THE EMERGING ROLE OF GLUTAMINE AS AN INDICATOR OF EXERCISE STRESS ANDOVERTRAINING

Glutamine is an amino acid essential for many important homeostatic fu nctions and for the optimal functioning of a number of tissues in the body, particularly the immune system and the gut. However, during vari ous catabolic states, such as infection, surgery, trauma and acidosis, glutamine homeostasis is placed under stress, and glutamine reserves, particularly in the skeletal muscle, are depleted. With regard to glu tamine metabolism, exercise stress may be viewed in a similar light to other catabolic stresses. Plasma glutamine responses to both prolonge d and high intensity exercise are characterised by increased levels du ring exercise followed by significant decreases during the post-exerci se recovery period, with several hours of recovery required for restor ation of pre-exercise levels, depending on the intensity and duration of exercise. If recovery between exercise bouts is inadequate, the acu te effects of exercise on plasma glutamine level may be cumulative, si nce overload training has been shown to result in low plasma glutamine levels requiring prolonged recovery. Athletes suffering from the over training syndrome (OTS) appear to maintain low plasma glutamine levels for months or years. All these observations have important implicatio ns for organ functions in these athletes, particularly with regard to the gut and the cells of the immune system, which may be adversely aff ected. In conclusion, if methodological issues are carefully considere d, plasma glutamine level may be useful as an indicator of an overtrai ned state.