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Nutrition is an extremely essential component of an athlete’s lifestyle for performance purposes. Although overconsumption of food is a common issue in Australia today, it is not uncommon for athletes to under consume the recommended calorie intake for their level of activity. This can cause a serious syndrome called Relative Energy Deficiency in Sports (RED-S).

RED-S is more common in female athletes but can be an issue for both male and female alike. Put simply, an athletes calorie intake requirements often sit higher than a sedentary individual due to the amount of energy they burn to train. If an athlete does not consume enough calories to meet the demands of the activity, they’re expending more energy than they’re intaking. For women, the stress placed on the body from insufficient fuel can lead to a loss of menstruation (also known as amenorrhea). This tends to evolve into detrimental effects on the hormonal pathways in the body, including decreasing oestrogen levels, which can weaken bones. The end results from an sporting perspective is increased occurrence of stress fractures, reduced energy and endurance levels as well as reduced concentration. For female athlete’s the syndrome is characterised by these three issues; disordered eating, loss of menstrual periods and decreased bone mineral density. These three interlinking problems are often referred to as the female athlete triad.

It is important to note that NOT all three symptoms (poor calorie intake, amenorrhea and decreased bone mineral density) must be present to have a diagnosis of RED-S. Sometimes only two of the three components are present. Not only are stress fractures and low energy a concern when RED-S is occurring. RED-S has also been related to cardiovascular issues, lowered immunity, reduced protein synthesis and limitations on growth and development.

Symptoms to watch out for:

  1. The athlete hasn’t had their first period by the age of 16 or has missed three cycles not due to pregnancy (if female).
  2. The athlete has repeated stress fractures, shin splints or persistent hip pain.
  3. The athlete has a low body mass index

The bottom line for RED-S:

Not only will the performance of the athlete be compromised with RED-S, but a multitude of serious health risks can also occur. Therefore, it is particularly important that we educate both younger athletes, and coaches of athletes, to monitor any who may present with disordered eating habits/low eating habits/low BMI. Importantly, a simple lack of education regarding dietary intake requirements may be the causative factor; this can be rectified with some guidance to provide a dietary intake solution. It should however be noted that athlete stereotypes and mental health has the potential to play a major role for athletes with RED-S. Assistance regarding the athletes psychology should be sought where education alone is unsuccessful. If left untreated this syndrome could not only end an athlete’s career through injury, but could also have serious detrimental effects to long-term health – increasing the risks of cardiovascular disease and osteoporosis, both of which decrease life expectancy in individuals.

Stress Fractures:

Repetitive loading of bones can lead to increased stress within the bones. This then has the potential to develop into stress fractures as a result of fatigue failure of the bone. Stress fractures account for  up to 20% of all sports medicine clinic injuries under normal circumstances without additional influence from RED-S. Track and field athletes have the highest incidence of stress fractures (Brukner, Bennell & Matheson 1999).

In a normal environment, musculoskeletal integrity is maintained by a balance of fatigue damage with remodelling activity, stimulated by normal repetitive low-intensity loading forces. The rate of remodelling responds to the loads through the bone, which includes the forces transferred from surrounding muscle activity. High levels of bone stress, through an increase in activity, may lead to higher rates of fatigue damage where the remodelling response may not be able to cope. This then manifests clinically as a bone stress injury.

Overload can be applied to the bone through two mechanisms:

  1. The redistribution of impact forces resulting in increased stress at focal points in the bone.
  2. The action of muscle pull across the bone.

There are two important risk factors to consider for bone stress injuries. The first being a rapid increase or change in the load on the bone, the second being the energy imbalance between calories expended and calories taken in. As mentioned, energy imbalance causes hormone irregularity and impaired bone health.

A runner suffers from ankle pained centred at the Achilles tendon

Stress fractures can be categorised into low-risk and high-risk fractures. Low-risk fractures generally require no treatment other than rest. The sites where these fractures occur tend to be on the compressive side of the bone and respond well to activity modification. Low-risk fractures are also less likely to reoccur, become a non-union, or have any significant complication should they progress to a complete fracture. High-risk fractures are often harder to diagnose, and often tend to progress to non-union or complete fracture, may require surgical management, and may reoccur.


  1. Dull pain along the bone which can increase with activity
  2. Potential mild swelling around the affected area
  3. Tenderness around the affected area


Treatment is often multidisciplinary requiring a general practitioner, a dietician and a Physiotherapist for stress fracture. In addition there is potential for a sports psychologist to be required if RED-S syndrome is the primary factor for the stress fracture. Physiotherapist provide guidance in two ways:

  1. They can give advice and education on correct exercise loading of the athletes program; how often, how far, how heavy, what surfaces are appropriate to train on, and when it is pertinent to return to sports after stress fracture.
  2. The can advice on technique and prescribe exercise to address poor biomechanics that lead to increased load (or stress) in one limb or one area of bone.

Please seek the advice of your Physiotherapist and Dietician if you have concerns with calorie intake, program loading or pain from suspected stress fractures.

Mountjoy M, Sundgot-Borgen J, Burke L, et al 2014. The IOC consensus statement: beyond the Female Athlete Triad—Relative Energy Deficiency in Sport (RED-S) British Journal of Sports Medicine 2014;48:491-497.

Brukner P., Khan K,. 2015. Clinical Sports Medicine, Sports concussion; 600-617