Submitted to: Experimental Biology
Publication Type: Abstract only
Publication Acceptance Date: 2/3/1998
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: The purpose of this study was to determine the effects of pregnancy on fitness. Women were evaluated at 36 wk gestation (N=65), and at 3 mo (N=74) and 6 mo (N=69) postpartum and were grouped according to infant feeding mode as formula-fed or breast-fed. Fat mass (FM) and fat-free mass (FFM) were assessed by a 4-component model using underwater weighing, dual-energy yx-ray absorptiometry and total body water. Submaximal heart rate (HR) and oxygen consumption (VO2) were measured while cycling at two workloads. VO2max was then predicted from submaximal HR (VO2max = (0.634xHR)-30.79, by Sady et al. (1988)). Questionnaires (7-d) were completed to evaluate activity level. Repeated measures analysis of covariance was used. The overall model for VO2max indicated significant time (P<0.0001) and feeding mode (P<0.05) effects. FFM, but not FM, was a significant covariate (P<0.0001). VO2max was significantly lower at 36 wks than at 3 mo and 6 mo postpartum (unadjusted means+/-sd=1851+/-397, 1997+/-495, 2032+/-482 ml/min, respectively). Activity level did not differ by feeding type, but differed by time (P=0.05, 36 wk=4.1+/-3.7, 3 mo=6.7+/-8.0, and 6 mo=5.2+/-4.9 METs/kg/day). In conclusion, the lower VO2max adjusted for FFM observed during pregnancy may be due to lower physical activity levels compared to the postpartum period.