Walk, Don't Run

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http://www.nytimes.com/2004/08/31/health/31exer.html

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VITAL SIGNS

Exercise: Walk, Don't Run, the Knees Say

By MARY DUENWALD

Published: August 31, 2004

Running may get you places faster than walking does, but it is a less

efficient form of locomotion because of the demands it places on the

knees, researchers have found.

For humans, running a given distance requires 50 to 80 percent more

energy than walking the same distance does. Horses and other

four-legged animals, in contrast, use roughly the same amount of

energy to run a mile as to walk it.

To figure out why humans are different in this way, researchers at

Harvard's Concord Field Station in Bedford, Mass., filmed four

healthy

young men as they walked and ran at steady speeds. As the men

progressed from walking to running, they steadily increased the

amount

of strength used to work their hips until it almost doubled. The

amount of force at their ankles stayed fairly constant. But their

knees used five times as much force when they ran.

The research is reported in The Journal of Applied Physiology.

The extra force is needed because, during running, the knees must

stay

flexed to enable the leg to act as a spring. And bending the knees

means working the large quadricep muscles of the thighs.

" In running, the leg must compress and extend like a pogo stick, "

said

Dr. J. , an assistant professor of biology at Brown

University and an author of the study. " In walking you conserve

energy

because you move like an inverted pendulum. You sort of pole-vault

over your legs. "

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Well that's interesting. Always have read that the calories expended

for walking or running a mile were roughly equal. So according to

the article you get more bang for your buck by running three miles as

opposed to walking three miles. And if you run on a treadmill with

a flexible surface, like I do, you'll probably have no problems with

your knees. So run don't walk - just do it mostly with a flexible

surfaced treadmill.

Aequalsz