A growing body of evidence, primarily from animal models, suggests that estrogen has the potential to reduce muscle damage and inflammation. They have also found that it may enhance muscle tissue repair. While not yet conclusive, a number of studies suggest that estrogen may also help preserve muscle strength and size in post-menopausal females. These studies seem to suggest that estrogen plays a role in muscle repair and also can enhance muscle recovery.

Estrogen Enhances Strength Gains

One study found that on a pound per pound basis, researchers investigating the strength gaining abilities between men and women actually showed females to increase more in strength. This may be in part due to estrogen’s muscle enhancing effects in women.

Estrogen has proven to be beneficial for female athletes, as it has been shown that it:

  • Prevents muscle breakdown
  • Increases protein synthesis
  • Enhances muscle recuperation
  • Reduces the actions of cortisol

Several lines of research point to the ability of estrogen to protect muscle from injury by enhancing the stability of muscle membranes, either through its antioxidant effects or its ability to directly stabilize muscle membranes. Some female athletes may pay a price for using birth control pills: lower strength gains from resistance exercise.

A previous study reported that birth control use limited strength gains in women. Whether or not birth control pills increase or decrease your estrogen levels completely depends on timing. If you are a woman of reproductive age who has a healthy hormonal system able to produce estrogen, the pill will decrease your estrogen.

The Study

Researchers had women train three times a week for 10 weeks. The researchers had 73 young women (18 to 34 years old) complete 13 different exercises. The regimen was intense, working muscles throughout the entire body. None of the recruits had been regularly working out beforehand. Each had to complete her resistance training against weights that were individually tailored to work her muscles at 75 percent of their maximum strength.

At the end of the study, those women taking birth control pills had 40 percent less gains in lean muscle mass than the group not on the pill. One finding that the researchers suspected was causing this was that women using oral contraception had dramatically lower blood levels of the anabolic hormones including DHEA and its more abundant sulfated form, DHEA-S. Compared to non-pill-users, women taking oral contraceptives also had substantially higher concentrations of cortisol, a hormone associated with the breakdown of muscle.

New Research

New research published reported that estrogen is needed for muscle recovery. To explore how gender and the use of oral contraception each affect the response to the exercise-induced muscle damage that follows from eccentric resistance training. Eccentric exercise is a muscle damaging technique in which the muscle is overloaded and causes major muscle damage. A classic example of eccentric exercise is when you lower the weight during resistance exercise, this causes the muscle to stretch which makes the muscle more susceptible to muscle damage.

What if Men Took Birth Control?

Here is one study that gets a little bizarre. Researchers had men take birth control pills to examine how estrogen affected muscle recuperation in both men and women. They took 24 untrained, but physically active subjects, (8 males, 8 normally menstruating females, and 8 females using oral contraceptives). The subjects completed an eccentric resistance-exercise protocol and performed 6 sets of 10 maximal eccentric knee extension muscle actions. The normally menstruating females performed the protocol in the follicular phase of the menstrual cycle (days 2 – 6) while the females using oral contraceptives performed the protocol during the withdrawal phase (days 2 – 6 of placebo pill ingestion).

After the muscle damaging protocol, in the first 24 hours post-exercise, both the males and both groups of females displayed a significant reduction in peak strength. In addition, the males and the females using oral contraceptives both displayed a further significant reduction in torque in the subsequent 24 hours, but the normally menstruating females displayed no further reduction. The researchers reported that the male group reached peak serum concentration of creatine kinase (i.e. marker of muscle damage) that was higher than both female groups, while the female group using oral contraceptives displayed a peak creatine kinase level higher than that of the group of normally menstruating females.

Levels of myoglobin (another marker of muscle damage) displayed similar results. Males demonstrated higher levels post-exercise, and females using oral contraceptives displayed higher levels than normally menstruating females. The decline in leg strength was about 10% pre- to 24 hours post-exercise induced muscle damage in all groups. It further decreased 10-15% by 48 hours post-exercise induced muscle damage in the men and women on oral contraceptives only.

The Results

The researchers concluded that women taking oral contraceptives recover muscle strength more slowly relative to normally menstruating women. They propose that this may be related to lower estradiol concentrations, which affect the recuperative capacity of the muscle. So women taking birth control may need a few extra days of rest, compared to women not taking birth control, while performing high intensity exercise.

Minahan C, Joyce S, Bulmer AC, Cronin N, Sabapathy S. The influence of estradiol on muscle damage and leg strength after intense eccentric exercise. Eur J Appl Physiol. 2015 Feb 19.