What the research shows once you start taking cycling training seriously: almost everything you read about periodisation, intervals, recovery, and fuelling was built on research done on men.
Not just mostly men. Almost exclusively men. Before 2010, fewer than six percent of sports science studies included female subjects. Six percent. The entire edifice of training advice that you absorb through podcasts, coaching platforms, and club rides was constructed on data from bodies that do not experience a monthly hormonal cycle. And then it got handed to everyone as though it were universal.
It is not. Your body does not respond the same way on day five of your cycle as it does on day twenty-two. And once you understand why, you can stop fighting your physiology and start working with it.
Let me be really clear about this before we go any further. I am not a woman, I do not have lived experience of any of this, and I am not going to pretend otherwise. What I have done is spent a lot of time with the researchers and practitioners who have dedicated their careers to female athletic physiology — people like Dr Stacy Sims, Dr Kirsty Elliott-Sale, and Dr Georgie Bruinvels — and what follows is their science, applied to your bike.
The four phases and what is actually happening
Your menstrual cycle is roughly 28 days, though anywhere from 21 to 35 is normal, and it breaks into four distinct phases. Each one shifts the hormonal environment your muscles, cardiovascular system, and nervous system are operating in.
Phase one is menstruation, typically days one through five. This is where both oestrogen and progesterone are at their lowest. Despite what you might assume, this is not necessarily your worst phase for performance. It is a hormonal reset.
Phase two is the follicular phase, running from the end of menstruation through to ovulation, roughly days six to thirteen. Oestrogen is climbing steadily. This is where things get interesting from a training perspective, and we will come back to it.
Phase three is ovulation, a brief window around day fourteen where oestrogen peaks and there is a small surge in luteinising hormone. Some research suggests a slightly higher injury risk here due to oestrogen's effect on ligament laxity, though the evidence is still being debated.
Phase four is the luteal phase, from after ovulation through to the start of menstruation, roughly days fifteen to twenty-eight. Progesterone rises sharply and oestrogen has a secondary, smaller peak before both drop off a cliff in the final days before your period. This is where the most significant performance implications sit.
That is the textbook version. Your version will differ. Cycle length varies, phase length varies, and hormonal contraception changes the picture entirely. But the underlying mechanism is consistent enough to be useful.
When to push: the follicular window
The early to mid follicular phase — after menstruation, before ovulation — is when most women are best set up for high-intensity work. The research here is fairly consistent, and Sims has been making this case for over a decade through her books ROAR and Next Level.
Rising oestrogen during this phase does several useful things at once. It has an anti-catabolic effect on muscle tissue, which means your muscles are better protected during hard efforts and recover more efficiently afterward. Pain tolerance tends to be higher. Glycogen stores are more accessible, so you can fuel high-intensity efforts more readily. And for most women, perceived exertion at a given power output is lower than it will be two weeks later.
This is your window for the sessions that matter. Threshold intervals. VO2max work. The efforts where you need to be mentally and physically sharp and where you are asking your body to produce and recover from genuine training stress.
Stephen Seiler's polarised training model — the 80/20 split between easy and hard that we have discussed extensively on the Roadman Podcast — still applies here. You are not throwing out the structure. You are placing your hard sessions where your body is most ready to absorb them. The follicular phase is where those 20 percent high-intensity sessions land best.
Kirsty Elliott-Sale's research group at Nottingham Trent has done some of the most rigorous work on exercise performance across the menstrual cycle, and one of their consistent findings is that the follicular phase advantage is real but modest in population-level data. At the individual level, though, the differences can be pronounced. Which is exactly why tracking matters, and we will get to that.
When to back off: the luteal reality
Here is where it gets really interesting, because the luteal phase is where most women feel the training plan stop working, and it is entirely explainable once you understand the hormonal shift.
Progesterone is the dominant hormone in the luteal phase, and it does three things that directly affect your training.
First, it is thermogenic. Sims' research shows that women in the high-hormone luteal phase have a resting core temperature roughly half a degree Celsius higher than in the follicular phase. Half a degree does not sound like much until you understand that your body starts active cooling at a set point above resting temperature. Starting closer to that threshold means you overheat faster and your cardiovascular system is working harder to manage temperature before you have even started producing real watts.
Second, progesterone reduces plasma volume. Less blood volume means less oxygen delivery to working muscles at any given cardiac output. Your capacity to sustain high-end aerobic work is measurably reduced, not just a perception issue.
Third, progesterone is catabolic. Where oestrogen protects muscle, progesterone breaks it down. The recovery environment in the luteal phase is less favourable for hard training adaptation.
Put those three together and the picture is clear. The late luteal phase is not the time for your biggest interval session of the block. It is not the time to chase a power PB. And it is definitely not the time to do a hard session in thirty-degree heat and wonder why you blew up at a power you normally handle.
This does not mean you stop training. It means you shift the emphasis. Steady endurance rides. Skill work. Technique focus. Lower-intensity volume that builds your aerobic base without asking your compromised thermoregulatory and recovery systems to do more than they comfortably can. Think of it as your base training window within the month.
