During prolonged physical exercise, the plasma values of BCAAs (because they are used for energy purposes) and glutamine (because used to neutralize hyperammonaemia) decrease and the plasma value of aromatic amino acids, including tryptophan, increases.
The more the concentration of BCAA decreases, the more tryptophan reaches the brain and the greater the sensation of fatigue.
During prolonged exercise there is an increase in plasma fatty acid levels resulting from their mobilization to satisfy energy demands.
Also the fatty acids circulate linked to the albumin for which they have a very high binding affinity; their increase in circulation displaces the tryptophan from the albumin with consequent increase of the free tryptophan.
Increased free TRP makes it easier for the brain to pass and increases serotonin production in the brain. An increase in serotonin in turn increases the degree of fatigue and fogging at the central level, resulting in the onset of fatigue.
Therefore an adequate integration of branched chain amino acids could prevent the appearance of the fatigue symptom during strenuous exercise.
