Pregnancy-related changes in physical activity, fitness, and strength

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, VO2max, adjusted for weight, dropped by ∼ 385 ml-min(-1) from 0 to 6 wk postpartum (P < respiratory exchange ratio, and strength. VO2max, 0.0001) and by ∼ 234 mL-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.