posted 10th April 2026
As a coach, I’ve sat across from athletes who are doing "everything right." They hit their interval splits, they never miss a Sunday long run, and their discipline is solid. Yet, they are stuck. Their performance has plateaued, their sleep is fractured, and they feel like they are fighting a losing battle against their own biology.
Often, they think they need to train harder. They think they need to "clean up" their diet even more.
But the truth is usually the opposite. They are hitting an invisible ceiling known as RED-S (Relative Energy Deficiency in Sport). Understanding RED-S isn’t just for elite, Olympic-level athletes. It is an important concept every endurance athlete—especially the Female Masters athlete—should aim to master if they want to remain competitive and healthy for a lifetime.
What is RED-S?
In 2014, the term RED-S was introduced by the International Olympic Committee (IOC). Updated 2023 https://www.olympics.com/ioc/news/ioc-publishes-new-consensus-statement-on-relative-energy-deficiency-in-sport-reds-to-protect-athlete-healthThe definition recognises that energy deficiency doesn't just affect your period or your bones; it affects every single system in the human body, from your heart and your metabolism to your immune system and your brain.
RED-S is a state of Low Energy Availability (LEA). It occurs when there is a mismatch between the energy you take in through food and the energy you expend during exercise, leaving your body with nothing left to run on.
Systemic Fallout : Why Every Athlete Should Care
When you live in a state of energy deficiency, you aren't just "leaner." You are functionally breaking your internal hardware.
The Skeletal System and Bone Health
As we discussed in our Strength Primer, oestrogen is a bone-protector. When you are in RED-S, your body downregulates reproductive hormones to save energy. This leads to a drop in oestrogen, which effectively turns off your bone-building cells. For a Masters athlete, this is a fast track to stress fractures and early-onset osteoporosis.
The Hormonal Command Centre and Cortisol
RED-S triggers a massive rise in Cortisol (your stress hormone). Chronically high cortisol is the enemy of the Masters athlete. It causes muscle breakdown, promotes mid-section weight gain, and disrupts your sleep.
The Nervous System (The Software)
Our "Infinite" philosophy is built on the Central Nervous System (CNS). RED-S is the ultimate CNS disruptor. Without enough glucose, your brain cannot maintain focus, your Mental Spark vanishes, and your Heart Rate Variability (HRV) will stay consistently low or "Red," no matter how much you rest.
The Masters Nuance: RED-S vs. Menopause
This is where it gets difficult for the Female Masters athlete. The symptoms of RED-S almost mimic the symptoms of perimenopause and menopause.
- Brain fog? Could be low oestrogen... or it could be low glycogen.
- Poor sleep? Could be night sweats... or it could be a cortisol spike from under-fuelling.
- Fatigue? Could be age... or it could be your body powering down to survive your training load.
Many women in this transition mistakenly try to "train harder" or "eat less" to combat menopause weight gain, which inadvertently pushes them straight into RED-S. This creates a "perfect storm" of hormonal chaos that can end a sporting career prematurely.
Red Flags: How to Spot the Deficit
As your coach, I’m looking for these subtle signals that your energy balance is off:
| Category | Warning Signs |
|---|---|
| Physical | Recurring "niggles" or stress injuries, constant coldness, low resting heart rate, or digestive issues. |
| Performance | Stalled progress, inability to hit high-intensity intervals, and prolonged recovery times. |
| Psychological | Irritability, loss of "Mental Spark," and an unhealthy obsession with "clean" eating or the scale. |
| Physiological | (If still cycling) Irregular periods or a sudden loss of the cycle. |
The Infinite Solution: Balancing the Scales
At Infinite Endurance, we don't believe in "grinding" through a deficit. We believe in fuelling for the work required. Here is how we balance the energy equation:
1. No Fasted Training
Fasting is a massive stressor for the Female Masters CNS. By eating even a small amount of carbs and protein before your workout, you signal to your brain that "energy is abundant," preventing the cortisol spike that leads to RED-S.
2. The 30g Protein Floor
Protein is the building block of your "hardware." Ensuring 30–40g of protein at every meal—especially post-workout—helps protect your lean muscle mass and supports bone repair.
