Fitness and strength decline during pregnancy, but recover in approximately six months

May 16 2005

Fitness and strength decline during pregnancy and the early postpartum period, but improve by approximately 27 weeks postpartum regardless of the mother’s body mass index (BMI), according to research in the May issue of Medicine & Science in Sports & Exercise, the official journal of the American College of Sports Medicine (ACSM).

The study was designed to examine changes that occur in a woman’s body with pregnancy and to determine what role physical activity may play among pregnancy-induced changes in body composition and physiology. Because pregnancy may decondition a woman’s body, researchers measured fitness before pregnancy and postpartum in order to determine the overall effect of pregnancy on a woman’s fitness level.

The study recruited124 women, 76 of whom became pregnant during the course of the study. Each woman was assessed for body composition, physical activity, physical fitness and strength at prepregnancy (0 week gestation), 6 weeks postpartum and again at 27 weeks postpartum. Physical activity was evaluated by questionnaire, physical fitness was measured by a cycle ergometer test, and strength was assessed on leg press, leg extension, bench press, and latissimus pull-down by the one-repetition maximum (maximum amount of weight that could be lifted successfully at one time).

Pregnant women were found to have lower maximal oxygen consumption and leg strength from prepregnancy to 6 weeks postpartum. However, fitness levels and strength began to improve, with almost complete recovery by 27 weeks postpartum.

The decline in fitness and strength was seen in participants regardless of their initial BMI. Researchers found the women changed their postpartum activities to include more walking and home-based activities. The changes in intensity of these activities, and the changes in a woman’s responsibilities when becoming a parent, likely influenced the fitness levels of the participants during the postpartum period.

“Experts recommend that pregnant women who have no obstetric or medical problems exercise at least 30 minutes a day,” said Margarita Treuth, Ph.D., lead author of the study. “Moderate activity, like brisk walking, will help maintain health and fitness of the changing pregnant body. We don’t yet know at what point during pregnancy fitness levels and strength decrease the most, although previous research suggests physical activity levels and activity energy expenditure decline most during the third trimester. But, we do know that physical activity throughout pregnancy and postpartum is highly recommended to maintain health benefits.”

ACSM recently hosted a scientific roundtable, chaired by James Pivarnik, Ph.D., on exercise during pregnancy. Researchers from the National Institutes of Health and the U.S. Centers for Disease Control and Prevention gathered with other experts at Michigan State University April 26-27 for a discussion of the safety of physical activity during pregnancy and to summarize current research on the role of physical activity during pregnancy and postpartum on a woman’s health and chronic disease risk and that of the offspring. Outcomes from the roundtable will establish directions for future research on the role of physical activity during pregnancy/postpartum on chronic disease and health.

The American College of Sports Medicine is the largest sports medicine and exercise science organization in the world. More than 20,000 international, national, and regional members are dedicated to advancing and integrating scientific research to provide educational and practical applications of exercise science and sports medicine.