get the arms to help out with the rebalancing 🙂