Overtraining revisited


Overtraining is a well-studied phenomenon in sports medicine, but it may also be viewed as adrenal fatigue in integrative health practices. Ian Craig pulls together a few physiological models and considerations to help us understand this term better. 

Overtraining interests me a lot, not just because during own athletic career I often pushed my own boundaries, but because if you take away the word ‘training’, you’re left with over (or excess), meaning that this phenomenon is influenced by each and every one of our daily behaviours. Overtraining starts to merge with health imbalances such as ‘burnout’, adrenal fatigue or exhaustion, immune compromise, and the more complicated myriad of health complications, such as chronic fatigue, fibromyalgia and autoimmunity.

In the recent words of my overtrained long distance trail runner, who I will call Roger: “I have come down with a cold and am man down. Lasted one month of 2018 before I got ill. I am incredibly frustrated with my body and feel betrayed by my health and body. Despite a healthier diet, supplements and slightly more rest, I am still getting sick.” He, like most of the athletes that I see in my practice, view their bodies like machines – if I put a, b c into it, by this calculation, I should get x, y and z out of it. Books, training programmes, certain coaches, and especially Apps, can leave you with a mechanical expectation of a certain return for your investment. 

In the sports science/medicine literature, overtraining syndrome (OTS) is a topic that has been discussed and described since the 1980’s, but scientists still struggle to pin down an exacting description and diagnosis of the condition, or what I’d prefer to call a ‘health imbalance’. If you view Table 1, you’ll see that there are a few terms used in the OTS literature, especially overreaching (of a functional or nonfunctional variety) and overtraining.


Adrenal fatigue

Adrenal fatigue is a notion that I have always been incredibly aware of from my nutritional therapy background when working with general population. However, in the early 2000’s, I had a sudden thought that it was one and the same as overtraining syndrome. I actually wrote a long paper entitled ‘Adrenal Stress as a Model of Overtraining’ in The Nutrition Practitioner in 2007 (3) and a shorter version in FSN magazine during it’s first year of publication in 2010 (4). I used the adrenal stress index test, which analyses salivary DHEA levels and the circadian rhythm of cortisol, as a benchmark for overtraining syndrome. This was a novel idea at the time because nobody else was writing about it – the sports scientists were talking in their language and the functional medicine guys were speaking a different language.

Times have now changed. Sports scientists are starting to recognise adrenal fatigue as a real phenomenon. For example, Brooks & Carter from the Department of Kinesiology at Texas A & M University describe a direct link between stress and the adrenal glands, and note that the physical stress of overtraining may cause the hormones produced in these glands to become depleted (2).

In cases such as my client Roger, adrenal fatigue is an extremely good model to work from. His cortisol levels were severely disrupted, with a clear reverse circadian rhythm, and his DHEA levels were theoretically that of a 90-year old. Roger is a talented runner in his early 30’s – his strength is that he hasn’t been racing since early in childhood like most athletes, so in my mind he has (or at least had) decent physiological reserve.

Life load and OTS

But, something I haven’t yet told you about Roger is that he is an investment banker and you know how hard these guys work? If you do what most athletes do and view his training as a separate entity from the rest of his life, he possibly under-trains compared to some of his rivals. However, many of them would be doing much less demanding jobs, perhaps even part time, to make their running ambitions a priority. So, in this regard, I like to view the ‘3 P’s of Stress’ model by British psychoneuroimmunologist Dr Alex Concorde (5). An individual might not be physically pushing themselves too much in training, but within the overall life that they lead, psychologically and physiologically they are adding to their total load, meaning eventual burnout in some manner or other.

I view the adrenal glands like a bank balance. If, for example, we have a daily using account, which starts off with £100 in it, this should get you through most days quite comfortably. But, if we turn the currency into adrenal effort (i.e. stress of a physical or psychological nature), what will happen if on most days we’re withdrawing £20, but only depositing £18 (via good food, ‘me’ time and restorative sleep)? It won’t take very long before we only have £10 left in our bank account – when our balance is this low, it will only take one stressful meeting or one hard training session to push you into the red.

It is at these times of dropping into the red when practitioners such as myself will receive emails complaining of being ‘man down’. My response to Roger’s concerns about his body was: “It takes a long time to get into an adrenal depletion, so it unfortunately takes a long time to truly get out of it, and to stay out of it you need to do things differently from before.”

Expanding our understanding of OTS

Looking back, I was actually quite naive to think that overtraining syndrome could be explained simply by the model of adrenal fatigue. Examining the most recent overtraining literature, we have descriptions of: blunted hypothalamus-pituitary-adrenal (HPA) hormone responses to stress tests (6,7); multiple proteomic changes (8); growth hormone and prolactin depletion (9); thyroid hormone alterations (10); depressed regulatory function of the autonomic nervous system (11); altered mitogen-activated protein kinases (MAPK) expression (12); negative impacts on immunity, energy metabolism and gut microbial diversity (13); downregulation of hepatic activating transcription factors (14); and even hepatic fat accumulation in mice (15).

Didn’t somebody say that exercise was good for us? From the perspective of getting the general population to move on a daily basis, the prevailing message should be just that. But, the message that should be coming through sports science and medicine literature more strongly is that we should be putting the reigns on some of our elite, semi-elite and highly motivated recreational athletes, especially the ones who have a demanding job and a family to look after, like my client Roger.

In the exercise immunology literature, Dr David Nieman (16) introduced the inverted-U concept. Through his own research, he observed that sedentary population and heavily training athletes were the individuals most likely to catch an upper respiratory tract infection, whereas moderately active individuals had the most robust immune systems. In my mind, this model should be extrapolated out across our entire physiology. As evidenced by the diversity of the prementioned physiological balances that are associated with overtraining syndrome, we can now assume that doing too much is fundamentally damaging to our health – how that plays out in terms of symptoms will most likely relate to the individual constitution of the athlete in question.

