Submitted to: Medicine and Science in Sports and Exercise
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2004
Publication Date: 5/2/2005
Citation: Treuth, M.S., Butte, N.F., Puyau, M. 2005. Pregnancy-related changes in physical activity, fitness, and strength. Medicine and Science in Sports and Exercise. 37(5): 832-837.
Interpretive Summary: The objective of this study was to examine the pregnancy-related changes in physical activity, fitness, and strength in women of varying body mass indices. Women were studied prior to pregnancy, and after pregnancy or postpartum (6 week and 27 week) for body composition and for physical activity, fitness and strength. Physical activity was measured by questionnaire. Fitness was measured by a test on a stationary bike. Total physical activity differed qualitatively in that the type of activities that women chose differed from before to after pregnancy. However, the total amount of activity did not change over time. Fitness dropped from before to after pregnancy at both 6 week postpartum and 27 week postpartum. The women with the highest body mass indices had a lower fitness than normal-weight women. Strength decreased in the legs and in the upper body from before to 6 week after pregnancy, but then rose again. In conclusion, fitness and strength decline immediately postpartum, but then improve by 27 weeks postpartum.
Technical Abstract: 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 years) were studied prior to pregnancy (0 wk), and postpartum (6 wk 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 ~385 ml/min from 0 wk to 6 wk postpartum (P<0.0001) and by ~234 ml/min from 0 wk 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 pulldown 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.