The effects of strenuous exercise on maternal rats and their developing fetuses

Twenty young female rats were familiarized over 19 days to run comfortably on a treadmill at 30 m/min (approximately 80% VO2 max.) on a 10 degree incline for one hour. After this 19 day accustomization period the rats were separated into two groups and mated. One group (PR) continued to run on the treadmill at the prescribed rate throughout gestation and the other group (PC) was allowed to continue a normal laboratory routine. The maternal rats were weighed daily including the first day following birth and the numbers and weights of the fetuses born in each litter were noted. The results show that the fetuses were spared from any gross effects of the maternal exercise with average fetal weight and litter size being unaffected. However, there were significant differences between the maternal weights of the two groups at the end of gestation. The prepartal weight difference was 36.0g (PC group heavier) and this was reduced post-partally to 14.9g which remained significant. These differences in maternal weights were suggested to reflect a decreased amount of amniotic fluid for the fetuses of the PR group during gestation and also a reduction in maternal body fat for the PR group.