In the days before their period, many of the women I work with sleep less well, find their workouts heavier and feel hungrier, with more sugar cravings. Those who keep exactly the same routine all month often come unstuck at that point, with food as much as with motivation. That week, I keep the sessions, lighten them, and plan a little more food.
What research has measured
The most thorough study to date compared each woman with herself, at the end of the follicular phase, when oestrogen peaks, then in the middle of the luteal phase, when progesterone is at its highest. The participants were young, healthy women with very regular cycles and no hormonal contraception, followed for months to pin down their ovulation. Muscle building and breakdown were then measured over a whole week, and there was no difference between the two phases. You can build muscle at any point in the month.
These studies involve small groups, over a few days or a few weeks, and they measure what happens inside the muscle fibre. Fatigue, sleep, appetite and the urge to get to the gym are not part of it, yet that is where things play out over several months.
Why that week feels so hard
After ovulation, body temperature rises slightly, which makes effort feel harder, especially in the heat. The body is working to build the uterine lining, appetite goes up, and sleep often gets worse during those few days. A session can feel harder without the weight you lift going down, and it is that feeling that decides whether you come back the following week.
Not every woman is affected to the same degree. Some are at their lowest on the first day of their period and can barely get out of bed. Others set personal bests that very day, so much so that I can sometimes guess their period has started just by watching their session.
How a few days end up costing you muscle
Take a woman who wants to lose fat while keeping her muscle, eating 300 calories a day below her needs for three weeks. If hunger takes over in the last week of her cycle and four days go 1,500 calories over her needs, almost the whole month's deficit is wiped out. She did what she had to for three weeks and her shape does not change. If your weight has not moved for weeks, I go through the other possible causes in the article on a weight-loss plateau.
Sleep plays a part too. A few poor nights every month mean less complete recovery and weaker sessions afterwards. And forcing an intense session when you are exhausted often leads to sloppy technique, sometimes a small injury, and then sessions you end up skipping.
Track yourself for two or three cycles
Apps that tell you which phase you are in work from a theoretical calendar, and the body often strays from it. Two women with a 30-day cycle can ovulate one on day 9 and the other on day 19. For two or three months, without changing anything, note each day the day of your cycle, counting the first day of your period as day 1, your energy and motivation on a scale of 1 to 5, the quality of your sleep, your hunger and sugar cravings, and what you lifted.
If a pattern emerges, you know which week to lighten. If it does not, keep your routine, you are one of the women who go through the month without much variation.
The lighter week in practice
Keep the same sessions and lighten them. Do two sets instead of three or four, stop each set when you feel you still have two or three reps left, and reduce the weight a little on the most demanding exercises, such as Bulgarian split squats or Romanian deadlifts. Abductions and cable exercises, which are not very tiring, can stay as they are. A slightly lighter week will not cost you muscle.
If the bar across your hips becomes uncomfortable during hip thrusts, switch to kickbacks or quadruped hip extensions. You can also swap a heavy squat for leg presses or lunges, or an intense session for walking, mobility work, yoga or swimming. On the days when nothing feels right, with cramps, nausea or real exhaustion, I do not push, I shorten the session and keep the exercises you enjoy rather than cancelling it.
In Building muscle as a woman, the three-session-a-week programme includes this lighter week, with the exercises to lighten and the ones that can stay as they are.
Your plate in the week before your period
Rather than fighting late-cycle hunger, I prefer to plan for it. That week, increase your protein and whole carbs from the Totem list a little, such as rice, potatoes, sweet potatoes or fruit, with complete meals that genuinely fill you up. Keep high-protein snacks within reach for craving moments, a high-protein yoghurt for example.
This small surplus, planned in advance, costs far less than several days of unplanned overeating, and it leaves you energy for your sessions. Look after your sleep on those days too, it often makes the biggest difference to fatigue.
When to see a doctor
Periods that become irregular or stop in a woman who trains a lot and eats little are often the first sign of a lack of energy, and always warrant a conversation with a doctor.
This article is for information only and does not replace medical advice.