Running Shoe Design: Protection and Performance

2 ABSTRACT The overuse injuries commonly experienced by runners can be attributed to a number of risk factors. The primary risk factor is repetitive impact loading of the lower extremity, but anatomical predispositions, excessive subtalar joint pronation, running surfaces, shoes and training habits all contribute to the probability of injury. Running shoes are rarely the sole cause of an injury and equally rarely are they a panacea. However, appropriately designed shoes can reduce injury risk by moderating the effects of repeated impacts and excessive pronation. Cushioned soles redistribute the loads on the foot, reduce peak pressures on the plantar surface of the foot and attenuate the impact shock wave transmitted to the skeleton. Similarly, design features such as varus wedges, variable density cushioning systems and mechanical stiffening elements can be used to control subtalar joint pronation. Such features directly intervene in the putative mechanisms of patello-femoral pain, Achilles tendonitis, stress fractures and other lower extremity injuries. It is commonly believed that wearing lighter shoes with fewer protective features can save energy. While oxygen uptake my be reduced by 1% or so for every 100 grammes of shoe weight saved, the runner's kinematic adaptations to reduced cushioning has been found to produce a similar increase in oxygen consumption. Therefore, most runners have little to gain by selecting shoes that lack risk-reducing features.