“Humans tend to swing their arms when they walk, a curious behaviour since the arms play no obvious role in bipedal gait. It might be costly to use muscles to swing the arms, and it is unclear whether potential benefits elsewhere in the body would justify such costs.”
If you’re a living thing, energy is a very precious resource. Not the sort of thing to be wasted. So it’s easy to jump to the conclusion that actively swinging your arms while walking could be squandering precious energy. But two experimental studies : Umberger, B. R. (2008). Effects of suppressing arm swing on kinematics, kinetics, and energetics of human walking J. Biomech. 41, 2575–2580, and Collins, S. H., Adamczyk, P. G. and Kuo, A. D. (2009a). Dynamic arm swinging in human walking. Proc. Biol. Sci. 276, 3679–88. showed that people who walk with their arms purposely held at their sides actually consume more energy rather than less, Nevertheless, excessive arm swinging could well be wasteful – leading to the question ; What is the optimum amount to swing one’s arms?
A new paper in the journal Biology Open addresses such a question – for the first time.
“ […] increasing arm swing amplitude leads to a reduction in vertical angular moment and ground reaction moments, but it does not lead to a reduction in cost of transport for the most excessive arm swing amplitudes. Normal or slightly increased arm swing amplitude appears to be optimal in terms of cost of transport in young and healthy individuals.“
The best energy efficiency was found to be an arm swing amplitude of between 0.3 and 0.6 m. Any swing above or below that (or walking with folded arms, or with arms swinging in-phase with the legs rather than the normal out-of-phase) increased energy consumption above normal levels.
The authors also note that :
“Independent of how arm swing is executed, it appears to play an important part during human locomotion. However, what this role is exactly, is still unknown”
Image credit: Eadweard_Muybridge c. 1884.