Physical Fitness Prolongs Lives

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Boosting our exercise capacity may be the most important contributor to longevity.

The News
Everybody knows that exercise is essential to good health, but according to a study in the March
14 New England Journal of Medicine, physical fitness may be even more important to health
than quitting smoking or avoiding diabetes. Men with the greatest capacity for exercise live
longest, reports the study, and exercise capacity is a better predictor of longevity than any other
single health marker.
More than 6,000 middle-aged men, many of whom had heart disease, underwent an exercise
stress test that involved walking on a treadmill with increasing speed and upward incline until
the participant became exhausted and intolerant of further exercise. By calculating the energy
needed to walk or run at that maximal speed and incline, the researchers determined each
participant's exercise capacity - expressed in "metabolic equivalent units", or METs. (While at
rest, you expend roughly 1 MET of energy, whereas while jogging, you expend about 7.)
The researchers followed the participant for an average of six years and studied the relation
between exercise capacity and mortality. Not surprisingly, participants with the highest exercise
capacities had the lowest death rate. Men with exercise capacities of more than 8 METs had
roughly twice the survival rate of men with exercise capacities of less than 5, regardless of
whether they smoked, were obese or had high blood pressure (hypertension), high cholesterol or
diabetes. And each additional MET of exercise capacity increased the chances of survival by 12

The Physicians Perspective
Mary Norine Walsh, MD

Having just unlaced my sneakers after a walk on the treadmill, I am eager to use the information
in this NEJM study to further encourage my patients to fit exercise into their daily schedules.
The role of physical fitness in the prevention of cardiovascular disease has been well recognized
for some time. Many studies have shown that increasing one's level of physical activity decreases
the risk of death. Other studies have shown that regular exercise can affect the conditions that
often lead to heart disease.
For example, regular exercise can reduce the chances of developing diabetes and hypertension,
and it can lower blood pressure among people with existing hypertension. Obesity is now well
known as an independent risk factor for the development of heart disease, and regular exercise is
important in preventing obesity through weight loss and weight control. The current study adds
to our knowledge about the benefits of physical fitness because it examines outcomes in people
with and without heart disease. This information is a little different from that in previous studies
because all the men in this study were referred by their doctors for a stress test. This presumably
means that they had previously diagnosed heart disease or had symptoms or risk factors for heart

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For this group of men with or at risk for heart disease, peak exercise capacity was a more
accurate predictor of their health outcomes than all other noted health characteristics - the
presence of diabetes, hypertension, smoking habits, or even an abnormal exercise test.
However, these findings do not suggest that hypertension, smoking, diabetes, obesity, and
abnormal cholesterol levels should be ignored as predictors of heart disease. They do suggest
that people with such risk factors can significantly lower their risk by maximizing their exercise
This information puts a powerful, relatively simple, and inexpensive tool in the hands of
physicians: an exercise test that can often be done at the time of a yearly physical and can predict
a patient's risk of death. For patients with very low exercise capacities (less than 5 METs, for
example), such testing can help us determine a very concrete exercise prescription. Because each
additional MET conferred a direct increase in survival, mapping out a MET-based goal tailored
to an individual's baseline is pretty straightforward.
Even though this study was quite large, it included no women. Although it’s not always
legitimate to extrapolate research results from one sex to another, we are probably safe in
applying this study's results to female patients. Some parameters of exercise testing differ greatly
between men and women, but previous studies of exercise capacity have demonstrated survival
benefits for both women and men.
To improve exercise capacity, you should adopt activities that require higher energy
expenditures than you currently perform. For example, if your preferred form of exercise is
walking (which uses 3.5 METs), consider taking up dancing or golf (which use 4.5 METs) to
increase your capacity. But any increase in physical activity must occur gradually and with the
direction of a doctor, especially if you've been sedentary or have heart

Mary Norine Walsh, MD, is a cardiologist and clinical assistant professor
of medicine at the Indiana School of Medicine

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