Summer 2002

Begin an exercise program—it’s never too late!

by Jeff Novick, M.S., R.D., L.D./N.

Many people do not exercise because they either think that they do not have the time to exercise, or because they can’t engage in more vigorous exercise and believe that less vigorous exercise isn’t beneficial.

The Centers for Disease Control and Prevention and the National Institutes of Health recommend that Americans should accumulate at least 30 minutes of moderate-intensity physical activity on most (preferably all) days of the week.

Two studies took a closer look at this issue, and reported on just how much exercise is enough in order to get health benefits.

In one study, published in the October issue of the Journal of the American Geriatrics Society (1999; 47:1208-1214), it was shown that lifting weights as little as once a week can increase strength and functional performance in individuals aged 65 to 79 years.

In people over 65 years, resistance training “is now recognized as a safe and effective method for strength development and an important contributor to maintaining independence and enhancing physical capabilities,” according to Dr. Dennis Taaffe from the Veterans Affairs Medical Center in Palo Alto, California, and colleagues. The investigators assigned 19 women and 34 men to one of four 24-week regimens: three sets of eight muscle strength exercises once, twice, or three times weekly, or continuation of usual activity alone. All three exercise groups increased their muscle strength — ranging from 37% to 42% during the 24-week program — significantly more than the control group (4%), the report indicates. The exercise groups also experienced an increase in lean body mass compared with the controls without an increase in fat mass.

Interestingly, the team found no difference among the three exercise groups for upper body, lower body, or whole body strength.

As tests of physical function, the exercise groups all performed more quickly in rising from a chair and in toe-to-heel backward walking for 6 meters (nearly 20 feet) compared with the control group, according to the results.

Thus, “participation in resistance exercise twice, or even once, each week achieves substantial strength gains similar to those accomplished in a standard 3-day per week program, and these gains are accompanied by improved neuromuscular performance,” the investigators conclude.

“As declining muscle strength and balance promote falls and fractures in older adults, we suggest that a high-intensity, progressive resistance training program of only one session per week may prove useful in reducing the risk of falls and, hence, fracture,” Taaffe and colleagues propose. While the benefits of regular exercise are well known, many of us don’t engage in exercise often because we think we do not have the time.

Obesity and a sedentary lifestyle are major risk factors for several diseases like type 2 diabetes. Type 2 diabetes, also known as non-insulin dependent diabetes, is strongly associated with obesity. Losing weight is usually the first step in treating the disease. Physical activity can help reduce the risk of type 2 diabetes by assisting in weight reduction and by helping the body use the hormone insulin more

efficiently.

Another study, reported in the October 20th issue of The Journal of the American Medical Association (JAMA, 1999; 282:1433-1439), looked at the relationship between exercise and diabetes risk. They found that just one hour per day of walking (or another form of moderately intense physical activity such as doing housework) can substantially reduce diabetes risk, even as much as the reduction in diabetes risk linked to more vigorous exercise, such as running or jogging, report researchers. One hour of brisk walking everyday can cut the risk of developing type 2 diabetes in half.

In the study the investigators evaluated responses to questions about the intensity and duration of physical activity provided in 1986 by roughly 70,000 women participating in the Nurses Health Study. The women were free of heart disease, diabetes, and cancer at the time they answered the questions. During 8 years of follow-up, 1,419 women developed diabetes. After taking into account known risk factors for diabetes, a relationship between physical activity and the risk of type 2 diabetes emerged. “Increasing physical activity substantially reduced the risk of type 2 diabetes,” said Dr. Frank B. Hu of the Harvard School of Public Health, who led the study. “What is particularly interesting,” he said, “is that the risk reduction for moderate-intensity activity such as walking is the same as that for more vigorous forms of activity such as running or jogging, if the energy expenditure is the same. Total energy expenditure is the most important (factor).”

The finding that moderate exercise such as walking reduces the risk of diabetes just as more vigorous exercise does is “reassuring,” Hu and colleagues write in the JAMA paper. “Walking is a physical activity that is highly accessible, readily adopted and rarely associated with physical activity-related injury,” they note. It appears from this study, Hu added, that “it doesn't matter how you (expend energy) as long as you do.”

These two studies clearly indicate the benefits you can receive from just one weight lifting session per week and one hour of daily walking. And, as the study on weight lifting showed, it is also never to late to begin an exercise program.

To give you an idea of how quickly your body can part with calories, here are some activities people enjoy and the number of calories they burn per hour for a 150-pound adult.

Activity Calories Burned per Hour

Bicycling 400

Canoeing 180

Cooking 180

Dancing, ballroom 240

Gardening 480

Golf 345

Jumping rope 570

Ping-Pong 285

Playing piano 165

Racquetball 615

Swimming 525

Tennis—doubles 270

Tennis—singles 435

Volleyball 330

Walking, brisk 360

Reprinted from The Cancer Project/The Roles of Exercise and Stress Management, Physicians Committee for Responsible Medicine.