April 15, 2003 -- You can run, but you can't walk away from the risk of early death due to heart disease, according to a new study. Researchers found that low-intensity exercise such as walking may provide other health and mental benefits, but it isn't likely to ward off heart disease and premature death.
The study, published in the May 2003 issue of the journal Heart, suggests that only more strenuous exercise and physical activity, such as jogging, swimming, and climbing stairs, on a regular basis can significantly reduce the risk of early death due to heart disease.
Researchers say many studies have shown regularly engaging physical activity can help people live longer, healthier lives. But it's not clear what intensity of exercise provides the most consistent health benefits.
Current U.S. Surgeon General guidelines recommend that people engage in moderate exercise or physical activity, such as brisk walking, for at least 30 minutes most days of the week to reduce the risk of heart disease.
But some studies suggest that only vigorous exercise provides significant benefits in staving off heart-related death, while others say light and moderate physical activity, like walking, can also reduce the risk of heart disease and premature death.
In this study, researchers compared the intensity of leisure time physical activities and the risk of premature death among a group of 1,975 men with evidence of heart disease from Caerphilly, Wales, over a period of 11 years.
Researcher John Yarnell, MD, of Queens University in Belfast, Northern Ireland, and colleagues asked the men about what type of non-work-related physical activity they usually participated in. The men were then were divided in to three categories according to the intensity of their usual form of exercise:
- Light -- Walking, bowling, and sailing
- Moderate -- Golf, digging, and dancing
- Heavy -- Climbing stairs, swimming, and jogging
Aside from the cancer-related deaths, the study found that men in the least active group had the highest rates of premature death. But the men who engaged in the heaviest levels of exercise had the lowest risk of death from all causes as well as heart disease.
The study found that the 20% of the men who regularly participated in heavy exercise were 62% less likely to die early from heart disease -- even though they only expended an average of about 54 calories a day. That energy expenditure translates to about nine minutes of jogging or seven minutes of climbing stairs.
Researchers say the intensity of the exercise rather than the calories burned seemed to be the critical factor in reducing the risk of heart-related death. Men in the light-to-moderate exercise group burned an average of 343 calories per day (equivalent to a 90 minutes of walking or an hour of ballroom dancing), but they did not experience any reduction in the risk of early death due to heart disease.
Cardiologist Richard A. Stein say this study suggests that there is a threshold to how low you can go when it comes to reaping the benefits of exercise and physical activity.
"This is an interesting study that suggests that very slow walking or strolling does not afford much cardioprotective value," says Stein, who is chief of cardiology at the Brooklyn Hospital Center and a spokesman for the American Heart Association (AHA).
He says the light level of physical activity examined in this study falls well below the moderate-intensity exercise recommended to reduce the risk of heart disease. A brisk walk, for example, equates to about a mile per 15 minutes and burns about 100 calories per mile, which is about twice as fast as the rate mentioned in the study.
"Some exercise is better than none, but more is better than less. And more intensity is better than less intensity," Stein tells WebMD. "Many of the heart health gains can be achieved with moderate physical activity for 30 minutes five to seven days a week or moderately vigorous activity for 40 minutes three times per week."
Stein says people can determine their own level of moderate activity by asking themselves what their perceived level of exertion is while exercising on a scale from one to 10, with one being sitting in front of the TV and 10 being finishing a race. He says a self-reported rate of about 7 or 8 is a good level of exercise.
But the AHA recommends that people who are sedentary should gradually build up to a level of exercise and physical activity that is appropriate for them under a doctor's supervision.