Women, Hormones and the Ultra Long Run
Trail Notes · Evidence Informed
fuel the body that carries you.
The ultra long run is not just a training session. It is a hormonal event. How you fuel it, recover from it, and place it in your week shapes what your body decides to do next.
Endurance training places significant energetic demands on the body. For women, those demands sit alongside hormonal regulation, bone health, immune function and recovery capacity. When energy in does not meet energy out, the body shifts into a protective state called low energy availability. This Trail Note works through what that means on the ultra long run, how it interacts with the menstrual cycle and the menopause transition, and the practical fuelling moves that protect both the run and the runner.
Section 01 · The Hormonal Cost of the Ultra Long Run
Why the long day asks more from a woman's body
A four hour run is not four times a one hour run. As duration extends, the body works progressively harder to maintain blood glucose, body temperature, and muscle function. Stress hormones rise, glycogen stores deplete, and tissue damage accumulates. In women, that same long effort is layered on top of a hormonal system that is already doing complex work in the background.
What the long run touches
Cortisol and stress response. Long efforts elevate cortisol. Without enough fuel, that signal stays loud and starts interfering with reproductive and thyroid hormones.
Oestrogen and progesterone. Both shift across the cycle and across the years. They influence substrate use, fluid balance, recovery and perceived effort.
Bone turnover. Long, repetitive load with low fuel quietly raises stress fracture risk, especially with disrupted cycles.
Immune and gut function. Both blunt under chronic energy deficit, which shows up first as colds, niggles and gut sensitivity on long days.
Section 02 · Low Energy Availability
The quiet driver of most long course problems
Low energy availability happens when the calories left after exercise are not enough to support normal physiological function. It is rarely dramatic. It is usually a small daily gap that adds up across a build, especially as long runs grow.
Signals to take seriously
Persistent fatigue. Sessions feel disproportionately hard even when load has not increased.
Cycle disruption. Lengthening, shortening, or missed cycles. In peri and post menopause, hot flushes, sleep loss and mood shifts intensifying with training.
Slower recovery. Soreness lingers. Easy runs do not feel easy. Heart rate stays elevated overnight.
Frequent illness or injury. Repeated colds, niggles that move around, bony tenderness that does not settle.
Mood and motivation drop. Running stops feeling rewarding. Sleep gets light. Appetite becomes erratic.
Many runners assume that feeling depleted is just part of endurance training. It is not. Consistent energy availability is one of the most reliable predictors of sustainable performance, and one of the most common things to drift in a long ultra build.
Section 03 · Fuelling the Long Run
Numbers that protect the long day
These are starting points, not prescriptions. Bigger bodies, harder courses, hotter days will all push the numbers up. Use them as a floor, then adjust to what your gut and energy tell you.
Pre run
1 to 3 g of carbohydrate per kg body mass, 1 to 3 hours before. Familiar foods. Practise this on training long runs, not race day. Do not start a long run in a fasted state if it lasts more than 90 minutes.
During · Under 2 hours
30 to 60 g of carbohydrate per hour from a single carbohydrate source. Start fuelling in the first hour, before fatigue appears.
During · 2 to 3 hours
60 g per hour as a baseline. Begin shifting to a glucose plus fructose mix to improve absorption and reduce gut load.
During · 3 hours plus and ultra
60 to 90 g per hour using glucose to fructose at roughly 2:1 or 1:0.8. Build in planned shifts to real food, savoury options, soup or broth as the day wears on. Trained gut tolerance is required for the upper end.
Post run
Within the first hour, a meal or snack combining carbohydrate and protein. Roughly 1 g carbohydrate per kg with 20 to 30 g protein. Keep eating across the rest of the day. The long run is not finished when the watch stops.
Spread intake evenly across each hour rather than taking a large amount at once. Most women tolerate small repeated doses far better than larger irregular ones.
Section 04 · The Menstrual Cycle and the Long Run
Working with the cycle, not against it
A regular cycle is a sign that the body has enough fuel to run its hormonal systems. It is also a useful map. The two halves of the cycle ask slightly different things on the long run.
