Glutamine is an amino acid that is found in your muscles. Research has shown that after an intense workout, the glutamine levels in your body can drop by as much as 50%. Glutamine is also essential to keep your immune system functioning properly. As we all know, a poor immune system can leave you feeling weak and sick. According to a study by Trinity and All Saints University College, a routine supplementation of glutamine post-workout can help lessen the change of injury, improve immune function and help you recover faster after over training. 2 grams of L-glutamine daily is all that you need.