This is less debilitating for the final team, but also means the ice-cap is cracking. "Part of the dilemma is that if we carry extra food and water, to keep us going for longer, that will weigh us down so we won't be able to cover so much ground each day."If we run out of supplies without reaching the Pole we'll just have to keep going without wasting time sleeping."The women will also be racing the effects of spring. "It sounds like a conspiracy to keep the North Pole for men," she said. Whatever the truth of the theory, it appears polar bears are far too sensible to venture as far north as Penguin Echo will go.As a member of Echo, Ms Hamilton shares the pressure of being in the final team. "The others who have gone before have done such an amazing job that we are all terrified of letting them down," she said. "We made it a relay so that ordinary women who couldn't afford to take months off work could take part," she explained.She is mystified by the idea that women do not take to the Arctic because polar bears smell them more easily they do male explorers and might attack them.

"Because the geographical North Pole moves all the time it will be a very private experience, a different Pole from anyone else's."A keen explorer of far-flung terrain, the 33-year-old film financier's dream grew from a fascination with deserts into a desire to achieve something no one else had. Still others use adjoining chambers or a honeycomb effect so that shocks can be distributed along the shoe. Midsoles are often made with air capsules, or gel using "energy return" chambers designed to cushion the shock generated when your foot hits the ground - which may otherwise travel up to your knees or lower back, with potentially painful results.Some manufacturers use a shock-absorbent, spongy material in the midsole Others use a hi-tech foam. Many of today's more expensive trainers have a "midsole" between the upper (toe box, heel box and fastenings) and "outside" or rubber bottom of the shoe. "This is the new underfoot cushioning and stabilising system," explains Mr White."It has been tested on more than 700 runners over thousands of miles and is better than and dramatically different from anything out there."What is "out there" is already pretty sophisticated.

"But every foot is a different shape; every individual moves differently and has different needs." His aim was to make a running shoe which could supply all these needs, and with the new DMX Series 2000 he believes he has done it.These trainers feel as light as a feather and look entirely synthetic, with semi-transparent blue soles rather like outsized bubble wrap. Sometimes, real live athletes come to play basketball in the gym which is part of the laboratory, so that high-speed videos can record and monitor the performance of their shoes."There have been dramatic improvements in footwear for athletes over the last 20 years," says Spencer White. "Your foot is an extremely complicated mechanism, and if it's not a stable platform it can cause pain in the knee and as far as your lower back."Proper footwear protects you from injuries such as planar fasciitis (sore heels caused by impact or not enough support) and shin splints (aches in the shins caused by lack of cushioning and stability).Mr White's Human Performance Engineering Laboratory also has computer simulator machines which twist and bend and pound the latest Reebok prototypes in the new science of bio-engineering. As Reebok's Director of Research Engineering, he warns that without decent trainers many of us who do aerobics, running or other sports would be hobbling around injured. "Your foot bone is connected to your leg bone, and so on up the chain," he says. So are they really necessary? I put this heretical idea to Spencer White, a genial American boffin who runs a hi-tech laboratory in Boston peopled by jogging robots in Reeboks and professors from MIT. After all, the ancient Greeks didn't wear trainers to run the original marathon. Not so hard for their parents, who may still remember a time when daps served just as well, weren't scorned as totally "sad" and didn't cost a fortune.

Impossible, perhaps, for this generation of teens, whose very identity can depend on what they have on their feet. Imagine a world without trainers. The Design Museum, 28 Shad Thames, London SE1 (0171-378 6055).Stride is available from Offspring, 60 Neal Street, London WC2; Aspecto, 85 Bridge Street, Manchester; branches of Cobra Sports; branches of JD Sports and Hip, 9 & 14 Thorntons Arcade, Leeds.. Deakin is passionate about keeping them reasonably priced - and pounds 69.99 (or pounds 64.99 for the girls) is a small price to pay for an instant design classic.Stride will be on show at the Review Gallery at the Design Museum until August. "I wish I'd bought more of them, they appeal to everyone: it's not a black thing or a gay thing, although both groups are buying them, it's a fashion and club thing."He is waiting for the red, white and blue variations on the current styles to come out next month, and will increase his order Until then, catch them if you can.