Glutamine is the most common amino acid found in your muscles - over 61% of skeletal muscle is Glutamine. Glutamine consists of 19% nitrogen, making it the primary transporter of nitrogen into your muscle cells. During intense training, Glutamine levels are greatly depleted in your body, which decreases strength, stamina and recovery. It could take up to 6 days for Glutamine levels to return to normal - and Glutamine plays a key role in protein synthesis. Studies have shown that L-Glutamine supplementation can minimize breakdown of muscle and improve protein metabolism.