Fertility and Exercise: How Much Is Too Much?

When I was trying to conceive, I was doing HIIT four times a week. I felt strong, fit, and healthy. And I had absolutely no idea that my workout routine might be working against my fertility.

Nobody told me — and I see this same story with my clients all the time. My GP didn't mention it. The fertility articles I read talked about diet and supplements, but exercise was always a footnote — "stay active" — without any nuance about what kind, how much, or why it matters.

So let me be the one to tell you — and I always say this with care: exercise and fertility have a much more complex relationship than most people realise. And finding the right balance changed everything for me.

How Exercise Affects Your Fertility

In my experience working with women trying to conceive, exercise isn't inherently good or bad for fertility — it's about dose, intensity, and type. The research consistently shows a J-shaped curve: moderate exercise improves fertility outcomes, while too much can impair them (Gudmundsdottir et al., 2009).

The good news: Regular moderate exercise (150 minutes per week of brisk walking, swimming, cycling, or similar) improves insulin sensitivity, reduces inflammation, helps maintain a healthy BMI, and lowers cortisol — all of which support ovulation and fertility (Hakimi & Cameron, 2017).

The complication: Vigorous exercise — especially when combined with a calorie deficit — can suppress the hypothalamic-pituitary-ovarian (HPO) axis, which controls ovulation. Your brain essentially decides your body is under too much stress to support a pregnancy, and it shuts down reproductive function (Loucks et al., 1989).

This isn't about being "too fit." It's about energy availability — whether your body has enough fuel left over after exercise to run all its other systems, including reproduction.

The Evidence: What Studies Actually Show

Let me walk you through the key findings from the research, because the picture is more nuanced than "exercise is good" or "exercise is bad."

Moderate exercise improves fertility: A large Danish cohort study found that women who did moderate exercise (walking, cycling, swimming) for 5 or more hours per week had a significantly shorter time to pregnancy compared to sedentary women — about 2.4 months faster (Gudmundsdottir et al., 2009).

Vigorous exercise can delay conception: The same study found that women doing more than 7 hours per week of vigorous exercise (running, aerobics, competitive sports) took longer to conceive — about 3 months longer on average.

IVF outcomes: A review in Fertility and Sterility Reports found that regular moderate exercise before and during IVF either had no effect on cycle success or a small beneficial effect (Morris et al., 2023). However, one earlier study found that women exercising more than 4 hours per week had slightly reduced IVF success rates (Morris et al., 2006).

Body fat matters: Women with very low body fat (under 17-22%) are more likely to experience amenorrhoea (absent periods) because they don't have enough energy reserves to sustain both exercise and reproduction. This is common in elite athletes, dancers, and women doing very intense training (Drinkwater et al., 1984).

Signs You Might Be Exercising Too Much

If you're trying to conceive, watch for these signals that your exercise routine may be affecting your hormones:

• Irregular or absent periods
• Short luteal phase (less than 10 days between ovulation and period)
• Feeling exhausted despite sleeping well
• Getting sick frequently (weakened immune system)
• Difficulty recovering from workouts
• Loss of libido
• Hair thinning or brittle nails
• Feeling cold all the time

If you have two or more of these, it's worth having a conversation with your GP about whether your exercise intensity is contributing to hormonal disruption.

The Sweet Spot: What to Do Instead

Based on the evidence, here's what I recommend to my clients who are trying to conceive:

Keep exercising. Don't stop moving — sedentary lifestyles carry their own fertility risks. The goal is to find the right intensity, not to stop.

Aim for 150-300 minutes per week of moderate activity. That's roughly 30-45 minutes most days. You should be able to hold a conversation while exercising — if you can only gasp a few words, you're probably too intense.

Prioritise low-impact activities:

• Walking — the most underrated fertility exercise. Twenty to thirty minutes outdoors lowers cortisol and improves blood flow to the reproductive organs.
• Swimming — full-body, low-impact, excellent for stress reduction.
• Yoga — particularly fertility-focused or restorative yoga. Studies show yoga reduces cortisol and anxiety in women undergoing fertility treatment (Domar et al., 2015).
• Pilates — builds core strength and pelvic floor health without high impact.
• Cycling — gentle to moderate cycling is fine. Avoid very intense spin classes.

Scale back high-intensity training. If you currently do HIIT, CrossFit, or competitive running, consider reducing frequency to 1-2 sessions per week and filling the rest with moderate alternatives. You don't have to give it up completely — just rebalance.

Exercise by Cycle Phase

Your hormonal environment changes throughout your cycle, and your exercise can adapt accordingly:

Follicular phase (day 1 to ovulation) — You have more energy and can handle slightly higher intensity. This is a good time for brisk walks, light jogging, strength training, or moderate circuit work.

Ovulation (around day 14) — Exercise is fine, but if you're tracking ovulation, be aware that very intense exercise on ovulation day could theoretically affect implantation. Keep it moderate.

