Consider for a moment, that estrogen (alone) is elevated for a short time during our menstrual cycle- it spikes quickly prior to ovulation then drops back down. It also elevates during the luteal phase, but many of the beneficial anabolic effects of estrogen during this phase may be blunted by elevated progesterone levels (Kriengsinyos et al 2004; Faria et al, 1992).
So, there is some merit to the idea that providing our body a consistent amount of exogenous estrogen (ethinyl estradiol; EE) has the potential to improve athletic performance- assuming (of course) that EE has the same impact on physiology as our endogenous estrogens.
As we can see in the graph below, a typical combined OC might maintain EE levels at around 25pg/ml as compared to our endogenous estrogen spike of 200-500pg/ml prior to ovulation. We do need to consider that the EE in OC has 6-10 times the effects of our endogenous estrogens making direct comparisons difficult.
Figure from Chidi-Ogbolu & Baar (2019)
So then the question becomes: Does the suppression of endogenous hormone production and the simultaneous replacement with exogenous hormones lead to improved performance metrics over time?
You can see the challenge with answering this research question- there are so many variables- training age of the athlete, sport modality, type of OC (combined or progestin-only), androgenicity of progestin, amount of EE, AND whether we are interested in acute (short-term) training adaptations or chronic (long-term) training adaptations.
In the event you are not interested in reading any further, here is the main take away: The research overwhelmingly supports the conclusion that women who take OC do not perform better OR worse than women who do not take OC. You read that correctly, there really seems to be no effect. Some studies have found slight improvements in performance while some studies have found slight decreases in performance- but overall there does not appear to be significant differences.
According to Tenan (2016), the research points to the idea that “sex hormones may profoundly increase or decrease human performance but (1) capturing these effects and leveraging them for athletic or rehabilitatioin gains is difficult (2) intraindividual varability is likely extremely high and (3) the complete underlying mechanisms are astronomically complex.” Agreed Tenan, agreed :))
Personal note: I was surprised by this finding. I honestly went into this expecting to find research consistent with what I have heard about OC: that is, that OC use impairs strength adaptation and has the potential for increased fat mass gain.
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Brief aside… the research evidence supports an association with a “small” amount of weight gain in progestin-only contraceptives (with depo provera appearing to be responsible for much of the variance) but not in combination formulations (progestin + EE).
There are two systematic reviews on the topic- one looking at combination contraceptives (progestin + EE) and one looking at progestin-only contraceptives. Both conclude the following:
From the Gallo et al (2014) paper looking at combination contraceptives; “We found no major effect on weight.”
And from the Lopez et al (2016) paper; “We found little evidence of weight gain when using progestin-only contraceptives (POCs)…Three studies showed differences for users of the injectable ‘depo’ versus no hormonal method. Depo users had a greater weight gain in two studies. In the third study, adolescents had a greater increase in body fat (%) and decrease in lean body mass (%). Two studies showed a greater increase in body fat (%) for users of hormonal IUD versus women not using a hormonal method. One also showed a similar difference with a progestin-only pill. Both studies showed a greater decrease in lean body mass with POC use…Mean weight gain at 6 or 12 months was less than 2 kg (4.4 lb) for most studies.”
To be honest, I don’t think the conclusion that this is “little evidence” of weight gain is consistent with the findings. This seems pretty convincing that there is some association between weight gain and progestin-only contraceptives.
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Okay so back to birth control and performance…
I will say that the whole goal of research is to eliminate individual differences so that we can make conclusions that apply to most people. This does not mean that individual differences do not exist and that birth control won’t impact your performance (positively or negatively). You might find that performance is terrible on a formula that has a progestin with high androgenicity and that you feel much better on a formula that has a lower androgenicity. Maybe you perform better with a formulation with a higher level of EE. Or maybe you feel better with no OC at all!!
One other caveat I will mention is that we have absolutely zero evidence to help us navigate the long term effects of birth control on performance- I think the longest study I found followed up with women after a 2-year period (Proctor-gray et al, 2008). As many of the women I work with have been taking hormonal birth control for 10+ years, I think we need to interpret the potential “null” effect on performance cautiously- AND of course consider whether or not the potential performance benefit is worth some of the adverse effects.
