Emma, Clinical Biomechanics recently published a nice review regarding mechanics of shoe design, and the relation to injury prevention. The results are confronting to say the least (for e.g., an argument is developed that the foot and leg work to find the most efficient pattern IN SPITE OF the footwear, and may be hindered by our well meaning efforts at shoewear design.) The last time I looked, there were half a dozen sample review papers up for looks at ClinBiomech's website (try searching for 'Clinical Biomechanics' on
www.google.com or similar. It's an Elsevier Publication.) If you REALLY can't find it, mail me, and I'll send you the reference. In short, there's a lot more to athletic footwear than would first meet the eye (and I guess, at the risk of starting a flame war, a lot more than the Podiatrists would like us to believe)
cheers,
Rod