Writer Liz Connor takes a comprehensive look at how the menstrual cycle affects your exercise regime, and how to adapt it to get the best out of your workouts

It’s no secret that exercise feels harder on some days than on others. For every training day where you destroy sets and slay your PBs, there’s another where it's a struggle to simply get through the warmup.

When you’re not feeling your workout, there are a variety of factors that could be at play – poor sleep, diet, a bad hangover – but for women who experience periods, your menstrual cycle can have a considerable effect, too.

As conversations around the topic of menstruating become less taboo, the fitness industry is waking up to the fact that fluctuations of hormones across the menstrual cycle can lead to different outcomes in women’s training.

Dubbed ‘cycle mapping’, there’s now a strong argument for a type of strategic training that adapts your workouts to the hormonal changes that happen throughout the month. 

By scheduling gym sessions in this way, many women find that they can build more strength and power with fewer high-intensity sessions. In short? Work less, gain more.

Closing the gender data gap

You’ve probably heard of the gender pay gap, but what about the gender data gap? 

Right now, the majority of data we have around the world is based around the male body and the typical male life pattern; an uncomfortable omission given that approximately half of the world population is made up of women.

According to a 2020 review of research published in the Journal of Physiology, just 8 percent of health studies exclusively feature female participants, and those that do tend to relate to aspects of health that only apply to women, such as menopause, endometriosis and pregnancy. 

In the field of sports science, it gets worse. Data indicates just 4 to 13 percent of articles from leading journals in sports and exercise science included only women as participants. The result? Women are taking fitness advice and following workout plans that are based on data collected mostly from men.

The problem with this, which Caroline Criado Perez outlines in her recent book ‘Invisible Women’, is that a one-size-fits-all approach puts women at a disadvantage as it may not always garner the best outcomes for their health.

For example, women are unlikely to display the same heart attack symptoms as men, yet men’s symptoms are classified as the ‘official’ symptoms of a heart attack. As a result, women are twice as likely to die in the 30 days following a heart attack, as the symptoms can go misdiagnosed. 

The gender data gap is important to address as it informs everything from the products we use (did you know that the design of many smartphones is slightly too big for women’s hands?) to the food we eat to stay well.

Thankfully, steps are now being taken to change the narrative. In 2019, The World Health Organisation’s (WHO) Global Health Statistics were disaggregated by sex for the first time. 

Encouragingly, UN Women have also just launched their Making Every Woman and Girl Count initiative, a gender data programme that seeks to bring about a radical shift in how gender statistics are used, created and promoted. 

What’s happening during the menstrual cycle?

Talking about periods has been fairly taboo until recent years and research shows that 1 in 4 UK women don't understand their menstrual cycle.

The menstrual cycle can last between 21 and 40 days, with 28 days being the average length, although there’s no ‘normal’ and every woman is different. 

“Whether you’re planning to have a baby or not, the biological purpose of the menstrual cycle is for fertility,” says Dr Nicky Keay, a leading expert in endocrinology and the author of the upcoming book ‘Hormones, Health and Human Potential’. “To produce an egg for fertilisation, there’s a conversation that happens between the various fluctuating hormones of the menstrual cycle.”

There are four main hormones involved in the regulation of the menstrual cycle: follicle-stimulating hormone (FSH), luteinising hormone, oestrogen and progesterone.

Many of us think of our period in two parts: the times when we’re bleeding and those when we’re not. In reality, it’s actually composed of four distinct phases: menstruation, the follicular phase, ovulation and the luteal phase. 

“The beginning of the menstrual cycle is when you have your period, and you shed the lining of the uterus,” explains Keay. “From here, your body is building up to ovulating (producing an egg), which is reflected in an increase in oestrogen.”

The second act of the menstrual cycle is when “oestrogen dips and the progesterone hormone reigns supreme in preparation for fertilisation,” says Keay. “If the ovulated egg isn’t fertilised, progesterone levels drop in the body, signaling for the womb lining to shed and the period to happen all over again.”

As Keay notes: “This repeating pattern of oestrogen and progesterone taking it in turns to dominate will happen to a woman from their first period around the age of 12 until the menopause, of which the average age is around 51.”

How does your menstrual cycle impact your workouts?

Because so few sports science studies are conducted on women, the majority of fitness plans don’t account for the role that hormones play when it comes to fitness.

The fluctuating fertility hormones have a major impact on our energy levels, comfort and sleep at different times in our cycle. Around 81 percent of women experience pain and cramping around their bleed days, and a further 55 percent say that the pain is severe enough to interfere with their daily life, causing them to call in sick to work and skip out on social plans.

It’s for this reason that your male friend might crush an ‘eight week shred’ fitness challenge while you feel a progress dip midway through. As research is continually proving, men and women are built differently. 

