Moderate movement supports your hormones. The risk sits at one specific extreme. Here's where the line is, and how your cycle tells you when you've crossed it.
Something that comes up a lot: can working out too much affect your fertility?
It's a fair question, especially if fitness is a real part of your life. The last thing you want is to find that something you do for your health is quietly working against another part of it.
Here's what the research shows.
Regular, moderate exercise supports hormonal health in some direct ways. It improves insulin sensitivity, which matters a lot if you have PCOS (polycystic ovary syndrome), since insulin resistance is one of the main drivers of the hormonal imbalances that come with it. It also keeps cortisol, your primary stress hormone, from staying chronically elevated, which is important because high cortisol can disrupt the signals between your brain and your ovaries.
Women who exercise consistently at moderate levels tend to have more regular cycles and better ovarian function than women who are sedentary. So the baseline is simple: movement is a good thing.
The concern is about a specific pattern at the other extreme.
Your body has priorities. When energy availability drops significantly, whether from training hard, undereating, or both at once, it reads that as sustained stress. And under sustained stress, it starts to conserve resources.
Reproduction gets deprioritised. The hormonal pathway responsible for ovulation, called the HPO axis (hypothalamic-pituitary-ovarian axis, the chain of signals from your brain to your ovaries that triggers ovulation each month), begins to quieten down. The hormones that normally drive follicle development, ovulation, and progesterone production get weaker. Sometimes they stop altogether.
In practice, this can show up as irregular cycles, delayed or absent ovulation, a shortened luteal phase (the second half of your cycle, more on that below), or in more severe cases, periods stopping completely. The medical term for that last one is hypothalamic amenorrhoea.
This has a name in sports medicine: RED-S, or Relative Energy Deficiency in Sport. It was originally thought to affect only elite athletes, but research over the past decade has broadened that picture considerably. It can happen to anyone who is consistently burning more than they're replenishing, regardless of how seriously they train.
The key point: intensity alone isn't the issue. It's the ratio of energy out to energy in. Women who train at high volumes but eat enough to support that training often don't experience any disruption at all.
Your cycle is one of the best feedback mechanisms you have.
If your periods have become irregular since your training increased, with longer gaps between them, shorter cycles, or skipped months, that's data worth paying attention to rather than explaining away.
The luteal phase is worth knowing about too. It's the stretch between ovulation and your period, ideally around 12 to 14 days. Consistently under 10 days can affect the conditions needed for implantation, which matters if you're trying to conceive. Most people don't track it, but if you do, it's useful information.
Other signals: fatigue that doesn't improve with rest, noticeable mood changes, and performance that stalls even though you're training consistently. These all point to the same thing, output exceeding recovery.
To an extent, yes.
Strength training at moderate intensity has solid evidence for supporting hormonal health, particularly for insulin regulation. Walking, yoga, and Pilates are consistently well tolerated and beneficial from a hormonal standpoint. Not just lower impact, but good for your cycle.
High-intensity cardio and distance running aren't inherently a problem. The question is load: how often, at what intensity, and whether your nutrition and recovery are matching what you're asking of your body.
For most women who exercise regularly, this isn't something to worry about. The specific risk zone is high training volume, sustained, without enough fuel. That combination is more common than people expect, but it's also quite specific.
If your cycle has shifted alongside a change in your training, it's worth a proper conversation with a specialist rather than adjusting your routine on your own. A baseline fertility assessment gives you the actual numbers to understand what's going on.
If you've noticed changes in your cycle and aren't sure whether they're training related, a fertility assessment is a good starting point. We can look at your hormone levels, including AMH (a measure of your egg reserve), and give you a clear picture of where your reproductive health sits today. From there, you'll know what, if anything, needs attention.
Does exercise lower egg count? Exercise doesn't reduce your ovarian reserve. What overtraining combined with energy deficiency can affect is ovulation, whether an egg is released in a given cycle. Your total reserve, measured by AMH, isn't meaningfully changed by your exercise habits.
Is yoga good for fertility? There's evidence that yoga supports cortisol regulation and menstrual regularity. It's one of the most well tolerated forms of movement from a hormonal standpoint, and more than just a gentler alternative.
Can I exercise during an egg freezing cycle? During ovarian stimulation, most clinics recommend skipping high-intensity work and anything with a twisting or impact risk. The ovaries are enlarged during stimulation, which raises the risk of torsion (the ovary twisting on itself, as uncomfortable as it sounds). Light walking is generally fine. Your clinical team will walk you through the specifics.
How do I know if I'm overtraining? Your cycle is the clearest signal. Irregular or absent periods, a shortened luteal phase, persistent fatigue, and plateauing performance are all worth paying attention to. If a few of these show up together, it's worth speaking to a doctor.
The Pearl Journal is an editorial publication from Pearl by Zoi Fertility. Content is for informational purposes and does not constitute medical advice. For personalised guidance, book a consultation with our clinical team.
