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If you need yet another reason to work on improving your fitness level, you might find it in the results of a study published Monday in Circulation: Journal of the American Heart Association.
Researchers found that cardiovascular fitness level predicts death in women with no symptoms of heart disease more than in men, also with no symptoms. They found that the higher the fitness level, the lower the risk of death.
Here's how researchers arrived at that conclusion:
They started the study in 1992 and followed 5,721 Chicago women through 2000. The women did not have heart disease, but many had risk factors such as high blood pressure, high cholesterol and diabetes. The average age of the women was 52.
To begin the study, each woman underwent an exercise stress test on a treadmill that became steeper and faster every three minutes until she became breathless, dizzy or exhausted. Researchers measured fitness level, or exercise capacity, in metabolic equivalents, or MET.
Fitness levels ranged from 1.5 MET for the least fit to 20 METs for the most physically fit. The average fitness level was 8 METs.
Then, researchers compared women's exercise capacity to death from all causes during the next eight years. They found that for every one MET increase in exercise capacity, there was a 17 percent drop in risk of death.
The risk of death doubled for those whose fitness levels ranged from 5 METs to 8 METs compared to those higher than 8 METs.
There have been studies on the relationship between fitness level and risk of death among men with no symptoms of heart disease. One study showed that for every 1 MET increase in fitness level, the risk of death dropped by 7.9 percent.
Researchers concede that the study has an important limitation: Fitness levels usually are determined by measuring how much oxygen a person consumes during physical activity, not by the amount of METs.
Still, the study has important value because it's the first to look at the relationship between fitness level and risk of death with results that can be applied to the general population. The only comparable study excluded women with diabetes and hypertension, conditions which are risk factors for heart disease.
"You could draw the conclusion that improving your fitness will probably improve your survival," said Dr. Martha Gulati, co-author of the study and assistant professor of medicine at Rush University in Chicago. A separate study needs to be done to prove this, wrote Gulati and her colleagues.
Some might argue, "Well, what about the occasional endurance athlete who dies during physical activity? Doesn't that demonstrate that higher fitness levels can trigger a fatal heart attack?"
No, Gulati said. Those cases are rare but dramatic and therefore, get a lot of attention, she said. Most people who exercise can safely increase fitness levels gradually.
(Lisa Liddane is a health and fitness writer for The Orange County Register and an American Council on Exercise-certified group fitness instructor. Write to her at the Register, P.O. Box 11626, Santa Ana, Calif. 92711 or send e-mail to email@example.com.)
(c) 2003, The Orange County Register (Santa Ana, Calif.). Distributed by Knight Ridder/Tribune News Service.