The study, published in Circulation: Journal of the American Heart Association, finds intensive exercise helps prevent the shortening of telomeres -- DNA that protects chromosomes from damage.
The shortening of telomeres, say the researchers, limits the number of divisions cells can make and speeds up the "biological clock." Longer telomeres slow the aging of the cardiovascular system.
The researchers measured the length of telomeres in blood samples from two groups of professional athletes -- professional runners with an average age of 20 and middle-aged athletes with a history of continuous endurance exercise since their youth whose average age was 51.
The exercisers were matched by age to two groups who were healthy nonsmokers, but not regular exercisers.
"The most significant finding of this study is that physical exercise of the professional athletes leads to activation of the important enzyme telomerase and stabilizes the telomere," lead author Dr. Ulrich Laufs of Saarland University in Homburg, Germany, says in a statement.
"This is direct evidence of an anti-aging effect of physical exercise. Physical exercise could prevent the aging of the cardiovascular system, reflecting this molecular principle."