Purpose: The objective was to examine the pregnancy-related changes in physical activity, fitness, and strength in women of varying body mass indices (BMI).
Methods: Women (N = 17 low BMI, N = 34 normal BMI, and N = 12 high BMI, mean age +/- SD = 30.7 +/- 4.1 yr) were studied before pregnancy (0 wk) and postpartum (6 and 27 wk) for body composition and for physical activity, fitness, and strength. Physical activity was assessed by questionnaire, fitness by a maximal oxygen consumption (VO2) test on a cycle ergometer, and strength by the one-repetition maximum test. Data were analyzed by repeated measures ANOVA testing for time and BMI group.
Results: Total physical activity differed qualitatively, but not quantitatively, with time. Significant time effects were observed for maximal workload, heart rate, respiration rate, ventilation, VO2, respiratory exchange ratio, and strength. VO2max, adjusted for weight, dropped by approximately 385 mL x min(-1) from 0 to 6 wk postpartum (P < 0.0001) and by approximately 234 mL x min(-1) from 0 to 27 wk postpartum (P < 0.01). The high-BMI group had a lower VO2max (adjusted for weight or fat-free mass) than the normal-BMI group (P < 0.05). Strength decreased for the leg press by 24% (P < 0.02) and for the latissimus pull down by 8% (P < 0.01) from 0 to 6 wk postpartum, and then increased by 44 and 12%, respectively (both P < 0.05), by 27 wk postpartum.
Conclusion: Relative to prepregnancy performance, fitness and strength declined in the early postpartum period but improved by 27 wk postpartum.