Lance Armstrong, who recently dropped his fight against doping charges.
The excitement of the London 2012 Olympics and Paralympics has now passed; over a month of athletes pushing themselves to the limits of their physical capabilities, and spectators around the world watching in awe.
It is startling to think that the molecule that allowed Usain Bolt to fly down the track and defend his title is the very same used to keep us onlookers on the edge of our seats.
Every action, whether leaping off a starting block or shouting words of encouragement, requires energy. This is obtained from the breakdown of glucose, which releases chemical energy used to make a molecule called adenosine triphosphate, or ATP.
It is in turn the breakdown of ATP that releases the energy required for muscle contraction. The more physical the activity, the more ATP you use, so enough would be produced by Bolt for a gold medal performance.
Endurance sports rely on efficient oxygen delivery to the muscles in order to keep them working for a continuous period of time; so the better the oxygen uptake in muscles, the greater the endurance.
While the maximal oxygen uptake for an average male is 35-40 millilitres or kilograms per minute, an elite male runner can achieve an oxygen uptake of up to 85 per minute.
Oxygen is carried from the lungs to muscles by erythrocytes (red blood cells). The production of these cells is controlled by a hormone called erythropoietin, or EPO. It functions by binding to a specific receptor and stimulating erythrocyte precursors, found in the bone marrow of humans.
Low oxygen levels trigger the production of EPO in the kidneys and liver, which helps maintain healthy erythrocyte numbers. More erythrocytes allow greater oxygen uptake, but regulation is important as having too many can increase blood viscosity, reducing blood flow and increasing chances of blood clots and in turn heart attack and stroke.
Athletes can increase their oxygen delivery by altering their red blood cell count; this is known as “blood doping” and was banned from the Olympics in 1985.
The methods used to achieve these effects include red blood cell transfusions, a process involving a transfusion from either a compatible donor (homologous) or the athletes themselves (autologous), and injections of pharmaceutical EPO, usually used to treat certain cases of anemia.
Altitude training, and machines used to simulate these low oxygen conditions, can also stimulate EPO production. Haematocrit, the percentage of blood made up of red blood cells, varies naturally between people, and certain genetic mutations can confer huge advantages. Finnish skier Eero Maentyranta, winner of seven Olympic medals, had a mutation in his EPO receptor gene, giving him 40-50% more red blood cells than an average competitor.
Director of the Oxford Uehiro Centre for Practical Ethics, Professor Julian Savulescu, puts forward an interesting perspective, proposing that focus should be on which risks athletes should be exposed to rather than the origin of that risk.
In terms of blood doping, he suggests rather than the ban, a blanket haematocrit limit, above which athletes should be excluded for health reasons.
More permissive policies may reduce both the risk of unsafe drug dosages, and the focus on developing undetectable drugs, regardless of health concerns. Understanding the biology of performance can help us judge what enhancement really entails.
Photo: Flickr – Puliarf.