Effect Of Upper Vamp And Midsole Design In Ground Reaction Forces In Running
Keywords: sport shoes, running, midsole material, thickness, ground reaction force
AbstractDuring the past decades a great effort in the field of biomechanics assessment of sport equipment has been dedicated to the study of sport shoes and specially of running shoes. The main subjects in which the research has been focused have been the control of pronation and the reduction of impact forces. Several studies have been dedicated to analyse the effect of midsole construction in ground reaction forces or pronation. Nevertheless in some of them no effect associated with different hardness has been found. In a previous work it has been found that a post associated with an external heel counter was an effective feature to control pronation. Besides a new methodology has been developed to characterize the mechanical characteristics of the materials simulating real loads. In this paper a study of the effect of the material the midsole is made with, the midsole thickness and the presence or not of a post associated with an external heel counter in GRF is investigated. Twelve different prototypes of running shoes were specially made for this investigation. The prototypes were specified following a factorial experiment design with the following factors: two thicknesses of the midsole, three materials and presence or absence of a post associated with an external heel counter. Six subjects were selected for the study. Each subject was asked to participate in a session in which the ground reaction forces of running were measured by means of a DINASCAN force plate. Prototypes were randomized and 10 valid measures were collected with each prototype. Velocity of running was measured by means of a pair of fotocellules and trials with velocities lower than 3.6m/s or higher than 4m/s were not considered for the study. From the ground reaction forces the following parameters were considered for the statistical analysis: maximum vertical force at the impact peak and time from the initial contact to the maximum vertical force at the impact. A multifactor analysis of variance of the results was done, considering subject, material, midsole thickness and presence or not of the heel counter and post as factors. Statistically significant differences between levels of the factors as well as some interactions were found. The most significant differences were found between thicknesses of the midsole in impact peak and time of impact peak as well as differences owed to the presence of an external heel counter. Significative interactions between thickness and material were also found.
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