Though humans share a lot of qualities with other mammals, we are unique in terms of posture, locomotion and gait. (In fact, we're among the only two-legged mammals who walk and run.) For instance, horses consume about the same amount of energy to cover a mile when running or walking, while humans consume substantially more energy when they run than when they walk.

But with our unique patterns of limb kinematics, a group of scientists wanted to study exactly how that affects how we use our muscles while walking and running, and to better understand why it's more "efficient" to walk than to run.

Harvard research finds five-fold increase in knee torque, muscle force

The researchers, most of whom at one time were graduate students of the late C. Richard Taylor at Harvard University, filmed four healthy males walking and running at six self-selected speeds. They measured vertical force on the ground and velocity as the subjects chose "slow," "preferred" and "fast" speeds for both running and walking.

They found that with an increase of speed and gait, the maximum muscle force increased steadily at the hip, remained fairly constant at the ankle, but increased sharply at the knee when the subjects changed from a walk to a run. In most instances (except for the hip at a run), they found that limb muscles were primarily acting to generate force on the ground and the muscle's role in overcoming inertia and gravity was minimal.

Results of the research are reported in a paper entitled "Muscle mechanical advantage of human walking and running: implications for energy cost," which is online at the Journal of Applied Physiology, one of 14 peer-reviewed journals published by the American Physio
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Contact: Mayer Resnick
mresnick@the-aps.org
301-634-7209
American Physiological Society
23-Aug-2004