Plantar Pressure Reduction in an Incremental Weight-Bearing System

Harness-supported treadmill ambulation has been advocated for patients to provide reduction in weight bearing to healing tissues and to reduce the energy cost of treadmill ambulation. The purposes of this technical report are to analyze the ability of one of these devices (Zuni Exercise System) to support a specific percentage of a subject's body weight during walking and running and to explore the relationship of unloading to pressure reduction in selected plantar surface regions of the foot. Ten male volunteers with no known foot pathology participated. In-shoe plantar pressure and vertical ground reaction forces (GRFs) were measured during walking and running at full body weight and at 20% of body weight supported. Walking at a setting of 20% of body weight supported resulted in a reduction of the first and second vertical force peaks of 23.8% (SD = 7.3%) and 27.2% (SD = 4.1%), respectively. The total force-time integral during walking unloaded was 22.8% (SD = 3.3%). During running, the active vertical force peak and total force-time integral were reduced by 19.9% (SD = 6.0%) and 20.0% (SD = 3.3%), respectively, in the unloaded condition. Plantar pressures were reduced from 6.8% to 27.8% in the body weight-supported conditions. The reduction was variable across different regions of the foot. The Zuni Exercise System appears to reduce the vertical component of the GRF during walking and running with 20% of body weight supported. Plantar pressures were reduced during body weight-supported conditions, but the reduction varied at different regions of the foot.