Efficacy of plantar loading parameters during gait in terms of reliability, variability, effect of gender and relationship between contact area and plantar pressure

Background: The purpose of this study was to determine plantar pressure and contact areas of the foot inside the athletic shoe during activity. The objectives were to determine if plantar pressure and contact area measurements collected on multiple trials from the same subject were reliable, to determine the variability of measurements between subjects as compared to that found between steps within a single subject, to determine the relationship between contact area and plantar pressure, and to ascertain whether there were any systematic gender differences in these measurements. Methods: Sixteen healthy adults volunteered for participation in the first part of the study that was designed to determine reliability and variability of the testing methodology. A separate group of fifty healthy high school and collegiate athletes participating in soccer, field hockey, basketball, and lacrosse comprised the second part of the study that was designed to investigate gender differences in terms of normalized midfoot plantar pressure and contact area, and the interrelationship between the two measurements. Data were collected during the midstance phase of gait, using the Pedar in-shoe measurement system (Novel GMBH, St. Paul, MN). Athletes wore their own athletic shoes and performed walking trials on a surface similar to that used in their sport. The foot was divided into four regions based on radiographic measurements. Results: The midfoot region demonstrated excellent reliability across multiple trials of the same subject in contact area and plantar pressure, and the variability between steps within a single subject was small when compared to that between subjects. Normalized midfoot contact area and plantar pressure values were highly correlated with r values of 0.862 on the left foot and .912 on the right foot. No significant differences were found in normalized midfoot contact area or plantar pressure values between males and females. Conclusions: The Pedar in-shoe pressure measurement system can be used reliably to quantify contact area and plantar pressure beneath the midfoot region during the midstance phase of gait. This measurement technique can now be used in risk factor studies designed to identify individuals at risk for injury to the foot, ankle, and other lower extremity structures.