Inosine belongs to a chemical family known as purine nucleotides. It penetrates cell walls of both cardiac and skeletal muscle and once inside promotes the manufacture of ATP, the substance in the body that allows muscles to contract. Athletes wishing to exercise longer without experiencing muscle fatigue often use Inosine. Inosine also promotes the production of a substance known as 2,3-DPG that is necessary for the transport of oxygen molecules from the red blood cells to body tissues for energy. Inosine may also be beneficial to the health and energy of the heart.