Overtraining syndrome
Issue: Volume 27 Number 2
In the simple model of overtraining, the adrenal and nervous system down regulation is caused by repeated bouts of hypoglycaemia due to insufficient use of carbohydrate. In the complex model, the mechanism that causes the down regulation is different. In the article 'Overtraining syndrome in endurance athlete' we discussed hypoglycaemia associated autonomic failure (HAAF). The initial research into HAAF showed that two repeated bouts of hypoglycaemia created a down regulation in the autonomic nervous system. The researchers working on the original study expanded the work to find that high cortisol levels, plus one single bout of hypoglycaemia caused exactly the same down regulation of the adrenal and nervous systems as the repeated bouts of hypoglycaemia. They demonstrated that cortisol levels were the key mediator of the HAAF response. Cortisol is a stress hormone that has a lot of different activities in the body. One of these activities is to convert protein into glucose for fuel for the brain, nervous system and working muscles.
Normal training stress will cause elevated cortisol levels. Elevated cortisol promotes the production of glucose from protein. This process is called gluconeogenesis. If an athlete is maintaining normal protein intake at approximately 1.0 gram per kilogram of bodyweight, a protein deficiency will ensue. An endurance athlete’s protein requirement is a minimum of 1.5 grams per kilogram of bodyweight. This cannot be achieved through a normal diet and must be supplemented with a protein powder.
The body will secrete different hormones at different times of the day. The cycle of hormone secretion is called circadian rhythms or circadian cycles. Normal circadian secretions of cortisol peak in the early morning to maintain a constant glucose supply to the brain and nervous system while you are asleep. This glucose is made from the available protein via gluconeogenesis.
The circadian secretion of cortisol adds to already elevated cortisol levels created by training stress. Athletes with a protein deficiency and high cortisol levels are going hypoglycaemic during their sleep and inducing the subsequent hypoglycaemia required for autonomic failure. Therefore it is possible for a protein-deficient athlete to use the correct amount of carbohydrate during training and still induce the subsequent hypoglycaemic condition required for autonomic failure. A protein-deficient athlete does not have the necessary substrates (protein) available for the production of glucose from protein while the athlete is asleep.
In a study that contrasted the plasma-free amino acid (the building blocks of protein) patterns in elite athletes with fatigue and infection showed a correlation between under-performance and a decrease in plasma amino acids. The study noted three amino acid patterns:
- a normal pattern in those without lasting fatigue
- marked but temporary changes in those with acute fatigue
- a persistent decrease in plasma amino acids, mainly glutamine, in those with chronic fatigue and infection, for which an inadequate protein intake appeared to be a factor.
This study demonstrated that protein deficiency was correlated with under-performance and recovery, and that additional protein intake was required.
The degree to which overtraining occurs is determined by the severity of the first bout of hypoglycaemia. When the blood glucose levels drop to 3.9mmol/l the theoretical category of the sympathetic type of overtraining occurs. This condition blunts the adrenaline response but not nor-adrenaline and reduces muscle sympathetic nerve activity. The reduced muscle sympathetic nerve activity may account for the performance decrements noted in this stage of overtraining.
When the blood glucose levels fall below 3.3mmol/l in the first bout of hypoglycaemia, the theoretical category of the parasympathetic type of overtraining occurs. This condition blunts both the adrenaline and nor-adrenaline responses.
Once overtraining that is caused by protein deficiency is established, it becomes a self-perpetuating cycle. The protein deficiency causes nocturnal hypoglycaemia. The nocturnal hypoglycaemia in turn causes a HAAF condition. Severe HAAF reduces cortisol secretion, reduced cortisol secretion reduces the amount of glucose made from an already deficient supply of protein and so the overtraining cycle reinforces itself.
Chronic viral infections can also produce the same results. The viral infections also raise cortisol levels. Chronically raised cortisol levels will eventually deplete protein reserves by constant stimulation of gluconeogenesis. Once a protein deficiency has been induced, the conditions exist to produce autonomic failure via nocturnal hypoglycemia. It is my view that this mechanism is an accelerating factor in chronic fatigue. One of the symptoms of chronic fatigue is tiredness of central origin on waking, possibly due to nocturnal hypoglycaemia.
It should also be noted that alcohol inhibits gluconeogenesis, and that alcohol intake can also exacerbate the nocturnal hypoglycaemia.
To prevent overtraining due to dietary deficiencies, it is important to do the following:
- Ensure that you use 60 grams of a quality carbohydrate source per hour when training. This reduces the rise in cortisol and prevents hypoglycaemia. Preventing chronically raised cortisol levels helps to preserve your protein levels.
- Ensure that your dietary intake of protein is 1.5 grams per kilogram of body weight. This is achieved by using a protein shake. I use Mushsashi 85 per cent whey protein concentrate (WPC) vanilla flavoured. There are technically better protein products on the market, but they are all artificially flavoured, which I do not recommend. The Mushsashi 85 per cent WPC vanilla is naturally flavoured and does the required job well. If you are training well and your health is good, add the protein shake to your breakfast meal. This will help to smooth out your energy levels during the day. If you are waking up tired and not feeling like you have had a good night’s sleep, take the protein right on bed time. This helps prevent the nocturnal hypoglycaemia.
