On Your Mark, Get Set, Go!

Reported July 2006

ORLANDO, Fla. (Ivanhoe Broadcast News) -- To get from one place to another, we walk or run without thinking much about why. But these two engineers did wonder why humans move the way we do.

They look funny doing their research, but Manoj Srinivasan, Ph.D., and Andy Ruina, Ph.D., aren't comedians. They're mechanical and aerospace engineers studying human locomotion, or how people get around.

"You can imagine a person being able to go from point A to point B in all kinds of crazy ways. But people mostly choose to walk," Srinivasan, of Princeton University, tells Ivanhoe. "The question is why?"

Srinivasan and his advisor, Ruina, designed a computer model to reveal the most energy-saving ways a person can move. Out of the thousands of possibilities, the computer chose walking and running, confirming a theory that's been around for hundreds of years.

Srinivasan says, "Walking is the least energy consuming at slow speeds, and running is the least energy consuming at fast speeds."

In a nutshell, we walk and run instead of skip because it takes less effort.

Andy Ruina, Ph.D., of Cornell University in Ithaca, N.Y., says, "So walking's the gait that people use where there's at least one foot on the ground, where your body moves approximately in a sequence of circular arcs."

The researchers were surprised, however, when the computer also chose a third gait.

"And as far as we can tell, this thing looks -- would look something like a tired run. Something like ... like that," Ruina says.

By studying the way we move, not only will researchers uncover more mysteries of the human body, but they hope to develop better prosthetic and orthotics devices.

Ruina and Srinivasan compared the three natural movements with what they call "many other strange and unpracticed gaits." Their computer model simulated human traits including leg length, force, body velocity and trajectory, forward speed and work.

Click here to Go Inside This Science or 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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