An experimental review of the McMahon/Cheng model of running

Sports shoe design has evolved at a rapid pace over the last few years with many different models being available in the marketplace, each model having its own unique qualities and price tag. Recent research studies show that expensive athletic shoes account for 123% greater injury frequency than cheaper ones (Robbins & Waked 1997, British Journal of Sports Medicine, 31, 299–303). If one aims to design shoes and surfaces which minimize the risk of injury then the reaction of an athlete to varying underfoot compliance needs to be understood. The aim of this paper is to investigate the effects of running with and without sports shoes (i) to assess the athletes’ reactions; and (ii) to generate sufficient data to analyse the mechanics of running by comparison with a mathematical model proposed by McMahon and Cheng [1990, Journal of Biomechanics, 23 (Suppl. 1), 65–78]. Subjects ran on a treadmill with and without running shoes. From measurements of the stride pattern, the vertical leg spring constants were derived, and the variation with speed compared with the model predictions. In the main, the trends for individual athletes agreed with the model. However, the athletes were found to vary their stride lengths and leg angles in ways that the model did not foresee. Overall, one may regard the model as a limited approximation that has, nevertheless, shown itself to be capable of useful prediction. Departures from the model are attributed to the basic model assumptions and to the qualitative differences between running shod and barefoot.