This summary is from the IAAF 2nd International Consensus Conference on “Nutrition for Athletics“ held in Monaco from April 18-20, 2007. Copies of the CD and booklet are available from the IAAF website www.iaaf.org.
Fatigue and Illness in Athletes
Presenter: Myra Nimmo (GBR)
Recommendations to keep immunity high include: maintain energy equilibrium, keep CHO stores high, have a moderate amount of fat in the diet, stay well hydrated. Use of vitamin C and A-tocopherol is equivocal, with some positive findings. However, it should be noted that anti-oxidants might dampen the training adaptation.
Adequate nutrition before, during and after training and competition is a key element of maintaining health and warding off early fatigue and possible immuno-suppression. A period of immuno-suppression after an intense exercise bout is inevitable and can last up to 72 hour. However, it can be attenuated by proper nutrition.
The cytokine IL-6 can lead to fatigue and poor sleep quality and have profound negative effects on performance. Low glycogen and other training and life stressors can elevate IL-6. IL-6 seems to playa central role in acquired immunity. It is considered the “switch” from innate to acquired immunity. IL-6 can only be active when bound to the receptors IL-6R and gp130. It is therefore important to look not only at levels of IL-6, but also at levels of IL-6R and gp130.
IL-6 seems to serve as an energy sensor: low glycogen levels prior to exercise elevate IL-6 compared to placebo controls and CHO feeding during exercise attenuates IL-6 release. When IL-6 was administered prior to exercise, it induced an increased sensation of psychological and physical fatigue, possibly through central mechanisms.
Ensuring adequate glycogen and delaying depletion of glycogen is clearly a key goal for athletic events.
Overtraining is defined as an accumulation of training and/or non-training stress that results in a long-term (weeks and months) decrease in performance. Overtraining is associated with an increased incidence of infections, persistent sore muscles, general malaise and disturbed sleep. The etiology is complex and the syndrome’s the existence has even been challenged.
Chronic stress can cause elevated IL-6 levels, which in turn can cause a disturbed balance in T-helper cells. This will lead to increased susceptibility to viral infections. At present, there is no clear guidance on the cause, the identification or the remedy for the overtraining syndrome. Despite many possible markers, a good psychological test (Profile of Mood States) still seems to be the most accurate measure of overtraining.
Different deficiencies have an effect on fatigue and immune system. Energy deficiency can cause a reduction in memory T-cells. Elevated fatty acid availability may decrease immune function by increasing the amount of prostaglandin. Too little fat in the diet can cause immuno-suppression as well.
The above summary was written by Peter Res
If you wish to download this handy Grams and Calorie Calculator for Carbohydrate, Protein, and Fat, click here for the Excel spreadsheet.
This is part 10 of 14 in a series from the 2007 2nd IAAF International Consensus Conference “Nutrition for Athletics”