Your Metabolism Shifts Throughout Your Menstrual Cycle—So Should Your Training.

One week, your endurance is effortless, intervals feel smooth, and you recover fast. The next, your legs feel heavy, your heart rate is higher than usual, and everything feels harder than it should.

It’s not a coincidence. It’s your cycle.

Your menstrual cycle isn’t just a reproductive cycle—it’s a metabolic cycle that affects how you burn fuel, regulate energy, and recover. Understanding it will enable you to train and fuel in a way that works with it rather than against it.

Menstrual Phase (Days 1–5): The Reset

Oestrogen and progesterone are at their lowest, and so is your energy. Blood volume drops slightly, meaning less oxygen reaches your muscles, making endurance work feel harder. You may notice a higher heart rate at a given intensity, slower recovery, and an overall feeling of fatigue.

At the same time, insulin sensitivity is high, meaning your body uses carbohydrates more efficiently, and lactate clearance is improved, so if you feel up to it, high-intensity work is still possible. However, longer aerobic sessions may feel more taxing.

By day three or four, oestrogen starts rising, and energy levels often follow.

Best Training Approach

Short, higher-intensity efforts like interval training are well supported due to efficient carbohydrate metabolism. Long, steady-state endurance sessions may feel harder due to lower oxygen delivery and blood volume. If fatigue is high, focus on lower-intensity movement, such as Zone 2 work, or take an extra rest day.

Best Fuelling Strategy

Carbohydrates are well tolerated, so they should be prioritised to fuel training. Ensure iron-rich foods (red meat, spinach, legumes) are included to counteract potential losses from menstruation. Hydration is also key, as fluid balance may be slightly reduced.

Follicular Phase (Days 6–14): The Performance Window

Oestrogen is rising, and so is your ability to sustain harder efforts. Your body becomes more efficient at using both carbohydrates and fat for fuel, meaning steady-state and high-intensity work are both well supported. Mitochondrial efficiency improves, glycogen storage increases, and lactate is cleared more effectively.

This is the phase where everything feels good. Strength, endurance, and power output are all at their peak. You can push harder, recover faster, and adapt better to training.

Best Training Approach

High-intensity interval training (HIIT), VO2 Max and threshold work are all well supported. Longer endurance rides or runs also feel easier, as fat and carbohydrate metabolism are both optimised. This is the ideal time to push both volume and intensity.

Best Fuelling Strategy

Carbohydrate availability is key to supporting high-intensity sessions, so focus on fuelling before and afterworkouts. Protein intake should remain high to support muscle recovery and adaptation. Hydration is easier to maintain, but electrolytes can still aid recovery.

Ovulation (Days 12–15): The Edge

Oestrogen peaks, and for a few days, you may feel stronger and faster than usual. However, this hormone spike also increases joint laxity and collagen turnover, meaning ligaments and tendons are slightly more prone to strain.

Your aerobic system is still functioning optimally, but recovery may take slightly longer. If you feel unusually fatigued after a hard session, this could be why.

Best Training Approach

High-intensity work is still well supported, but this is the time to pay extra attention to warm-ups, mobility, and technique—especially during explosive efforts. Aerobic endurance remains strong, making this a great time for sustained efforts at threshold.

Best Fuelling Strategy

Continue prioritising carbohydrates for high-intensity sessions. Protein intake should remain high to support muscle repair, and omega-3-rich foods (salmon, walnuts, flaxseeds) can help manage inflammation and support tendon health.

Luteal Phase (Days 16–28): The Shift—Endurance Rises, Intensity Drops

Progesterone dominates, and your body begins relying more on fat for fuel. While endurance work remains well supported, high-intensity efforts feel harder due to reduced carbohydrate metabolism and lower glycogen storage.

Resting metabolic rate increases by 5–10%, meaning your body burns more calories at rest. While this might sound beneficial, it also raises overall energy demands, which—combined with shifts in fuel metabolism, higher core temperature, and increased sweat losses—can contribute to earlier fatigue and slower recovery. You may notice a higher heart rate during workouts and slower lactate clearance.

As oestrogen and progesterone drop toward the end of this phase, PMS symptoms can peak—low energy, disrupted sleep, and reduced motivation.

Best Training Approach

Shift towards longer, steady-state endurance work (Zone 2 and tempo efforts) and lower-rep strength training. High-intensity intervals may feel harder, so reducing frequency or intensity can help maintain quality without excessive fatigue.

Best Fuelling Strategy

Carbohydrates are still needed but may not be as efficiently stored, so spreading intake throughout the day can help maintain energy. Increasing healthy fats (avocados, nuts, olive oil) can support the body’s increased reliance on fat oxidation. Hydration needs increase, so prioritising electrolytes is key.

Work With Your Cycle, Not Against It

Your cycle isn’t a barrier to endurance performance—it’s a tool for optimising it. Fuel utilisation shifts, recovery fluctuates, and your ability to sustain intensity changes week to week. While these patterns are well-documented, every athlete’s response is unique. Some feel strongest mid-luteal, others notice little variation at all.

You don’t need to overhaul your training programme, but knowing when to push and when to adjust can be the difference between progress and burnout.

Tracking your cycle—whether through an app or simply by noting energy levels, performance, and cravings—helps you recognise your own patterns, anticipate changes, and adapt your training accordingly. Over time, this allows for more informed decisions about fuelling, recovery, and training load, so you can work with your cycle rather than against it.

References:

1. Menstrual Cycle Hormonal Changes and Energy Substrate Metabolism: Research supporting how hormonal fluctuations affect exercise physiology, particularly energy substrate metabolism and macronutrient oxidation. https://pubmed.ncbi.nlm.nih.gov/34639326/

2. Influence of Menstrual Cycle Estradiol-β-17 Fluctuations on Energy Substrate Utilisation-Oxidation during Aerobic, Endurance Exercise: Examines how estradiol affects energy metabolism across the menstrual cycle, particularly fat and carbohydrate utilisation. https://www.mdpi.com/1660-4601/18/13/7209

3. The Influence of the Menstrual Cycle on Substrate Metabolism during Exercise: Highlights how oestrogen and progesterone impact substrate metabolism in female athletes. https://www.physoc.org/abstracts/the-influence-of-the-menstrual-cycle-on-substrate-metabolism-during-exercise-applications-for-female-athletes/

Individual responses to hormonal changes vary. Tracking personal trends and adapting training accordingly is the best approach for long-term performance.