Runners: Leaning Forward Increases Force on Hip Extensors Interview with:
Anna Warrener Ph.D.
Department of Anthropology
University of Colorado Denver
Denver, CO

Dr. Warrener  What is the background for this study?

Response: We became interested in looking at trunk position during running because one of us (Daniel Lieberman) had anecdotally observed people running with a variety of trunk positions, and when we went looking for academic literature on the topic, we found it was fairly scarce. We suspected that trunk position could have a major impact on the forces experienced by the lower limbs during running and even affect aspects of gait (stride length and time). So we developed a model predicting how these forces and movements might change as trunk flexion/forward leaning increased.

Our primary predictions were that more forward lean would increase “overstride” which is the distance in side view between the hip and the heel as it contacts the ground (a measure of how far your are extending your leg when you step). This in turn would increase the impact forces experienced by the lower limb at initial contact which have previously been shown to increase the risk of repetitive stress injuries. We also predicted that stride would get longer and take more time because extending the leading leg out farther forward (overstriding) would be necessary to keep the body center of mass within a base of support above the limbs. This more extended limb, we predicted, would change the angles and forces about the ankle, knee and hip joints.

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