The heat problem nobody talks about
The thermoregulation issue deserves its own section because it catches people out, especially in summer racing.
Sims has written extensively about this, and the practical implications are significant. When you start a session or a race with core temperature already elevated, your time to exhaustion in the heat is reduced. Your perceived effort at the same absolute intensity is higher. And the usual cooling strategies — pre-cooling, ice vests, cold drinks — become more important, not less.
If you are racing or doing a big event that falls in your luteal phase, you need to plan for it. Pre-cool more aggressively. Start hydration earlier. Accept that your power numbers may be a few percent below what you would produce in the follicular phase and pace accordingly rather than trying to match numbers that belong to a different hormonal state.
Georgie Bruinvels' work at Orreco, tracking menstrual cycle data across elite athletes, has shown that awareness alone makes a difference. Athletes who know where they are in their cycle and adjust expectations perform more consistently than those who train and race as though every day is the same. It is not about lowering ambition. It is about being realistic with today's physiology.
Iron: the hidden fatigue driver
One more thing that gets overlooked, and it is directly fixable once you know about it. Menstrual blood loss means iron loss. Iron is essential for haemoglobin, which carries oxygen to your muscles. Chronic low iron — even without full-blown anaemia — shows up as persistent fatigue, flat performance, and sessions that feel harder than they should for reasons your training log cannot explain.
Female endurance athletes are already at higher risk of iron deficiency because of the combination of menstrual loss, training-induced haemolysis from repetitive impact, and sometimes inadequate dietary intake. If you are consistently tired, your power is flat, and you cannot explain it through training load or sleep, get your ferritin checked. Not just your haemoglobin — your ferritin, which shows iron stores rather than just circulating levels.
This is not a training periodisation issue. It is a health issue with direct performance consequences. And it sits underneath everything else in this article, because no amount of clever phase-based periodisation will help if you are iron-depleted.
How to actually periodise a training block
So how does this look in practice? Here's something you can actually use.
In the early follicular phase, roughly days one through five during menstruation, start easy if you need to and ramp up as you feel ready. Many women find that days two or three onward feel surprisingly good for training, and there is no hormonal reason to hold back once discomfort subsides.
In the mid to late follicular phase, roughly days six through thirteen, schedule your hardest sessions here. Threshold work, VO2max intervals, race simulation efforts. This is your performance window, and it is where the biggest training adaptations are most available.
Around ovulation, days thirteen to fifteen, you may feel strong but be slightly more mindful of connective tissue if you are doing off-bike loading work. On the bike, push if you feel good.
In the early luteal phase, days fifteen to twenty-one, you may still feel fine. Moderate intensity is workable for most women here. Listen to your body and do not force high-end efforts if perceived exertion is climbing at the same power.
In the late luteal phase, days twenty-two to twenty-eight, shift toward endurance volume, recovery rides, and lower-intensity work. Fuel more deliberately before and during sessions. Accept that your numbers may drop a few percent and do not chase them. This is your recovery and aerobic base window.
That is a framework, not a rulebook. And this is the point I want to land hardest on.
Your pattern is yours
Everything above is population-level science. It describes what happens on average, across groups, in controlled studies. Your body is not an average. Some women feel their absolute strongest during menstruation. Some sail through the luteal phase without noticing a thing. Some have a clear and predictable pattern. Others have a cycle that varies month to month in ways that make phase-based planning notably difficult.
Elliott-Sale's research makes this point consistently: individual variation in performance across the menstrual cycle is larger than the average phase effect. Which means the most important thing you can do is not follow a generic phase-based plan. It is to build your own data set.
Track for at least three full cycles before making any structural changes to your training. Log your cycle day, your energy on a simple one-to-five scale, your session quality, your sleep, and any symptoms. You do not need expensive technology for this. A notes app works. FitrWoman or Wild.AI will automate the cycle-day tracking. Bruinvels' work at Orreco started with exactly this kind of self-reported data and it was enough to identify meaningful patterns in elite athletes.
After three months, look at your data. Do your best sessions cluster in a particular phase? Do your worst? Is there a three-day window where you consistently feel flat? That is your pattern. Build around it.
Start here
If this is new to you, do not try to restructure your entire training plan overnight. Start with awareness. Know what day of your cycle you are on when you train. Write a one-line note after each session about how it felt relative to what you expected. After a few months, the patterns will emerge on their own.
And if you want to go deeper on this and train with a community that takes this stuff seriously, the Roadman community on Skool is where we do exactly that. Real conversations about training, physiology, and performance — including the stuff that mainstream cycling culture has been slow to catch up on.
The good news is this. The science exists. The researchers have done the work. The gap is not knowledge anymore — it is application. Your training plan does not have to pretend you are a man. It just has to be honest about your physiology, flexible enough to move with it, and built on your own data rather than someone else's assumptions.