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Avatar Animation: Why Human(oid)s Swing Their Arms

Arm swinging in VR seems a bit hit or miss.

Biomedical researchers from the United States and the Netherlands have stated that they can explain why when a human body walks, their arms swing at their sides. This has for many years remained a mystery, and to date, has been duplicated in avatars in virtual environments with hit and miss regularity - half of environments include the feature, half don't. Understanding why it happens, is key to understanding when an avatar's arms should also swing.

Swinging the arms consumes energy, and with the perceived benefits being slim, most experts have suspected it's a vestigial trait like the appendix, left over from a previous bodily form for humans.

The researchers built a mechanical model to get an idea of the dynamics of arm-swinging and then recruited 10 volunteers, who were asked to walk with a normal swing, an opposite-to-normal swing, with their arms folded or held by their sides.

Arm-swinging turned out to be a plus, rather than a negative, the investigators found. The arms' pendulum swing helps dampen the up-and-down motion of walking, which is itself an energy drain for the muscles of the lower legs. In effect, swinging the arms saves energy for the human body. It has little to no effect on balance, and since conservation of energy is not a factor in an entirely energy-constructed environment, can indeed be safely discounted as an essential part of avatar makeup.

The study, headed by Steven Collins at the University of Michigan at Ann Arbor, says we should give the thumb's-up to arm swinging.

"Rather than a facultative relic of the locomotion needs of our quadrupedal ancestors, arm swinging is an integral part of the energy economy of human gait," says the paper.

It appears in Proceedings of the Royal Society B, the biological research journal of the Royal Society of Great Britain.


Out on a limb: Arm-swinging riddle is answered

Dynamic arm swinging in human walking

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