Stresses of the Endurance Athlete


The training stresses on the endurance athlete are considerable. Ian Craig explores the functional consequences of heavy training and what to do about them.

Endurance training demands large quantities of energy; it is catabolic in nature; it releases stress hormones; it can deplete the immune system; it may cause leaky gut syndrome (1); it increases the likelihood of an over-use injury; it pressurises nutrient reserves in the body; and endurance exercise can potentially even age you quicker (2). In a nutshell, endurance training is very hard on our bodies – I’m not talking about heading out for a family bike ride on a Saturday plus gyming with mates during the week. I’m talking about ‘real’ athletes who push their bodies to the max several times per week with the goal of shaving a half second off their best time or finishing ahead of somebody who pipped them at the post last time.

Exercise physiologists understand this whole-body stress that athletes place themselves under, but mostly people unfortunately do not and actually still think that ‘more is better’. And this includes the athletes and coaches themselves – I see a lot of top amateur cyclists in Cape Town, who are on the roads for hours every day and whose bodies are simply cooked with the effects of overtraining. It might just be one final race that tips their body into a state of non-recovery in the guise of a chronic virus like Epstein Barr (Glandular Fever) or an injury that refuses to heal. Many athletes have a vague idea of this thing called ‘overtraining’, but often don’t really embrace it until they have no choice, like poor Andrew Steele in Adam Carey’s article. Prior to something as serious as Glandular Fever and Chronic Fatigue Syndrome, there have been many months (and possibly years) of subtle overtraining. It’s like the male executive who drops dead of a heart attack at age 50 – according to medical records, he was previously ‘healthy’. Medically, he was ‘sub-clinically’ (not picked up by medical exams) sick for many years because it generally takes 20+ years to build up to a heart attack. Endurance athletes are no different, and yes, there are cases of heart attacks in so-called healthy runners, cyclists and cross-country skiers. We can gradually be digging a health hole for ourselves over a long period of time by unwittingly embracing the daily grind of training.

So, that’s the bad news, guys. Before giving you the good news though, I want to remind you of the whole-body stress that athletes are under and try to join some of the dots from previous articles in FSN.

The functional model

Displayed below is ‘The Web’ of health interactions, as represented by the Institute for Functional Medicine in the States (3). In a simple way, the web signifies how several systems in our body interact and influence each other. Like a spider’s web, if one corner is damaged (ie. one of the systems is out of balance), the rest of the web can actually collapse. Here lies the meaning of ‘Functional’ in Functional Sports Nutrition – biochemically, neurologically, hormonally, structurally and immunologically, every part of our body is connected in some way. To fully understand our health, we need to consider these large body systems in an integrated (or functional) way. Previously in FSN, the topics of Gastrointestinal Imbalance, Detoxification and Hormones have been covered (4-7); the topics of the immune system, inflammation and oxidative stress are eloquently discussed in this issue by Dr Hannah Moir and Professor Mike Gleeson and Neurotransmitters and Mind & Spirit will surely make their way into future issues with interesting topics like Psychoneuroimmunology!

The physical stresses of training, as noted by Dr Moir, are translated into the biochemical stresses of inflammation and oxidative stress, which are a systemic phenomena. That is, not one part of our body will be untouched by the stress of training, to the extent that it probably won’t be a coincidence if you’re a bit depressed or anxious or ‘not quite yourself’ after hitting your highest mileage one particular week (see Figure 1, opposite).


Figure 1 – The Functional Medicine Web (2)

The good news!

After all that bad news, what could ever be good about endurance training? Well, ever since the Jim Fixx (8) marathon movement of the late ‘70s, aerobic conditioning has had a myriad of research supporting its benefits. Benefits are whole-body and too numerous to name here, but include: cardiovascular health & fitness; musculoskeletal function; energy; metabolic support; gastrointestinal health; bone mineralisation; and promotion of mental health, such as strongly countering depression and anxiety.

Jim Fixx, incidentally, died of a heart attack at age 52 whilst out running, but it was revealed that he had a strong hereditary risk of heart disease plus his diet wasn’t

All these benefits of exercise can also be diminished in function if you push your body too hard. So, like almost everything in life, it’s all a matter of BALANCE. The harder you train, the harder you must recover. According to many learned coaches, there is only one thing that’s more important to an athlete than training and that is recovery. The job of training is to break down the structural apparatus of your muscles and pressurise all of the physiological systems involved in the endurance activity. The job of recovery is to allow time for these systems to be reinforced to a stronger level than before. So, the clever athlete can have his or her cake and eat it, whereas the over-motivated or obsessed, but not necessarily un- intelligent, athlete may simply run their body into the ground.

