Andrew Yegian

ANDREW K. YEGIAN, then a graduate student at Harvard University, Cambridge, Massachusetts, received funding in April 2017 to aid research on ‘The Costly Load Phenomenon: How Does Loading Experience Affect Load Carriage Energetics and Biomechanics?,’ supervised by Dr. Daniel E. Lieberman. This study investigated whether experience with carrying loads affects the mechanics of walking and the energetic cost of moving the extra mass. Studies of Western populations carrying backpacks show transporting a load is costly. Intriguingly, two studies of Kenyan women suggested that they were able to carry loads on their heads with little energetic cost because of more efficient walking mechanics. These results, based on a limited sample, had yet to be replicated, and the mechanism affecting walking efficiency was unknown. In order to address these two questions, sixteen women from western Kenya participated in an experiment measuring the mechanics and energetics of carrying loads on the head. The women all regularly transport loads, mostly water, during their day-to-day lives. On average the women were quite efficient, spending less energy to move the extra mass than predicted by the size of the load. Efficiency was driven by a more compliant gait, with more flexion at the knee during each step. However, even within the experienced sample population, there was large variation in efficiency. Carrying loads on the cheap appears to be a skill that can be learned through experience, but is not learned by everyone.