Does your menstrual cycle affect how you cycle (and perform other sports)?

Understanding Sex Differences in Health and Wellness: The Impact of the Menstrual Cycle

Let's talk about something that doesn't get enough attention: how the menstrual cycle affects  health and fitness. Unfortunately, in the earlier days of medical research, we often adopted a ‘one size fits all approach’ and studies predominantly focused on male participants, with results extrapolated to other demographics. Yet recent research has demonstrated that this extrapolation is not entirely accurate, unsurprisingly, and likely oversimplifies the changes experienced throughout the menstrual cycle and various stages of life (puberty to menopause). From sleep and nutrition to exercise performance, the hormonal fluctuations throughout a cycle can significantly impact fitness and wellness. In this episode, we will take a closer look at what the research says and how you can tailor your health and fitness strategies according to your cycle.

(Author’s note: Many of the studies cited focus on women who menstruate, as more research needed to broaden our understanding to people who menstruate, regardless of gender identity and sex at birth. I chose to use gender-neutral language in this article due to the generalized nature of the key takeaways and tips.)

Sleep Patterns and the Menstrual Cycle

The menstrual cycle can have quite a profound impact on sleep. Studies show that people who menstruate often experience poorer sleep quality during the luteal phase (the second half of the cycle) due to hormonal changes. Specifically, fluctuations in estrogen and progesterone can lead to more frequent awakenings and less restful sleep. During menstrual bleeding days, study participants spent more time in bed and more time in deep sleep, with recent research suggesting that sleep requirements should be slightly higher in this part of the cycle(1).​  

What to Do:

• Follicular Phase (Days 1-14): Focus on establishing a consistent sleep schedule. This is when you might find it easier to fall and stay asleep.

• Luteal Phase (Days 15-28): Implement sleep hygiene practices such as reducing caffeine intake, creating a calm sleep environment, and perhaps incorporating relaxation techniques like meditation before bed.

• Add even more time to sleep on your menstrual bleeding days.

Nutritional Needs and Strategies

Your nutritional needs and metabolic profile can also vary throughout your cycle and your lifespan. For example, between males and females over the age of 18, the NIH recommends more than twice as much iron daily for female patients compared to male patients (18mg compared to 8mg) (2). This helps compensate for bleeding that occurs in the menstrual cycle. 

Additionally, studies have shown that cholesterol profiles can change throughout the menstrual cycle, along with blood sugar levels, as the ovarian hormones play a role in regulating these processes. That said, with increased physical activity and fitness, these glucose changes were minimized (3). 

Another study highlighted that metabolic profiles change across the menstrual cycle, affecting how your body processes and utilizes nutrients (4). I highly recommend taking a look at this study if you are interested in making detailed applications to your individual life, but here are some takeaways (4).

Takeaways:

• Protein: During the luteal phase of the menstrual cycle (second half) persons who menstruate use more protein for bodily processes, including building uterine tissue as part of the menstrual cycle. Because of this (especially if you are focused on muscle growth) you may need to increase your protein intake at this time.

• Fats: Fat metabolism is increased during the luteal phase of the menstrual cycle, as well. Studies show that compared to male bodies, female bodies tend to utilize a bit more fat for bodily function. However, with lower estrogen levels during the follicular phase, less fat is needed. Ultimately, people who menstruate should look to have roughly 20-30% of their intake be fat, predominantly unprocessed (and mostly unsaturated) such as nuts, seeds, and lean meats. 

• Carbohydrates: Carbohydrate use is heavily linked to needs related to exercise and energy expenditure. Therefore, while there are some differences in metabolism throughout the menstrual cycle, intake should still be geared toward your anticipated needs. With prolonged exercise, or planning for upcoming events, carbohydrate intake and carb loading should remain similar between phases (8-10g per kilogram for carb loading).

