Biology, Seattle Pacific University, Anthropology, University of Washington
Friday Afternoon, Ballroom B
An increased understanding of changes in women’s locomotor energetics during pregnancy would elucidate possible places where and when selection might act on mobility strategies. In this study, five women (mean age=31.8 years) were recruited prior to pregnancy and were followed through their pregnancies as well as during post-pregnancy infant carrying. The collections consisted of the women walking at 4 walking speeds (1 slow, 2 medium, 1 fast) in a randomized order while their metabolic rates were collected. Each woman’s metabolic rate was collected prior to her pregnancy, and then every 4 weeks during her pregnancy; the metabolic rate for each speed from each trimester was averaged. Post-partum, each woman walked at the same four speeds unloaded, with her infant in a sling and also in her arms. For each participant’s pre-pregnancy, first through third trimesters, and post-partum (loaded and unloaded) conditions, a curvilinear Cost of Transport (CoT) equation was calculated. From these equations, the following measures were determined: the acuteness of the CoT curve, the minimum cost of transport (MinCoT), and the speed at which the MinCoT occurred (optimal speed). From pre-pregnancy to the third trimester, the CoT curvature became significantly more acute (p=0.01) and the MinCoT became significantly more energetically expensive (p<0.001); however, while the optimal speed reduced, this was not significant (p=0.396). These changes do not immediately disappear following pregnancy. When compared with reports of pregnant women’s mobility choices, these results suggest that despite low daily gestational costs, mobility costs for pregnant women are high.