Hormones and Performance: A Deep Dive

Cycle syncing your training is all the rage right now - but is it actually necessary? How much influence do our hormone fluctuations have on our performance? A new study, published in "Medicine & Science in Sports & Exercise" is offering some insights into how the menstrual cycle and the pill affect endurance in well-trained female cyclists. Let’s have a look at what they found.

Study Overview

17 female cyclists were divided into two groups, based on their menstrual status. One group had natural cycles (eumenorrheic), the other used an oral contraceptive (the pill). Both groups did strenuous cycling trials, designed to mimic race conditions, at different points of their hormonal cycles. This way, the researchers wanted to see how the women’s hormones were influencing their energy levels and how their bodies utilise nutrients like carbs and protein. 

The Natural Cycle’s Influence on Performance

Luteal Phase Challenges: During the second half of their cycles (luteal phase), the female cyclists struggled more during the trial than in the first half of their cycles (follicular phase). This indicates that increased levels of hormones like progesterone and oestrogen decreased their ability to resist fatigue under race conditions. The scientists observed that the women’s bodies were burning through carbs quicker, and that they had more trouble breathing.  

Carbohydrate Management: If these results tell us anything new, it’s that carbohydrates might be even more critical for performance than we thought. Naturally menstruating women might particularly benefit from eating more carbs, especially in the second half of the hormonal cycle and during high-intensity endurance efforts. 

The Pill and Performance

Stable Performance: Contrary to the women experiencing a natural cycle, those on the pill didn’t see their performance decreased or increased during particular times of the month. There were slight differences in metabolic rates on pill days vs. 7-day break days, but none of them was severe enough to lead to a difference in fatigue resistance during the tests. 

Metabolic Adaptations: While the synthetic hormones found in the pill didn’t have a negative or positive impact on the athlete’s performance during high-intensity cycling, they still slightly altered their blood glucose levels, among other factors - something that might be of consequence in other sports and for long-term health.

Hormones and Performance: Applications and Recommendations

Nutritional Strategies:

If you’re an endurance athlete with a natural menstruation cycle, you should probably prioritise carb loading in the second half of your cycle (even more than you already do). It’s the best way to fill up your muscle glycogen stores before an intense training session or race and combat the increased metabolic demand caused by your hormones. Carbohydrate-rich beverages or snacks during very long endurance events might help, too.

Training Adjustments:

While the observed effects are probably not big enough to make a difference for everyday athletes and hobbyists, professional athletes might benefit from doing their highest intensity sessions during the first half of their cycles to recover from them quicker. 

Using the Pill: 

It might seem tempting to just use oral contraceptives to cancel out these fluctuations caused by hormones and maintain a stable performance week-on-week. However, as we mentioned above, this isn’t without consequences to certain metabolic factors - not to mention other possible side effects of the pill like increased risk of thrombosis and depression.

The Road Ahead

There’s clearly a lot more to learn about female physiology in the context of sports performance. Studies like the one we looked at in this article are just laying the groundwork for more investigations to come. While it seemed like the pill didn’t acutely influence performance, we have no data on its long-term effects, or if performance might increase once these women stop taking oral contraceptives. 

The research highlights that there’s a need for more discussions and awareness around menstrual health in the fitness space. This way, female athletes can better navigate and leverage the challenges and opportunities posed by their hormonal fluctuations throughout the cycle. It also shows that you might not need a perfectly cycle-synced workout plan if you’re not a professional athlete - but you might still benefit from eating slightly more carbs during your luteal phase! 

Sources

[1] Lee SJL, Sim MP, VAN Rens FECA, Peiffer JJ. Fatigue Resistance Is Altered during the High-Hormone Phase of Eumenorrheic Females but Not Oral Contraceptive Users. Med Sci Sports Exerc. 2024 Jan 1;56(1):92-102.