The new shoes could make a big difference for marathon runners

The shoes contain conventional materials that are altered to reduce vibrations and thus energy loss.

They were designed by Benno Nigg and James Wakeling - colleagues at the Human Performance Laboratory in the University of Calgary, Canada.

The new shoes emerged from studies of the damaging effects of vibrations on the body.

By manipulating the viscosity, elasticity and stiffness of the sole of a running shoe, the researchers believe some athletic performances can be boosted by up to 4%. In marathons, they think the technology could help runners chop as much as four minutes off their times.

World records predicted

"We think we will see some world records," said Professor Nigg.

A number of leading athletes are set to use the new shoes at the Olympics. They include the reigning Olympic 100 metres sprint champion, Canadian Donovan Bailey.

The Trinidadian sprinter Ato Boldon and British heptathlete Denise Lewis will also put the new shoes to the test next month, Reuters news agency reports.

The German sportswear and equipment maker Adidas-Salomon AG is planning a worldwide launch of the shoes in early 2001.

Professor Nigg said that on average about 30 top athletes who tested the shoes in the laboratory boosted their performance by 1.8%.

To mimic the leg vibrations caused by running, the researchers strapped runners on to a suspended bed with their feet held at a steady angle to a wall.

Dampening leg vibrations

The bed was then swung like a pendulum so the runner's heels struck the wall every two seconds. By measuring electrical activity, the researchers found that muscles naturally tighten to dampen vibrations in the legs, using energy.

Britain's Denise Lewis is set to test the new shoes in Sydney

"The muscles retune the natural frequency of the leg," said Dr Wakeling. This process stops the leg resonating when the foot strikes a surface.

The researchers then designed a shoe that would do the retuning using the least amount of energy.

Soft soles were best for dampening vibrations. But ideally, the shoes should be tuned to the vibrations of each individual by varying the blend of materials. It seems people's muscles resonate at different frequencies.

The new shoes may also reduce the wear and tear on athletes' legs caused by repetitive training.

Professor Nigg said the shoes might 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," he said.