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Running and Running related Injuries – RED-s

Part 2 of our Series on Running and Running Injuries

RED-S: The Invisible Risk for Athletes – Understanding, Identifying, and Treating It

The passion for sports drives many athletes to train harder, whether to achieve peak performance or improve personal fitness. But what happens when energy intake doesn’t keep up with energy expenditure? The result could be Relative Energy Deficiency in Sport (RED-S).

Relative Energy Deficiency in Sport (RED-S) – a complex syndrome with serious health and performance-related consequences. This article explores what RED-S is, how it develops, the associated risks, and how physiotherapy can help prevent and treat it.

What is RED-S? A Definition

What is RED-S? A Definition

RED-S stands for Relative Energy Deficiency in Sport, a syndrome that can affect both female and male athletes. According to the 2023 consensus definition by the International Olympic Committee (IOC), it arises when the body’s energy intake is insufficient to simultaneously support vital functions and athletic demands. This condition, also referred to as Low Energy Availability (LEA), negatively impacts almost every body system and carries both health and performance risks (1).

How Does an Energy Deficit Develop?

An energy deficit can result from various causes, often due to a combination of factors. Many athletes simply consume too little food—whether by skipping meals, poor meal planning, or unconscious oversight. Sometimes, however, it is intentional: the desire for an idealized body image or the attempt to reach certain athletic goals leads to eating less than the body actually needs (2,6).

But the demands of intense training sessions also play a major role. Increased training volume significantly raises energy expenditure. If the diet is not adjusted accordingly, the body cannot make up the resulting energy gap. In the long run, this inadequate supply puts the body under excessive strain (4).

The result? The body goes into “power-saving mode” and tries to conserve energy wherever possible. This adaptation can have serious consequences—both for health and for athletic performance.

Common Consequences of RED-S

RED-S leaves its mark throughout the entire body, affecting both physical and mental health. The body responds to the energy deficit by adjusting its metabolism: resting energy expenditure is reduced to save energy. However, this means that basic bodily functions can no longer be optimally carried out—a condition that significantly impairs health in the long term.

One particularly sensitive system is the hormonal system. Women often experience the absence of menstruation (amenorrhea), while men may be diagnosed with low testosterone levels. Both conditions not only impact athletic performance but also general recovery and well-being (1,2).

Bone health also suffers under RED-S. The body is unable to provide adequate resources for bone stability and regeneration, leading to decreased bone density that significantly increases the risk of painful, long-lasting stress fractures (2,4). At the same time, the immune system is weakened: those who suffer from a prolonged energy deficit become more susceptible to infections and illnesses (1).

Even the cardiovascular system is not spared. Elevated cholesterol levels and other cardiovascular risk factors can appear, endangering long-term heart health (3).

These complex bodily changes illustrate just how serious the consequences of RED-S can be—often underestimated and in need of timely recognition.

Impact on Athletic Performance

RED-S not only has far-reaching effects on health but also significantly influences athletic performance. The energy deficit resulting from insufficient nourishment hampers many of the fundamental processes crucial for athletic success.

One commonly observed problem is decreased endurance. When the body’s energy stores—especially glycogen reserves—are not sufficiently replenished, the foundation for sustaining longer or more intense efforts is lacking. This is particularly noticeable in endurance sports, where a stable energy supply is essential (1). At the same time, the risk of injury increases markedly. Reduced bone density, a key consequence of RED-S, raises the likelihood of stress fractures. These injuries often develop gradually and can lead to lengthy downtime if the strain persists (4).

Additionally, training effects are often less pronounced than they would be with a healthy energy status. The body simply cannot make the adaptations needed for performance improvements. This results in stalled or absent progress—a particularly frustrating state for ambitious athletes (1).

Muscle strength also suffers due to the energy deficit. The general weakness many affected individuals experience is a direct consequence of inadequate nutrient supply. Without sufficient energy, the body can neither build muscle nor maintain previous levels of strength under stress (1).

The combination of these factors demonstrates how substantially RED-S can limit athletic performance. Early intervention is vital to protect not only health but also athletic achievements.

Psychological Factors in RED-S

Psychological aspects play a central role in both the development and persistence of RED-S. They not only influence the behavior of those affected but also often exacerbate the physical consequences of the energy deficit. Three key factors frequently come into play.