Returning to the OTS definition

As mentioned, scientists have been attempting to come up with a definitive definition (or diagnosis) of OTS for a long time, but we are actually getting further away from that possibility. In the words of Kreher (1) and Carfagno and Hendrix (17); “The diagnosis of OTS is a complicated clinical endeavour. Therefore, much of the prevention of OTS is simply education of risk factors and ways to prevent excessive stress.” In terms of health interventions they add; “Because the manifestation of OTS can vary greatly in individuals, treatment must be appropriate for the specific cluster of symptoms in each person.”

Additionally, according to Dr Elaine Lee (18) from the Department of Kinesiology at the University of Connecticut, in terms of tracking health, performance and recovery in athletes, we should be monitoring a comprehensive set of biomarkers, including:

  • - nutrition and metabolic health
  • - hydration status
  • - muscle status
  • - endurance performance
  • - injury status and risk
  • - inflammation

These are, in my mind, routine measurements that can be made by exercise professionals, without having to make excessive use of sophisticated laboratory tests that might reveal some useful information in one overtrained athlete, but miss a ‘diagnosis’ in another. If any of these bulleted items are under-par, it means that the athlete is not performing at their best and they need a health intervention of some type. As a practitioner who likes to use a bit of technology (not too little and not too much), laboratory tests are really important, but we shouldn’t get too hung up on specifics variables that may or may not be associated with OTS in the literature. After all, I haven’t found much mention of DHEA as a biomarker of overtraining, but when I’m faced with 90-year old levels in a 30-year old fit man, I’m going to take action…


To close, I want to address a term that I’ve noticed in the OTS literature: ‘unexplained under-performance syndrome’. I will argue that all under-performance can be explained if you really want to look hard enough – I’m yet to meet an under-performing athlete with whom I shake my head in confusion and send them back out the door. Perhaps when a sports physician does a lab test for certain biomarkers and none of them come back out of range, they might not see what’s wrong with their athlete. But when you just open your eyes and look, you can see. Ask the following questions: how hard is my athlete training; how much does he or she work; what are their stress levels; what is their exposure to environmental pollutants; does their food intake and quality match their physiological stresses; how much and how well do they sleep; what is their personal beliefs and cultures around hard work? You will then understand why they are under-performing. Our body is not a machine and it therefore needs to be nurtured from a nutritional, lifestyle, movement and compassion point of view.


  1. Kreher J (2016). Diagnosis and prevention of overtraining syndrome: an opinion on education strategies. Open Access Journal of Sports Medicine. 7:115–122.
  2. Brooks K & Carter J (2013). Overtraining, exercise, and adrenal insufficiency. J Nov Physiother. 3(125).
  3. Craig I (2007). Adrenal stress as a model of overtraining – a case study. The Nutrition Practitioner. Autumn 2007.
  4. Craig I (2010). Stress and overtraining: A cycling case study. Functional Sports Nutrition. November/December 2010.
  5. Concorde A (2014). Psychoneuroendoimmunology: the holy grail of performance gain in sports. Functional Sports Nutrition. July/August 2014.
  6. Cadegiani F & Kater C (2017). Hormonal aspects of overtraining syndrome: a systematic review. BMC Sports Science, Medicine and Rehabilitation. 9:14
  7. Cadegiani F & Kater C (2017). Hypothalamic-pituitary-adrenal (HPA) axis functioning in overtraining syndrome: findings from endocrine and metabolic responses on overtraining syndrome (EROS)-EROS-HPA Axis. Sports Medicine - Open. 3:45.
  8. Dalle Carbonare L et al (2018). Can half-marathon affect overall health? The yin-yang of sport. J Proteomics. 170:80-87.
  9. Cadegiani F & Kater C (2017). Growth hormone (GH) and prolactin responses to a non-exercise stress test in athletes with overtraining syndrome: results from the endocrine and metabolic responses on overtraining syndrome (EROS) - EROS-STRESS. J Sci Med Sport. [Epub ahead of print]
  10. Nicoll J et al (2018). Thyroid hormones and commonly cited symptoms of overtraining in collegiate female endurance runners. Eur J Appl Physiol. 118(1):65-73.
  11. Kajaia T et al (2017). The effects of non-functional overreaching and overtraining on autonomic nervous system function in highly trained athletes. Georgian Med News.(264):97-103.
  12. Nicoll J et al (2016). Changes in resting mitogen-activated protein kinases following resistance exercise overreaching and overtraining. Eur J Appl Physiol. 116(11-12):2401-2413.
  13. Yuan X et al (2018). Influence of excessive exercise on immunity, metabolism and gut microbial diversity in an overtraining mice model. Scand J Med Sci Sports. [Epub ahead of print].
  14. Pinto A et al (2017). Levels of hepatic activating transcription factor 6 and caspase-3 are downregulated in mice after excessive training. Front Endocrinol. 8:247.
  15. da Rocha A (2017). Exhaustive training leads to hepatic fat accumulation. J Cell Physiol. 232(8):2094-2103.
  16. Nieman D & Pedersen B (2000). Nutrition and Exercise Immunology. CRC Press.
  17. Carfagno D & Hendrix J (2014). Overtraining syndrome in the athlete: current clinical practice. Current Sports Medicine Reports. 13(1):45-51.
  18. Lee E et al (2017). Biomarkers in sports and exercise: tracking health, performance, and recovery in athletes. J Strength Cond Res. 31(10):2920-2937.