The Hidden Game Changer

How the menstrual cycle affects athletic performance

In recent years, a growing number of elite athletes have broken their silence about a topic long considered taboo in the world of sport - their menstrual cycles. From Brittany Brown, the sprinter who won a 200m Olympic bronze medal while living with endometriosis, to Iga Swiatek who openly discussed how PMS impacted her performance in the WTA finals in 2021, these athletes are rewriting the narrative around being a woman in sports. Their stories shine a light on the unique challenges women face, both on and off the field, when it comes to their menstrual and reproductive health.

Brittany Brown’s success, while remarkable, also underscores the ongoing struggle many women face in accessing proper care for conditions like endometriosis - a condition that affects 1 in 10 women. “I don’t think my period is supposed to feel like this,” Brittany recalls thinking during a particularly painful episode. Yet, like so many others, her symptoms were initially dismissed by doctors. For many women, it takes an average of 7.5 years to receive a diagnosis for endometriosis - a timeframe that, in the context of an Olympian’s career, could mean the difference between reaching their full potential and falling short.

Iga Świątek, following a tough loss in the WTA Finals in 2021, opened up about how PMS affected her performance, stating, "PMS really hit me that day. I'm sharing this for any young girl who doesn't know what's going on. Don't worry, it's normal. Everybody has it." Her openness about the impact of PMS serves as an important reminder that even at the highest levels of sport, these experiences are normal and shared by many.

It’s not just the elite athletes who are impacted by menstrual health issues. A study by Always found that 2 in 3 women and girls believe that being on their period puts them at a competitive disadvantage in sports. Puma’s collaboration with Modibodi, a period underwear brand, revealed that 1 in 2 teens skip sports because of their period. Clearly, the fear of leaks, discomfort from menstrual products, and the stigma surrounding menstruation are still significant barriers to participation.

Do periods lower performance?

In light of the increased conversation around menstrual cycles and sports, it’s essential to examine the clinical research on how these cycles affect athletic performance. The research is frustratingly sparse. Women are grossly underrepresented in sports science studies, comprising only 30 to 40% of participants, with just 6% of studies focusing exclusively on women. Despite these limitations, we’ve compiled the most prominent studies below. 

Increased injury risk in the luteal phase

A study titled "Injury Incidence, Severity, and Type Across the Menstrual Cycle in Female Footballers" tracked injury rates among 26 elite female football players over three seasons. The findings revealed a significant increase in injury risk during the luteal phase, suggesting that hormonal fluctuations could contribute to phase-specific vulnerabilities. This highlights the urgent need for more research and intervention strategies to reduce injury risk in female athletes.

Cognitive performance and the menstrual cycle

Ronca et al (2024) explored why injury risk might be higher during certain menstrual phases. A study investigating cognitive processes across the menstrual cycle found that cognitive performance worsened during the luteal phase, marked by slower reaction times and poorer timing anticipation. Interestingly, despite self-reported worsened moods and cognitive symptoms during menstruation, the study revealed that women actually performed better during this phase, with faster reaction times and fewer errors. This suggests a disconnect between perception and reality, highlighting the complex relationship between mood, cognition, and menstrual cycle phases.

Perception vs. performance

This finding is echoed by a 2024 study that examined the impact of menstrual cycles on elite British track and field athletes. The study found that athletes overwhelmingly perceived their performance to fluctuate throughout their cycle, with many reporting inferior performance during the late luteal or early follicular phases when oestrogen and progesterone levels are low. This perception alone can have a significant psychological impact, potentially affecting physical outcomes, and emphasising the need for more comprehensive support and education around menstrual health for female athletes.

The power of cycle tracking

Despite the challenges, understanding and tracking the menstrual cycle can actually empower athletes to optimise their performance. Every body is unique, and some athletes, like British diver Andrea Spendolini-Sirieix, even report performing better during their period. Andrea has noted that she jumps her highest and feels her strongest when menstruating. Such anecdotal evidence suggests that period tracking can help athletes harness their strengths at different stages of their cycle, rather than seeing menstruation as a disadvantage.

This approach is already being implemented by various sports teams and bodies across the globe:

• In France, the National Institute of Sport’s Empow’her program is pioneering research by analysing hormonal, cardiac, and psychological data to tailor training based on menstrual phases, offering a model for wider integration of menstrual health into elite sports.
• The U.S. women’s national soccer team famously used menstrual cycle tracking during their 2019 World Cup win, adjusting training and nutrition to align with each player’s cycle. 
• In the UK, Chelsea FC have started using menstrual cycle apps and using the outputs to fine-tune training schedules for their women’s team. This personalised approach not only enhances performance but also sets a new standard in the Women’s Super League for leveraging menstrual health as a competitive advantage.

Start-ups are also seeking to empower female athletes. Wild.AI, an innovative app, promises to help women "turn their hormones into their superpower" by optimising training, recovery, and nutrition based on their hormonal cycle. 

Brain-based technologies: the future of performance optimisation?

Enhancing your performance - whether athletic, cognitive, or otherwise - throughout your cycle is one of the key benefits of Nettle’s technology. Early users have reported significant improvements in functionality, such as going to the gym on the first day of their period or finding it easier to get out of bed in the morning. They felt sharper, stronger, and more prepared for whatever the day had in store.

Further, Nettle’s underlying technology, transcranial direct current stimulation (tDCS), is backed by a growing body of research demonstrating its effectiveness in a sports setting:

Sprint cycling and cognitive performance

Halo Neuroscience found that tDCS can sharpen both physical and mental performance. In a study on sprint cycling, athletes experienced enhanced speed and mental acuity, proving that tDCS can deliver the dual benefit of physical power and cognitive clarity.

Muscular endurance and time to exhaustion

Another study by Halo Neuroscience revealed that tDCS significantly extends time to exhaustion (TTE), enabling athletes to push through their limits and maintain peak performance longer. 

Running performance and motor cortex stimulation

A specific study on running performance found that when tDCS was applied to the primary motor cortex (M1) - a key area targeted by Nettle - it significantly improved TTE during submaximal running (intensity lower than 85% of your maximum heart rate). Participants who received tDCS could run longer before reaching exhaustion without any changes in cardiorespiratory responses, indicating that the benefits were primarily due to enhanced brain function rather than changes in physical capacity.

Mechanisms behind enhanced exercise performance

A comprehensive review study examined the underlying mechanisms of exercise performance and how tDCS can enhance both physical and psychophysiological responses in athletes. The review highlighted that tDCS modulates brain activity in ways that reduce perceived effort and delay fatigue, making it an effective tool for improving overall athletic performance.

Ultimately, the key to unlocking an athlete’s full potential may rest in understanding and leveraging the menstrual cycle rather than fighting against it. By integrating knowledge and technology, we can create a future where menstrual health is no longer a barrier but a powerful tool for athletic excellence. As more athletes like Brittany Brown and Andrea Spendolini-Sirieix speak out, they pave the way for a new era in sports—one where every woman can compete at her best, regardless of the time of the month.

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