Creatine

 Creatine is an acid that is produced in the liver and made from three amino acids: arginine, glycine and methionine. Dreatine supplies energy to muscle cells and helps recycle ATP energy.  When ATP energy is spent it becomes ADP. Creatine phosphate converts ADP back to ATP and restarts the cycle. This process has many advantages, including an increase in muscular contraction time that allows you to work out harder before experiencing muscle failure.