Follicular phase · Period to ovulation
Lower hormone levels overall. Many women find recovery faster, gut tolerance easier, and harder long efforts more sustainable here. Good window for higher carb loads, harder back to back days, key long sessions.
Luteal phase · Ovulation to period
Higher oestrogen and progesterone. Core temperature runs a touch hotter, heart rate sits higher at the same pace, and the body uses more fat at lower intensities. Hydration and sodium needs rise. Carbohydrate needs in the long run rise too, especially in the late luteal phase.
Period week
Iron loss and lower oestrogen can make the first one to three days feel heavy. Long runs are not off limits, but expect a slightly higher perceived effort. Eat more, hydrate more, and let the run be what it is on that day.
A disappeared cycle is information. It is not a performance win, and it is not "just what happens" with high mileage. It is a signal worth listening to.
Section 05 · Perimenopause and Beyond
The long run after oestrogen shifts
As oestrogen and progesterone decline through perimenopause and into post menopause, recovery slows, lean tissue is harder to maintain, and the body is less forgiving of under fuelling. The long run does not have to get smaller. It does have to get smarter.
Fuel earlier, fuel more
Aim for the upper end of carbohydrate ranges. Front load the run with breakfast. Take in something within the first 30 to 40 minutes. Do not save fuel for "when you need it."
Protein with intention
Aim for 25 to 40 g of protein at each main meal, with one serving within an hour of the long run. Total daily protein around 1.6 to 2.0 g per kg supports muscle maintenance in this stage.
Strength alongside the long run
Two short strength sessions per week, with real load, protect bone and lean tissue and make every long run more economical. This is not optional in this stage. It is what allows the long run to keep being possible.
Sleep and heat
Sleep gets thinner. Heat tolerance shifts. Move long runs earlier in the day, build cooling into your pre run routine, and treat sleep as a training input. A bad sleep week is a sign to soften, not to push.
Section 06 · Practical Habits Across The Build
Small daily moves that protect the big day
Habit 01
Eat before training when the session is long or hard. Fasted long runs are not a hormonal advantage. They are a fast track to under fuelling and disrupted cycles.
Habit 02
Refuel within the first hour after every key session. This is non negotiable. Carbohydrate plus protein, sitting down where possible, not standing in the kitchen.
Habit 03
Train the gut deliberately. Take target race carbohydrate amounts on long runs, not just race day. Practise the drink, the gel, the bar, the broth in the conditions you will actually meet.
Habit 04
Track signals, not just sessions. Cycle, sleep, mood, appetite, resting heart rate. Two or three of these drifting in the same direction is the early warning system.
Habit 05
Get help early. Sports dietitians and physicians who understand female athletes can shorten years of guessing. Bloods, bone scans and a structured review are not over reactions. They are how high performers stay healthy.
Section 07 · The Closing Word
Run long, but run fuelled
Consistent fuelling is not just about the next race. It protects the hormonal, structural and immune systems that make training possible in the first place. The runner who fuels her long days is the one still long running in five years, ten years, twenty.
your body is not the obstacle.
Fuel it. Trust it. Run with it.
Specialists We Recommend
Trusted experts in fuelling and hormones
Fuelling for Endurance
Tamara Madden
Specialist in fuelling for endurance sport. Trusted by Her Trails athletes for individual fuelling, energy availability and hormone informed nutrition support.
Hormone Experts We Recommend
Dr Kirstey Holland
Medical doctor with expertise in women's hormonal health across the lifespan. A trusted voice for runners navigating the menstrual cycle, perimenopause and post menopause with their training in mind.
Feature Conversation · One Hour with Dr Kirstey
An hour on hormones, training and women who run long
Sit down with us for an hour with Dr Kirstey Holland. A wide ranging conversation on the menstrual cycle, perimenopause, post menopause and what each of those means for the woman who keeps lacing up. Practical, honest, and built for runners.
Written by
Her Trails Coaching
Coaching built around women's physiology. Long runs that respect hormones, fuel, and the runner who has to live in this body tomorrow.
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