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  • Writer's pictureKristin Bignell - PT, MScPT, BScES(hons), CMAG

Athletes - Relative Energy Deficiency in Sport (RED-S)

--> Decreased endurance

--> Increased injury risk

--> Decreased training response

--> Impaired judgement

--> Decreased coordination

--> Decreased concentration

--> Irritability

--> Depression

--> Decreased glycogen stores

--> Decreased muscle strength

(Mountjoy et al 2018)

We need energy to fuel our bodies. We need fuel in order to maintain good health, to perform our best, to recover efficiently after activity and to keep our body resilient to injury.

RED-S is an energy problem that is relatively common, under recognized and has potentially dire consequences for athletes of all ages and skill levels. While it is more common in female athletes, it does also affect male athletes.

If you are expending more energy than you are taking in, you are running at an energy deficit. If you are running at an energy deficit, you have the potential of ending up with RED-S, Relative Energy Deficiency in Sport. RED-S was formerly known as “The Female Athlete Triad”, however, the manifestations of RED-S are much more widespread and RED-S is NOT exclusive to female athletes. Let’s use a cellphone analogy to help paint a picture. Our cellphones use battery power to run. They use a base amount of battery power to remain in a dormant mode but when we use our phones to email, chat, cruise Instagram, they use more power. When our battery gets low, we charge it so that our phone has enough power to do both the necessary and fun things. If we let the battery run too low, we end up in “low power mode”. Our phone still works but not all of the functions are readily available. If we let the battery run out, the phone no longer works until it is recharged. Over time, this wears away at the life of the battery. Like a phone, we need energy to be able to perform. If we don’t have enough energy to perform our sport, our body cannot perform at its full capacity. When there is a mismatch between energy availability (through the diet) and energy expenditure (through exercise), our body doesn’t have enough energy to carry out the functions necessary to maintain optimal health. We end up with impaired physiological functioning with significant consequences.

Low energy availability can be due to an intentional limitation of calories in order to change appearance or under the misguided belief that being leaner will improve performance. Or, it can be due to an unintentional mismatch between energy consumption and energy output. In other words: not increasing calories enough to match an increase in training. Unlike a phone, our bodies are much more complex and energy requirements are multifactorial. It is not enough to simply track caloric intake. We require a steady intake of water, quality macronutrients (fats, proteins and carbohydrates) and a balanced intake of micronutrients (vitamins and minerals) to facilitate the processes necessary to maintain life and support optimal performance. We also require proper sleep and mental rest to keep our tank full.

As our activity level increases, so does our fuel requirement. In the short term, if we have not taken in enough energy, our ability to compete at our full capacity is diminished. We aren’t as strong and we aren’t as mentally sharp.

Over the long term, if we are experiencing a consistent energy shortage, we may start to lose bone mineral density causing an increased risk for fractures or have changes in our metabolic ability. There may be alterations in hormones that impact performance and have long term impacts on reproductive function. In female athletes, menstrual cycles may become irregular and/or stop all together. Our immune systems may become dysfunctional and we may end up getting sick more often or developing autoimmune conditions. We may not be able to synthesize protein properly, a process necessary for tissue repair, healing and growth. This may make it harder to recover from exercise and may set the stage for an overuse injury. The list goes on. No athlete is exempt from this risk. If you are using up too much energy and/or not taking in enough energy you have an energy deficiency and while the effects of this RED-S start silently, the consequences can be devastating and potentially career ending for athletes.

Figure 1: Health Consequences of RED-S (Adapted from Mountjoy et al. 2018) In terms of performance, athletes with low energy may experience: decreased muscle strength, decreased endurance, increased injury risk, decreased energy stores, depression, irritability, decreased concentration, decreased coordination and/or an impaired training response.

Figure 2: Performance Consequences of RED-S (Adapted from Mountjoy et al. 2018)

The Relative Energy Deficiency in Sport (RED-S) Specific Screening Tool (RST) is a tool that can be used by the general public to identify and spread awareness of the effects of low energy availability. *Scroll to the bottom for the questionnaires* The questionnaires are designed to be completed by the athlete themselves. The RST has been validated for use in middle and high school-aged individuals. Its use by coaches, athletic trainers, physical therapists, and other healthcare practitioners may increase knowledge and identification of the signs and symptoms related to the Triad and RED-S. Athlete, parent, coach etc, I would highly recommend checking it out!

If you or someone you know is currently experiencing any of these symptoms, I would highly encourage you to reach out to a trusted health care provider who has experience with The Female Athlete Triad and/or RED-S and can help develop a plan to correct this energy difference. If you aren’t experiencing symptoms, I challenge you to think of ways that you can to help your body best recharge so that you are able to perform and compete without compromising your health and performance. If you would like to know some of these strategies, check out my FREE ebook: The Female Athlete's Guide to Lifelong Athleticism.


Mountjoy, M., Sundgot-Borgen, J., Burke, L., Ackerman, K. E., Blauwet, C., Constantini, N., Lebrun, C., Lundy, B., Melin, A., Meyer, N., Sherman, R., Tenforde, A. S., Torstveit, M. K., & Budgett, R. (2018). International Olympic Committee (IOC) Consensus Statement on Relative Energy Deficiency in Sport (RED-S): 2018 Update. International Journal of Sport Nutrition and Exercise Metabolism, 28(4), 316–331.

Mountjoy M, Sundgot-Borgen J, Burke L, et al. 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. Foley Davelaar C M, Ostrom M, Schulz J, et al. (June 12, 2020) Validation of an Age-Appropriate Screening Tool for Female Athlete Triad and Relative Energy Deficiency in Sport in Young Athletes. Cureus 12(6): e8579. doi:10.7759/cureus.8579

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About the author: Kristin is a Registered Physiotherapist and the Owner of East Mill Physio in Elora, ON. She has a special interest in Neurofunctional Acupuncture, Sports Performance and Female Athlete Development. She enjoys pushing the boundaries of what we traditionally believe to be possible with respect to injury rehabilitation and performance optimization by using a holistic treatment style.


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