The Hardest Conversation.
Trail Notes | Female Athlete Health
knowing when to hold the line
The Hardest
Conversation.
RED-S is not a failure of willpower or commitment. It is what happens when energy demand exceeds energy supply for long enough that the body begins to protect itself by shutting down systems it considers non-essential. Our job as coaches is not to diagnose it. It is to notice, to name what we are seeing, and to hold a clear line about what we can and cannot support.
Relative Energy Deficiency in Sport, known as RED-S, sits at one of the most uncomfortable intersections in coaching: the place where training, health, body image, identity and clinical responsibility meet. It requires us to be informed enough to recognise the signs, boundaried enough to not step into the role of clinician, and caring enough to have a conversation that the athlete may not want to have.
This Trail Note is written for coaches and athletes both. If you have ever found yourself wondering whether something is not quite right, or wondering how to raise it, this is the resource we wish had existed earlier.
RED-S is not a diet problem, a training problem, or a mindset problem in isolation. It is an energy availability problem with wide-reaching consequences for performance, health and long-term athlete wellbeing.
The earlier it is recognised, the better the outcome. Which is why the coach's ability to notice matters enormously.
Trail Note · 01
What RED-S actually is
RED-S was defined by the International Olympic Committee in 2014 as a broadening of what was previously called the Female Athlete Triad. Where the Triad focused on the relationship between low energy availability, menstrual dysfunction and low bone density, RED-S recognises that energy deficiency affects far more systems than those three alone.
When energy availability drops below what the body needs to maintain basic physiological function, it begins rationing. Reproductive function is often one of the first things affected. So too is bone metabolism, immune function, thyroid function, cardiovascular health, mood regulation and cognitive performance.
RED-S can be intentional, through deliberate restriction, or inadvertent, through the combination of high training load and insufficient fuelling without conscious awareness of the gap. Both require the same response: increasing energy availability with appropriate clinical support.
Trail Note · 02
Why trail runners are at risk
Female trail runners occupy a sport with a specific set of risk conditions. Training volumes are high. Sessions are long. The aesthetic culture of trail running, while generally more diverse than road running, still carries undercurrents of leanness being valued. Social media amplifies this. And the endurance athlete identity can make it genuinely difficult to separate self-worth from training capacity.
Prevalence data on RED-S in trail running is limited, but studies across endurance sports consistently show rates of low energy availability in female athletes ranging from 40 to over 60 percent, with many athletes unaware they are in deficit.
Trail Note · 03
The signs a coach can see
We are not in a clinical position to diagnose. But we are in a relational position to notice. Over time with an athlete, we develop a sense of what is usual for them. When something shifts in a way that training alone does not explain, that is the signal to pay attention.
Signs that may indicate energy deficiency
Persistent fatigue that does not respond to rest or reduced load.
Performance declining despite adequate training.
Menstrual cycle changes: irregular cycles, missing periods or a loss of periods that were previously regular.
Frequent illness or slow recovery from minor infections.
Stress fractures or recurring bone injuries.
Mood changes, increased anxiety, irritability or emotional withdrawal.
Comments that suggest preoccupation with food, weight or body composition.
Describing specific foods or eating patterns in increasingly rigid, rule-based ways.
Not every athlete with RED-S will show every sign. Some will show very few. The absence of an obvious presentation does not mean energy availability is adequate. Periodic loss of menstrual function in female athletes has historically been normalised as a side effect of high training, when in fact it is a clinical flag.
Trail Note · 04
What is not our job as coaches
It is not our job to assess whether an athlete has RED-S. It is not our job to prescribe a nutrition plan, evaluate bone density, or determine what a healthy body weight looks like for a specific person. It is not our job to comment on an athlete's body shape or size, to suggest they eat more or eat differently, or to estimate their energy balance.
And critically: it is not our job to keep training an athlete who we have concerns about while waiting for those concerns to resolve themselves. Continuing to prescribe high training loads to someone who may be energy deficient is not support. It is complicity.
Our job is to notice, to name what we are seeing with care, to refer to the right people, and to hold the line on training load while that process unfolds.
Trail Note · 05
The referral conversation
Raising concerns is hard. Athletes may feel defensive. They may minimise what is happening. They may feel that if they acknowledge something is wrong, it confirms a fear they have been carrying quietly. Going gently and clearly at the same time is a skill worth practising.
A framework for the conversation
Name what you have observed, not what you believe the cause is. "I have noticed your fatigue has not improved with rest. Your performance has also been declining despite the training you are doing."
