Ovulation: what it is and how it affects your training

What ovulation is

The ovary releases an egg, triggered by the surge of luteinising hormone (LH). It is the point that separates the follicular phase — where oestrogen has been climbing — from the luteal phase, where progesterone takes over. It usually comes with a small rise in basal temperature, which is why temperature methods confirm it: they detect it once it has already happened, not before.

Day 14 is an average, not your cycle

This is the most widespread error, and it is not harmless: if you infer your phase by counting days, you land in the wrong phase more often than you think. In the reference study on the fertile window, on EVERY day between day 6 and day 21 there was at least a 10% chance of being in the fertile window. And only around 30% of women had that window fall entirely between the days 10 to 17 named in classic guidance — most reached it earlier, and others considerably later (Wilcox et al., 2000).

The knee: the real fact and the useless advice

The true part: the sex difference in anterior cruciate ligament injury is large and well documented. In comparable sports, the rate in women was 2.49 times that of men at college level and 2.30 times at high school (Stanley et al., 2016). From there people very often jump to a recommendation that does not hold: lower the intensity or avoid certain movements around ovulation. There is no evidence that this reduces injuries, and skipping training has a cost that is certain.

What does work, and by how much

Here the evidence is solid and surprisingly practical. Preventive neuromuscular training programmes — landing mechanics, valgus control, strength and balance — substantially reduce anterior cruciate ligament ruptures.

• Recent meta-analysis: pooled relative risk of 0.46, a little under half the ruptures (Watson et al., 2026)
• Translated into real-world numbers: from 1 rupture in 54 athletes to 1 in 111 (Petushek et al., 2019)
• The average dose of effective programmes: about 24 minutes per session, 2-3 times a week — a little over an hour weekly
• The effect was larger in younger athletes: under 18, relative risk dropped to 0.35

And eating around ovulation?

Little you can turn into a rule. Intake tends to be at its lowest around ovulation and to rise afterwards in the luteal phase (Dye and Blundell, 1997), which fits with many women finding it easier to eat well on these days. Use that if it helps — batch-cooking on these days for the week ahead is a reasonable idea. What has no basis is changing your macronutrient split: the substrate-oxidation meta-analysis finds no differences between phases (D'Souza et al., 2023).