WASHINGTON (AP) -- You don't have to be a super-athlete to significantly reduce your risk of stroke, but you do have to exercise consistently, a recent study finds.

"It adds to evidence that an active way of life may prevent stroke death," said researcher Steven N. Blair of the Cooper Institute of Dallas, co-author of the report in the April issue of the journal Medicine and Science in Sports and Exercise.

Blair and colleague Chong Do Lee of West Texas A&M University looked at data on 16,878 men ages 40 to 87 who had no history of heart attack or stroke at the start of the study.

The researchers gave the men treadmill tests of their fitness levels, and sorted them into low-, medium- and high-fit groups.

The men in the highest fitness group had a 68 percent lower risk of stroke death than the men who were in the lowest group, the study found. But the men in the moderate group had almost as much benefit - a 63 percent lower risk.

Other studies have indicated that simply being active - doing things like walking regularly - might reduce stroke risk. "I would strongly recommend to those 50 million inactive adults to participate in any kind of exercise, to protect against stroke mortality," Lee said.

But this study documented a striking benefit from strenuous activity that can produce fitness gains.

To be moderately fit, a person would have to run regularly for 20 to 40 minutes, three to five times a week, Lee said. To be highly fit, a person would have be at the recreationally competitive level, Lee said.

The findings are in line with previous research on the protection that exercise gives against dying of a heart attack.

Early studies on heart disease commonly focused on runners, and sparked the running boom of the late 1960s and early 1970s.

Later research, including work done by Blair, found that it took far less intense activity to get out of the highest risk group for heart disease - those people who do no exercise. These studies led to the Surgeon General's recommendations that people do at least 30 minutes of moderate activity such as walking or gardening on at least most days of the week.

The new findings on stroke are similar to those on heart disease in that the biggest benefit comes from getting out of the lowest-fit group, said researcher Barry Franklin of William Beaumont Hospital, Royal Oak, Mich, who was not involved in the study.

The study also indicates that the effort required to be a super-athlete doesn't mean there is automatically much greater protection against stroke death, compared with a moderate level of fitness. "That kind of finding is coming up with increasing frequency in the last decade or more," said researcher Carl Foster of the University of Wisconsin-La Crosse.

Of the 16,878 men who were followed for an average of 10 years, there were 32 stroke deaths. Fourteen of them were in the low-fit group.

The study authors and outside experts agree that 32 deaths do not create enough comparison cases for scientists to prove that the risk reductions among the more fit men were due to exercise. But they also agree that the connection between exercise and a reduced risk of stroke death is likely.

For one thing, heart attack and stroke can arise from similar conditions, such as high blood pressure, obesity and diabetes. For another, the benefit of exercise seems similar. For instance, exercise seems to keep arteries healthier, reducing the chance that clots may form in blood vessels of the heart or brain.

The authors note that the study did not look at whether exercise would prevent stroke or simply reduce the risk that the stroke would be so severe that the victim would die.

"I would hope studies would be able to show the effect on occurrence of stroke as well," said Dr. Ralph L. Sacco of Columbia Presbyterian Medical Center in New York.

However, the benefits against the risk factors for stroke are well known, and physical activity is commonly prescribed for stroke victims, Sacco said. "Physical activity needs to be emphasized as a preventive, modifiable behavior that can translate into a reduced number of strokes," he said.

Copyright 2002 The Associated Press. All rights reserved.