| On Your Mark, Get Set, Go! -- Inside Science
Reported July 2006
BACKGROUND: People's legs are capable of a broad range of gait patterns, but we mostly use just two: walking and running. Cornell University researchers in Ithaca, N.Y., have developed a computer model that could compare walking and running with an infinite variety of other gaits. It turns out that walking is the most energy-efficient gait for slow speeds and running is the most energy efficient gait for fast speeds. The new simulation also uncovered a new, seldom-used gait for intermediate speeds that looks like "tired" running with slow motion landings.
THE STUDY: The Cornell researchers compared the mechanics of walking and running with many other gaits (such as skipping), using a set of computer models that simulated physical measurements such as leg length, force, body velocity and trajectory, forward speed, and work. The aim was to discover the most efficient means for a person to get from one place to another with the least amount of muscle work. When people walk, they swing their body over a relatively straight leg with each step; when they run, they bounce up off a bent leg between aerial phases. Both these use less energy than more unusual gaits.
ABOUT BIOMECHANICS: Biomechanics is the study of the anatomical principles of movement, such as how birds and insects fly; how fish swim; and the most efficient ways a human can move. When we walk, with every step, the foot strikes the ground on the outside edge of the heel, the shinbone twists inward, and the foot rolls inward to bear the weight, absorbing the shock of impact. Then the shinbone twists outward and the foot begins to lift at the heel, providing a springboard for the toes to push the body's weight forward off the ground. The foot then swings forward to repeat the cycle. Running has similar mechanics, but can be seen as a series of alternating hops from left to right leg.
If you would like more information, please contact:
Andy Ruina, Ph.D.
Biorobotics and Locomotion Lab
Theoretical and Applied Mechanics
Cornell University
Ithaca, NY
(607) 255-7108
ruina@cornell.edu
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FACTOID...
Eadweard Muybridge famously photographed a horse galloping, thereby proving that when a horse gallops, at a particular point all four feet are off the ground simultaneously.
ON THE WEB...
Body Motion in Human Gait
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