Unveiled almost 50 years ago, “the pill” continues to be the most popular and one of the most effective forms of reversible birth control ever invented. Since their introduction in 1960, oral contraceptives (OCs) have been changed to include less hormones, resulting in fewer side effects. Today’s OCs even provide health benefits. Studies show that the incidence of ovarian cancer, endometrial cancers, benign cysts of the ovaries and breasts and pelvic inflammatory disease (PID) decreases with pill use. OCs also reduce the odds of getting colorectal cancer. But despite these advantages, young women who are trying to build muscle mass may want to choose another form of contraception.
Researchers from the Department of Health and Kinesiology at Texas A&M University in College Station, as well as the Human Energy Research Laboratory at the University of Pittsburgh, have found that OCs actually limit muscle gain from strength training in women under 35. The research involved 73 relatively healthy women aged 18 to 31. Of these, 34 used OCs and 39 did not. Both groups participated in a whole-body resistance exercise program consisting of 13 exercises performed three times per week for 10 weeks. At each session, they completed three sets of six to 10 repetitions of each exercise at 75 percent of maximum strength. The women were encouraged to eat enough protein to promote muscle growth.
According to lead researcher Chang Woock Lee and colleagues, there were significant differences in muscle growth between the two groups. Lean muscle mass increased by just 2.1 percent in the OC users, compared to 3.5 percent growth in non-OC users. However, other muscle responses such as strength gains and arm/leg circumferences were similar in both groups. “We were surprised at the magnitude of differences in muscle gains between the two groups, with the non-OC women gaining more than 60 percent greater muscle mass than their OC counterpart,” the researchers acknowledged.
Tests on the women showed that OC users had significantly lower levels of three muscle-building hormones—DHEA, DHEAS, and IGF-1—and elevated levels of one muscle-breaking hormone—cortisol. Lee said these findings “could help explain” why OC users showed diminished muscle gains from resistance exercise training, but that “vigorous future studies with more stringent control and clever design will be definitely needed to confirm the results and/or elucidate the underlying mechanism conclusively.”
“The factors that explain the differences in the magnitude of the responses to resistance exercise training between individuals are largely unknown,” Lee said. “Numerous health and performance benefits including improved exercise/athletic performance, body composition, esthetic beauty, and self-image can be attained from the increased muscle mass and strength associated with resistance exercise training. OC users may not be able to fully enjoy those benefits while experiencing impaired exercise performance and difficulties achieving athletic goals due to diminished muscle responses they get from resistance exercise training.”
Past research has shown that the pill lowers the levels of these hormones in users, but this was the first study to show the implications for active women and trained female athletes, who often use OCs to control their menstrual cycle. “I think the implications are that so many women are taking BCP (birth control pills), and if they are active or competing, and want to achieve the highest level of performance, they need to consider whether birth control is a negative influence on that,” said senior investigator Dr. Steven Riechman, also of Texas A&M.
Other experts say these findings are no reason for women to stop taking birth control pills. “It’s just one small, a very small, group of women. If you think of how many women actually are on the pill, how significant is the difference in terms of patients noticing anything or even an actual health effect?” said Dr. Jennifer Wu, an obstetrician/gynecologist at Lenox Hill Hospital in New York City. “This might make a difference for a high-performance athlete in a competition, but, for your normal patients who have a healthy exercise routine, this might not make a difference.”
“I don’t disagree with the statistical significance, but the clinical significance is very questionable,” said Dr. Amanda Weiss-Kelly, director of pediatric sports medicine at Rainbow Babies and Children’s Hospital, part of University Hospitals Case Medical Center in Cleveland. “The difference didn’t translate into improvement in performance,” she added.
The study findings were presented at the 122nd annual meeting of the American Physiological Society, which is also participating in the scientific conference “Experimental Biology 2009” being held in New Orleans.
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