Young at heart, according to the old 1950s tune, is an attitude rather than a number. When doctors talk about being young at heart, they mean something far more tangible–vitality and strength in the body’s most essential organ. And again, this youth has nothing to do with biological age.

In study after study, scientists have demonstrated the benefits of exercise in keeping the heart young, healthy and vital, regardless of age. Whether you’re a competitive athlete, a recreational cyclist or a person who walks for an hour or two a week, your heart is stronger as a result of the physical effort.

One recent study involving 39,372 women aged 45 and older concluded that even those who walked as little as one hour a week had a significantly lower risk of heart disease. Those who exercised for longer periods or more vigorously enjoyed even greater benefits.
Physical inactivity is an official risk factor for heart disease; combined with diet, it’s the second most common underlying cause of mortality in the United States, contributing to at least a quarter of a million deaths each year.

The devastating effects of doing nothing were dramatically demonstrated by a study conducted nearly 40 years ago. Five healthy young male subjects in their 20s saw their bodies age several decades simply by staying in bed for three weeks. In that short period, their muscle mass and maximal oxygen intake (the ability of the heart to distribute and use oxygen) reached a level usually seen only in individuals in their 60s or 70s. Fortunately, after an eight-week intensive training program, all regained their former level of fitness.

The American Way
For most Americans, of course, inactivity takes its toll gradually over the course of several decades. Excess pounds accumulate with the passing of the years, and even those who are reasonably successful at controlling their weight are likely to have an increased percentage of body fat. That is not normal aging, most experts believe, but primarily a result of inactivity, and it can be reversed by exercise.

When subjects of the bed rest study were brought back for a follow-up 30 years later, they were typical of sedentary Americans: they had gained an average of 50 pounds and had doubled their body fat. Even though they were now in their 50s, the men once again reversed most of these effects through exercise–a six-month training program that included four to five hours a week of jogging, brisk walking or riding an exercise bike.
It’s easy to see that exercise is better than doing nothing at all. But scientists are still trying to determine the specific effects of exercise, exactly how it benefits the heart and what types of exercise are most beneficial.

It’s been clearly established that regular exercise, in addition to burning excess calories, has a positive effect on serum cholesterol, an important risk factor for heart disease. Persons who exercise regularly have higher levels of HDL (good) cholesterol and lower levels of harmful LDL and triglycerides.

Most studies suggest that the effect on cholesterol is dependent primarily on the volume of exercise. While one hour a week of exercise may be beneficial, three hours is better and five or six better yet.

Exercise is also known to lower blood pressure, and this too keeps the heart young and vital. For the effect on blood pressure, however, studies suggest that intensity may be more important than volume.
Aerobic exercise, defined as activities that get the heart beating faster for at least 20 to 30 minutes at a time, is directly beneficial to the heart by getting the heart muscle actively involved in pumping blood vigorously through the body.

Studies have consistently shown that competitive athletes have enlarged hearts with greater capacity for work. They have a slower resting heart rate and a quicker recovery after exercise. Recent research has also demonstrated that regular aerobic exercise keeps the lining of the blood vessels young and healthy by ensuring an adequate supply of nitric oxide, a substance that helps dilate arteries and keep blood flowing freely.
All of the above are signs of being physically fit, and another recent study concluded that fitness may be one of the most powerful predictors of how long and how well a person will live.

If you’ve worked out in a health club or gym, you’re probably familiar with the term metabolic equivalent, or MET. One MET equals the amount of oxygen used by an average person seated in a chair. You use about two MET walking at a pace of two miles per hour, five MET at a brisk four mph pace and eight MET when you’re jogging at six mph.
In this study, subjects who could exercise at a level no greater than four MET on the treadmill had double the risk of dying compared to those who could reach eight MET. For every one MET increase in peak exercise capacity, a subject’s chances of staying alive increased 12 percent. Aside from biological age, fitness was the best indicator of potential lifespan.

Fitness is a matter of degree, of course, but a level high enough to keep your heart healthy does not necessitate vigorous or strenuous training–or even formal exercise. It does require physical activity of some kind most days. The total volume should be enough to consume calories, reduce body fat and control weight–usually 30 to 60 minutes a day. At least some of the activity should be intense enough to make you breathe harder than usual and make it somewhat difficult to talk.

Before starting any new exercise routine, Individuals who have previously been sedentary–and especially men over age 40 and women over 50–should consult their physicians and learn what limitations, if any, they might have to observe.
At any age and any level of health or fitness, exercise is a magic formula that can turn back the clock. Even persons recovering from a heart attack are usually prescribed a closely monitored exercise program to strengthen the heart.

In one 14-year study involving 30,000 subjects aged 20 to 93, the most physically active were about half as likely to die during the course of the study as those who were most inactive.