Why do we just run and walk when our bones and muscles could do much more?

Main Category: Sports Medicine / Fitness
Article Date: 16 Sep 2005 - 6:00 PDT

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Despite having the bones and muscles to perform a variety of gaits, human beings have developed an overwhelming preference for just two: walking and running. Now, computer analysis that allows simulation of infinite two-legged locomotions has shown our favored modes of bi-pedal travel use the least amount of energy.

Indeed, in an article published in the current online edition of the British journal Nature, Cornell engineers Andy Ruina and Manoj Srinivasan compare the mechanics of walking and running with "many other strange and unpractised gaits." They used a set of computer models that simulated physical measurements such as leg length, force, body velocity and trajectory, forward speed and work.

"We wish to find how a person can get from one place to another with the least muscle work," they report. "Why do people not walk or even run with a smooth level gait, like a waiter holding two cups brim-full of boiling coffee?"

The engineers' computer simulations conclude that walking is simply most energy efficient for travel at low speeds, and running is best at higher speeds. And, they report, a third walk-run gait is optimal for intermediate speeds, even though humans do not appear to take advantage of it.

The findings help to explain why the possible--but preposterous--gaits in the Monty Python sketch, "Ministry of the Silly Walks," have never caught on in human locomotion. The researchers add that extensions of this work might improve the design of prosthetic devices and energy-efficient bipedal robots.

NSF-PR 05-161

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering, with an annual budget of nearly $5.47 billion. NSF funds reach all 50 states through grants to nearly 2,000 universities and institutions. Each year, NSF receives about 40,000 competitive requests for funding, and makes about 11,000 new funding awards. The NSF also awards over $200 million in professional and service contracts yearly.

Leslie Fink
lfink@nsf.gov
703-292-5395
National Science Foundation
nsf.gov

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