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. 鈥淭hat鈥檚 the difference between finishing first or twenty-second,鈥� says
Nigg. 鈥淲e have athletes that have tuned spiked shoes at the Olympics. We think
we will see some world records.鈥�
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.
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To mimic the leg vibrations caused by running, Wakeling鈥檚 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. 鈥淭he muscles retune the natural frequency of the leg,鈥�
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鈥檚 muscles
resonate at different frequencies. 鈥淭his might explain why there is no such
thing as a sport shoe that suits all,鈥� says Wakeling.
The shoes may also reduce the wear and tear on athletes鈥� legs caused by
repetitive training. And Nigg hopes they will one day be adapted to make walking
less physically tiring. 鈥淚f you do it right, an elderly person may be able to
walk two miles rather than one and a half miles.鈥�
