PURPOSE: The purpose of this study was to determine if a relationship between forefoot stiffness and intersegmental foot kinematics exists. We hypothesized runners with high stiffness values would exhibit decrease foot motion. METHODS: A convenience sample of 20 asymptomatic recreational runners participated in this study. At the completion of a warm-up protocol, subjects underwent a measurement of their non-weight bearing midfoot torsional stiffness using a foot torsion measurement device. Retroreflective markers were placed over select bony landmarks located on the subject’s lower legs and feet and then recorded using an 18-camera motion analysis system sampling at 240 Hz while running at their self-selected speed. Data analysis: Torsion-angle curves were fit with a one-degree polynomial and the intercepts and first term coefficients (FTC) recorded. The rearfoot and forefoot three-dimensional angular kinematics of the first third of the stance phase of the running trials were obtained for each subject. A linear regression model was used to assess the relationship between the maximum eversion and inversion rearfoot and forefoot angles and the FTC. The statistical level of significance for this study was set at the p = .05 level.
RESULTS: The mean eversion and inversion FTC were -0.44 ± 0.44 and -0.08 ± 0.20 Nm/degree. The mean maximum rearfoot eversion and inversion angles were 2.0 ± 2.1 and 1 ± 2.3 degrees, respectively. The mean maximum forefoot inversion and eversion angles were 1.0 ± 2.4 and 1.0 ± 2.3 degrees, respectively. The regression model did not reveal a significant relationship (p > .05) between the eversion and inversion FTC and the kinematic variables.
CONCLUSIONS: During the first third of the stance phase of running passive stiffness of the foot does not appear to be related to dynamic motion.