Metabolic effects of exhaustive training of athletes

Sixteen athletes (11 men, 5 women), averaging 21 years of age, were studied before and after four weeks of daily exhaustive exercise (six days/week) during an endurance training course. In comparing blood chemistries before and after training, concentrations of blood glucose, total serum lipids, serum triglycerides, and serum cholesterol were significantly reduced; serum free fatty acid ( SFFA ) level was significantly increased; and serum protein and serum phospholipid concentrations remained unchanged. It was concluded that exhaustive training produces reduced blood glucose (but not clinically significant hypoglycemia) with increased fat utilization as a result of depletion of carbohydrate storage and that such training reduces the resting levels of serum cholesterol and serum triglycerides. The increased hematocrit, serum Na+, and serum K+ concentrations observed were presumably due to plasma water loss from excessive perspiration. Concentrations of blood urea nitrogen (BUN) and serum glutamic-oxaloacetic transaminase (SGOT) were increased significantly; serum glutamic-pyruvic transaminase (SGPT) and serum creatinine showed no significant changes. None of the athletes showed evidences of water-electrolyte deficiency syndrome, renal dysfunction, or liver cell damage, despite a persistent mild degree of dehydration and catabolic state noted after training.