Some of the adverse effects of birth control include an increased risk for nutrient deficiencies (including B6, B12, folate, calcium, magnesium, vitamin C and vitamin E; Mohn et al, 2018), an increase in serum cortisol and HsCRP (Cauci, Frencescato & Currio, 2017; Cauci et al, 2008; Boisseau et al, 2018), an increase in SHBG and decrease in testosterone (Rickenlund et al, 2004; Fotherby & Caldwell, 1994; Crewther et al 2015), and an elevation in markers of oxidative stress (Cauci et al 2016). These have the potential to negatively impact performance over long periods of time- in a way that we might not capture in 8-12 week studies. Additionally, combined formulations (ethinyl estrogen + progestin) can have negative effects on the accumulation of peak bone mineral density in young women (Hartard et al, 1997; Warren & Chua, 2004; Gosthasebi et al, 2019) with reported incident fracture risks of 7‐30% higher than in controls who were non-users.
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Okay and now, finally, a summary of some of the key papers around OC use and performance:
Casazza et al (2002) found no performance differences before OC use and after OC use. OC use significantly increased BW and fat mass and decreased VO2 max. They concluded that exogenous steroids in OC decreased peak exercise capacity in moderately physically active young women.
Larsen et al (2018) found no difference between long-term OC users (during the active pill phase) and normally menstruating women (during the early follicular phase- when both estrogen and progesterone are low). They looked at performance across moderate and hot environments. There was a trend for elevated resting CRP in women taking OCs, which could be indicative of inflammation. For the most part, however, the results indicate similar function in users and non-users of OCs at rest and after exercise in both moderate and hot environments.
Romance et al (2019) evaluated 1RM squat, bench press and countermovement jump (CMJ) test following an 8-week resistance training program. They found that fat free mass (FFM) increased significantly in oral contraceptive (OC) users but not in non OC-users (worth noting: the measures of FFM include all non-fatty tissues and do not necessarily represent change in muscle mass- it is possible that differences in water retention impacted this variable). They did not find any changes in fat mass for either group. Significant changes were found in squat and bench 1RM in both groups. The authors concluded that the use of OC did not negatively affect body comp or strength in women with a history of resistance training.
These findings are supported by Nichols et al (2008) who found similar strength increases between OC users and non-users. They had all athletes participate in the same 12-week strength program. They tested 1RM bench, isokinetic peak torque bench press, isokinetic peak torque leg extension. Data were collected at 0, 4, 8 and 12 weeks. They found significant increases in strength over time, regardless of group. No significant differences were found between the OC users and non-users. They concluded that the use of combination OC’s did not provide sufficient androgenic effects to increase strength beyond the stimulus of the training protocol.
Lee et al (2009) found decreases in fat free mass (FFM) and decreased levels of DHEA after 10 weeks of resistance training. The authors speculated that the reduction in FFM may be related to the androgenicity of the progestogen which can bind to the androgen receptor and inhibit its function. These results may vary based on the level of the athlete; The use of monophasic OC in active women has been associated with an increase in body mass where the same OC has been associated with a decrease in body mass in sedentary women (Burrows & Peters, 2007).
Subsequent research has failed to find significant differences in performance between OC formulations with high vs low androgenicity of progestins (Thompson, Drover, Sculley & de Jonge, 2019). Rechichi et al 2009 conclude that “despite previous speculation that the sex hormones may affect muscular strength, it appears that the modern OC formulations do not provide enough androgenic influence to substantially alter muscular strength and anaerobic power throughout an OC cycle.” Burrows & Peters (2007) also asserted that the androgenic component of current OC formulations is not great enough to influence strength gains.
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And finally Thompson et al (2019) conducted a systematic review of the literature to clarify the impact of the menstrual cycle and oral contraceptives on response to resistance training. “This systematic review highlights the lack of research examining the effect of endogenous female hormones and OC use on resistance training outcomes.”
