These shoes are tuned to an athlete's vibes
OLYMPIANS competing in Sydney this year may shatter several world records thanks to running shoes individually tuned to damp down the vibrations shuddering through their bodies. The shoes could also one day be used to boost the performance of elderly walkers.
The shoes, designed by Benno Nigg, James Wakeling and their colleagues at the Human Performance Laboratory in the University of Calgary, Canada, contain conventional sport shoe materials. But by manipulating the viscosity, elasticity and stiffness of the sole, the researchers believe they can boost performance by up to 4 per cent. This could slice around 4 minutes off the time of a marathon runner. "That's the difference between finishing first or twenty-second," says Nigg. "We have athletes that have tuned spiked shoes at the Olympics. We think we will see some world records."
The new shoes emerged from research into the damaging effects of vibrations on the body. Studies of drivers and people working machinery revealed that long-term exposure to vibrations can reduce blood circulation and the speed of nerve impulses to muscles. So it is important to minimise such vibrations, says Wakeling.
To mimic the leg vibrations caused by running, Wakeling's team strapped subjects onto a suspended bed with their feet held at a steady angle to the wall. The bed was then swung like a pendulum so that their heels struck the wall every two seconds. By measuring electrical activity in their leg muscles, the researchers found that muscles naturally tighten to help dampen vibrations in the surrounding tissue. "The muscles retune the natural frequency of the leg," says Wakeling. And this stops the leg resonating when the foot hits the floor.
But this retuning requires energy, so the researchers designed a shoe that could do the job instead. Wakeling found that a relatively soft sole is best for damping the vibrations, and allows the muscles to do the least work. Ideally, the shoes should be tuned to the vibrations of each individual by varying the blend of material. Depending on their training and build, people's muscles resonate at different frequencies. "This might explain why there is no such thing as a sport shoe that suits all," says Wakeling.
The shoes may also reduce the wear and tear on athletes' legs caused by repetitive training. And Nigg hopes they will one day be adapted to make walking less physically tiring. "If you do it right, an elderly person may be able to walk two miles rather than one and a half miles."
Author: Mark Robins
In New Scientist issue: 12th August 2000
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