The way you swing

OUR nomadic ancestors had to quicklycover long distances while hunting. Aprey that ran faster had to be outrun.While running after the animal theyconstantly moved their arms; it reducedthe effort and counterbalanced the bodyweight. People now run after buses,sprinters run to win a medal. But thedynamics of running have not changed.What a team was interested in knowingwas why humans swing their arms evenwhile walking.

The researchers from the Universityof Michigan, USA and Delft University ofTechnology, Netherlands, studied armswinging that goes into a walk and concludedthat it is an energy conservationmeasure. If humans do not swing theirarms normally while walking, they willburn more energy. Health enthusiastswho take early morning walks in parksto lose some flab should change the waythey swing their arms.

The team developed a walkingmodel to test its theory. Even with noforce driving it, the model easily produceda walking gait similar to humans.When the model swung its arms in away that opposed the normal mode ofwalk, it required muscular effort. Thisproved that swinging arms normallywhile walking requires little musculareffort. Whether it yields energetic benefitsor not the team found out next.

Ten people were asked to walk infour ways: normally, arms clamped bythe sides, arms held loosely by the sidesand arms swinging anti-normally. In theanti-normal mode, the right arm movedwith the right leg and vice-versa.

Barring the normal swing, the bodyburnt energy in all the other modes.Metabolic rate was the lowest in thenormal walk. It increased 7 per cent inbound condition, 12 per cent in the heldposition and was 26 per cent greaterthan normal in the anti-normal mode."Swinging one's arms normally doesindeed save energy. To get better exercise,one could swing them in the oppositedirection. This is not the funniestway to burn calories," said Steven HCollins, key scientist of the study andfrom the Michigan University. "Ourinterest is in saving energy for patientswith gait disorders who use too muchenergy as it is," he added. The study is inthe August issue of Proceedings of theRoyal Society B.