Andrew Yegian

Grant Type

Dissertation Fieldwork Grant

Institutional Affiliation

Harvard U.

Grant number

Gr. 9444

Approve Date

April 18, 2017

Project Title

Yegian, Andrew K., Harvard U., Cambridge, MA - To aid research on 'The Costly Load Phenomenon: How Does Loading Experience Affect Load Carriage Energetics and Biomechanics?,' supervised by Dr. Daniel E. Lieberman

Preliminary abstract: Human load carriage energetics have been extensively studied, with a common result: carrying added mass is more energetically expensive than carrying one’s own body mass: the ‘costly load phenomenon’ (CLP). Why is added mass more expensive to transport than body mass? An exception to the CLP may provide the answer: Central African women have been shown to carry head loads with remarkable economy. Critically, these subjects were highly experienced with the loading technique. More efficient walking mechanics with less external work (i.e. less work to move the body’s center of mass) measured in a Kenyan population compared to a Western control presents a plausible mechanism for avoiding the CLP, but does not address the internal (joint-level) mechanics and muscle use that determine external work. Also, a recent study on South African women showed experienced subjects were not an exception to the CLP, muddying the waters. This project uses two groups of Kalenjin-speaking women in Kenya (experienced and inexperienced) to address three hypotheses: (1) There is an exception to the CLP related to loading experience, (2) Experienced load carriers have less external work and more efficient gait compared to inexperienced carriers, and (3) Higher muscle torques in the joints and more internal work maintain the natural energy-saving aspects of walking and mitigate the CLP. The results from this project will support or refute previous evidence that loading experience can mitigate the CLP, and will be the first to link internal mechanics with external work and efficiency. Further, they will explore the link between culture (loading experience) and biology (biomechanics and energetics), an understudied aspect of understanding how humans move.