Relative Energy Deficiency in Sport Monitoring for Road Cyclists preparing for the Tour de France

How should the multi-disciplinary performance team monitor road cyclists in the build up to the Tour de France to detect relative energy deficiency in sport (RED-S) and reduce potential negative impacts on performance? 


Authors: Ms Niamh McIntosh [1] and Dr Neil Heron [1,2] (MRCGP, F.FSEM (UK), PhD)

Email address:

[1] Centre for Public Health Research, Queen’s University, Belfast

[2] Dept of Medicine, Keele University, Staffordshire, England. 



The Female Athlete Triad is a condition originally described in female athletes involving three interrelated components: (1) low energy availability with or without disordered eating, (2)  low bone mineral density, and  (3) menstrual dysfunction (1).  It has been found that energy deficiency also affects male athletes. Therefore, the term ‘Relative Energy Deficiency in Sport’ (RED-S) was introduced by the International Olympic Committee in 2014 as a broader, more comprehensive term describing the overall syndrome that results from energy deficiency in any athlete (2). They defined RED-S as a syndrome involving impairment of various aspects of physiological function caused by relative energy deficiency including, but not limited to, menstrual function, bone health, immunity, and psychological health (2). 

The importance of maintaining optimal energy availability in athletes and identifying those who have low energy availability can be explained by the health and performance consequences of RED-S (2) – that is, athletes should be encouraged to maintain optimal energy intake to minimise the risks of developing RED-S and the consequences of RED-S. Indeed, RED-S can result in many short- and long-term health consequences such as menstrual cycle disturbance, increased risk of bone stress injuries and depression. Moreover, RED-S can negatively impact athletic performance, as it is  associated with reduced muscle strength and an increased injury risk. Elite athletes want to be in optimal physical and mental condition for competition and ensuring adequate energy availability is a major part of this. Appropriate monitoring and early detection of RED-S is crucial to avoid the negative effects and ensure maximal performance.

It is common for athletes to reduce their energy availability in the build-up to a sporting event. This may be due to a loss of appetite with post-exercise fullness, increased training loads or pathological disordered eating. Certain athletes intentionally reduce their energy availability to achieve a desired physique, attempting to maximise their sporting performance (3). One problem with this, contrary to many athletes’ beliefs, is prolonged low energy availability is detrimental to performance (2). Road cyclists are a population of athletes who are at high risk for developing RED-S due to the emphasis on leanness within the sport, particularly in the build-up to the hardest race in the competitive calendar, the Tour de France. The focus of this blog is therefore to illustrate how elite road cyclists can be monitored to avoid the development of RED-S, based on an unpublished scoping review on this topic, conducted by the authors of the blog. 

Can we monitor for Relative Energy Deficiency in Sport (RED-S)?

  • Low energy availability has been shown to alter the levels of metabolic hormones and substrates such as growth hormone, cortisol, 3,3,5-triiodothyronine (T3), leptin, and glucose (2,6). 
  • Previous authors have developed questionnaires such as the Low Energy Availability in Females Questionnaire (LEAF-Q), a screening tool that focuses on key physiological changes that occur due to low energy availability (7). 
  • Despite the multitude of potential tools and markers of RED-S, the best approach to RED-S monitoring is yet to be identified. 

How should cyclists be monitoring for RED-S pre-Grand Tour?

  • A multi-disciplinary approach is key for RED-S monitoring. 
  • Input from coaches, medical staff, nutritionists, physiotherapists, sport science and the athlete themselves, is necessary to minimise the risk of RED-S and ensure optimal conditioning and performance in the Tour de France. 
  • Figure 1 is a monitoring plan for road cyclists pre-Tour de France that was created based on the results of a scoping review (unpublished) undertaken by the authors. 
  • Blood markers should be monitored at around six, three- and one-week pre-competition. This allows adequate time for hormonal markers to shift in response to short-term energy deficiency (32) and time to intervene and track the progress of such interventions. 
  • All the results should then be discussed in a fortnightly performance meeting of the multidisciplinary team, starting at eight weeks pre-competition.  
  • In addition, it is useful to regularly measure BMD in this high-risk group using DEXA (dual-energy x-ray absorptiometry) scans, e.g. every 2 years.

Issues to consider

  • To form an appropriate RED-S protocol for road cyclists, it is necessary to know the time course of the change in markers, particularly blood markers, in response to low energy availability, which was only explored in three studies within the scoping review. 
  • Another limitation of this review is the lack of studies researching how markers respond to regaining normal energy availability, which would be useful in assessing the effectiveness or compliance of an athlete to an intervention. 
  • Some of the studies limited their athletic population to Caucasians, reducing their applicability to other athletic populations. 


  • Sport-specific RED-S monitoring protocols are necessary to account for the different physical demands and expectations of various sports. 
  • Road cyclists are a population of athletes who are at high risk for developing RED-S due to the emphasis on leanness and ‘making-weight’ within the sport, particularly pre-Grand Tour. 
  • If low energy availability is not corrected before a Grand Tour this could be detrimental to the rider’s performance. 
  • Based on the scoping review findings, a pre-Grand Tour RED-S monitoring protocol was developed that incorporates a multi-disciplinary approach to cover all aspects of the athlete’s wellbeing. This protocol involves regular medical evaluations, with physical evaluations, and blood monitoring done at six-, three- and one-week pre-competition. When forming this protocol, a marker’s sensitivity, time course of change and financial costs were considered.
  • This scoping review highlights several gaps in the literature, for example investigating blood marker changes in energy deficient athletes after re-feeding to determine the efficacy of treatment strategies. RED-S is a growing area in sports medicine with significant health and performance consequences for athletes. Through continued research, increased awareness of the condition, and early detection, RED-S can be prevented, helping to optimise athletes’ health, wellbeing and performance. 


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  6. Friedl KE, Moore RJ, Hoyt RW, Marchitelli LJ, Martinez-lopez LE, Askew EW, et al. Endocrine markers of semistarvation in healthy lean men in a multistressor environment. J Appl Physiol. 2000;88:1820–30. 
  7. Koehler K, Gibbs JC, Zinner C, Braun H. Low energy availability in exercising men is associated with reduced leptin and insulin but not with changes in other metabolic hormones. J Sport Sci. 2016;34(20):1921–9. 
  8. Papageorgiou M, Elliott-Sale KJ, Parsons A, Tang JCY, Greeves JP, Fraser WD, et al. Effects of reduced energy availability on bone metabolism in women and men. Bone [Internet]. 2017;105:191–9. Available from:


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