Women with no heart-disease symptoms who had below-average stamina on a treadmill or whose heart rate dropped more slowly than average after exercising were 13 times more likely to die of heart problems than those who were above average on either measure, a 20-year study of nearly 3,000 women, average age 47, found.

You can safely test your own heart-rate recovery if you have no heart-disease risk factors or symptoms. Here's how: Exercise very strenuously until your heart rate reaches its peak, then stop and immediately take your pulse. Sit down for two minutes, take your pulse again and compare the two numbers. A difference of 55 or more beats per minute is ideal. Don't despair if your score is below par, though; just get moving, says study author Samia Mora, M.D., M.H.S., of Johns Hopkins University in Baltimore: "We found that even if a woman was overweight, if she exercised regularly, she had a higher heart-rate recovery and exercise capacity than a woman who didn't."