Persistent fatigue, recurring injuries, declining performance, irregular or absent periods… What if these signs were not simply caused by overtraining?
In an episode of the BPM by RunMotion Coach podcast, elite athlete and sports physician Marion Delespierre discusses a syndrome that is still too little known in the running and trail running world: RED-S, or Relative Energy Deficiency in Sport.
This syndrome affects many female athletes, sometimes without them even realising it. Yet, if it is not identified early enough, it can have major consequences for health, performance and recovery.
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What is RED-S?
RED-S is a chronic energy deficiency. In other words, the body does not receive enough energy to meet the demands of training, metabolism and essential bodily functions at the same time. The body runs short of fuel and has to prioritise where it uses its resources.
The concept was developed by the International Olympic Committee in 2014 to expand on the “female athlete triad” and better account for all the consequences of prolonged low energy availability.
While RED-S can affect all athletes, it is particularly common in endurance disciplines such as trail running, marathon running, triathlon, cycling, swimming and ultra-endurance events. Contrary to popular belief, it does not only affect elite athletes. Recreational female athletes can be affected too.
Why are female endurance athletes at greater risk?
Women who take part in endurance sports often face several factors that can lead to low energy availability. Training volume can be high without nutrition being adjusted accordingly. This may be compounded by the pursuit of a lower race weight, insufficient recovery, a high mental load or a lack of awareness of women’s specific energy needs.
Some female athletes feel that they eat a balanced diet while unknowingly remaining in a chronic energy deficit. When this situation continues, the body gradually reduces energy expenditure on functions that are not essential for immediate survival. The hormonal system, bone health, fertility, immunity and recovery can all be affected.
RED-S symptoms you should not ignore
RED-S usually develops gradually. Many female athletes continue training for months, or even years, before understanding the source of their struggles.
Unusual fatigue, slower recovery, a drop in performance or recurring injuries should raise concern. Stress fractures, sleep disturbances, a persistent feeling of cold, irritability and loss of motivation can also be warning signs.
For women, the menstrual cycle is a particularly valuable health indicator. Irregular periods or their complete absence, known as amenorrhea, should never be considered a normal consequence of intense training. They often indicate a hormonal imbalance related to insufficient energy availability.
Why RED-S also harms performance
In endurance sports, it can be tempting to associate weight loss with better performance. Yet, when an energy deficit becomes established, the opposite often happens.
The body has fewer resources to recover, build muscle, adapt to training sessions and improve. Performance plateaus, fatigue increases, injuries become more frequent and recovery takes longer.
As Marion Delespierre explains on the BPM by RunMotion Coach podcast, preventing RED-S is not only a health issue. It is also an essential requirement for long-term progress.
What are the long-term consequences?
Untreated RED-S can have significant effects on several body systems.
Bone health is often among the first areas affected. Reduced bone mineral density increases the risk of stress fractures. Hormonal function can also be disrupted over the long term, leading to persistent menstrual disturbances and, in some cases, fertility issues.
There can also be consequences for mental health, including chronic fatigue, anxiety around food and an obsession with performance that may gradually take hold. Finally, the immune system becomes more vulnerable, increasing the likelihood of infections, inflammation and episodes of overtraining.
How can you prevent RED-S in trail running and running?
Prevention starts with a better understanding of your body’s needs.
It is essential to consume enough energy to cover the demands of training. Eating well is not always enough. You also need to eat enough food for your training load.
Prolonged food restriction and repeated dieting increase the risk of low energy availability and should be avoided, especially during periods of intensive training.
Tracking your menstrual cycle is also an excellent health indicator. Any significant change deserves attention rather than being dismissed as normal.
Finally, recovery is an integral part of training. Quality sleep, lower-load days and appropriate training planning allow the body to recover and keep progressing. Because needs change throughout the menstrual cycle and at different stages of life, it is also important to individualise your training.
When should you seek professional advice?
If several symptoms persist despite reducing your training load or taking a few days of rest, it is recommended that you consult a healthcare professional who understands women’s sport.
Depending on the situation, a sports physician, sports dietitian, gynaecologist, endocrinologist or strength and conditioning coach can help identify possible RED-S and put suitable support in place.
Even today, this syndrome remains widely underdiagnosed, including among experienced female athletes.
Women’s trail running: know your body to go the distance
Through this Women’s Trail Running series, we want to remind you that listening to your body is not a barrier to performance. On the contrary, it is one of the keys to sustainable progress.
A better understanding of female physiological characteristics helps prevent injuries, improve recovery and fine-tune training. It is also the best way to build a trail running and endurance practice that supports good long-term health.
Listen to the BPM by RunMotion Coach podcast episode
In this episode, Marion Delespierre explains what RED-S is, why it particularly affects female endurance athletes, how to recognise the early signs and which habits can help prevent it.
🎧 RunMotion Coach Podcast: RED-S and female endurance athletes