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Should Women Climbers Take Oral Contraceptives?

Seeking information on whether supplementing estrogen is good or bad for athletes, Gym Climber interviewed Keith Baar, Ph.D., a professor of Physiology and Behavior at UC Davis.

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Let’s cut to the chase: For many girls and women, training or performing on your period sucks.

Menstruation can affect your weight, mood and ability to perform. When symptoms land on game day, they’re usually unwelcome. For decades, to mitigate these symptoms and even to avoid otherwise unfortunate timing, many women athletes have used hormonal contraception. Contraceptives can alleviate cramps, regulate and lighten periods and even clear up skin.

But introducing extraneous hormones into the body can be troubling for a host of reasons. For an athlete, the effects of estrogen go far beyond developing boobs and regulating a monthly cycle. Estrogen can impact overall performance by impacting recovery, rate of injury and power.

Seeking information on whether supplementing estrogen is good or bad for athletes, Gym Climber interviewed Keith Baar, Ph.D., a professor of Physiology and Behavior at UC Davis and renowned expert in tendon health. Baar has published 168 papers, totalling nearly 8,000 citations throughout his career. One of his studies, published early in 2019 in Frontiers in Physiology, directly addressed the role of hormonal contraception and athletic development.

In Effect of Estrogen on Musculoskeletal Performance and Injury Risk, Baar and Nkechinyere Chidi-Ogbolu, a Ph.D. student at UC Davis, discussed the role estrogen plays in the development of muscle, tendons and ligaments and thus, athletic development and performance. The simple answer: it’s complicated.

Estrogen and Muscle

Based on animal and human studies on aging, estrogen is decidedly beneficial to building muscle mass and strength. For example, in a 2016 study published in the Journal of Endocrinology, ovariectomized rats showed a 10 percent decrease in strength and 18 percent decrease in the cross-sectional area of muscle fiber (cross-sectional muscle fiber area is proportional to the force a muscle can produce) after just 24 weeks. Similar studies (for example one published in the Journal of Applied Physiology) have also shown an increase in injured muscle fibers in ovariectomized rats. When ovariectomized rats were supplemented with estradiol, a form of estrogen, their cross-sectional muscle fiber area and recovery-rate returned to normal. Lack of estrogen, in other words, resulted in muscle loss and strength, while restoring estrogen levels (via a supplementation similar to oral contraception) returned muscle area and strength to that of previous levels.

It has been demonstrated that postmenopausal women, who have lower levels of estrogen following cessation of menstruation, lose muscle much faster than their male counterparts. In a 2012 study published in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences, postmenopausal women were given estrogen-replacement therapy to raise their estrogen levels to that of premenopausal women and the result was a normalized anabolic, or muscle-building, response. In other words, giving estrogen to postmenopausal women helped them to build muslce at the same rate at their younger, premenopausal counterparts.

In another study published in Clinical Science, 80 postmenopausal women were assigned to one of four groups: exercise, hormone-replacement therapy, exercise and hormone-replacement therapy, or no treatment, with all studied for a year. The group doing both exercise and hormone-replacement therapy saw the biggest increase (7.1 percent) in muscle cross-sectional area and a 17.2 percent increase in vertical jump (the highest point reached from a standing jump). The hormone-replacement group saw similar, albeit smaller, increases in muscle area (6.3 percent) and vertical jump (6.8 percent). Of note, exercise alone was less effective than hormone-replacement therapy alone at maintaining muscle mass.

Birth-control pills contain synthetic forms of the naturally occurring hormones estrogen and progesterone. While estrogen can increase anabolic (muscle-building) response, it’s also clear that progesterone has a negative impact. A 2011 study published in the Scandinacian Journal of Medicine and Science in Sports, scientists compared formulations of oral contraceptives and found that a contraceptive with high progesterone, by contrast, inhibits muscle-protein synthesis. Athletes that choose to use oral contraception should choose contraceptives high in estrogen and low in progesterone.

So given that estrogen will help athletes build muscle, what are the practical implications? Think of a woman’s natural estrogen cycle as a series of high and lows. Introduce the pill, and the line flattens out—fewer highs, and the lows only occur during menstruation. This flattening-out tends to have a negative effect on healthy women who are trying to build muscle because it diminishes the physiologically high estrogen spikes. Therefore, it would follow that healthy women that are trying to build muscle should not take hormonal contraceptives because it will inhibit their ability to do so.

Estrogen and Ligaments

Estrogen, however, also affects tendons and ligaments, which complicates the simple conclusion that hormonal contraceptives are bad for athletes. Estrogen has been shown to make ligaments more lax. That partly explains why women are two to eight times more likely to tear their ACLs than their male counterparts. Lax ligaments mean loose joints, which can put athletes at risk of serious injury.

Rahr-Wagner and his colleagues found that women who had never used oral contraception had a 20 percent higher relative risk of ACL injury than long-term users. According to that research, because women’s estrogen levels are highest during the preovulatory and ovulatory phases of their cycle, female athletes who are not using oral contraceptives are at greater risk at those times than those who do, and may wish to exercise more caution in their training routines during those phases.

So, oral contraceptives are bad for building muscle, but good for protecting ligaments by keeping joints tighter.

Estrogen and Tendons 

While studies indicate that estrogen makes ligaments lax, to ill effect, estrogen has a similar effect on tendons, which can be both good and bad. A stiff tendon will pull muscle faster, allowing the athlete to achieve better peak power. A stiff tendon is also more likely to pull or tear a muscle.

Because of naturally occuring spikes in estrogen, women’s tendons are generally looser than men’s, and consequently, women suffer fewer muscle injuries, strains and groin and hamstring pulls. Women also have a lower risk of Achilles tendon ruptures—that is, until menopause. Likewise, a 2015 study published in the European Journal of Applied Physiology, showed that oral-contraceptive users (meaning women without the estrogen highs) have been linked with greater muscle damage and soreness and a 2006 study, published in Foot and Ankle International, showed increased risk of Achilles tendinopathy when using oral contraceptives.

It would follow that oral contraceptive users may be able to generate a higher peak force than their counterparts, but they will also be less able to recover and more at risk for muscular and tendon damage.

The Formula

So what’s a woman to do?

Baar and Chidi-Ogbolu summed it up in this strategy: by their recommendation, a woman in a training, off-season phase is better off not using oral contraception because the body’s naturally occuring high levels of estrogen generally allows athletes to build muscle, recover quickly and be less prone to tendinopathy. When a female athlete is in game season, however, then taking oral contraceptives may be beneficial. Lower levels of estrogen can increase power because tendons become stiffer. The athlete may not need to recover as quickly as she might normally want, as she is likely to have more time between comps or send gos. She may also not need to build muscle—only maintain. The oral contraceptives may also help protect her ligaments from injury during competition.

But to add to the complexity, every woman is different and will respond differently to oral contraceptives. This formula is a good place to start, but it’s not a formula for everyone. Climbers will need to experiment, with guidance from their health-care professionals, with their own formulas and training programs to see what works best for them.