It’s no longer news that working out during pregnancy is not just harmless but helpful for most healthy women. Countless moms-to-be are running, doing yoga and Pilates or taking exercise classes designed specifically for them. British marathoner Paula Radcliffe ran at a level many of us would envy until the day before she delivered a healthy daughter in 2007.

Women who are in shape have fewer problems during delivery, and their children tend to start life healthier than the newborns of obese women.

So I was surprised, and somewhat skeptical, when I received a news release about a “first of its kind” study that had determined that resistance training — strength training in its various forms — can be beneficial to mother and child and shows no correlation to complications during pregnancy.

Didn’t we know that already? It’s 2011. A lot of pregnant women lift weights.

It turns out we really didn’t. “There isn’t a ton of medical research” on resistance training during pregnancy, said George Macones, chairman of the committee that wrote the guidelines for exercising during pregnancy for the American College of Obstetricians and Gynecologists. In fact, that policy statement, written in 2002 but reaffirmed periodically since, contains nothing about strength training. Neither do government recommendations on exercise during pregnancy.

Leela Payne, who is eight months pregnant, did the "Bird dog" pose while doing yoga while working out at the Any Time Fitness. (Mark Gail/THE WASHINGTON POST)

“Forgive the pun, but we’re at baby steps” on this subject, said Jim Pivarnik, a professor of exercise physiology at Michigan State University who supervised the new study, which is the ongoing doctoral dissertation of a student, Erin Kuffel. The bottom line, Pivarnik said, is that although many women keep strength training well into their pregnancies, there really are no good, specific recommendations for them on how much to lift, how often, at what intensity and when to slow down, he said.

“We haven’t been studying it,” Pivarnik said.

Usually such decisions are made individually between patient and doctor, and physicians may have little or no experience with strength training, he said. “That’s a medical school issue,” he said.

Pivarnik and Kuffel worked with the Anytime Fitness chain to study 214 women, 57 of whom used free weights, weight machines or other strength training methods about three times a week for 30 minutes during their pregnancies.

The strength training group showed no difference from those who did no resistance work in maternal weight gain, gestational age at delivery, length of infant at birth and birth weight (which confirmed previous controlled studies by other researchers on similar issues). And they may have achieved small benefits in weight control and reducing the risk of gestational diabetes and hypertension, the research found. The study is continuing.

It’s not as if pregnant women have been flying blind on weight training. The Internet is full of articles on the subject, and if it’s not always clear whether the advice is trustworthy, there is always the guidance of a trainer, nurse practitioner or obstetrician. Health professionals may have to speak more generally than trainers on the topic of exercise, but they have good firsthand knowledge of their patients’ needs.

“In general, doing some resistance training is okay,” Macones said. Most programs emphasize low-weight, high-repetition regimens, Pivarnik said. As the pregnancy progresses, it’s a good idea to scale back, but many women do this on their own as their fatigue increases.

Leela Payne, 39, said she sought out a trainer at the Anytime Fitness in Kensington who could continue helping her with resistance training if she became pregnant. When she did, the routine helped “keep my strength up and keep fit for before, during and after” the pregnancy.

“It’s like preparing for a marathon,” said Payne, who is nine months pregnant and plans to deliver her second child at home.

“Strengthening your core muscles is not easy when you’re pregnant,” she added. “You can’t breathe. Your whole body is changing.” But her trainer designed workouts with exercise balls and resistance bands and others for the pool that Payne has been able to do throughout her pregnancy, she said.

Anytime Fitness, working with Pivarnik, has developed the FITT — frequency, intensity, time and type — principle for expectant mothers, which calls for three days a week of lifting small amounts of weight 12 to 15 times for 20 to 30 minutes. The chain considers free weights, weight machines, resistance bands and kettle bells acceptable methods.

Almost everyone advises certain precautions, however. Pregnant women should always consult their physicians about their exercise regimens and generally avoid lifting weights on their backs. Some experts rule out squats and lunges. Joint laxity and balance difficulties may become hindrances as the pregnancy continues. And no pregnant woman should do the Valsalva maneuver — vigorous exhaling without actually letting out breath — which can constrict blood flow to the heart and uterine arteries, Pivarnik said.

One old recommendation does seem to be dying slowly, he added. Contrary to earlier recommendations, pregnant women should not worry about raising their heart rates above 140. Radcliffe kept hers below 160. Of course, when she is racing, her heart rate is often above 180 for more than two hours.

Warning signs to stop exercise when you’re pregnant

Amniotic fluid leakage

Decreased fetal movement

Preterm labor

Calf pain or swelling

Muscle weakness

Chest pain


Shortness of breath before exertion

Vaginal bleeding

SOURCE: American College of Obstetricians and Gynecologists