SIMPLY wearing shoes with textured insoles improves people鈥檚 awareness of the position of their feet and could help prevent knee and ankle injuries.
The smooth insoles and high shock-absorbing properties of many sports shoes mask pressure cues from the soles of the feet, says George Waddington, a physiotherapist at the Canberra Hospital in Australia. For instance, a study of basketball players in 2001 found that those who wore expensive air-cell shoes were four times as likely to suffer an ankle injury as those wearing standard trainers.
鈥淪hock absorption has been the focus of design,鈥� Waddington says. 鈥淭hat is important for some sports, such as running, but the process of interlinking to the natural sensory system in the sole has been missing.鈥�
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To see if this link could be restored, he tested the ability of 17 members of the Australian women鈥檚 soccer squad to sense the extent of ankle inversion, in which the foot tilts inwards towards the body. The women鈥檚 scores dropped when they wore their usual boots, compared with being barefoot. But wearing rubber insoles with four 3-millimetre-high nodules per square centimetre restored performance to the barefoot level (British Journal of Sports Medicine, vol 37, p 170).
The angle at which someone holds their foot as they swing it forwards is important not only for preparing for the impact with the ground but also for avoiding obstacles, says Waddington. There is an optimum path for the foot (see Graphic): keep it too low and you are in danger of tripping over any bumps. Tilting the foot too much further reduces clearance, increasing the chance of tripping.
So by improving ankle sensing and positioning, less cushioned shoes with textured insoles should cut injuries. Work is also under way to see if the insoles could help prevent falls in elderly people. But Waddington says talks with shoe manufacturers have so far produced only a lukewarm response.