3. Cycle-Aligned Fuelling
If you are in perimenopause, your energy needs change throughout the month. During your Luteal Phase, your metabolic rate actually increases. You need more calories and more carbohydrates during this time. If you don't adjust, you fall into a deficit by default.
Final Thoughts: Longevity is the Ultimate PB
Pull yourself away from the culture that celebrates "doing more with less." In the world of endurance, "less" eventually leads to "nothing."
RED-S isn't a sign of discipline; it's a sign of a broken strategy. My goal as your coach isn't to see how lean we can get you; it's to see how powerful and resilient we can make you.
When you balance your energy, you aren't just fuelling a run. You are fuelling your bone density, your heart health, your cognitive function, and your ability to keep doing what you love for the next thirty years.
Stop fighting the machine. Start fuelling the mission.
Reflection for the Week
Look at your Weekly Athlete Reflection. Under "What felt hard?", did you notice a lack of energy or a "flat" feeling? Compare that to your fuelling log. Is there a gap?
The following sample day is designed for an athlete performing a moderate-to-high intensity session (e.g., a 60-minute interval run or a heavy strength session).
A DAY IN THE LIFE: Optimal Fuelling for the Masters Athlete
This day focuses on the "Infinite" pillars: No fasted training, the 30g protein floor, and CNS-supporting carbohydrates.
| Time | Milestone | Goal | The Plate / Drink | The "Why" (Physiology) |
|---|---|---|---|---|
| 06:30 | The "Pre-Flight" Snack | Signal "energy abundance" to the brain and lower cortisol | 1 banana or a slice of sourdough toast with almond butter or honey | Training fasted in perimenopause signals a "scarcity" state to the CNS, triggering a cortisol spike; this snack protects muscle and mood |
| 07:00 – 08:00 | TRAINING SESSION | Maintain fluid and nerve function | Water with added electrolytes (Sodium, Potassium, Magnesium) | Prevents dehydration and supports muscle contraction and nerve conduction |
| 08:30 | Recovery "Window" (Breakfast) | Hit the 30g protein floor and refill glycogen | 3-egg omelette with spinach and feta, plus oats with berries/seeds OR a 35g protein smoothie | Post-training, the body is catabolic (breaking down); Protein + Carbs within 90 minutes shifts it to anabolic (repair) |
| 12:30 | The Fuelling Lunch | Prevent the "3 PM Brain Fog" crash | "Power Bowl" with 150g chicken/tempeh, quinoa/sweet potato, avocado, and vegetables | Complex carbs support the thyroid and stabilise blood sugar, preventing afternoon energy dips |
| 15:30 | The CNS "Bridge" Snack | Keep cortisol low during workday stress | Greek yogurt with walnuts OR an apple with peanut butter | Gaps that are too long between meals can trigger a stress response; this snack keeps the CNS calm |
| 19:00 | The Restorative Dinner | Support overnight repair and hormone production | Baked salmon or tofu, steamed broccoli/asparagus, and 1 cup of brown rice or baby potatoes | Omega-3s lower inflammation, while carbs help produce serotonin—a precursor to the sleep hormone melatonin |
| 20:30 | The Nighttime Ritual | Deepen non-interrupted sleep | Tart cherry juice mixed with a Magnesium glycinate supplement | Tart cherry juice provides natural melatonin; Magnesium downregulates the nervous system |
THE FUELLING AUDIT: How Does This Compare?
| The "Red Flag" Day | The "Infinite" Day |
| 06:00 Black coffee only | 06:30 Banana + 15g carbs |
| 09:00 Green juice after run | 08:30 35g Protein + Oats |
| 13:00 Salad with no carbs/protein | 12:30 Quinoa, Chicken, & Veggies |
| 19:00 Huge pasta meal (starving) | 19:00 Balanced Salmon & Rice |
| Result: High Cortisol, Poor Sleep | Result: Stable Energy, CNS Recovery |
Final Tip on Fuelling
The most common mistake can be "back-loading" calories—eating very little all day and a massive meal at night. To prevent RED-S, we want to front-load your energy. Eat more around your training window when your body is "ready" to use it. This tells your brain it is safe to build bone and muscle.
