The Impact of Jenny Simpson

Many runners suffer injuries to their joints due to the repeated impact of their feet hitting the ground. U.S. runner Jenny Simpson relies on new treadmill technology to help rehabilitate from a stress fracture as she trains for the 2012 Summer Olympics. "Science of the Summer Olympics" is a 10-part video series produced in partnership with the National Science Foundation.

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LIAM McHUGH, reporting: In 2011, Jenny Simpson took the world of track and field by surprise, becoming the first U.S. woman since 1983 to win the 1500 meter race at the World Championships.

JENNY SIMPSON (U.S. Track & Field Team): I crossed the finish line and I knew that I was first, you just almost-- you like have to pinch yourself.

McHUGH: While she is a strong medal contender for the 2012 Summer Olympics, Simpson's road to London almost never happened due to a stress fracture she endured in her right femur, a direct result, she says, from the impact of running.

SIMPSON: Very clearly there's no doubt it's because of the consistent and constant impact on my legs.

McHUGH: Whether a world champion runner or a weekend jogger, the repeated impact between a runner's feet and the ground can cause stress fractures in bones or soft-tissue injuries in the joints.

RORY COOPER (University of Pittsburgh): The risk of injury is typically in your shins, your knees, and your hips. Knees tend to be the area where most runners get their injury.

McHUGH: Rory Cooper is a biomechanical engineer at the NSF Engineering Research Center at the University of Pittsburgh. For years engineers have worked on solutions to the problem, developing such things as cushioned running shoes and softer track surfaces to alleviate the impact running has on the human body. Justin LaFerrier is a physical therapist in Cooper's lab.

JUSTIN LAFERRIER (Physical Therapist, HERL): Depending on how you land on your limb will depend on how your body is able to accept these forces.

McHUGH: Every time a foot comes down, the ground provides a force to stop it. The size of the force depends on the runner's mass and how fast the foot is stopped by the ground. Like a hammer to an anvil, each running step pounds away at the joints, passing the force from the foot, to the knees, up through the hips and even the back.

LAFERRIER: That's when you're going to run into those forces being over and above what your body can handle and compensate for. So then you're going to run into the issues such as stress fractures.

McHUGH: Cushioned running shoes and softer track surfaces help reduce some of this impact, by allowing the foot to stop more slowly. But now, engineers have designed an "anti-gravity" treadmill to help decrease impact.

LAFERRIER: Running on an anti-gravity treadmill would relieve a good deal of pressure from the joints because you don't have the same forces coming back through the ground into the lower extremities and back up through the spine.

McHUGH: In spite of its name, the anti-gravity treadmill does not actually reduce gravity.  Instead, it solves the problem by cushioning not just the athlete's foot, but also by supporting some of the weight of the body. Jenny Simpson uses one at the U.S. Olympic Training Center in Colorado Springs.

SIMPSON: Ok, we'll get started.

McHUGH: The runner first slips into a suit, which seals to a small pressure chamber on the treadmill. As the chamber fills with air, it creates a pressurized environment around her lower body, which actually helps bear some of her weight as she runs, making the runner feel lighter.

SIMPSON: It's fascinating. You feel like you're running on the moon or something. You just feel like you're bounding.

McHUGH: In preparation for the 2011 World Championships, Simpson trained on the anti-gravity treadmill while she was recovering from her stress fracture. Now healed, Simpson still uses it as part of her training regimen. Because of the reduced impact, she is able to run more miles per week than she would regularly.

SIMPSON: So you're running on the treadmill and your workout feels very similar to a workout as if I was doing it on a regular treadmill without the compression, without the bubble around my legs.

McHUGH: With the help of modern engineering and technology, runners have a solution to the problem of impact, and Jenny Simpson has the chance to prepare for the race of her life at the Olympics.