EFFECT OF FOOT ORTHOSES AND STRIKE PATTERN ON REARFOOT MOTION

Abstract

Introduction: Foot orthoses have been shown by some to be effective in controlling rearfoot motion in rearfoot strikers. Forefoot strikers, representing 20 percent of the running population, have increased rearfoot eversion excursions and velocities and may also benefit from orthotic intervention. Orthotic devices, however, may be ineffective in controlling rearfoot motion in forefoot strikers, as their heel does not contact the ground in early stance. Therefore, the purpose of this study was to compare the effect of orthotic intervention on rearfoot motion between a rearfoot and forefoot strike pattern. Methods: Three-dimensional kinematic and kinetic data were collected on 15 recreational runners. The kinematic variables of peak eversion (PEV), eversion excursion (EVEXC) and eversion velocity (EVVEL), and the kinetic variables of peak inversion moment (INVMOM) and eccentric rearfoot work in the frontal plane (INVWORK) were calculated. Comparisons between the no orthotic condition and the orthotic condition for both a rearfoot (RFS) and a forefoot strike (FFS) pattern were made using a two-way repeated measures ANOVA. Results: FFS had significantly greater EVVEL and EVEXC when compared to RFS. While PEV, EVEXC, and EVVEL decreased slightly with orthotic intervention, no statistical differences were found. Reductions in the kinetic variables were greater with a 24% decrease in INVMON and 33% decrease in INVWORK, however, these differences were also not statistically significant. Conclusions: Based on the results of this study, strike pattern had a greater influence on rearfoot mechanics than orthotic intervention. Foot orthotic devices did not have a differential effect on rearfoot mechanics between a RFS and FFS pattern. Orthotic devices appear to provide a greater reduction in muscle demand as opposed to joint motion. This finding may provide greater insight into the mechanism by which orthotic devices provide relief. Supported by Foot Management, Inc(Salisbury, MD) and Joyner Sportsmmedicine Institute (Harrisburg, PA)