Trail Notes | Female Athlete Racing

Oh no, my period falls on race day!

Racing in the

luteal phase.

You cannot reschedule the race. But you can understand what your body is doing and stop fighting it on the start line.

The race date is set. Your cycle does not care. For roughly half of your training cycles you will be racing in the luteal phase — days fifteen to twenty-eight — where progesterone is elevated, resting heart rate is slightly higher, core temperature starts higher, and your gut processes food more slowly. None of this makes you slower. But all of it changes how the race should be managed.

The research on female pacing strategy at ultra distances shows no consistent sex-based difference in how races are run — but it does show that the athletes who struggle most are the ones who let early RPE signals panic them into slowing before they need to, or push through those signals and blow up by hour four. Knowing what is hormonal versus what is performance helps you separate the two.

Trail Note  ·  01

What is actually different

Resting heart rate increases by two to five beats per minute in the luteal phase. This means your heart rate zones — if you use them — are sitting artificially high at any given effort level. A pace that felt like a solid Zone 2 in week two of your cycle may feel like Zone 3 in week three. It is the same fitness. It is a different hormonal environment.

Core temperature at rest is approximately 0.3 to 0.5 degrees higher in the luteal phase. In practice, this means your thermoregulatory system reaches its ceiling earlier in warm conditions, and you begin sweating at a lower ambient temperature. At trail events where conditions are warm or weather is unpredictable — which is most of them in Australia — this is a meaningful variable.

Gastric emptying slows under elevated progesterone. Food sits longer, liquid moves more slowly. For an athlete fuelling with sixty to ninety grams of carbohydrate per hour across a ten-hour event, this is the variable most likely to end her race early if she has not trained for it specifically.

Trail Note  ·  02

How to adjust on race day

RPE becomes your primary tool. Heart rate is not a reliable anchor in the luteal phase — it will read higher than effort justifies, and chasing zones will either slow you unnecessarily or cause you to dismiss signals you should not. Use breathing and leg feel instead. Can you speak five words? That is your check.

Fuel earlier and smaller. Rather than waiting for the standard forty-five to sixty minute fuelling window, move your first intake to the thirty-minute mark and keep portions slightly smaller and more frequent. The goal is to keep the gut working continuously rather than filling it at intervals it may struggle to process.

Hydrate with sodium rather than plain water wherever possible. Progesterone-driven fluid retention increases hyponatraemia risk — drinking large volumes of plain water compounds this. Sports drink, broth at aid stations, or electrolyte tablets alongside water all manage this more safely than water alone.

If conditions are warm, plan for more aggressive cooling from the start. Ice under the collar, wet sponges at aid stations, starting slightly slower than you otherwise would. The thermoregulatory ceiling is lower in this phase — you are not weaker, you are just managing heat differently.