Exercise recommendations for women who are pregnant have changed quite a bit over the years. Moderate intensity aerobic activity is currently recommended for those who are pregnant without complications because of the many health benefits activity offers to both the mother and the baby. Little has been known, however, about the safety and efficacy of resistance training during pregnancy which has lead to a reluctance to suggest this type of physical activity. That is--until now. A recent study published in the Journal of Physical Activity and Health found that a supervised, low-to-moderate intensity resistance training program is both safe and beneficial for pregnant women^1!

Thirty-two women with low-risk pregnancies not participating in a resistance training program who had back pain or a history of back pain participated in the study. The women, who were between 21 and 25 weeks gestation, performed supervised, low-to-moderate intensity resistance training twice per week for 12 weeks. Because back pain is so common during pregnancy, their program consisted of six exercises that are thought to play an important role in back pain and function that they completed for 2 sets of 15 reps. The external loads used (or the weight lifted) were based on ratings of perceived exertion (RPE). The 6-20 RPE scale was used and a rating of 11 represented low intensity exercise and 13, moderate. The load was progressively increased based on RPE responses to each exercise. At the start of the program, participants were instructed on proper breathing and proper training techniques to minimize injury.

At the end of 12 weeks, there was a statistically significant increase in the weight lifted for each exercise ranging from a 36% increase up to 56% increase while RPE did not change. This shows that a tremendous increase in strength occurred for the same perceived level of work. What may be of even greater importance is that there were no musculoskeletal injuries during the training period. Because pregnant women produce a high level of relaxin, a hormone that helps the body become more lax in preparation for birth, many have theorized that this would lead to an increase of injury with training. This research shows that this isn’t the case. In addition, problematic symptoms were infrequent, with the most common being dizziness and pelvic pain. Pelvic pain is common during pregnancy as the body adapts to the growing fetus and is not surprising. Dizziness subsided as participants learned and became more comfortable with proper exercise breathing techniques. Blood pressure was also monitored and no change in systolic or diastolic blood pressure was seen in response to either the actual session or as an adaptation to the 12-week program. Blood pressure is of interest because hypertension is a leading cause of maternal and fetal death and anything that might raise blood pressure might be contraindicated. 

So what does this all mean? Starting a supervised resistance training program during an uncomplicated pregnancy can be safe and effective! The authors noted that the low incidence of injury was probably in part due to the careful supervision and education about proper technique that was provided making this an important part of starting a resistance program during pregnancy. The occurrence of dizziness, even though only in a few, also shows the importance of monitoring this during exercise, especially when beginning this type of training, as well as stressing proper breathing technique.

What should pregnant women do? Below are some exercise guidelines for women who are pregnant according to the 2008 Physical Activity Guidelines for Americans. 

• Healthy women who are not already highly active or doing vigorous-intensity activity should get at least 150 minutes (2 hours and 30 minutes) of moderate-intensity aerobic activity per week during pregnancy and the postpartum period. Preferably, this activity should be spread throughout the week. In some women, the 150+ minute goal may need to be worked up to over several weeks. 
• Pregnant women who habitually engage in vigorous-intensity aerobic activity or are highly active can continue physical activity during pregnancy and the postpartum period, provided that they remain healthy and discuss with their health-care provider how and when activity should be adjusted over time. 

And according to the American College of Sports Medicine²:

• Pregnant women may participate in a resistance training program that incorporates all major muscle groups with a resistance that permits 12-15 repetitions to be performed to moderate fatigue.
• Isometric muscles actions and the Valsalva maneuver (breath holding during exertion) should be avoided as should exercise while laying on the back after the first trimester. 

Have you or someone you known performed resistance training during pregnancy? What was your/their experience? Share with us!

¹O'Connor, P.J., Poudevigne, M.S., Cress, M.E., Motl, R.W., & Clapp, III, J.F. (2011). Safety and efficacy of supervised strength training adopted in pregnancy. Journal of Physical Activity and Health, 8, 309-320.
²ACSM's guidelines for exercise testing and prescription, 8th edition. (2010). Philadelphia: Lippincott Williams & Wilkins.