Meeting Abstract

86.2  Tuesday, Jan. 6  Biomechanics of foot strike in habitually barefoot versus shod runners LIEBERMAN, DE*; WERBEL, W; DAOUD, A; Harvard University danlieb@fas.harvard.edu

Hominins evolved to run long distances, possibly as much as 2 million years ago, and until recently, humans ran either barefoot or in soft sandals with minimal cushioning or arch support. Here we investigate whether heel strikes, characteristic of approximately 80% of modern shod runners, are typical of habitually barefoot runners. We also investigated how the foots initial contact with the ground influences the rate and magnitude of the heel strike transient (HST), an impulse several times body weight that travels from the ground to the head in less than 10 ms, and which is thought to be a major cause of injury among distance runners. Leg kinematics, HST ground reaction forces, and foot strike patterns were recorded in habitually shod runners, habitual barefoot runners, and in a group of habitually shod runners training to run in Vibram FiveFingers (VFF, a shoe that protects the sole of the foot but provides no arch support or cushioning). We found that habitual barefoot runners while running barefoot avoid heel strikes, and tend to exhibit lower rates of HST loading than do habitually shod subjects in the same condition. In addition, after several weeks of training in VFF, runners transitioned to a higher percentage of midfoot strikes. For all groups in the barefoot condition, decreased HST loading rates were significantly correlated with a lower angle of incidence of the foot at heel strike and with greater limb compliance during the initial part of the stance phase. Although running shoes with large cushioned heels decrease the magnitude and rate of loading from the HST, habitual barefoot runners face different HST loading regimes than habitually shod runners.