After 30 aerobic fitness declines rapidly

Jul 27 2005

As if you did you didn't already know, without a team of scientists telling you, your physical fitness is on the decline once you hit 30, but now, even more depressingly for the grey brigade of fitness fanatics out, a new study shows that the decline gains speed with each decade, regardless of a person's previous exercise habits.

In a study of 810 healthy adults it was found that the rate of decline in aerobic fitness was about four times greater among people in their 70s or older, compared with those in their 20s and 30s, and regardless of the fact that it boosts aerobic fitness, regular exercise did not change a person's rate of age-related decline.

But hold on, don't chuck in the towel yet, according to the study authors, at any given age, people who were at least moderately active were more fit than their sedentary peers.

Lead author Dr. Jerome L. Fleg of the National Heart, Lung, and Blood Institute (NHLBI) also says that his research shows that older people can improve their aerobic capacity by getting regular, moderate exercise like walking.

According to Fleg, the point of it all is to encourage elderly people to stay fit enough to perform daily activities such as housework or gardening, and maintain their independence as long as possible.

Fleg and his colleagues at the National Institutes of Health looked at changes over time in individuals' VO2max, a measure of aerobic fitness that refers to how much oxygen the body uses during a given activity.

The VO2max is the point at which the body can no longer ramp up its oxygen use to keep up with the intensity of the exercise, and the activity rapidly becomes unsustainable.

Although the researchers already knew that a person's VO2max declines with age, the rate of that decline was unclear, because other studies on the subject have usually compared different age groups, rather than following the same people over time.

This study included healthy men and women between the ages of 21 and 96 who periodically underwent treadmill tests to gauge their VO2max.

The researchers also charted changes in participants' blood pressure, body composition and lifestyle habits, over an average of eight years of follow-up.

As a rule, the team found that VO2max declined by 3 to 6 percent per decade while people were in their 20s and 30s, and the rate of decline increased with age, going above 20 percent per decade among adults in their 70s or older.

But Fleg says there was some good news; active people appeared to maintain a higher VO2max than sedentary people of their age, indicating yet again the importance of staying active throughout life.

Fleg advises that older, sedentary adults who want to improve their fitness should consult their doctors before starting to exercise, as should anyone with heart disease.

The study findings are published in Circulation, the medical journal published by the American Heart Association, August 2, 2005.