Humans have engaged in endurance running for millions of years1, but the modern running shoe was not invented until the 1970s. For most of human evolutionary history, runners were either barefoot or wore minimal footwear such as sandals or moccasins with smaller heels and little cushioning relative to modern running shoes. We wondered how runners coped with the impact caused by the foot colliding with the ground before the invention of the modern shoe. Here we show that habitually barefoot endurance runners often land on the fore-foot (fore-foot strike) before bringing down the heel, but they sometimes land with a flat foot (mid-foot strike) or, less often, on the heel (rear-foot strike). In contrast, habitually shod runners mostly rear-foot strike, facilitated by the elevated and cushioned heel of the modern running shoe. Kinematic and kinetic analyses show that even on hard surfaces, barefoot runners who fore-foot strike generate smaller collision forces than shod rear-foot strikers. This difference results primarily from a more plantarflexed foot at landing and more ankle compliance during impact, decreasing the effective mass of the body that collides with the ground. Fore-foot- and mid-foot-strike gaits were probably more common when humans ran barefoot or in minimal shoes, and may protect the feet and lower limbs from some of the impact-related injuries now experienced by a high percentage of runners.
We are grateful to the many volunteer runners who donated their time and patience. For help in Kenya, we thank M. Sang; E. Anjilla; Moi University Medical School; E. Maritim; and the students and teachers of Pemja, Union and AIC Chebisaas schools, in Kenya. For laboratory assistance in Cambridge, we thank A. Biewener, S. Chester, C. M. Eng, K. Duncan, C. Moreno, P. Mulvaney, N. T. Roach, C. P. Rolian, I. Ros, K. Whitcome and S. Wright. We are grateful to A. Biewener, D. Bramble, J. Hamill, H. Herr, L. Mahadevan and D. Raichlen for discussions and comments. Funding was provided by the US National Science Foundation, the American School of Prehistoric Research, The Goelet Fund, Harvard University and Vibram USA.
Author Contributions D.E.L. wrote the paper with substantial contributions from M.V., A.I.D., W.A.W., I.S.D., R.O.M. and Y.P. Collision modelling was done by M.V. and D.E.L.; US experimental data were collected by A.I.D., W.A.W. and D.E.L., with help from S.D’A. Kenyan data were collected by D.E.L., A.I.D., W.A.W., Y.P. and R.O.M. Analyses were done by A.I.D., D.E.L., M.V. and W.A.W.
This movie shows an adolescent Kalenjin female, habitually barefoot, unshod condition (forefoot strike).
This movie shows an adolescent Kalenjin male, habitually barefoot, unshod condition (forefoot strike).
This movie shows an adult Kalenjin runner, habitually barefoot until adolescence, unshod condition (forefoot strike).
This movie shows an adult Kalenjin runner, habitually barefoot until adolescence, shod condition (midfoot strike).
This movie shows an adolescent Kalenjin student, habitually shod, shod condition (rearfoot strike).
This movie shows an adolescent Kalenjin student, habitually shod, unshod condition (rearfoot strike).
In this we see a pressure pad movie of forefoot strike (toe-heel-toe running).
In this file we see a pressure pad movie of rearfoot strike (heel-toe running).
In this file we see a pressure pad movie of midfoot strike.