Gender Bias, Sex Differences in Exercise & Menstrual Cycle

I was watching the morning news one morning this week. One of the topics was gender bias in healthcare, which got my juices flowing so I wanted to dive deeper into the topic.

Based on my experience, a lot of coaches and personal trainers are not able to take these things into account when working with people who menstruate so this is my effort to make a difference.

Gender Bias in Healthcare and Exercise Science

Gender bias in healthcare can be described as the difference in care that individuals receive based on their gender. Gender bias can impact diagnosis, treatment, research, and the interaction between professionals and patients.

For example, heart disease is frequently underdiagnosed in women, as it is often considered a predominantly male condition.

According to an article by Samulowitz et al, studies have found that women’s pain responses are affected by genetic, biological or even psychosocial factors. For example, the menstrual cycle, pregnancy, and oral conceptive use confirm that hormones are related to pain response (Samulowitz et al 2018).

Most of the studies in resistance training were conducted on men; 287 studies included both sexes, 205 male-only and 92 female-only studies (Pandit et al 2023).

This holds also in sports psychology research. Across the sport psychology research, Walton et al (2022) looked at between 2010 and 2020, 62% of the participants were men and boys. Further, around 22% of the sports psychology studies we examined had samples with only male participants. In contrast, this number was just 7% for women and girls.

What does this mean?

In healthcare, for example, gender bias can lead to women's pain not being taken as seriously as men's, leading to longer wait times for treatment. Since men have typically been the default subject in research, this focus can lead to overdiagnosing and overtreating men while underdiagnosing and undertreating women.

In sports & exercise science, understanding of exercise physiology is mostly based on men whereas women's hormonal factors have often been neglected. This leads to giving the same exercise and nutritional recommendations to everyone. If you are training a lot, this can be detrimental to your health and performance.

Luckily, the wheels are turning and the importance of sex as a biological variable in research has been emerging in recent years.

Key Differences in Physical Performance

A recent article by Hunter & Senefeld summarizes the differences between biological men and women.

Males generally outperform females in strength, power, speed, and endurance. This is primarily due to the effects of sex steroids like testosterone. Testosterone significantly increases muscle mass and strength in males. Additionally, differences in heart size, lung capacity, and haemoglobin levels enable males to sustain prolonged physical activity more effectively than females.

Interestingly, while males may have greater absolute strength, females often exhibit less muscle fatigue when performance is measured relative to their capacity. These nuanced differences highlight the complexity of physical capabilities.

What about the menstrual cycle?

Concentrations of sex hormones fluctuate across the menstrual cycle, which could have implications for exercise performance in women. According to a meta-analysis by McNulty et al (2020), exercise performance might be reduced by a trivial amount during the early follicular phase of the menstrual cycle when compared with other phases (check out the phases below). In practice, during periods.

I want to highlight that this can be very individual and some people might experience changes in a totally different phase of their cycle. What it comes to elite sports, olympic and world champion medals have been won in every phase of the menstrual cycle.

However, there was a lot of variance between the included in the studies which might influence any group-level effects. Like with many things, more research is needed.

Practically, the current evidence does not suggest using general guidance on adjusting exercise across the menstrual cycle. A personalised approach should be taken based on individual's response to exercise performance across the menstrual cycle.

One way is to track your performance and motivation for exercise during your cycle. The average length of menstrual cycle is 28 days so I usually plan the easier days around the time when performance dips or you don't feel like doing anything. For some people, no changes are needed but for some, it's worth making the plan around the cycle.

Conclusion

Gender bias in healthcare and sports science has implications for diagnosis and treatment. Historically, research has often focused on men, leading to gaps in our understanding of women's health and performance. This bias results in women’s symptoms being overlooked or misdiagnosed, while also providing exercise and nutritional recommendations that may not be optimal for female athletes.

As awareness grows, we are recognizing the importance of considering sex as a variable. By more inclusive research and acknowledging these differences, we can move towards more equitable healthcare and sports practices.

Hope you learned something. Menopause has been on my mind to dive deeper to learn more since that affects half of the world as well.

References

What is Gender Bias in Healthcare? | Quality Interactions. (no date). 26.8.2024 https://www.qualityinteractions.com/blog/what-is-gender-bias-in-healthcare

Samulowitz, A., Gremyr, I., Eriksson, E., & Hensing, G. (2018). “Brave Men” and “Emotional Women”: A Theory-Guided Literature Review on Gender Bias in Health Care and Gendered Norms towards Patients with Chronic Pain. Pain Research and Management, 2018(1), 6358624. https://doi.org/10.1155/2018/6358624

Pandit, A., Tran, T. B., Letton, M., Cowley, E., Gibbs, M., Wewege, M. A., & Hagstrom, A. D. (2023). Data Informing Governing Body Resistance-Training Guidelines Exhibit Sex Bias: An Audit-Based Review. Sports Medicine, 53(9), 1681–1691. https://doi.org/10.1007/s40279-023-01878-1

Hunter, S. K., & Senefeld, J. W. (2024). Sex differences in human performance. The Journal of Physiology. https://doi.org/10.1113/JP284198

McNulty, K. L., Elliott-Sale, K. J., Dolan, E., Swinton, P. A., Ansdell, P., Goodall, S., Thomas, K., & Hicks, K. M. (2020). The Effects of Menstrual Cycle Phase on Exercise Performance in Eumenorrheic Women: A Systematic Review and Meta-Analysis. Sports Medicine, 50(10), 1813–1827. https://doi.org/10.1007/s40279-020-01319-3