Researchers study effects of caffeine on cyclists' performance
Amid the flurry of accusations of doping in professional cycling, it turns out there's a perfectly legal performance-enhancing drug for these road racers. It's the same stimulant that many of us rely on to jumpstart our day: caffeine.
But while research has shown that caffeine can boost athletic performance, its effects are far from universal. "If you look at the individual data, it really varies," said Dr. Christopher Womack, associate professor and head of kinesiology at James Madison University and a researcher in the area of exercise science. "For some people, it obviously does a lot, for some people there's no effect and for others it's worse. Often times when you see that, there's a genetic factor at work."
In the spring of 2007, Womack, along with Dr. Michael Saunders in kinesiology and Dr. Marta Bechtel in biology, set out to study whether genetic differences among cyclists would affect their performance on caffeine. For purposes of the study, the researchers focused on a common variance in the CYP1A2 gene, an important enzyme for drug metabolism found in the intestines and liver. "People either have an A allele or a C allele in that position," Bechtel explained. "That one difference, a single nucleotide, determines how well their body metabolizes caffeine."
The team, which included undergraduate and graduate students, tested 35 recreationally competitive cyclists in JMU's Human Performance Laboratory in Godwin Hall. Each participant completed two 40-km time trials about a week apart using a road cycling simulator. "It was just like a competitive situation, just in the lab so we could control for everything," Womack said.
Sixteen of the cyclists had the A allele while the other 19 had the C allele. A group of JMU biology majors performed the genotyping using a technique called Restriction Fragment Length Polymorphism, which is commonly used in forensic science and paternity suits.
Each cyclist completed their trial in the morning following at least 12 hours of fasting and 24 hours of abstinence from caffeine. Prior to testing, participants were randomly given a pill containing either 6 mg of caffeine per kg of body weight — the equivalent of about two medium Starbucks coffees — or white flour (placebo). Neither the cyclist nor the researcher administering the pill knew which substance he was getting. The process was later repeated to test the cyclist's performance on the other ingredient.
The results of the study were significant: the group with the A allele was an average of 3.8 minutes faster on caffeine compared to placebo, while cyclists with the C allele only improved by about 1.3 minutes. "These were recreational cyclists," Bechtel said. "Think about it in the context of the Olympics, where world records are broken and medals are separated by hundredths or even thousandths of a second. That's a huge difference in time."
After initially being turned down for publication, mostly due to sample size, the team tested additional cyclists. The results were finally published in March in the Journal of the International Society of Sports Nutrition.
Womack said there have been numerous studies over the years looking at how small genetic variations can impact a person's health (risk for cancer or heart disease) or physical fitness (cardiovascular endurance, muscle mass, body fat), but to his knowledge, "ours is the first to look at how genetic variances influence the effects of caffeine on athletic performance. We were lucky in that we stumbled on the right genetic variation with the right supplement."
"The idea of a one-size-fits-all supplement has been debunked a little bit," Saunders added. "As an athlete, you may want to consider the individual responses to anything you choose to use as a supplement."
Womack acknowledges that there are other factors that could account for the varying effects of caffeine, including metabolites. He and Bechtel would like to continue the study, especially if they were able to secure external funding.
The study provided students in both departments with valuable clinical experience and brought together faculty with specific areas of expertise. "I've always been interested in exercise physiology, and I'm also drawn to interdisciplinary projects," Bechtel said. "Working with other faculty members can introduce a unique perspective, and it helps with our understanding of the world."
Added Womack: "It's a project none of us could have ever accomplished on our own."
By James Heffernan ('96), JMU Public Affairs
Video by Katie Casey ('13), JMU Public Affairs