Aerobic Exercise Affects Genes

By Jennifer Viegas, Discovery News 

Oct. 6, 2005 - Regular aerobic exercise awakens mostly inactive genes that can result in improved cardiovascular fitness, but only when the person's body adapts to the stepped-up exercise regime, according to a new study.

While exercise at any level may help to enhance muscle tone and reduce weight, the latest research suggests the greatest improvements to health can occur after regular periods of exercise over time, when genes responsible for the formation of new blood vessels jump into action.

"Aerobic training activates them to enhance oxygen delivery to the muscles," explained James Timmons, lead author of the study. "Aerobic exercise kick-starts these genes to do their job. Otherwise these genes are only found at low levels."

Timmons and his colleagues asked 24 sedentary males to undergo six weeks of high-intensity aerobic cycle training. For four days a week, each subject cycled for 45 minutes at approximately 75 percent of his maximum heart rate.

At the end of the six-week period, the researchers ranked the subjects based on improvements in aerobic fitness.

Some men greatly improved their peak rate of oxygen consumption and were labeled as "high-responders," while others showed little improvement and were called "low-responders."

The scientists obtained muscle biopsies from each study participant both before and after the training period. Tissue samples were analyzed for gene activity, and the results were startling.

Gene activity for high responders increased by as much as 900 percent. Low responders exhibited little, if any, gene activity changes.

The findings are published in this month's BMC Biology journal.

"Our study introduces a new complication - that is, it is possible that some people can't benefit from exercise as much as others, and these people may ultimately be at greater risk of developing cardiovascular disease," Timmons, a scientist at the Center for Genomics and Bioinformatics at the Karolinska Institute in Sweden, told Discovery News.

He added, "On a practical level, the low responders may simply have to invest much more time and effort training to gain the same benefits. This last point is, however, only speculation. The low-responders may always remain low-responders."

Timmons said elite athletes like Lance Armstrong probably were born as "very high responders," which could be why they persist with their sports and ultimately become successful.

Stuart Phillips, associate professor of kinesiology at McMaster University in Ontario, told Discovery News that the new findings "are intriguing and give us further insight into how exercise can affect changes in skeletal muscle."

While he agrees that it is likely some people respond better to exercise than others, Phillips said, "It makes as much sense as ever that we exercise, whether or not we have a good genetic response, since exercise and good health are intimately linked. My advice would simply be that some of us may not be able to change our genetic response, but maximize your chances of good health and keep struggling!"