a comparison of the free moment pattern between normal and hyper-pronated aligned feet in female subjects during the stance phase of gait

Background: excessive range of adductory free moment of the ground reaction force may potentially increase the risk of lower extremity injuries by applying a higher torsional load transmitted to the proximal parts. objective: it was hypothesized that the free moment pattern might be different between hyperpronated and normal feet subjects. moreover, a correlation would exist between peak adduction free moment and peak anklefoot complex abduction at the stance phase of walking. material and methods: in this cross sectional study, thirty female participants were divided into two groups of asymptomatic hyperpronated and normal feet. kinetic and kinematic data were collected using a single force plate and a sixcamera motion analysis system during three successful free speed walking trials. ensemble average curves were extracted from the time normalized individual trials of the stance phase for both free moment and peak anklefoot complex abduction parameters. results: significant differences in peak adductory free moment, peak anklefoot complex eversion and peak anklefoot complex abduction were found between normal and hyperpronated groups (4.90±0.97 vs. 5.94±0.88, p < 0.01), (3.30±0.95 vs. 6.28±1.47, p < 0.01) and (4.52±1.16 vs. 8.23±2.52, p < 0.01) respectively. a significant positive correlation was found between the peak adduction free moment and peak anklefoot complex abduction in both groups, which was more strongly positive in hyperpronated group (r = 0.745, p < 0.01 for normal group and r = 0.900, p < 0.01 for hyperpronated group). conclusion: as a good measure of torque which is transmitted to the lower extremity, may free moment be a useful biomechanical indicator for both clinical and research purposes.