EPO, which is short for ERYTHOPOIETIN.
EPO is a hormone, which causes an increase of red blood cells, which results in being able to carry more oxygen to the muscles. This hormone was developed to treat patients during blood transfusions.
During exercise especially running when red blood cells are damaged from the pounding on the roads resulting in a decline in red blood cells and reduction in performance and even anemia. The illegal drug EPO allows the person to perform at higher levels and cover greater distances with fewer declines in performance.
Many athletes have died from taking EPO because if it produces too many red blood cells then the blood will become so thick blocking arteries and resulting in a heart attack. Very little is known about the side effects and risk to health from EPO.
Tour de France cyclists have recently been caught blood doping and taking the illegal sports hormone ERYTHOPOIETIN (EPO)