Eating Disorders and Disordered Eating
A distorted relationship with food is one of the most common psychological traits associated with RED-S. Many athletes become overly fixated on calorie intake, body weight, and body composition. The desire to achieve certain athletic or aesthetic goals often leads to intentional food restrictions. While these restrictions may be seen as “discipline” in the short term, they create a chronic energy deficit in the long term and endanger overall health (6).
Insufficient Nutrition Planning
Not every energy shortfall is deliberate. Especially during phases of intensive training or periods of increased performance pressure, nutrition is often simply neglected. The lack of a structured meal plan or insufficient knowledge about the body’s actual energy needs leads many athletes to unknowingly slip into a deficit. This demonstrates how crucial it is to have comprehensive support that also addresses nutritional aspects (2).
Exercise Addiction as an Intensifier
Exercise addiction—an obsessive need to train—can further worsen RED-S. Those affected feel compelled to continue training even when ill or exhausted. This behavior not only increases energy expenditure but also interferes with the essential recovery period. Exercise addiction is often driven by a strong desire to control one’s body or a need for validation. While it is not the primary cause of RED-S, it significantly amplifies the problem and hinders recovery (7,8,9).

Diagnosis and Screening: Early Detection is Key

One of the biggest challenges in RED-S is that it is often diagnosed late. Many individuals only recognize the syndrome when health consequences are already substantial—persistent fatigue, hormonal imbalances, or even injuries such as stress fractures. Yet early detection is crucial to prevent long-term damage and safeguard the performance and health of athletes.

Screening Tools: Prevention Through Targeted Questions and Examinations

To identify an energy deficit early on, the International Olympic Committee (IOC) recommends specific questionnaires. Particularly effective are:

LEAF-Q (Low Energy Availability in Females Questionnaire): Specifically developed to detect signs of low energy availability in women.
LEAM-Q (Low Energy Availability in Males Questionnaire): A similar questionnaire tailored to the specific needs of male athletes (5).

In addition, medical examinations play a key role in the diagnostic process. Checking bone density can give an early warning of problems before serious injuries like stress fractures occur. Hormone analysis—especially estrogen levels in women and testosterone levels in men—also provides valuable insight into whether the body is getting enough energy (5,6).

Treatment and Prevention: A Multidisciplinary Approach

Treating RED-S requires an interdisciplinary team comprising sports medicine, nutrition counseling, psychology, and physiotherapy. The goal is to restore the balance between energy intake and energy expenditure and help affected athletes develop a healthy approach to training and nutrition (3,6).

Adjusting Nutrition

A central step is increasing energy intake. The diet should include a balanced ratio of carbohydrates, proteins, and fats to meet the body’s basic needs while supporting athletic demands. Regular, sufficiently sized meals are also crucial. Professional nutritional counseling can help identify individual needs and set realistic goals (2).

Modifying Training Volume

In addition to nutrition, reducing training intensity and volume is essential. Targeted adjustments allow the body the necessary recovery time to repair the damage caused by an energy deficit. Coaches and physiotherapists can help develop a balanced training plan that promotes recovery without losing sight of the athlete’s overall objectives (6).

Psychological Support

Because RED-S often involves psychological factors such as disordered eating behaviors or compulsive training, psychological support is indispensable. Cognitive Behavioral Therapy (CBT) can help individuals recognize and change unhealthy thought patterns. A key focus is developing a healthy relationship with food, body image, and exercise. Moreover, psychological care also supports managing performance pressure and building alternative coping strategies (7,9).

The Role of Physiotherapy in Managing RED-S

The Role of Physiotherapy in RED-S

Physiotherapy occupies a central position in the treatment and prevention of RED-S. Physiotherapists guide individuals back to healthy physical resilience and play a crucial role in preventing future injuries and relapses (6).

Key Physiotherapeutic Measures

A fundamental component of physiotherapeutic care is education. Athletes learn how overtraining and insufficient energy availability negatively impact the body. This knowledge transfer forms the foundation to avoid future energy deficits and to achieve a long-term balance between training and recovery (1,5).

Targeted exercises help strengthen bone density and reduce muscle weakness. This not only increases the body’s resilience but also lowers the risk of injuries such as stress fractures. Stabilization exercises are particularly important to improve biomechanics and minimize improper loading—an essential part of rehabilitation (4).

Physiotherapists also assist with a controlled return to training. Through close monitoring, they ensure that the body is not overtaxed and can gradually adapt to increasing demands. Individual training plans and regular assessments support a safe and effective recovery process (6).

Conclusion: Raising Awareness and Minimizing Risks

RED-S is a serious syndrome that can significantly impair both the health and performance of athletes. Often, an energy deficit arises not only from intentional calorie restriction but also from inadequate nutritional planning or the increasing demands of intensive training phases. Psychological factors such as eating disorders and an obsessive relationship with sports, including exercise addiction, can further exacerbate the problem.

A comprehensive approach – incorporating early detection, tailored adjustments to diet and training, and professional support, especially through physiotherapy – is essential to mitigate the consequences of RED-S and ensure sustainable performance.

Do you have experiences with RED-S, eating disorders, or questions about the topic? Share this article on social media and let us know your thoughts. We look forward to your feedback!

Sources

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