Transfusions with a person's own blood can also bump up red blood cell counts. Using this approach, athletes draw and store their own blood during training, then re-inject red blood cells taken from the blood (they can be separated out using a centrifuge) before the competition. In the interim, the body has produced more red blood cells, so that the re-injected red cells create a higher volume of these oxygen carriers.
Other than looking for unnaturally high hematocrit, there currently is no accepted test to detect for transfusions with an athlete's own blood. But other circumstantial evidence — such as the presence in blood of plastic additives found in I.V. bags — has helped authorities sniff out this method of blood doping in the past.
The effects of blood doping are short-lived; when the body senses the unnatural levels of red cells in the blood, it attempts to return things to normal by not replacing the extra cells as they die. So that means that athletes who want to maintain the benefits of doping will engage in repeated cycles.
Ethics aside, doping carries health risks. The hard work of pushing unnaturally thickened blood through the veins increases the probability of cardiovascular events such as strokes or heart attacks, as well as kidney damage. Although doping may cut a few minutes from athletes' race times, it can also cut years from their lives.
Prescott, a physician and medical researcher, is president of the Oklahoma Medical Research Foundation. Cohen is a marathoner and OMRF's senior vice president and general counsel.