Luteal phase (ovulation to period) — Progesterone is dominant and you'll naturally feel less energetic. This is the time for gentle movement: walking, restorative yoga, swimming. Avoid starting new intense programmes in this phase.

Two-week wait (after ovulation) — There's no evidence that moderate exercise affects implantation. But many women prefer to be gentle during this time, and that's absolutely fine. Listen to your body.

For Women Doing IVF

Exercise during IVF cycles requires extra consideration. Most fertility clinics advise:

• Continue light to moderate exercise during stimulation (walking, gentle yoga)
• Avoid strenuous exercise once follicles are growing — enlarged ovaries can be at risk of torsion with vigorous activity
• After egg retrieval, take it easy for a few days. Walking is fine, but avoid anything that jostles your abdomen
• After embryo transfer, most clinics advise returning to normal moderate activity. Bed rest has not been shown to improve outcomes (Bar-Hava et al., 2000)

Always follow your clinic's specific advice — protocols vary.

Dani Recommends: Gentle Morning Movement

The Bottom Line

Exercise is one of the most powerful tools you have for supporting fertility — but only when you get the dose right. Moderate, consistent movement improves insulin sensitivity, reduces stress, and supports a healthy weight. Too much intensity, too often, can send your body into survival mode and shut down reproduction.

I learned this the hard way. I went from four HIIT sessions a week to gentle walks and yoga, and my cycle normalised within two months. That doesn't mean HIIT is bad — it means it was too much for my body at that time. Listen to yours. If you're exhausted, irregular, or not conceiving despite everything else being in order, exercise intensity might be the missing piece.

Frequently Asked Questions

References

1. Gudmundsdottir SL, Flanders WD, Augestad LB. Physical activity and fertility in women. Scand J Med Sci Sports. 2009;19(6):816-825. PubMed
2. Hakimi O, Cameron LC. Effect of exercise on ovulation: a systematic review. Sports Med. 2017;47(8):1555-1567. PubMed
3. Loucks AB, Mortola JF, Girton L, Yen SS. Alterations in the hypothalamic-pituitary-ovarian and the hypothalamic-pituitary-adrenal axes in athletic women. J Clin Endocrinol Metab. 1989;68(2):402-411. PubMed
4. Morris SN, Missmer SA, Cramer DW, Powers RD, McShane M, Hornstein MD. Effects of lifetime exercise on the outcome of in vitro fertilization. Fertil Steril. 2006;86(4):974-981. PubMed
5. Domar AD, Meshay I, Kelliher M, Alper M, Mahfoud Z. The impact of a group mind/body intervention on pregnancy rates in IVF patients. Fertil Steril. 2015;103(5):1345-1349. PubMed
6. Drinkwater BL, Nilson K, Chesnut CH 3rd, et al. Bone mineral content of amenorrheic and eumenorrheic athletes. N Engl J Med. 1984;311(5):277-281. PubMed
7. Bar-Hava I, Kerner R, Yoeli R, Ashkenazi J, Shalev Y, Orvieto R. Immediately initiated intravenous progesterone does not impair pregnancy rates after in vitro fertilization and embryo transfer. Fertil Steril. 2000;74(4):824-825. PubMed
8. Morris SN, Missmer SA, Cramer DW, et al. Maternal physical activity and sedentary behaviour before and during in vitro fertilization. Fertil Steril. 2020;114(5):1070-1078. PubMed

One thing I've noticed when speaking with people on their fertility journey is that exercise often becomes a source of guilt — either they feel they're not doing enough, or they're worried they're doing too much. The reality is that movement should feel supportive, not stressful. When exercise becomes another thing to "get right," it can add to the emotional burden that already comes with trying to conceive. I always encourage finding an activity you genuinely enjoy, because consistency comes from pleasure, not pressure.

It's also worth considering how exercise affects your sleep and stress levels — two factors that are deeply connected to fertility. Regular moderate activity helps regulate your circadian rhythm, which in turn supports the hormonal cascade needed for healthy ovulation. On the flip side, late-night high-intensity workouts can spike cortisol and interfere with sleep quality, creating a counterproductive cycle. I've found that morning or early afternoon exercise tends to work best for most people trying to balance activity with rest.

<2 id="exercise-during-ivf-and-fertility-treatment">Exercise During IVF and Fertility Treatment

If you're going through IVF or other fertility treatments, your exercise routine may need adjusting. During ovarian stimulation, your ovaries are enlarged and more sensitive, so high-impact activities like running, jumping, or heavy lifting can increase the risk of ovarian torsion — a rare but serious complication. Most fertility specialists recommend switching to gentle walking, light stretching, or prenatal yoga during this time. After embryo transfer, listen to your clinic's guidance, but gentle movement is generally encouraged and can help with stress management during the two-week wait.