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. Richard Wharton, from Offspring, a shop in Covent Garden dedicated to trainers, has been selling them for the past few weeks and watching them leave the shop in droves. mate".Stride is a complete design concept, from the brand name to the logo to the shoe, and it works. "They were crowding around the glass cabinets having a good look," says Atha.She is showing Stride alongside the ad campaign for the shoes, which features various styles in the context of greasy-spoon food: deep-fried with chips and peas, in a pie dish, or as boil-in-a-bag, with the catchline "put em on your plates ... "It's brilliant, to get into the Design Museum you'd think it would take years." It has taken him months.On Thursday, the opening night of the Design Museum's latest exhibition, The Power of Erotic Design, many visitors strayed to the glass cabinets featuring Stride, and the Just Deakin/Inflate collaboration, the inflatable flip-flop. They recall 1960s TV shows with their names, for example Stealth and Stingray, and also act as containers for so many references."When Atha first approached Deakin, she told him "you're part of the trainer revolution" Deakin, however, still can't believe his luck.

Christine Atha, curator of The Review Gallery, says, "The trainers are there as a contemporary idea, as well as a typical example of today's culture. "All we wanted to do was develop a new kind of footwear that used sports technology, but that people could wear every day," he says.The trainers are a visual feast, with references as diverse as Evel Knievel's Velcro-fastened motorcycling boots, to puffa jackets and work boots, as well as from mainstream trainers. He talks sole units, uppers, price points and construction with a broad Leeds accent and a jingle of his chunky silver jewellery. This is a designer who doesn't talk about ethereal creativity. When he talks about this monumental effort there is a twinkle in his eye. But his burning ambition was always Stride.Once they decided on a name and a logo for their sneakers it took two years, five prototypes, several trips to Korea, and more than pounds 250,000 to launch Stride.