Influence of shoe midsoles dynamic properties and ground stiffness on the impact force during running

摘要

Ground reaction forces, mainly vertical component, are widely used in order to characterise impact forces during human running. One of the principal ways to study the impact force during running is to develop a mechanical model of the body-shoe-ground system and to simulate the model to estimate the ground vertical reaction force. Simple spring-damper-mass models have been successfully developed to simulate human running (McMahon and Cheng 1990; Farley and Gonzalez 1996; Ferris et al. 1999; Figure 1). However, these models assumed only rigid body segments in their simulations. The human body corresponds to a mechanical system of rigid (bones) and non-rigid (muscles and other soft tissues) masses, which are attached to each other through elastic and viscous connections. Nigg and Liu (1999) and Liu and Nigg (2000) proposed a new model of the human body for modelling running, iaking into account rigid and wobbling masses. A few years later, Zadpoor et al. (2007) showed that this model was simulated incorrectly and the model is not capable of producing a simulated impact force in the range of the experimentally measured impact force. Then, these same authors brought some corrections to parameters (impact velocities, certain coefficients of the function of the ground reaction force) used by Liu and Nigg (Figure 2). The first aim of this study is to develop a global mechanical model assuming biomechanical properties of human body proposed by Nigg and Liu (1999) and Liu and Nigg (2000), which takes account of the viscoelastic properties of the shoe-sole and the ground stiffness. The second aim is to use the model to understand the influence of shoe-sole dynamic properties on the impact force during running. This model can then help shoe design by influencing the decision on the material choice.