I think that while people walk and run their motions are chosen to reduce effort, increase speed, and keep stable. If someone walked or ran with their arms hanging straight down instead of swinging them, they would get more tired. They couldn’t run as fast. And they might fall down more. How does swinging your arms make walking and running easier and faster? I don’t think anyone really knows, but here are a few ideas.
1) If you hang from a rope and swing your legs as if you were walking your body will twist back and forth. When you walk, that twisting tendency is still there. Swinging your arms opposite to your legs, like most people do, twists you the opposite way so its easier to walk straight.
2) If you just relax your arms, they will swing because your shoulders move when you walk. It takes effort to stop them from swinging. People are lazy so they let their arms swing.
3) Swinging arms can help push you forward. Each time you swing your arm you throw your fist forward like a ball. At the end of the forward swing your fist pulls your body to catch up. Why doesn’t the ‘throwing’ effect cancel the ‘catching’ effect? That’s the kind of thing we are still trying to figure out.
Andy Lee Ruina
Ph.D. Brown University
Biomechanics and Robotics
Mieke, at Belle Sherman Elementary School; Saskya
Walking, bikes, sleep
West Middle School