Plantar Stresses Induced by Inclined Surfaces While Standing: A Pilot Study

The purpose of this investigation was to determine the amount of plantar stress placed on the foot while standing on surfaces of various grades at four different positions. Forty subjects, 20 men and 20 women, aged 18 to 30 years, volunteered to serve as subjects. A Compusole forceplate was used to measure the forces on the plantar surface of the feet in four quadrants (anterior right, posterior right, anterior left, posterior left). Four levels of inclination or grades (0%, 2%, 6%, 10%) and four positions (facing uphill, downhill, left, and right) were studied. A treadmill was used to simulate the grades, which were measured with an inclinometer. The treadmill was set at the first randomly selected grade. The subject stepped barefoot onto the force plate, in the first position. The subject's feet were positioned by the examiner, with one foot placed on either side of the vertical midline of the forcepad and the frontal midline of each foot positioned onto the center horizontal midline of the forcepad. The subjects were asked to assume a comfortable stance with their weight evenly distributed and both knees straight. A static recording was then made, the subjects moved to a second position, they had their feet repositioned, and another reading was taken. Measurements were taken in a similar manner for the third and last positions. After the fourth position was recorded, the subject stepped off the treadmill while it was moved to the next randomly selected grade. The same procedures were repeated for all the remaining grades. Repeated-measures analyses of variance (ANOVAs) were calculated for each position (4) to determine the change in percentage of pressure in each quadrant (4) across all four grades. As the grade increased from 0% to 10%, there was a significant increase in the amount of pressure on the two quadrants that were positioned down the grade. There was significant change (p < 0.05) in all shifts in pressure moving directly and obliquely between quadrants except in the "facing right" position directly between anterior left and anterior right and between posterior left and posterior right and in the "facing left" position obliquely between anterior right and posterior left. A factorial ANOVA was run to determine any pressure changes between the grades. Sheffe post-hoc tests revealed significant changes (p < 0.05) in pressure during the 10% grade elevation in all positions except for facing downhill. As grade increased, the percentage of body wei