When Nike started to make a mark with its running shoes, they made a selling point of "waffle" soles.
Modern trainers have emphasised their comfort factor. This was made possible by the use of ethylene vinyl acetate (EVA), a mouldable plastic foam filled with tiny bubbles, which makes a shoe feel softer to walk in.
This was taken further by putting air pockets or pressurised gel into the heels, to lessen any damage to joints when exercising.
The lightness of training shoes was once a big selling point, because it meant athletes were carrying less weight, and modern, lightweight, synthetic materials such as polyurethanes are widely used in their manufacture. But there are also marketing pressures to pile on the extra features. And there are brands with cut-away soles to show the intricacy of their shock-absorbing springs.
The production of trainers is very labour intensive, as the shoes have to be assembled from a large number of parts. And most of this production is in Asia, where labour is cheaper.
These manufacturers, producing trainers for a whole range of rival brands, have grown into huge businesses, employing hundreds of thousands of workers in production centres across Asia, increasingly in China.
A breakdown of the costs is included on the Clean Clothes campaign website at www.cleanclothes.orgcampaignshoe.htm.
A geography worksheet based on the cost breakdown is also available at the QCA's website at www.qca.org.ukgeographyinnovatingkey3geography_plusprice_make_up.pdf.
This estimates that, for a mid-range trainer produced in Indonesia, the wages of the factory workers represent less than one per cent of the retail price. The manufacturers in Asia receive about 12 per cent of the price, with the largest cost being the raw materials, such as leather.
In contrast, advertising the shoes costs about eight times as much as the wages paid to make them. Research for all those hi-tech features accounts for another 11 per cent. And the trainer companies might take a profit of about 13 per cent from the retail price.
The largest slice of the shop price - about 50 per cent - will go the retailer, who will then take a profit margin after they've covered their own costs.