Immediate effects of shoe insoles on the frequency components of ground reaction force during the stance phase of running

Introduction: Foot insoles are widely recommended to prevent running related to injuries. However, their effects on the frequency of Ground Reaction Force(GRF) is still unclear. The purpose of this study was to elemental test the effect of four shoe insoles on frequency of GRF during stance phase of running. Materials and Methods: 15 female Students (mean age22±1/85 year, height162±4/71cm and weight56±5/59kg) were selected. Subjects were asked to run over a force plate, in a control and insole (normal, soft, semi rigid, rigid) conditions. Vertical and anterior-posterior (AP) of GRF were evaluated in frequency domain using fast furrier transformation. One factor repeated measures ANOVA was used to test the hypothesis.   Results: The statistical results showed that there was a significant difference between insoles in 99.5% frequency of vertical (p=0/001), AP GRF (P=0/049), and median frequency of AP GRF (p=0/012).   Conclusions: Increasing hardness of insoles reduces the 99/5% frequency power of GRF and median frequency of AP GRF. Accordingly, the 99/5% frequency power of GRF and median frequency of AP GRF can be an indicator of shoes insoles effects on the foot during running.   Key words: Insole, Frequency, Power spectrum, Ground reaction force, Running