How to tailor your workout plan to your hormones

While your period can present some obstacles, it can generally be considered a good thing when it comes to workouts. Here we go through each phase of your menstrual cycle and explore the ways in which you can lean into the hormonal changes and use them to your advantage.

Phase 1: Menstruation… take it easy

When conception doesn’t happen after the release of an egg, progesterone and oestrogen start to decrease in the body. “It’s this hormonal dip that causes common period symptoms like cramping, tenderness of the skin and breasts, sudden mood swings, tiredness, headaches and migraines, and lower back pain,” says Keay.

It’s a good idea to dial things down on your bleed days with some low-intensity steady-state cardio (LISS) activities to encourage the release of endorphins without pushing yourself too hard. Think yoga, barre, stretching, walking, and cycling. If your symptoms are really uncomfortable, don’t be afraid to take rest days.  

Phase 2: The follicular phase… go for a PB

During the follicular phase, the follicle-stimulating hormone (FSH) stimulates your ovaries to produce follicles, which contain immature eggs.

This process also involves an increase in the hormone oestrogen, causing the body to thicken the uterine lining. The rise in oestrogen is significant, as it’s your superstar hormone – it boosts your energy, mood and brain skills and makes you feel more confident and powerful.

The follicular phase is when you should chase your next PB, whether that’s a faster running time or a heavier set of weights. “It’s particularly good for strength training,” says Keay. “You might find that you feel you can lift more or perform additional reps than other times of the month.” As your muscles adapt better and fatigue less, this is a great time to focus on HIIT, strength training and speed running.

Phase 3: Ovulation… activate beast mode

During the ovulation phase, an egg is released from the ovary into the fallopian tube. You’re still on an oestrogen high right up until the end of this phase, so you'll be reaping the benefits of feeling energised, confident and ready to take risks.

You can continue to push yourself in the gym, particularly in the 48 hours around ovulation, so keep smashing your training goals with high-intensity strength and cardio sessions. Oestrogen can also give you a confidence boost to try out a new discipline, whether that’s a boxing class or a calisthenics session. 

Phase 4: The luteal phase… go for moderate endurance activities

The luteal phase begins as the egg starts traveling down the fallopian tube, where it may come in contact with a sperm to be fertilised. The body burns more fat during the luteal phase, as the rise in oestrogen and progesterone suppress gluconeogenesis (the pathway by which glucose is synthesised). Essentially, your body switches to fat rather than glucose as its main source of energy.

During the luteal phase, your basal metabolic rate (MBR) rises so you burn more calories at rest. Effectively, you can dial things down with moderate-intensity exercise and still lose fat, if that happens to be one of your fitness goals.

The luteal phase is a great time for longer endurance sessions like spin classes, distance runs, skipping and swimming. However, “the last week of the cycle is when you’re most likely to experience the symptoms of premenstrual syndrome (PMS), like mood swings, tiredness and bloating,” says Keay, so dial things down as you approach your period and opt for some gentle mobility sessions instead. 

Your menstrual cycle and nutrition

Alongside the training, syncing your nutrition to your cycle can help to fuel your workouts and ease the physical and mental symptoms that occur throughout the month. 

The menstrual phase… eat for comfort

Menstruating can be energy intensive and you tend to crave comfort foods as a result, so switch out takeaways for warming homemade dishes that include a good mix of lean proteins, healthy fats and low GI carbohydrates. To combat menstrual cramps, try drinking soothing herbal teas and avoid inflammatory foods like alcohol, caffeine and sugary snacks that can make flare-ups worse. 

You might also want to consider iron-rich foods like nuts and dried fruit. Our blood contains a significant amount of iron, so replenishing this lost iron, particularly if you have a heavy flow, can be a good idea – especially if you’re suffering from fatigue. 

Ovulation… cut the caffeine, if you can

Many women say that the ovulation phase is when they have the most natural energy, so if you’re thinking of cutting down on caffeine, this point of your cycle is the best time to break up with your coffee machine.

If you’re looking to make muscle gains too, make sure you’re consuming enough protein to support growth and repair – a nutrient important at all stages of the menstrual cycle.

The luteal phase… say no to salt

Many women experience PMS symptoms around this time, so avoid salty foods as they can exacerbate bloating and opt for comforting, complex carbohydrates such as brown rice, pasta, bread or Huel, which will give you all-day energy.

The final word

When it comes to hormones and fitness, cycle mapping can help you to see progress, but there’s no blanket approach.  

“Theoretically we can talk about hormones peaking and dropping, and that it typically has a certain effect on our physiology, but some women simply may not feel like that at all,” notes Keay. “We can’t apply one blueprint for all women.”

The key to tailoring your training is to get to know your own cycle. Keay recommends downloading a cycle mapping app to track your performance (you could try Jennis or Clue) or to simply just record symptoms in a paper diary. 

By doing so you can intuitively work out which days of the month feel best for you, building a training plan that’s unique to you and your cycle.  

Words: Liz Connor