College of LAS « Illinois

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Research on the Run

Finding the secret to sprinting and injury recovery.


It looks like something you might see on the set of a big-budget, special-effects movie—people wearing Ping-Pong-sized balls all over their body, enabling computers to capture their motion and create three-dimensional images. In Hollywood, this technique was used on an actor to create the computer-generated Gollum character in Lord of the Rings. At the University of Illinois, LAS anthropologist John Polk has used this technique to determine how world-class sprinters can reach great speeds.

“A U of I sprinter was in one of my classes and we got to talking about how different training regimes help people increase their sprint performance,” says Polk, who studies motion and its impact on the evolution of our skeletons. “I was interested in the mechanics of limbs during sprinting.”

So Polk had several top Illini runners wear the little balls while sprinting around the Armory track on campus. This enabled the researchers to capture their motion, create 3-D images, and determine the secret to their success.

“Sprinters use sheer power to get up to speed, and then they maintain their speed with the elastic characteristics of their limbs,” he says. “They’re like springs. They’re using the arches of their feet, and they’re using the Achilles tendons in their legs to bounce. But it’s a directed bounce. It’s not up and down, but a bounce in the direction they want to go.”

In addition to the study of runners, Polk’s lab has been working with researchers in engineering and psychology, measuring the motion patterns of people. They’re hoping to quantify motion patterns so physical therapists could use them to diagnose movement problems in patients, such as those recovering from injuries.

“Right now, if you go to a physical therapist, the therapist will look at how you’re moving, ask if you feel pain, and maybe take some simple measurements like stride length,” Polk says. “We want to develop new tools that clinicians and physical therapists can use to quantify motion.”

The result would be a state-of-the-art tool to determine where motion patterns are off kilter.

“There are simple ways of describing motion, but we know that our motion patterns result from complicated interactions among many muscles acting along all of our limb segments,” he says. “We want to figure out how an injury at one joint affects motion patterns at other joints.”

Fall 2011