An Analysis of the physiological effects of hormonally based ergogenic aids on elite performance.
...ow cells. The red blood cells are essential for transporting oxygen to the tissues and removing carbon dioxide, so this hormone is extremely important in our adaptation to training and altitude. Research has shown that part of the adaptation when training at high elevations is an increased release of erythropoietin, which in turn stimulates more red blood cell production, increasing the bloods oxygen carrying capacity. Because of this, some athletes have used injections of this hormone to build dup their red blood cell count, hoping to gain an edge over their competitors. (Wilmore and Costill, 1999) Figure 1.1: Erythropoietin mechanism for regulating the rate of erythropoiesis (Tarleton, 2003) Red blood cells play an important role in oxygen transport. EPO is a glycoprotein that stimulates the body to produce red blood cells. The levels of EPO in the body are regulated by a feedback loop from the brain to the kidneys to the bone marrow that appears to be governed by the body’s ability to measure and regulate the amount of oxygen in the blood. If there is too little oxygen in the blood, a condition known as hypoxia results, the brain senses this and sends a message to the kidneys. A signal is sent from there to the bone marrow to produce more EPO, which triggers the production of more haemoglobin – rich red blood cells. Figure 1.3: EPO Function (Zdravkovich, 2005) So if one lives at altitude where less oxygen is available, the body is stimulated to compensate by producing more EPO to increase the oxygen transport in the blood. The short term hypoxia experienced in hard training might also be a stimulus for the body to temporarily increase EPO production. These facts form some of the basis for training, and training and living at altitude. In light of these facts it is often not fully understood how the body turns this mechanism on and off. Scientists at the University of Toronto proposed the theory that the kidney serves as a “regulator” of sorts for the hematocrit. “By regulating red cell mass by erythropoietin and plasma volume through excretion of salt and water, the kidneys sets the hematocrit at a normal value of 45%” (Henderson, 2001) Dr Sandra Donnelly of the University of Toronto concluded, “This is not a random number but a value that maximises oxygen delivery, to peripheral tissues. The ability of the kidney to co-ordinate these two volumes to generate a hematocrit of 45% establishes it as the logical site of erythropoietin production” Donnelly and colleagues suggested that a portion of the Kidney known as critmeter is the control mechanism in this regulation. Proposed Ergogenic Benefits / why athletes do this? Theoretically if administered to athletes. Human erythropoietin would have the same effects as the reinfusion of red blood cells. The goal of its use is to increase the red blood cell volume, thus increasing the bloods oxygen carrying capacity. (Wilmore and Costill, 1999) Its overall effect is to increase endurance and, in athletics, it is used mainly by long distance-runners. It is injected under the skin and stimulates red blood cell production. The more red cells there are in your body, the more oxygen that can be delivered to the muscles. This delays the onset of fatigue, meaning an athlete can run harder and for longer. Proven Effects Erythropoietin’s ability to increase oxygen capacity was demonstrated in 1991 when the first study of the effects of subcutaneous injections of low doses of human erythropoietin on maximal treadmill time and VO2 max was done. The study involved moderately trained to well-trained subjects. Six weeks after erythropoietin administration, the following effects were observed: o Both haemoglobin concentration and hematocrit increased 10% o VO2 max increased for 6% to 8% o Time to exhaustion on the treadmill increased 13% to 17% Seven of the 15 subjects had been through a previous study of red blood reinfusion conducted four months earlier. Increases in VO2 max and treadmill time were almost identical in both studies and these improvements were attributed to increase haemoglobin. (Wilmore and Costill, 1999) Recently a test was conducted in 2004 by Dr Jones on Stuart Stevens, an amateur cyclist, who tested some of the most controversial supplements in sport which included EPO. Stevens wrote a report on the changes he noticed over a period of time. The first noticeable change was the hematocrit level. Before the first EPO injection the subject’s hematocrit level was 43.8% and within three weeks the subject’s hematocrit level had risen to 48.3%. It wasn’t until the subject took part in an event along the central coast of California that obvious improvements were seen. The cyclist explained: “About ten hours in, it dawned on me that something was definitely happening. Sure, I'd been training hard, but I'd done enough of that to know what to expect. All around me were good, strong riders who looked as worn out as you'd expect after ten hours in the saddle. I was tired, but I felt curiously strong, annoyingly talkative and fresh, eager to hammer the last 40 miles.” After this race the subject felt no soreness whatsoever: “I also felt like I could easily ride another 200, and I realized that I'd entered another world, the realm of instant recovery.” After consulting with Dr. Jones he explained: "With your hematocrit levels higher, you don't produce as much lactic acid, which means you can ride harder, longer, with less stress.” This test proved to show significant results. EPO injections enabled the cyclist to work harder and longer as well as quicker recovery times. This would enable an athlete to train harder and longer, while keeping the hematocrit level below the illegal limit of 50%. (Stevens, 2004) Risks of erythropoietin use Serious consequences can arise form erythropoietin use. Some deaths among competitive cyclists, reported in the early 1990s, were alleged to be linked to erythropoietin use. The outcome of erythropoietin use is less predictable than that of red blood cell reinfusion. Once the hormone has been put into the body, no one can predict how much red blood cell production will occur. This places the athlete at great risk of substantial increases in red blood viscosity, which could lead to clotting or heart failure. Other problems can occur such as headaches, hypertension and seizures. Detection Detection of injected EPO is particularly challenging for two main reasons. First, the drug is rapidly broken down in the body after it is taken. This means that the levels rapidly become too low to detect even though the performance-enhancing benefit may last for weeks. Second, because EPO occurs naturally...