The effects of orthotics on lower extremity variability during running

Abstract

Introduction: Abnormal foot mechanics may affect kinematics of the lower extremity, predisposing individuals to injury. Foot orthotics are often used to alter lower extremity mechanics. Little research is available examining effects of orthotics on lower extremity kinematic variability during running. Methods: 30 recreational runners (15 males, 15 females) identified as excessive pronators participated in this study. Subjects were tested with and without orthotics while running on a treadmill at 3.35 m/s. Ankle and knee joint kinematics were calculated using cardan angles. Kinematic variability of the ankle and knee joints was evaluated using traditional methods (standard deviation and coefficient of variation) and a non-traditional method (spanning sets). Results: There was a significant difference in transverse plane knee kinematics as an interaction effect of gender and condition (F = 4.544, P =.043). There were no significant differences upon other kinematic parameters of the ankle or knee data as an interaction effect between gender and condition. There was a significant difference in transverse plane knee kinematic variability measured via spanning set as an interaction effect of gender and condition (F = 5.306, P = .029). There were no other significant differences in kinematic variability measures of the ankle or knee data as an interaction effect between gender and condition. Conclusion: It is not clear if one could clearly suggest or refute the use of an OTC orthotic for direct control of ankle and knee mechanics. For some the less expensive OTC device may provide an inexpensive alternative to a higher priced custom device. For others there may be a definite need for a more custom fit appliance. There is no reason to suspect the changes in kinematics and variability reported in this study are the effect of a pathologic (abnormal) control strategy. It is not completely clear as to whether or not the SS method used is more sensitive to movement variability.