Cyclist Lance Armstrong recently admitted that he used performance enhancing drugs during his professional career, including the time during which he won the Tour de France seven consecutive times.

While this admission was in the news, it wasn’t much of a surprise. In October, the U.S. Anti-Doping Agency issued a report, called the “Reasoned Decision,” that laid out compelling evidence that Armstrong and his cycling team participated in a highly organized doping program. As a consequence, Armstrong was stripped of his Tour de France titles and was banned from professional competition.

You probably heard about Armstrong’s recent interview with Oprah even if you aren’t a sports fan or don’t follow cycling, but you may not understand what Armstrong did or why he did it.

The purpose of this column is to explain the techniques used by Armstrong and his teammates. And although several performance-enhancing substances were used, I will focus on blood doping.

First, a little physiology review. Endurance events like distance running and cycling are dependent on the delivery of oxygenated blood to the muscle to produce the energy needed to sustain exercise. For this reason, exercise of this type is called aerobic.

Oxygen use by the muscle is enhanced with training due to increases in the amount of blood the heart can pump to the muscle and changes within the muscle that allow it to take up and use more oxygen to produce energy. This allows athletes to exercise at a higher intensity for a longer time.

Since all of the athletes in a cycling race have trained vigorously, gaining an edge over the competition requires finding a way to improve oxygen delivery to the muscle even more.

Oxygen is transported through the blood by red blood cells. Increasing the number of red blood cells boosts the amount of oxygen delivered to the muscle.

This procedure is called blood doping. Traditionally, this required an athlete to remove a unit of blood and then reinfuse that blood later, closer to the event.

After the blood is removed, the blood oxygen level is lower than normal, leading to the release of a hormone called EPO, short for erythropoietin. EPO causes an increase in red blood cells production.

Since the body replaced the donated red blood cells, the reinfused blood adds extra red blood cells, which carry even more oxygen to the muscle to improve performance.

There is another way for athletes to get the same result without having to donate, store and reinfuse blood.

The hormone EPO can also be produced as a prescription drug that has the same effect.

This drug has legitimate use in treating anemia, including anemia caused by chemotherapy.

Unfortunately, the fact that Armstrong “doped” tarnishes his legacy. Even without the blood doping, he was one of the most highly trained and competitive athletes on the planet.

In a sport in which blood doping is thought to be so common, dedicated training likely contributed to his success as much as the use of banned substances.

His victories in the Tour de France increased the popularity of cycling in the U.S. and promoted the sport among young athletes.

His story of surviving advanced cancer and returning to competitive cycling is inspiring, to say the least, and led to the formation of his important charity foundation.

Hopefully, the fact that he was part of such a broad doping conspiracy won’t diminish these important contributions.

Brian Parr, Ph.D., is an associate professor in the Department of Exercise and Sports Science at USC Aiken where he teaches courses in exercise physiology, nutrition and health behavior.