Dual-function foot orthosis: effect on shock and control of rearfoot motion.

Orthoses have been designed that claim to both reduce shock and control rearfoot motion. It was hypothesized that the dual-purpose soft orthosis would reduce shock and control rearfoot motion greater than a no-orthotic condition. Three-dimensional kinematic and kinetic data were collected along with tibial acceleration while subjects ran in no-orthotic, the dual-purpose orthotic, and a rigid orthotic condition. Variables of interest were eversion excursion, peak eversion, eversion velocity, peak positive acceleration, loading rate, and leg stiffness. None of the evaluated variables were significantly different (p = .05) between the three conditions. These data suggest that shock attenuation and rearfoot motion cannot be controlled by the orthoses used in this study for a group of healthy runners.