Foot orthotics affect lower extremity kinematics and kinetics during running.

OBJECTIVE: To quantify the effects of posting and custom-molding of foot orthotics on lower extremity kinematics and kinetics during running.

DESIGN: Repeated measures.Background. Several kinematic and kinetic factors have been suggested to increase a runner's risk for injuries. It has been speculated that foot orthotics can be used to reduce injury related complaints or even prevent running injuries by affecting these factors.

METHODS: Twenty one volunteers participated in this study. Kinematic and kinetic variables obtained during overground running for medial posting, custom-molding, and the combination of medial posting and custom-molding of foot orthotics were compared to a control condition. Repeated measures ANOVA and student t-tests were used to detect significant differences (alpha=0.05).

RESULTS: Posting of foot orthotics reduced maximum foot eversion and ankle inversion moment and increased vertical loading rate and maximum knee external rotation moment (P<0.05). Molding and posting and molding reduced vertical loading rate and ankle inversion moment and increased maximum foot inversion and maximum knee external rotation moment (P<0.05).

CONCLUSIONS: The effects of posting and molding of foot orthotics are extremely different and when combining posting and molding, the effects of molding appear to be dominant. It yet remains to be determined whether posting or molding is more beneficial with respect to overuse running injuries.

RELEVANCE: The potential of foot orthotics for reducing pain and injuries is convincing. The current study provides valuable information about the role of specific structural components of foot orthotics and contributes to the knowledge about the mechanism underlying the effect of foot orthotics in running.