Chinese medicine uses the words ‘yin’ and ‘yang’ to indicate opposites. This could be hot and cold; expansive and contracting; dry and wet; hard and soft, thick and thin, dark and light etc. Yin and yang are complementary opposites that interact within a greater whole, as part of a dynamic system. Everything has both yin and yang aspects because, because for example, light can’t exist without darkness and vice versa, but either aspects can ebb and flow in intensity over time.

Within the context of this article that has considered the integrative nature of the human body, yin and yang provide us with a lovely analogy for obtaining the balance between work and rest. Yang is characterised as fast, hard, solid, focused, hot, dry and aggressive, whereas yin is characterised as slow, soft, yielding, diffuse, cold, wet and passive. We can therefore label training as yang and recovery as yin. As long as the two aspects are in reasonable balance most of the time, we can retain our healthy and vibrant status as an athlete, but as soon as yang becomes dominant for a prolonged period of time, we are diminishing our yin (or recovery) opportunities. Of course, we don’t want yin to become dominant either because then we might be deemed a lazy athlete!

Adding the Yin to the Yang of endurance training

• Watch for the signs of overtraining: irritability, lethargy, depression, sleep disruption, menstrual irregularities, hypoglycaemia, diminishing performance despite trying harder.
• Check your morning heart rate, which shouldn’t be rising more than 5bpm above normal.
• Consider a heart rate variability device which can tell you if your nervous system is in resting mode or stress mode (9).
• Use Active Recuperation methods rather than simply resting (10). These include: a regular massage; having body work such as osteopathy or cranial-sacral
therapy; laughing and having fun; surrounding yourself by nature and animals; spending time with friends and family who feed your energy.
• Consider all the other stresses in your life – your training does not sit on an island, un-influenced by your job, your family, your finances. Every commitment in your life can be translated into your body as a biochemical stress (11).
• Eat like a king: have a diet that suits your genetic type (12), avoid potential food sensitivities (13), stay fresh and local*, balance your blood sugar levels (14).
• Take supplements that are going to support your individual requirements. Dr Moir and Professor Gleeson have provided some good suggestions for immune- supporting, anti-inflammatory and anti-oxidants nutrients. Previous articles that I’ve referenced give suggestions for anabolic support (vital for an endurance athlete), digestive and detoxification, blood sugar balance and adrenal support.

*Much of our supermarket food has travelled considerable air miles and a lot of time has elapsed since it was picked. Instead, try local farmers’ markets and one of the numerous UK box schemes.

**In support of my suggestions, I have referred to a number of previous FSN articles that can help round your knowledge on this very large subject matter. Recent FSN issues can be viewed online ( and all back copies can be ordered.


  1. Clay L (2011). Does your fitness have holes in it? FSN Sep/Oct 11. 1(10):16-18.
  2. Craig I (2010). The effects of exercise on the ageing process. The Nutrition Practitioner. Autumn 2010.
  3. The Institute for Functional Medicine. What is Functional Medicine? (accessed Mar 2012).
  4. Walker A (2011). Do you have the guts to train? FSN Sep/Oct 11. 1(10):14-15.
  5. Craig I (2010). Clean up your sport. FSN Sep/Oct 10. 1(4):6-10.
  6. Bannock L (2011). The holy grail of sport – raising growth hormone. FSN Jan/Feb 11. 1(6):6-8.
  7. Hines S (2011). Manipulating testosterone and cortisol ratios. FSN Jan/Feb 11. 1(6): 12-14.
  8. Fixx J (1977). The Complete Book of Running. Random House.
  9. Hines S (2011). Can a new gismo prevent overtraining? FSN May/Jun 11. 1(8):18-20.
  10. Williams P (2010). Active restoration. FSN Nov/Dec 10. 1(5):20-21.
  11. Craig I (2010). Stress and overtraining. FSN Nov/Dec 10. 1(5):12-14.
  12. Craig I (2011). Biochemical Individuality. FSN Jul/Aug 11. 1(9):6-8.
  13. Bailey C (2011). Food allergies. FSN Sep/Oct 11. 1(10):6-8.
  14. Boswell C (2011). Herbs: The 3rd dimension of blood sugar regulation. FSN Nov/Dec. 1(11):12-15.