This BCAA supplement contains the branch chain amino acids L-Leucine, L-Isoleucine and L-Valine, along with the beneficial additions of vitamin B6 and L-glutamine.
BCAAs are naturally found in animal protein as well as supplement form. BCAAs are often taken 
for use by novice athletes or body builders for supporting normal muscle growth and repair. There are 20 amino acids that our body needs to function optimally, 9 of which are essential and cannot be synthesized within the body including leucine, isoleucine and valine. In addition to this, glutamine is conditionally essential meaning in times of illness or stress it becomes an essential amino acid. These amino acids are used to make proteins, the building blocks of cells and tissue. BCAAs represent 35-40% of all essential amino acids and 14-18% of these are found in muscles. They are broken down in the muscle rather than liver and therefore thought to play a role in muscle growth and endurance exercise. Research studies not only look at the link between BCAAs and physical fatigue during exercise, but also mental fatigue. There is a decline in serum BCAAs during physical exertion which lead to chemical messengers being released into the brain which may lead to an increase in perceived exertion and mental fatigue.
Sources
BCAAs and endurance exercise
BCAAs and mental fatigue