[Effect of walking speed on pressure distribution of orthopedic shoe technology]

Lesions to the diabetic foot have various causes. However, there is broad consensus that excessive plantar pressure plays a major role in the chain of events leading to ulcerations and gangrenes. During walking, on the other hand, peak values of plantar pressure are likely to increase with velocity even in therapeutic shoes. Therefore, the question arises whether a moderate velocity should be recommended to diabetic patients to reduce the risk of foot lesions. In this study, two velocities were compared for different types of therapeutic footwear. The velocities selected were considered moderate (0.7 m/s) and normal (1.3 m/s) for diabetic patients. A specially designed mathematical algorithm (velocity normalization) provided the pressure distributions from a common set of measurements: seven trials at different velocities for each subject and each type of footwear. Ten test subjects with healthy feet were studied. The shoes were ready-made and all had a midfoot rocker. The following four conditions were tested: flexible or rigid outsole respectively in combination with a flat insole or molded foot bed respectively. Pressure distribution measurements were performed with the Pedar in-shoe system, and the Pedar software package was used for analysis. The foot was divided into six regions: first toe, second to fifth toes, metatarsal region, medial midfoot, lateral midfoot, and heel. Only peak pressures were taken into account. Gait velocity was found to have an effect on plantar pressure distribution, mainly in the toes and heel region. Peak pressure in the heels increased significantly by about 20%. In the toe region, the increase was about the same, but was not statistically significant. At a higher velocity, pressure even slightly decreased in the midfoot region. The percentage variation was similar for all four conditions. Thus, walking slowly prevented the foot from high peak pressures, and the combination of rigid outsole and molded foot bed was best suited for both slow and higher velocities.