The Myth of Running Shoe Cushioning

The advent of the “Running Boom” in the late 1970’s coincided with the introduction of the first “technical” running shoe products incorporating cushioned soles and features intended to stabilize the foot during ground contact. The sensation of comfort provided by cushioned running shoes appears to have facilitated the participation of many “joggers” who would otherwise not have taken up the sport. The Running Boom also precipitated rapid growth in related scientific research. In both university and corporate laboratories, studies of the physiology of exercise, the biomechanics of running and the mechanics of running shoes became common. Numerous investigators sought to determine a link between running shoe cushioning and the impact loads experienced by the runner. The results of these experiments were generally inconclusive, however. Many researchers reported no differences in peak impact force among different cushioning systems and, in some instances, more compliant cushioning was found to increase impact force. These equivocal results have lead others to hypothesise that running shoe cushioning offers little benefit to athletes. Very compliant cushioning may increase injury risk in some instances, since there is a correlation between cushioning compliance and excessive subtalar joint motion, which has been linked with common running injuries (Clement et al, 1981). Some (e.g. Robbins and Waked (1997)) have interpreted the available data less equivocally, stating bluntly that cushioned athletic shoes are dangerous and that shoe companies offering cushioning as a benefit are guilty of deception. The purpose of this paper is to briefly summarise some of what is known about the mechanics of running shoe cushioning, in an attempt to determine why the expensively engineered shock attenuating systems built into athletic shoe soles apparently fail to attenuate shock.