Sports Health

Dr. Christine Thorburn

As racers navigate sharp curves , race down hills  and make steep climbs mile after mile, one wonders how they find the energy after they have cycled for so long already. The answer involves more than just well developed muscles. Top cyclists use training techniques that actually change their bodies’ cells.

“Human bodies generate energy to move muscles by breaking chemical bonds that hold molecules together,” explains Dr. Christine Thorburn, a rheumatologist at the Palo Alto Medical Foundation (PAMF) who competed in women’s cycling in both the 2004 and 2008 Olympics. “As part of this process, lactic acid is created. It used to be thought that this acid was just waste and the cause of muscle fatigue and soreness. However, research has shown that the body’s cells can actually take excess lactic acid and convert that to even more energy. Training improves this ability.”

As a medical resident at Stanford University during her first Olympics and a practicing physician during her second Olympics, Dr. Thorburn understood the importance of what was happening inside her cells to the outcome of her races.

“Part of what makes Lance Armstrong such a good cyclist is that he can process lactic acid into additional energy very effectively,” Dr. Thorburn says. “When someone is not very well trained – as I am now that I am retired – lactic acid will build up during strenuous cycling and one’s leg muscles will begin to burn. Once this happens, an untrained person has to stop and rest. They cannot recover. Keep going and one may start to feel dizzy and stop thinking clearly. However, a well trained cyclist can go above his or her lactic acid threshold for several minutes at a time, recover and then do it again two or three more times during a race.”

Cyclists have to go above their lactic acid threshold when “attacking” in a race to gain an advantage over the rest of the group of riders drafting one another. At the end of an “attack,” the body has to process the excess lactic that built up during the sustained burst of energy. Some lactic acid is processed by the liver, but much of it is taken up by a portion of individual body cells called the mitochondria. The mitochondria are the cells’ engines and create additional energy as they break down and get rid of the lactic acid.

Through interval training – which involves short bursts of high intensity exercise interspersed with low intensity exercise that allows the body to recover – cyclists can increase the number of mitochondria inside their cells. With more mitochondria, the cells become even better at processing lactic acid.

In training for the Olympics, Dr. Thorburn and other U.S. cycling team members used sophisticated tools that let them scientifically measure everything from the force they applied to the bike pedals to the lactic acid levels in their blood. They then used these measures in training to maximize their ability to process lactic acid during races.

“Training is all about knowing when you are going above your lactic acid threshold and knowing how long you can sustain that effort,” Dr. Thorburn says. “In training, you can use tools to help identify when you are in that zone, but in a race you have to go by what you are feeling.”

{ 0 comments }

Protecting Cyclists from Doping Pressures

As Stage 3 finishers of the Amgen Tour of California streamed across the finish line at the Santa Cruz Boardwalk in May this year, they were met by a small group of medical professionals and volunteers that stayed with the top five finishers until they completed an important post-race doping test. Like last year, this group included Leonard Moore, M.D., a Palo Alto Medical Foundation dermatologist and cycling enthusiast.

“Testing for performance enhancing substances does more than protect the integrity of the race,” Dr. Moore explains. “It protects the health of the athletes and that of young people who look up to them and seek to follow their example.”

The link between serious health problems and taking steroids, hormones, amphetamines and other performance enhancing chemicals have been well known for decades among cyclists. In a widely reported case, British cyclist Tom Simpson died during the 1967 Tour de France after taking amphetamines.

However, because the health problems that come from doping develop slowly over time and only very rarely touch a cyclist at the peak of performance – as in the case of Tom Simpson – the pressure to excel in a race can easily overwhelm concern for one’s long-term health.

“This is especially true for young athletes,” Dr. Moore explains. “Like most healthy young people, they are typically unconcerned about problems that may not affect them for decades, such as heart disease and cancer. In addition, they may be more easily influenced by the desire to please a coach, mentor or parent.”

As a dermatologist, Dr. Moore regularly sees how choices about sun exposure made as a young person can increase skin cancer risks, and the choice to take illegal performance-enhancing drugs is similar in that the effects of this choice may not be felt until much later in life.

“In all sports, when people are abusing drugs, young people may think that they can do that and get away with it,” Dr. Moore says. “Unfortunately, for most of us, the health consequences of taking these types of drugs will catch up with us sooner or later.”

The Amgen Tour of California Anti-Doping program starts before the race with blood testing of all riders and urine testing of 30 percent of the riders. In addition, every day, the stage winner, current leader of the general classification and additional riders are screened for steroids, hormones, stimulants and chemicals that can mask the presence of performance enhancing agents in blood and urine tests. There is also random full screen testing every day for additional riders.

“My small part is simply to follow an assigned cyclist from the moment he finishes the race until he provides a urine sample to ensure that there is no possible tampering with the test,” Dr. Moore says. “However, I am proud of even this small role. As both a race fan and a doctor, it is very important to me to ensure a level playing field, especially for the youth. If they know that it is a level playing field, they will be safer for the rest of their lives.”

Dr. Moore is an avid cyclist, California Triple Crown participant (5 times) and bicycle commuter. He is a skier (downhill, telemark), jogger, backpacker and trumpeter.

{ 0 comments }