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This study investigated whether rearfoot motion at heel contact during running attenuates the magnitude of the impact force traveling through the body. Fifteen subjects completed running trials for two conditions:(a) running on a treadmill at a self-selected speed and a cadence of 160 steps/min and (b) running at the same speed and cadence but with rearfoot motion limited by a medial wedge inserted into the subject's shoe. A paired t test was used to test for differences between conditions in the peak accelerations of each accelerometer and the time to peak of the tibia acceleration. The predominant impact frequency and amplitude of the frequency peak were also tested for significant differences. No significant difference was found in the variables compared between the two conditions. The results demonstrated that restriction of rearfoot motion using a medial wedge during the initial 15% of the stance phase has no effect on the characteristics of the impulse wave at the tibia.
The authors were with the Department of Physical Therapy and Exercise Science, State University of New York at Buffalo, at the time of this study. V. R. Yingling is now with the Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada N2L 3G1. H.J. Yack is with the College of Medicine, Department of Physical Therapy, University of Iowa, Iowa City, IA 52242. S.C. White is with the Department of Physical Therapy and Exercise Science, State University of New York at Buffalo, Buffalo, NY 14214.