Express care without diagnosis. "I am not in a position to tell you what is going on, but what I am seeing suggests it would be worth speaking to a doctor who understands the specific demands of female endurance athletes."
Be clear about training load. "While you are working through this, I am going to modify your training. I am not able to continue prescribing high loads when I have these concerns. This is me looking after you."
Useful referral points include a GP with sports medicine background, a sports dietitian, a psychologist with experience in athletes or eating concerns, and in more complex cases, a specialist in the Female Athlete Triad or RED-S.
Trail Note · 06
Modifying training load
When RED-S is suspected, the standard principle is to reduce training load rather than continue or increase it. This is not indefinite rest, and it does not mean abandoning the athlete's goals entirely. It means reducing volume and intensity while energy availability is being addressed and medical assessment is in process.
Her Trails coaching cue
Reducing training load in this situation is not failure. It is the right call. An athlete who recovers well from RED-S and returns to training with their health protected has a far better trajectory than one who pushes through to a bone fracture or a longer health crisis.
Trail Note · 07
Supporting the athlete through the process
Once referral has been made, the coaching relationship can continue in a supportive but bounded way. Your role shifts from prescribing training to providing consistent, non-judgmental connection. Check in. Be interested in how the person is going, not just whether their numbers are improving.
Do not speculate about timelines for returning to full training. Do not offer reassurances about performance that you cannot guarantee. And do not let the athlete's desire to return to full training pressure you into removing restrictions before the medical team has cleared them.
You are the coach, not the clinician. Your job is to hold the relational space and the training boundary while the medical team does theirs.
Trail Note · 08
When the athlete resists referral
Some athletes will push back. They will minimise what is happening, tell you they are fine, or express frustration that you are raising it at all. You can acknowledge their resistance without withdrawing your concern. You can say clearly: "I hear you. And I still have concerns I am not able to set aside. My care for you as a person is more important than keeping our coaching relationship comfortable."
If an athlete is unwilling to seek medical support and is asking you to continue prescribing high-load training that you have genuine concerns about, you are not obligated to do so. A coaching relationship built on one person's health being put at risk to avoid an uncomfortable conversation is not a relationship either person benefits from.
Her Trails coaching cue
Holding a boundary is not abandoning an athlete. It is refusing to participate in something that could harm them. That is good coaching. Sometimes it is the best coaching you will ever do.
Trail Note · 09
What recovery from RED-S looks like
Recovery from RED-S is possible and full athletic careers have continued after it. The process usually involves increasing energy availability under the guidance of a sports dietitian, reducing training load until energy availability is restored, and monitoring the return of menstrual function and bone health markers.
Return to training is gradual and led by the medical team. As a coach, your role in this phase is to resist the temptation to accelerate progression because the athlete is feeling better. Better is not the same as fully recovered, and many athletes hit setbacks when load is reintroduced too quickly. Patience from the coach during this phase is one of the most active and important things you can offer.
Trail Note · 10
Looking after yourself as a coach
Navigating RED-S with an athlete is one of the more emotionally demanding things coaching asks of you. You may feel unsure if you are reading the situation correctly. You may worry about damaging the relationship. You may carry a level of responsibility for the athlete's wellbeing that feels heavier than usual.
Connect with other coaches or a supervisor if you are unsure. Document your observations and the conversations you have had. Understand your duty of care and where your professional limits sit. And remind yourself that doing the hard thing for the right reason, even when it is uncomfortable, is the highest expression of what this work is.
The line you hold as a coach may be the most important coaching decision you make for that athlete.
Not the session plan. Not the race strategy. The moment you say: I care enough about you to do this difficult thing.
Trail Note · 11
If you are reading this as an athlete
If something in this piece has landed close to home, we want you to know this: recognising a problem early is not weakness. It is the smartest athletic decision you can make. RED-S, caught and addressed early, does not have to define your running story. Ignored, it can rewrite it in ways that take far longer to recover from.
If your period has been absent or irregular and you have normalised that as part of being a serious runner, please speak to a doctor. If you feel flat and exhausted in a way that rest is not fixing, please speak to a doctor. If your relationship with food has become rigid, anxious or rule-bound in ways that affect your daily life, please reach out to a professional who understands both athletes and eating.
Your best running years are not behind you because of a period of energy deficiency. But they may well be ahead of you once you have the support you need to move through it.
health first, performance always follows
Written by the Her Trails coaching team
Trail Notes are evidence-informed coaching journals written for women who train, race and run on trails. Made to be absorbed in ten minutes and remembered for a season.
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