Influence of treadmill design on rearfoot pronation during gait at different speeds

Understanding the dynamic function of the rearfoot is necessary for recognizing and treating several types of mechanical foot dysfunction. Although the motion of the rearfoot is often measured during treadmill locomotion, the effect of different types of treadmills on the motion of the foot is unclear. In this study, the kinematics of the right subtalar joint in 24 volunteers walking at three speeds on two motorized treadmills were examined. The two treadmills (a wide width and a soft surface versus a narrow width and a hard surface) were selected to maximize motion differences. Maximal change in angular position (positive: supination; negative: pronation) about each volunteer's subtalar joint axis was estimated during three gait phases: weight acceptance, midstance, and push-off. A factorial, repeated-measures analysis of variance determined that the treadmill design had a significant effect on subtalar joint position (F = 5.423; P = .029), albeit with moderate power (0.61). Descriptively, collapsed over all speeds, the subject's feet on the narrow/hard compared with the wide/soft treadmill showed more pronation (0.44 degrees ), less pronation (0.46 degrees ), and more supination (1.44 degrees ) during weight acceptance, midstance, and push-off, respectively. We conclude that treadmill design can affect an individual's rearfoot kinematics.