You've heard it over and over again - regular exercise is an important part of a healthy lifestyle. Not only can it help you control your weight, but it may help protect against certain diseases, such as heart disease, diabetes, and osteoporosis. But a recent study in the New England Journal of Medicine found a direct association between physical fitness and risk of death. In short, poor physical fitness was a strong predictor of death.

Testing men on treadmills

Researchers in California studied 6,213 men, average age 59, who were referred by their doctors for a treadmill test - a test in which the men exercised on a treadmill while their heart activity and blood pressure were monitored and their exercise capacity measured. The researchers also recorded detailed medical histories for all of the men, and, based on these histories and on their performance on the exercise test, the men were classified as having cardiovascular disease or not. Of the 6,213 men, 3,679 had heart disease and 2,534 did not.

After 6 years, the researchers documented how many of the men had died during that time (the cause of death was not known). They then compared the exercise capacity of the men who died with that of the men who were still alive at the end of the study.

Exercise capacity and risk of death

Men with the lowest exercise capacity were more than four times more likely to die than men with the highest exercise capacity. This was true for men with and without cardiovascular disease, suggesting that exercise capacity may even offset some of the risks associated with cardiovascular disease. Overall, as exercise capacity decreased, the risk of death increased.

After taking into account the men's age (because advancing age is another predictor of death), poor exercise capacity was the strongest predictor of death - stronger than factors such as smoking, high blood pressure, or diabetes - regardless of whether or not the men had heart disease.

Enhancing longevity and vitality

While this study does not prove that poor physical fitness causes death, it certainly adds to existing evidence that being physically fit may help you live a longer, healthier life. It may even improve your quality of life, because as exercise makes you strong, fit, and flexible, it can make day-to-day activities, such as yard work, housekeeping, babysitting, and grocery shopping easier and even more enjoyable.