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Overreaching and RED-S: are they the same?

Exercise physiology Ph.D candidate Alexandra Coates explains how the two are different, and where they overlap

Over the last few years, issues like relative energy deficiency in sport (RED-S), overtraining and disordered eating have become major topics of discussion in the running world. Many runners are hearing these terms for the first time, and are using them interchangeably, as is often the case with two terms in particular: RED-S and overreaching. While there is some crossover between the two, they are not the same. We spoke with runner, triathlete, exercise physiology Ph.D. candidate and c0-founder of the OneAthlete Project, Alexandra Coates, who explained why they are different and where they intersect.


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Overreaching vs. RED-S

As Coates explains, overreaching is a short-term reduction in performance due to inadequate recovery relative to training stress. It can last days to weeks in the case of functional overreaching, or weeks to months in the case of non-functional overreaching. She says overreaching tends to occur following training camp-type training blocks, where an athlete increases their training load for around three weeks and starts to see a decline in performance by the end of the block. She notes this is different from overtraining syndrome, which is the prolonged maladaptation of several biological, neurochemical, and hormonal regulation mechanisms, and can often take years to resolve.

RED-S, on the other hand, is driven exclusively by low-energy availability and causes disruptions to metabolic rate, menstrual function, bone health, immunity, muscle growth and repair and cardiovascular health. Low energy availability, Coates explains, is the mismatch between an athlete’s energy intake, or diet, and the energy expended during exercise, leaving inadequate energy to go toward health and athletic performance.

RELATED: Nutrition advice for runners dealing with RED-S

What’s the difference?


While researchers are still divided as to whether overreaching can occur independently of an energy deficit, Coates believes it is possible. “I think about it as a Venn diagram, where on one side you can have overreaching without low-energy availability, in the middle you have both, and on the right, you have RED-S without overreaching,” she says.

In the case of overreaching, most of the symptoms tend to appear during training. Symptoms include:

  1. reduced performance in training (not being able to hit your typical paces)
  2. a reduction in heart rate at a given pace/intensity of running
  3. faster heart rate recovery (how fast your heart rate returns to baseline) when you stop running
  4. feelings of being “unable to push” in workouts

Coates says symptoms of low energy availability and RED-S are most easily identifiable in menstruating athletes who are not on hormonal birth control, because they will experience disruptions in their menstrual cycle. Other symptoms include:

  1. lower resting heart rate and blood pressure
  2. reduced bone mineral density
  3. an initial weight loss (followed by stabilization and/or an increase in weight despite the caloric deficit)
  4. blood markers including increased cortisol and cholesterol, and decreased fasting glucose, insulin, IGF-1, ferritin, leptin, thyroid hormones and sex hormones (estrogen, testosterone)

RELATED: New tool to assess RED-S in males 

When they overlap

We know that low-energy availability and RED-S reduce an athlete’s ability to adapt and respond appropriately to training,” explains Coates, “so over a long period of low-energy availability, performance will likely be reduced. Performance will also be reduced when athletes have increased illnesses and injuries (particularly bone injuries) driven by low energy availability.”

Secondly, she adds that often when athletes increase their training load, they don’t also increase their caloric intake, which will cause this co-occurrence of overreaching and low energy availability. Finally, when you don’t eat enough to support your activity, your training stress will increase while your ability to recover properly will be impaired, which can be a driver for overreaching. 


Coates’ advice to runners

If you think you may be experiencing symptoms of RED-S, Coates encourages you to increase your calorie intake, especially around training. She also strongly recommends against fasted training and restrictive diets and to make sure you aren’t going long periods without eating (no four-hour windows without food). She emphasizes the importance of carbohydrates and says runners should make sure they’re taking in some carbs immediately after a workout, even if it’s just a sports drink.

With overreaching, the best thing to do is recognize that digging yourself into a hole isn’t going to make you faster, so if you feel like you are very fatigued and not able to push in a session, take a recovery day, even if it wasn’t planned,” says Coates. “High-intensity training seems to drive overreaching faster than volume, so if you have a lot of high-intensity work in your training plan, you also need a lot of recovery days.”

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