Everyone who has taken biology in school has either learned or read about metabolism, catabolism and anabolism. However, these studies did not go very into depth about the thermodynamics of these processes. This is useful to athletes, because metabolism is the source of energy in human beings and could be a major advantage if used to its fullest.
It is easiest to describe these constantly occurring reactions as a process in order to aid understanding. In this example, a molecule containing potential energy is broken down into many smaller particles, releasing energy. In the catabolic reaction, the system is exothermic and has a positive entropy change due to more moles being in the products. Thus, the Gibbs free energy value is negative and this reaction is spontaneous.
Anabolism, on the other hand, is the opposite, requiring energy and building a few larger molecules from many small ones. This makes the system endothermic with a negative change in entropy, which means the Gibbs free energy value is positive and this reaction is non-spontaneous.
One very important metabolic process is respiration.
This uses catabolism to take the energy of bonds in large molecules and transfer that to the cell in order for it to undergo necessary functions. This is a reaction that occurs in all cells of all people to keep them alive. However, one important piece of respiration is oxygen, because respiration is an aerobic reaction. When athletes stress their bodies, oxygen is not able to circulate to every cell in the body as efficiently and this usually causes a lactic acid fermentation reaction to occur.
This is where there is still a demand for energy in the cells, but there is no oxygen so another pathway to energy is used which has the by product of lactic acid. Lactic acid gets a lot of grief from athletes, but the science behind the legs of lead is more interesting than one might realize. What is actually happening is that so much lactic acid is being produced that not all of it can be flushed out fast enough and the increase in acid lowers the pH of the body, subjecting the athlete to temporary acidosis, which causes the pain and the screaming instinct to stop.
(Skip to 2:20 for the race)This video shows Michael Johnson, an American sprinter breaking the world record in the 400m. Johnson is probably one of the best at managing the pain of acidosis from running, and he is certainly the best athlete from his event. But how did he get such big muscles to have such efficient metabolic reactions?
The buildup of tissue comes from anabolism. This is what requires energy in the metabolic process and is associated with the feeling of soreness after a workout. However, this soreness will be worth it, because whenever the new tissue is created it is stronger and better suited for the job it is doing. Michael Johnson got to where he was from hard work and practice. However, there are some in the professional sports world who gain an unfair advantage from using anabolic steroids.
Steroids are banned from professional sports for two main reasons. Morally, the competition is not as legitimate and rewarding if all of the people are using muscles they did not develop themselves and naturally. Perhaps more importantly, anabolic steroids can also have adverse side effects that are dangerous to the health of the athlete.
The fact of the matter is that science does not care what the authorities have said and thermodynamics are still going to work even under a ban. Whether it is ethical or not is not relevant to the reaction, but it is clear that anabolic steroids can help to build muscle which is useful in breaking the home run world record.