Surveys show that 54% of adults get some exercise, but not regularly enough or intensely enough to protect their hearts. And one-quarter of American adults are not active at all. But summer is here, and there are lots of opportunities for exercise in the great outdoors. A vacation in a national park or even a softball game at a company picnic may inspire you to get your body moving again.

These statistics may help motivate you:

• Physical inactivity doubles your risk for developing heart disease, about the same as high cholesterol, high blood pressure, or cigarette smoking.
• Less active, less fit people have a 30% to 50% greater risk of developing high blood pressure.
• Studies estimate that 250,000 deaths per year from heart disease are due to a lack of regular exercise.

Even activities of low-to-moderate intensity, when done for as little as 30 minutes a day, can bring benefits. Summer gardening and chores, for example, help protect against heart disease. More vigorous activities, such as swimming or bicycling, done several times a week, are best for improving heart and lung health.

But there’s a cautionary note: heavy physical exertion may sometimes trigger a heart attack, particularly in people who are normally sedentary, Swedish researchers reported in the March 2000 issue of the American Journal of Epidemiology.

Among 700 men and women aged 45 -70, about 6% suffered their first heart attack after exerting themselves to the point of "panting and overheating." This rate was six times higher than heart attacks that occurred during lighter activity or rest. Heart attack risk was at its height during the activity, and disappeared 45 minutes after strenuous activity had ended, the researchers reported.

Prior physical fitness seemed to lessen the blow that heavy exertion had on the subjects’ hearts. The highest risk for heart attack was found in those who said they had exercised "very little" throughout their lives. Other studies have also shown that the risk of an exertion-triggered heart attack steadily declines the more a person exercises.

Don't let this preliminary study prevent you from exercising, however. In the long run, a moderate exercise program will help you decrease your risk of heart attack. As with any exercise program, talk to your doctor before you start. If you need a doctor, call 1-888-749-DrDr or click here.

If more exercise is part of your summer game plan, good for you! Now, plan to stick with it throughout the year.