Summary of some of the high quality articles from this systematic review:
Acute responses- comparison of menstrual cycle phases
Haines et al (2018) found a greater potential for recovery and repair in mid-follicular (vs luteal phase) following eccentric exercise. This finding makes sense based on anabolic effects of endogenous estrogens.
Kraemer et al (1995) found a significant positive association between growth hormone and estradiol. This could provide some insight into the mechanism behind the anabolic effects of estrogen.
Nakamura et al (2011) also found that circulating estrogen may affect exercise induced GH secretion.
**Take away from these studies is that naturally cycling women have a greater potential to increase strength gains during the follicular phase (with estrogen peak) than they do during the luteal phase (likely due to the presence of progesterone).
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Acute response- comparison of oral contraceptives with menstrual cycle
Kraemer et al (2008) found that OC (tricyclic) increases the secretion of growth hormone (GH) in the off-phase of the pill as compared to women who were in the early follicular phase of their cycle. This makes sense as we would expect GH to be low in normally cycling women during this time with low levels of estrogen and progesterone. The idea here is that this GH elevation (in women using tricyclic OCs) could potentially improve resistance training outcomes in untrained women.
Minahan et al (2015) found possible role of endogenous estradiol in protection against exercise induced muscle damage in active women (no formal resistance training or sport participation).
Savage & Clarkson (2002) found that non-resistance trained women (who were not using OC) have faster recovery than their OC (combined pill) user counterparts from eccentric exercise induced muscle damage. This finding is important in that it suggests that endogenous estrogens do in fact have a different impact on muscle than synthetic exogenous estrogens (such as those in OCs).
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Chronic adaptations- menstrual phase-based training
Sung et al (2014) found that follicular-phase based training was superior to luteal-phase based training for strength gains and muscle cross sectional area (CSA) in untrained women.
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Chronic adaptations- comparison of oral contraceptives with menstrual cycle
Dalgaard et al (2019) found that in untrained individuals low-androgenic OC may enhance the anabolic effect of resistance training on skeletal muscle mass compared to non OC users. Upon further investigation, the effects here were driven by the amount of exogenous estrogen in the OC (30mcg vs 20mcg)- suggesting that the level of exogenous estrogen might influence training adaptations. Ultimately, they found no difference in muscle strength gains between OC users and non users.
Nichols et al (2008) found that in athletes, OC (combined monophasic) use has no effect on strength development and torque production in response to resistance training compared to non-OC users.
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I wanted to include the final conclusion from Thompson et al (2019) because I simply can’t state this any better:
“The lack of clear resolution on the influence of exogenous hormones on resistance training responses contributes to the confusion females, and especially athletes, face when trying to make an educated decision on whether to use an OC- and if so what type.”
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The good news is that some methodological recommendations for menstrual cycle research have finally been published (thank you Janse de Jonge et al, 2019). FINALLY.
As always, the decision to use oral contraceptives or other forms of hormonal birth control is something to discuss with YOUR team of people who understand your unique situation and goals. At the end of the day, the best way to understand how hormonal birth control is affecting you is to track YOUR INDIVIDUAL DATA! Monitor food intake, body weight, mood, sex drive, performance, lab markers, etc so that you can understand your personal response.
Take aways:
- There is insufficient evidence to support that OC use is associated with improvements in performance
- There is insufficient evidence to support that OC use is associated with impairments in performance
- There are a number of adverse effects that have the potential to impact long term performance including an increased risk for nutrient deficiencies (including B6, B12, folate, calcium, magnesium, vitamin C and vitamin E), an increase in serum cortisol, HsCRP, SHBG, and markers of oxidative stress along with a decrease in testosterone and peak bone mineral density.
- Progestin-only contraceptives have been associated with small amounts of weight gain. Combination contraceptives have not been associated with weight gain
I’d love to hear your personal experiences with OC use and performance! Feel free to email me if you don’t feel comfortable commenting below! We definitely have a ton to learn in this area, but hopefully this research review provided some clarification around what we do and don’t know!
xo
Tiana
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