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Relative Energy Deficiency in Sport (RED-S)

What is RED-S?

Relative Energy Deficiency in Sport (RED-S) refers to a condition in which energy imbalance leads to impaired physiological function of multiple organ systems. 

RED-S is thought to be primarily caused by low energy availability (LEA) due to low energy diets, be it intentional or unintentional, and is often combined with the harmful aspects of overtraining syndrome and/or excessive exercising; thus, creating a relative negative energy imbalance. 

What is Low Energy Availability? 

LEA may be intentional, with the athlete intentionally restricting their dietary intake, or unintentional, in which the athlete's nutrition simply isn’t meeting the demands of their training load. Be it intentional or unintentional, the athlete will suffer the same implications to their health and performance. 

  • Intentionally: the athlete is restricting their diet, common in sports such as cross country running and gymnastics where weight effects overall performance. This can be difficult to manage as the athlete must address their complex relationship with food and psychology.

  • Unintentionally:  the athlete is not getting the energy availability out of their diet that their sports demand. This can be easier to manage as it may be sufficient to simply educate the patient on the nutritional demands of their training load. 

Who is most likely at risk of RED-S?

  • Most common in sports that unite the importance of a thin body type and success - gymnastics, figure skating.

  • Sports with frequent weigh ins – boxing, rowing 

  • Endurance sports – cycling, marathon running.

  • Regardless of the sport, team culture and coaching staff’s attitudes can contribute to the risk of RED-S in an athlete 

The understanding of REDS and its symptoms are poorly known by athletes and coaches therefore if often goes undiagnosed and untreated - this stresses the importance of the role of physiotherapists and sports clinicians in identifying the symptoms in their patients. 

What is the impact of RED-S on my health?

  • Bone Health – LEA causes a chronic state of hypoestrogenism which leads to lone bone density. 

  • Endocrine Health – negatively effects thyroid function.

  • Menstrual Health - can range from abnormal bleeding to amenorrhea which is when the female’s period is absent for more than 90 days. 

  • Fertility - due to the absence of ovarian follicular development, anovulation, or luteal-phase defects, menstrual dysfunction can further lead to infertility in females. 

  • Metabolic Implications 

  • Gastrointestinal Implications

  • Psychological – In individuals with REDS, there is an increased prevalence of eating disorders and disordered eating. This has significant implications for psychological well-being, by potentially exacerbating low self-esteem, anxiety and depression.

What is the impact of RED-S on my performance?

  • Increased risk of injury – stress reactions, stress fractures due to poor bone health 

  • Poor concentration 

  • Fatigue and poor recovery 

  • Impaired judgement 

  • Neuromuscular performance and reaction times are reduced. 

  • Impaired co-ordination 

  • Negative influence on muscular strength - because of a negative impact on muscle protein synthesis.

  • Negative influence on endurance performance – because of a negative impact on mitochondrial protein synthesis and strength

What is the role of the physiotherapist in treating RED-S?

Often patients will present to physios with injuries that have been a repercussion of RED-S. Most often this is a bony injury – stress reaction/fracture and/or an overuse injury that has not healed fully. In this case the physio should look out for other red flags such as: 

  • Oligomenorrhea/amenorrhea

  • Recent weight loss

  • Restrictive eating and body dysmorphia

  • Recurrent illnesses

  • Cardiac abnormalities

It is important for physios to be able to identify RED-S and ensure the patient gets proper screening. A multi-practitioner, patient-centred approach is needed to treat both the physical and psychological health implications. Management strategies should include:

  • Education

  • Optimising energy availability – altering diet. 

  • Modification of exercise and training – in some case this means only low impact exercise if BMD is very low or stopping exercise completely for a period of time.

  • Mental health support

Physiotherapists can modify and monitor an athlete’s activity levels during recovery, prescribe an appropriate training schedule for the athlete, and develop treatment goals for the patient. 


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