Why Do we Swing Our Arms While Walking?

Of course you might have noticed this but felt It wasn't really a big deal.

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Well it kinda is. Don't get scared, its a simple phenomenon.

Kinematics
In recent studies, it has been proven that swinging of arms while walking in an opposing direction to that of the legs improves human efficiency and conservation of energy. Sprinters use this phenomenon to run faster and even in the sports of race walk. Swinging arms create an angular momentum in the opposing direction of lower limb rotation, reducing the total angular momentum of the body.  Why do we swing our arms When We Walk?

BY MEGAN THIELKING
MAY 6, 2015

The way our arms swing when we walk doesn’t seem to make much sense. We don’t need to move our arms to move our legs, so why do it? It’s a question that’s long bothered scientists, whose theories included speculation that it was a good-for-nothing practice that we haven't evolved out of. But in 2009, researchers took a closer look to figure out why exactly we flail while we walk.

University of Michigan scientists measured the energy used by 10 people who walked a number of ways—swinging their arms, holding them to their sides, and so on. They ran similar tests on mechanical models of arms, and they found that the swinging actually has a purpose: It reduces the overall amount of energy it takes to walk.
Walking machines

Collins first became interested in the role of arm swinging through his work with walking robots, which he uses to test ideas about human locomotion. He works with ‘passive dynamic machines’, which walk down a small incline without any power source, as well as robots that use motor-driven springs to push off the ground.

However, the first machines had trouble walking without arms, tending to spin and fall. When Collins and his colleagues added free-swinging arms to the machines, they moved in a way similar to human arms.

The researchers designed an experiment to determine the purpose of this arm swinging. They had 10 people use their arms in different ways as they walked: either swinging normally, held at their sides, bound to their sides or moving out of sync to the walking.

They measured the effort required from the shoulder muscles, as well as the effort of walking overall, which was quantified as metabolic cost.


Arm Swinging And Stride
But although it happens passively, arm swinging plays an important role in making your stride more efficient. It does this by counterbalancing your torso and hips and keeping them from twisting and bobbing too much.

Holding your arms still against your sides while walking requires twelve percent more energy than if your arms are allowed to swing naturally. Forcing your arms to swing in sync with the leg on the same side of your body uses a whopping twenty-six percent more energy than normal walking.