The effect of shoe inserts on the kinematics of the lower extremity and center of pressure during treadmill running

Objective: The purpose of this study was to investigate the effect of different orthotic shoe inserts on kinematics of the lower extremity and center of pressure (COP) during treadmill running. Design: The study design was an experimental investigation of five different orthotic insert conditions. Background: Orthotic shoe inserts have been used to treat a wide variety of running injuries. Despite their high success rate, the mode of action of orthotics is not well understood. Orthotics are often prescribed to reduce overpronation that has traditionally been evaluated through tibiocalcaneal eversion. The increased use of three-dimensional (3-D) kinematic methods in recent years has created an emphasis on tibia internal rotation as a component of subtalar joint pronation. No studies have yet shown a systematic effect of a series of medial and lateral heel postings on kinematics during running. Methods: The subtalar joint axes of seven healthy male subjects (mean age: 25.1 ± 2.3 yrs.) were measured, and the subjects performed treadmill running at 3. 8 m s-1 in a running shoe with the factory insoles (control) and four other orthotic conditions: 5 ° lateral post, neutral, 5 ° medial post, and 10° medial post. 3-D kinematic data of the foot and leg segments were captured using a four-camera system at 120 Hz. (Vicon), and COP data were collected with an in-shoe plantar pressure system at 120 Hz. (F-Scan). A oneway repeated measures ANOV A with post hoc comparisons was used to determine significant differences between conditions. Results: The orthotics had no significant effect on frontal plane kinematics. Tibia internal rotation was reduced with the use of a 5 ° medially posted orthotic. • The COP was shifted significantly posteriorly with increasing height of the heel. Conclusions: More studies are needed in order to relate anthropometrics and orthotics to predictable changes in kinematics.