Does Taking Oral Contraception (Pill) Impact Lean Muscle Growth?

Elara Care -

We know that female reproductive hormones impact a number of different functions in our body, however, we are still learning what that really means for everyday life and how we can make adjustments to help us perform and feel better. Exercise is one of these areas.

In this article we review research studies focusing on whether oral contraception - also known as the pill - impacts muscle growth for people who menstruate.

Although previous studies investigated the effect of oral contraception (OC) use on exercise adaptation, its impact on exercise performance is poorly understood, despite many active women using this form of contraception.

According to a study by Nichols et al; ”Effects of Combination Oral Contraceptives on Strength Development in Women Athletes” (2008) oral contraception use had no significant effect on strength development compared to no oral contraception use.

However, in a comparison study, Ruzic et al. found antiandrogens had a negative effect on muscle strength, minimizing the effects of strength training in women, and as such hormonal contraception containing antiandrogens should be avoided in exercising women.

More recent studies continue to deliver inconsistent results.

Study 1: Oral Contraceptives Impair Muscle Gains In Young Women

The study: 73 generally healthy young women between the ages of 18-31 were assigned to two groups and completed a 10-week whole-body resistance exercise training.

  • Group 1 consisted of 34 women who used oral contraceptives (OC)
  • Group 2 consisted of 39 women who did not take birth control pills (non-OC)

The participants exercised three times per week for ten weeks under the supervision of exercise physiologists and performed a variety of exercises that included chest press, lat pulls down, leg extension, triceps extension, arm curl, and abdominal crunch.

The exercise was done using standard exercise machines and each volunteer performed three sets of 6-10 repetitions per exercise at 75 percent of their maximum strength.

They were also encouraged to consume at least 0.5 grams of protein per pound of body weight per day to make sure they consumed enough calories and protein to promote muscle growth.

Results of the study: The non-OC women gained more than 60% greater muscle mass than their OC counterparts.

However, even though the study has observed the negative effects of oral contraceptive use on muscle gain in the context of resistance exercise training, future studies are needed to help explain the reasons behind the results.

View full Study 1 here >>

Study 2: Influence of Oral Contraceptive Use on Adaptations to Resistance Training

The study: 14 young healthy untrained women regularly used oral contraception and 14 non-OC users (control group) performed a 10-week supervised lower extremity progressive resistance training program.

Results of the study:  The study found that while women who took oral contraceptives with lower doses (20 mcg) of estradiol as well as those not taking any OC increased both the size and strength of their muscles over the study period, women taking OC with higher levels (30 mcg) of estradiol saw increases in muscle hypertrophy, but not strength related to training.

Meaning their muscles got bigger, but not stronger. Something you definitely do not want happening when training or even simply working out.

View full Study 2 here >>

Study 3: Effects of oral contraceptive use on muscle strength, muscle thickness, and fiber size and composition in young women undergoing 12 weeks of strength training: a cohort study

The study: 74 young and healthy female students participated in the study. The participants were not conditioned to submaximal resistance training but were otherwise active (i.e., they performed less than 2 h of exercises such as yoga or aerobics weekly during the preceding 6 months).

They had regular menstrual cycles for at least the preceding year and had no history of endocrine disorders.

The entire study spanned 5 menstrual cycles, which was equivalent to approximately 140 days considering that a single menstrual cycle lasted approximately 28 day

Results of the study: Skeletal muscle adaptation to exercise was similar in women who were on OCs and those who were not, and women in both groups showed similar strength trainability.

Therefore, the data in the study indicates that young women can increase the muscle strength through conventional strength training irrespective of OC use.

However, it’s worth noting that the study had several limitations.

  • the nutrient intake of the participants could not be assessed
  • muscle biopsy was only performed on participants who consented to it, and certain analyses were performed on a smaller number of participants than others.
  • a previous study suggested that it is necessary to measure an average of 150 muscle fibers to reduce variability, however, this study measured an average of 62 fibers used to determine the MFT (which was a consequence of freezing-induced damage in some muscle cells)
  • only 1 exercise (leg press) was performed in this study; different results may have been obtained in a variety of exercises had been included in the training program.

View full Study 3 here >>

Contraceptive pill influences more than just muscle growth

Research has also found that oral contraceptives are associated with a decreased VO2 max peak (the highest amount of oxygen you can use during exercise), a decreased ability to adapt to high-intensity training, as well as significantly elevated oxidative stress which could be detrimental to physical activity and elevate cardiovascular risk.

Oral contraceptives are also associated with fat gain and fluid retention. There’s also the elevated risk for blood clotting and deep vein thrombosis (DVT), which for athletes who travel can be a serious problem.

Finally, because you’re not getting a true period, OC use makes it difficult to keep track of how your body is adapting to your training because you won’t see irregularities in your menstrual cycle, which are early indicators of low energy availability or RED-S.

Research Study Conclusion: Does oral contraception impact muscle growth?

Everyone is different, and there are a number of reasons why people choose to go on birth control besides preventing pregnancy.

Some athletes might decide to use oral contraception as a way of controlling period-related symptoms (i.e. heavy bleeding, and debilitating pain) as well as periods interfering with their physical performance.

Dr Simms, generally advises her athletes that if they need to use birth control, the IUD is the way to go. She states “It is a localized dose of progestin, so you don’t have systemic estrogen and progesterone as you get from oral contraceptives and other delivery methods like injections and patches.

If an IUD doesn’t suit you, the next best option is a progestin-only mini-pill, which has fewer side effects and will be less likely to disrupt your training gains than a combined oral contraceptive pill”.

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