As a female endurance athlete, having your period on race day can feel a bit daunting, but the question is, should it? A lot of women (not all) can feel bombarded with numerous unpleasant symptoms such as abdominal cramps, bloating, headaches, fatigue and gastrointestinal issues. Any of these alone or in combination could feel like your race day has finished before its even began. Though, a lot of these symptoms can be managed, and physiologically, will it affect how we perform? To start with, let’s examine what our menstrual cycle looks like. Menstrual Cycle Basics Image: Hormonal fluctuations in a eumenorrheic (regular) 28-day menstrual cycle. Adapted from McNulty et al. Although some will think of the menstrual cycle as their period, this merely signifies the start of a new cycle. The term cycle refers to the fluctuation of hormones, and each phase individually could impact exercise in different ways. Your menstrual cycle can be split into 6 distinct phases; early follicular, late follicular, ovulatory, early luteal, mid luteal and late luteal. In most women, this cycle will last between, 21 and 35 days, and your period signifies the start of a new cycle rather than the end of one. During the early follicular phase when your period occurs, our hormones are fairly low and stable. During the late follicular phase (just after your period), your oestrogen levels will increase as your egg matures. Once oestrogen reaches a critical point you will begin your ovulatory phase where a hormone called gonadotropin releasing hormone will cause a luteinising hormone ‘surge’. This surge signifies the release of your egg in this cycle. After ovulation, progesterone levels will start to rise, peaking in your mid luteal phase alongside a smaller peak in oestrogen preparing your body for a fertilised egg to be implanted in your womb. Of course, if your egg remains unfertilised, both oestrogen and progesterone will decline during the late luteal phase as your body prepares to start this cycle all over again. How do these hormonal fluctuations affect exercise performance? Oestrogen and progesterone have different physiological effects on our bodies, meaning there is reason to believe we should consider these hormonal changes for training and competition. The below table summarises the possible effects of your hormones on sporting performance. Factor Hormonal Influence Potential Effect on Performance Compensatory Consideration Metabolism Oestrogen favours fat availability in muscle with progesterone having the opposite effect, limiting fat utilisation. An increased preference for fat utilisation during the late follicular phase when oestrogen is high. The evidence for this is still inconclusive, and it seems the exercise demand of your training/competition may be more influential. Body Temperature Slightly elevated during the luteal phase when progesterone is high. Could impair longer duration exercise with basal temperature being higher leading to greater stress on the body trying to keep cool. During the luteal phase we seem to hold more water which could provide a compensatory mechanism in keeping us cool. Recovery Oestrogen is an anabolic hormone meaning it favours muscle building. Could improve force production when oestrogen is high. Oestrogen has also been shown to reduce DOMS. The opposite occurs when progesterone is high as it is a catabolic hormone favouring muscle breakdown. Consider eating more protein when progesterone is high. Overall, there is a fairly large body of research that has examined the effect of menstrual cycle phase on aerobic performance using measures such as endurance exercise to exhaustion and power output on a treadmill or exercise bike. The majority of this research as summarised in this review, concludes the menstrual cycle does not impact aerobic performance despite possible changes in metabolism. Further to this, it seems that your VO2max (your maximal oxygen uptake – a key predictor of endurance performance) and lactate threshold are also unaffected by the menstrual cycle meaning physiologically, you should be able to perform at your best regardless of where your race falls within your menstrual cycle! So, what does it mean to have your period on race day? Physiologically thinking about thermoregulation, exercise capacity and metabolism, having your period on race day is no disadvantage. This was famously proven by Paula Radcliffe when she broke the marathon world record in 2002 whilst on her period. However, there are still numerous uncomfortable or unpleasant symptoms that come with menstruation, and these could potentially still affect your performance. Managing the symptoms that affect you, is the best way to combat this. There is no one-size fits all solution and which menstrual symptoms affect us will vary drastically between individuals. Monitoring your cycle and symptoms so you can have strategies ready to combat your specific symptoms is advisable. Here are some tips for managing certain menstrual symptoms: Cramps: There is evidence to suggest magnesium supplementation can significantly reduce cramping during menstruation. Though this is a relatively small study and more research is needed. Fatigue: Vitamin B6 supplementation may reduce irritability and fatigue as shown in a research study of premenopausal women, however women who received the placebo in this trial also reported improvements, so this may be in part due to the placebo effect. Prioritising sleep and recovery during your taper period may be just as effective. Headaches: Generally, staying hydrated (always important before a race!) is key here in trying to minimise headaches. Gastrointestinal Distress: Learning your trigger foods before your race will help you most here and as always with race nutrition, avoid anything new! There is also the other obvious symptom to consider, managing menstrual loss. This will be a personal decision based on your preferences. In general, avoiding sanitary pads is recommended as these can become heavily saturated with sweat and if doing a triathlon, will be very ineffective during a swim. In general, tampons or intravaginal cups are more effective. If these are not something you usually use, it is best to try before a race to find what works best for you. During longer distance events you may also need to change your tampon so this should be considered in your race preparation. Consider where you can carry a fresh tampon and to minimise the chance of bacterial infection, a tampon with an applicator may be best. What do the pro’s do? We spoke to professional triathlete’s Eloise du Luart and Megan MacDonald about how they find racing on their period, and this is what they had to say: Eloise: “I used to worry about being on my period for racing not only from a practical point but also from a performance aspect. However, after spending time tracking my cycle and mapping how I feel, training etc, it turns out I am at my strongest during my period and the week after! However, I do suffer from very bad period pains, cramps and nausea in the first 24hrs. I have never raced on this day but from recommendations and testing in training, paracetamol can help relieve this without affecting my body’s ability to manage heat or put pressure on the gastro system. In terms of practicality, it comes down to planning. Don’t be ashamed of it, just plan for it. I usually put spare tampons in my race bag to ensure if I need them, I am covered and then control what I can. I used to be embarrassed, worry that I “may have a crisis” however, it really is human and having your period is just a sign you are healthy as an athlete and with it, much stronger than you would be without it.” Megan: “I normally feel quite flat the week I’m due on, so it’s more if I’m racing when I’m due it has an effect. But I remind myself that everyone goes through it and try not to overthink it as there are days that are good! It’s all part of being a woman and the challenges. Periods affect everyone in different ways, but the mind is also very powerful so if you can stay positive through an event and make sure it doesn’t affect you too much then that’s a big win. Then assess the day after and make notes on how you felt. The issue is not every cycle is the same so you will never feel the same way. In all honestly, it’s pot luck on how you will feel on race day when you are due on or not!” Take home messages: Physiologically, the research states there is no disadvantage to racing when on your period. Great news! The best strategy to manage your period on race day is to work out which strategies work best for you to minimise any symptoms and discomfort on the day. Tracking your cycle and symptoms alongside how you feel in training will give you a good indication of how you will feel on race day. Written By Dr Emily Jevons - PhD in Exercise Physiology & Nutrition, Clean Sport Advisor Emily has worked with Science in Sport since 2021. With a PhD in Exercise Physiology & Nutrition, she currently provides nutritional advice for endurance athletes. Emily not only understands the science behind performance nutrition solutions, but also the physiological and psychological demands of sport after competing competitively in swimming and triathlon for a number of years.