Are Rearfoot Motion Parameters Normally Distributed?

Abstract

Averaged rearfoot motion profiles and parameters in running gait have been reported in many past experiments however, small sample sizes have limited the interpretation of their estimates. If these parameters are not normally distributed, then we must use nonparametric statistics, which lack the generalize ability of inferential statistics. PURPOSE: The purpose of this study was to provide rearfoot motion estimates by studying a larger sample population than is usual in rearfoot motion studies and to determine if rear foot parameters are normally distributed. METHODS: Kinematics of the foot and leg were measured in 25 healthy male (age 20.9 ± 4.0) and 25 healthy female subjects (age 21.0 ± 3.2). Data were collected on the right side in 3D at 240 Hz. Marker triads were placed on the leg and calcaneus. Subjects wore running sandals and ran on a treadmill at 3.5 m/s. Joint angles were calculated with a Cardan XYZ sequence of rotations then smoothed and time scaled. Means and 95% confidence intervals were calculated for: inversion angle at heel strike (IN_HS); maximum eversion during stance (Max_EV); inversion/eversion excursion during stance (ROM); time to maximum eversion (TTMaxEv); eversion to tibial internal rotation ratio (EV/TIR); eversion/tibial internal rotation ratio (EV/TIR); and eversion/tibial internal rotation relative to the lab coordinate system (EV/TIR_lab). A Shapiro-Wilk test was used to test for the normality of each variable. RESULTS: CONCLUSION: One of the criteria in using inferential statistics to analyze rearfoot motion is that the scores are normally distributed. In general, it was apparent that the distributions of rearfoot parameters for males, females and combined were normal.Table