1Center for the Advanced Study of Hominid Paleobiology, Department of Anthropology, The George Washington University, 2Department of Human Evolutionary Biology, Harvard University, 3Department of Biology, James Madison University, 4Moi University Medical School, Eldoret, Kenya, 5College of Medical, Veterinary, and Life Sciences, University of Glasgow, 6Human Origins Program, Smithsonian Institution
Saturday 11:30-11:45, Ballroom C
Endurance running probably has a long evolutionary history within the genus Homo, and it was not until very recently that humans ran wearing shoes. Whereas most shod runners today strike the ground with their heels first, generating a large and rapid impact force peak, recent research has found that modern unshod runners most commonly use a forefoot strike in order to avoid generating impact peaks. This finding suggests that habitually unshod human ancestors may have run in a similar way, but variation in barefoot running kinematics has been poorly studied. Here, we present the results of studies of foot strike patterns during running among adolescents and adults from two habitually unshod groups, the Daasanach (n=38) and Kalenjin (n=49) of northern and western Kenya. Subjects ran at speeds ranging from 2.15 to 6.63 m/s. Daasanach subjects used a rearfoot strike in 67% of the trials, but their percentage of mid- and forefoot strikes increased significantly with speed. In contrast, only 15% of Kalenjin subjects preferred a rearfoot strike, and in this sample, speed had no significant effect on foot strike types or angles, but soft (versus hard) substrates significantly increased rearfoot strike frequency. Analyses of variation among subjects and between groups suggest that strike patterns are influenced by multiple factors, including substrate mechanical properties, speed, training level, and running distance and frequency. These differences highlight the need for further research into the factors underlying variation among unshod populations in order to refine hypotheses about the biomechanics and evolution of endurance running.
Funding for this research was provided by The Leakey Foundation, The American School of Prehistoric Research (Peabody Museum, Harvard University), the Hintze Family Charitable Foundation, The George Washington University Office of the Vice President of Research Undergraduate Research Award, a National Science Foundation Graduate Research Fellowship, the National Science Foundation grants BCS-0924476, BCS-1128170, and DGE-080163, The George Washington University Selective Excellence Program, and The George Washington University Research Enhancement Fund.