Exercise and the Menstrual Cycle

Exercise performance can vary significantly across the menstrual cycle due to hormonal influences on muscle strength and recovery. Some studies have noted exercise changes and muscle function based on hormone fluctuations (5). As far as resistance training (weight lifting) is concerned, it is still too early to make precise recommendations on the optimal timing and strategy, and further research is needed (6).​ Nevertheless, research is clear that performance, especially subjectively, is decreased during menstrual bleeding days (7).

Potential modifications:

• Follicular Phase: This is the time for high-intensity workouts and strength training. Your body may be more resilient and can recover faster. The early follicular phase may be the optimal time for performance events.

• Luteal Phase: If there is room for flexibility in your current training schedule, consider focusing on low-impact exercises to support recovery. You do not have to avoid high-intensity training but can have lighter impact alternatives at the ready that can help with mobility and recovery, as needed. 

Monitoring and Tailoring Your Approach

It's clear that monitoring your menstrual cycle can provide valuable insights into how to adjust your health and fitness strategies. Understanding and addressing the unique health and wellness needs of people who menstruate can lead to more effective and personalized strategies. By considering the menstrual cycle's impact on sleep, nutrition, and exercise, you can optimize your overall health and fitness outcomes.

But, with all of this variability, it is important to recognize your body's signals and adapt your routines accordingly. It's not just about training harder or eating differently—it's about training and eating smarter, in sync with your body’s natural rhythms.

Key Strategies:

1. Keep a Cycle Journal: Track your menstrual cycle, noting any changes in sleep, energy levels, mood, and physical performance.

2. Adjust Your Diet: Incorporate more of the nutrients you need during different phases of your cycle, focusing on complex carbs, iron, and calcium.

3. Tailor Your Workouts: Align your exercise intensity with your menstrual phases—high intensity during the follicular phase and with slightly lower intensity during the luteal phase, if needed. 

Sources and Further Readings:

1. Hrozanova M, Klöckner CA, Sandbakk Ø, Pallesen S, Moen F. Sex differences in sleep and influence of the menstrual cycle on women’s sleep in junior endurance athletes. PLOS ONE. 2021 Jun 17;16(6):e0253376. 

2. Office of Dietary Supplements - Iron [Internet]. [cited 2024 Jul 28]. Available from: https://ods.od.nih.gov/factsheets/Iron-Consumer/

3. MacGregor KA, Ho FK, Celis-Morales CA, Pell JP, Gallagher IJ, Moran CN. Association between menstrual cycle phase and metabolites in healthy, regularly menstruating women in UK Biobank, and effect modification by inflammatory markers and risk factors for metabolic disease. BMC Med. 2023 Dec 8;21(1):488. 

4. Wohlgemuth KJ, Arieta LR, Brewer GJ, Hoselton AL, Gould LM, Smith-Ryan AE. Sex differences and considerations for female specific nutritional strategies: a narrative review. J Int Soc Sports Nutr. 2021 Apr 1;18(1):27. 

5. Nakamura Y, Aizawa K. Sex Hormones, Menstrual Cycle, and Resistance Exercise. In: Hackney AC, editor. Sex Hormones, Exercise and Women: Scientific and Clinical Aspects [Internet]. Cham: Springer International Publishing; 2023 [cited 2024 Jul 28]. p. 227–43. Available from: https://doi.org/10.1007/978-3-031-21881-1_10

6. Colenso-Semple LM, D’Souza AC, Elliott-Sale KJ, Phillips SM. Current evidence shows no influence of women’s menstrual cycle phase on acute strength performance or adaptations to resistance exercise training. Front Sports Act Living [Internet]. 2023 Mar 23 [cited 2024 Jul 28];5. Available from: https://www.frontiersin.org/journals/sports-and-active-living/articles/10.3389/fspor.2023.1054542/full

7. Solli GS, Sandbakk SB, Noordhof DA, Ihalainen JK, Sandbakk Ø. Changes in Self-Reported Physical Fitness, Performance, and Side Effects Across the Phases of the Menstrual Cycle Among Competitive Endurance Athletes. Int J Sports Physiol Perform. 2020 Sep 21;15(9):1324–33.