Engineering for Mobility

At the 2012 Summer Paralympics, elite athletes with disabilities will rely on strength, speed and skill as they go for the gold in 21 different sporting events. Rory Cooper, a biomechanical engineer at the University of Pittsburgh, demonstrates how engineering can help wheelchair athletes maximize their performance in such diverse sports as wheelchair rugby, basketball and racing. "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: At the 2012 Summer Paralympics, elite athletes with disabilities will rely on strength, speed and skill when they go for the gold in 21 different sporting events.

RORY COOPER (University Of Pittsburgh): The Paralympics, they changed my life.

McHUGH: Rory Cooper is a National Science Foundation supported biomechanical engineer at the University of Pittsburgh. In 1988, he participated in four wheelchair racing events at the Summer Paralympics in Seoul, South Korea.

COOPER: I saw people's attitudes change towards me from being, you know, oh, it's great to see this poor person in a wheelchair out here with us to being viewed as an athlete and being viewed as a part of that running community and part of the community at large.

McHUGH: At the Human Engineering Research Laboratories, Cooper and his team of graduate students are demonstrating how engineering can help athletes in such diverse sports as wheelchair rugby, basketball, and racing.

COOPER: You have one set of goals in wheelchair racing, you have an entirely different set of goals in wheelchair rugby. And there's no one chair that's going to be the best for wheelchair racing versus wheelchair rugby.

McHUGH: Sometimes referred to as murder-ball, wheelchair rugby players need strength and stability as they blast down the court, crashing into each other in hopes of crossing the goal line.

AARON PHIPPS (Team Great Britain Wheelchair Rugby): When people see our sport I think it comes as a great shock. I don't think they expect to see people charging around in wheelchairs smashing each other out.

McHUGH: To withstand multiple impacts, rugby wheelchairs have bumpers and durable aluminum frames that go through rigorous testing at the lab.

COOPER: Rugby being a full contact sport, chairs have to be able to withstand those loads otherwise frames will crack.

McHUGH: Another thing rugby wheelchairs are designed to do is stay upright. Engineers add small wheels on either side of the axle to provide front and back stability.

COOPER: If you have wheels behind you and wheels in front of you then you can lean forward and lean back, you’ll have more weight on the rear wheels, but you won't tip over.

McHUGH: Close attention is paid to the wheelchair's center of gravity - the point at which both the chair and the athlete's mass is equally distributed in all directions. The points where a wheelchair can tip over sideways are called the fulcrums, represented by the two triangles. A wheelchair with a higher seat is easier to tip when struck because it is easier for the center of gravity to pass over the fulcrum. In a rugby wheelchair, the seat is placed lower to the ground and the wheels are angled outward, the chair has to rotate more before the center of gravity crosses from one side of the fulcrum to the other, making it harder for the chair to tip over. Wheelchair basketball is played on the same court, but it is more of a finesse game that relies on quickness and skill. These wheelchairs are optimized for a player's position.

COOPER: You really have to kind of classify them in two groups. There's basketball wheelchairs for forwards and centers and basketball wheelchairs for guards.

McHUGH: Forwards and centers are usually under the net, ready to rebound and score, so their wheelchairs are optimized for height.

COOPER: You made a tradeoff in speed by sitting up higher in order to get rebounds and to get closer to the basket for shots.

McHUGH: Guards are ball handlers. Their wheelchairs have a lower seat providing better mobility and quickness because the athlete is able to push with more force on the wheels.

COOPER: A strong guard can almost go the entire court in two pushes.

McHUGH: In a typical Paralympic race, athletes fly down the track at speeds approaching 20 miles per hour or 32 kilometers per hour. That is within two seconds of 400 meter world record holder Michael Johnson.

COOPER: It's really all about speed and how fast you can go.

McHUGH: The ideal racing wheelchair has three wheels, two in back and one in front to allow the athlete to sit more aerodynamically. It is made from composite materials like carbon fiber, which allow the chair to be lightweight and stiff without compromising stability. During the race, athletes sit low and forward generating maximum speed by applying as much force as possible to the entire hand-rim.

COOPER: You don't grab the rim in racing, you punch the hand- rim and you actually try to get all the way down to the bottom.

McHUGH: From the track, to the court, to the street with the everyday wheelchair, Cooper and his team are giving people with disabilities the cutting edge equipment they need.

COOPER: Seeing how we can help improve their function and improve their quality of life. And that's a real reward for me.

McHUGH: And for a select few athletes at the 2012 Paralympic Games, their reward will be gold.