Evolutionary Anthropology, Duke University
March 27, 2015 10:30, Grand Ballroom A/B
It is widely assumed that the demands of gestation have profound effects on bone health and strength. High demands for calcium provision are placed upon the mother to ensure optimal fetal skeletal mineralization without compromise to maternal bone strength during an increased load-bearing period. However, few studies have examined the longitudinal effects over a complete reproductive cycle on locomotion and musculoskeletal anatomy. Our study compared pregnant CD-1 mice and SD rats with aged-matched nulliparous controls to test the effects of increased load-bearing changes on gait patterns and bone strength. Rodents were video recorded every other day for 19 days while walking freely across a force platform. Temporal gait parameters, speed, and peak vertical ground reaction forces (GRFs) were collected. Animals were injected with three fluorochrome dyes every 6 days to identify new bone growth. Following the experiment, the rodents were micro-CT scanned and bones from their hind and forelimbs were prepared for histological analysis. On average the pregnant rodents gained 35-40% of their initial body mass, while the controls gained up to 5%. Pregnant animals had an overall increase in GRFs for both limb pairs compared to controls. Interestingly, the rats’ hind limb forces increased significantly as pregnancy progressed (p < 0.05), while the mice kept significantly higher forelimb peaks throughout gestation. These unexpected differences in limb loading patterns matched with the fetal skeletal mineralization demands on the mother, caution the reliability to infer behaviors from bone during the reproductive cycle.