Podcast, Science and Physiology

The menstrual cycle and oral contraception – impact on exercise performance with Kelly McNulty | EP#280

 April 5, 2021

By  Mikael Eriksson


Kelly McNulty is a PhD candidate at Northumbria University. Kelly's research investigates the effect of the menstrual cycle and hormonal contraceptive use on performance, recovery, and adaptation in women in sports. In this interview, Kelly walks as through the evidence-base and practical recommendations for all female athletes and coaches of female athletes.

In this Episode you'll learn about:

  • The different phases and hormonal changes of the menstrual cycles
  • How these changes (theoretically) might impact exercise performance
  • The actual evidence-base and state of the science on menstrual cycle phase and its impact on exercise performance
  • Practical advice for individualising your approach to training according to the menstrual cycle phases
  • The evidence-base and state of the science on hormonal contraception use and its impact on exercise performance
  • General advice and takehome messages for female athletes

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04:20 -

  • My name is Kelly McNulty and I’m a PhD student primarily focusing on the female athlete.

    I am extra interested in how the menstrual cycle and oral contraceptives affect the performance.

    I have always had a great interest in physiology and maximizing physical performance, which is why I went to University to study exercise physiology.
  • My own sport background is as a golf player, but I am not competing any longer.

The menstrual cycle

12:00 -

  • The menstrual cycle is designed to set up the woman for pregnancy, but if this does not happen, then the same procedure is being repeated, hence the ”cycle”.

    In short, in the time before menstruation, the hormones excreted are mainly anabolic (estrogen) while the dominant hormones after menstruation are catabolic (progesterone).

    It is believed that the anabolic hormones could enhance performance while catabolic hormones would inhibit performance.
  • One must also emphasize that the menstrual cycle differs very much between different women and can also differ plenty within the same individual over a life span.

A meta analysis of menstrual cycle’s impact on performance

19:20 -

  • We did find 76 articles comprising around 1000 participants that were included in the meta analysis.
  • The conclusion of the meta analysis was that you may see trivially reduced performance during the early follicular phase (day 1-5) of the menstrual cycle, which is were both estrogen and progesterone is down regulated.

    However, it should be stated that the results varied rather much between the studies and that only a minor percentage of the studies were designated as ”high quality”, which makes it rather difficult to give any generalized advice

    This is why my advice would be to take a personalized approach towards your own cycle.

    Try to get to learn your own cycle and identify the different states and relate them to fluctuations in performance.

    There are different tools (like apps) that you can use in order to track your cycle easier, which I would recommend.

    The differences between women in regards to during which phase they they perform best physically is quite large so it can most definitely be worth getting to know your own cycle to the best of your ability.

A meta analysis on oral contraceptives

37:40 -

  • Women who are taking oral contraceptives are creating a completely different type of hormonal cycle compared to the natural menstrual cycle.

    In our meta analysis we found that women who are taking oral contraceptives see a slightly reduced physical performance.

    However, once again, the number of high quality studies were slim and the results varied so it is hard to give any general guidelines.

    Therefore, I would recommend women to try and figure out how they react on oral contraceptives on an individual level and base their choice of contraceptive based on this instead.

    It is important to underline here that women who do get quite much ”symptoms” from the regular menstrual cycle can highly benefit from oral contraceptives, so it is once more a matter of great variability between individuals.

Should men and women train the same?

50:30 -

  • I think that is is naive to assume that all the physical differences between women and men do not have any relevance in terms of training applications.

    However, most things that has been researched on men will most certainly apply for women as well.

    In the future, I believe that research on women only will add more value to what we already know about exercise physiology.

Rapid fire questions

54:15 -

  • What is your favorite book, blog or resource related to endurance sports? The book ”How to Support a Champion” by Steve Ingham
  • Who is somebody who has inspired you? Jessica Ennis-Hill.
  • What is a personal habit that has helped you achieve success? Make sure to be planned and prepared and really organized.


Mikael Eriksson

I am a full-time triathlon coach, founder of Scientific Triathlon, and host of the top-rated podcast That Triathlon Show. I am from Finland but live in Lisbon, Portugal.

Please contact me if you have feedback on the podcast or want to make suggestions for improvement or send in a question for a Q&A episode.

If you are a long-time listener and appreciate the value the podcast brings, please consider taking a couple of minutes for leaving a rating and review on iTunes/Apple Podcasts, or wherever else you can think of leaving a rating and review.

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