TAKE A HIKE.

The Benefits of Exercise

Television. Cars. Computers. Remote controls. Elevators. Escalators. E-mail. Leaf-blowers. Golf carts. Automatic doors. Automatic windows. Automatic toilet-flushers.

It all adds up. Little by little, we're turning into a nation of couch potatoes. And we're paying a price for it. Inactive people have a higher risk of heart disease, diabetes, colon cancer, obesity, and osteoporosis.

That doesn't mean that everyone has to take up in-line skating or join a neighborhood soccer team. For many, the answer is simply to put activity back into everyday life.

Getting off the couch doesn't just ward off life-threatening illness. It may also help you function like you're 20 years younger, cut your odds of ending up in a nursing home, help you sleep better, ward off colds, and improve your outlook on life.

Need any more reasons to take a hike?

Warding Off Disease

Q: What benefits of exercise are the most certain?

A: Exercise can help you live longer and make you less likely to die of heart disease and stroke. It can reduce the risk of type 2 [adult-onset] diabetes and colon cancer. And almost everyone believes that an active life should prevent obesity, though that hasn't been studied in detail.

Q: How much longer would you live?

A: Regular exercise would increase average longevity by two or three years. That doesn't seem like very much, but if someone tomorrow found a magic bullet that completely cured all cancer, average longevity would increase by less than two years.

Q: If curing all cancer adds only a few years, why do we live 20 or 30 years longer than we used to?

A: Because we've prevented deaths in childhood. Only that can change average longevity dramatically.

Q: How does exercise protect the heart?

A: It lowers blood cholesterol and blood pressure. That's not the entire explanation, though, because if we factor out those variables, exercise has an independent effect. Part of it is that if you exercise regularly, your heart is a bigger, stronger, better pump. You're better able to survive your first heart attack, because you've got more heart muscle left. In addition, there are probably other as yet understood ways in which exercise reduces risk.

Q: How does exercise prevent diabetes?

A: It improves carbohydrate metabolism by increasing insulin sensitivity. In our new study, the rate of developing diabetes in unfit men was more than three times higher than in high-fit men. Fitness reduced the risk even in fit men who were overweight.

My belief is that type 2 diabetes is a disease of inactivity. It's virtually never seen in people who are highly active and have been highly active over their lifetimes. Runners just do not develop type 2 diabetes.

Q: What makes you say that exercise prevents colon cancer?

A: The documentation is really pretty consistent. Researchers see an association between inactivity and colon cancer even after they account for diet, obesity, and socioeconomic status. We've seen the association in several populations around the world for both men and women. That's why the 1996 Surgeon General's report concluded that activity protects against colon cancer.

Q: What kind of activity?

A: For colon cancer, we don't have a lot of data on different types or intensity. In fact, several studies measured on-the-job activity. But if you take all the studies on exercise and health, I think the single most important factor is simply the total energy expended in activity. The cells in your body don't know if you're jogging or doing aerobic dance or working hard in the fields.

Q: So you add up the calories you burn every week or every day?

A: Yes. If you do 1,000 calories of exercise in a week--that's walking about two miles a day for five days for a 150- or 160-pound person--I don't think the pattern, type, intensity, or duration matters. I can't say that it makes absolutely no difference, but we can be fairly confident that total work done is the most important factor.

Q: How might exercise prevent colon cancer?

A: One theory is that people who exercise more tend to have different bowel habits--waste moves through their systems more quickly. If colon cancer is caused by carcinogens in the fecal waste, they may not be in contact with the intestinal lining as long. Exercise also enhances immune function, so that's another possibility.

Q: Does exercise prevent other cancers?

A: A lot of people have high hopes for breast cancer and I hope they're right, but the studies are equivocal. Some show that active women have a lower risk, one or two show a higher risk, and several studies show no relationship. So it's just not clear what role, if any, activity may have in breast cancer.

Q: Is it clear that exercise lowers blood pressure?

A: Yes, in most people. And exercise prevents high blood pressure in the first place.

Q: Is that because exercise helps prevent obesity?

A: Not entirely. In our studies, we have an objective measure of fitness from a maximal exercise test--we see how long people can exercise on a treadmill. We look at fitness when people enter the study and then see who develops high blood pressure over time. High-fit people are much less likely to develop high blood pressure than low-fit people. That's true for men and women, the young and the old, the fat and the lean, and for those with and without a family history of high blood pressure.

Fit and Fat

Q: So you can be fat and fit?

A: Yes. We haven't studied this yet in our women, but in the men who are overweight or obese, but also moderately or high-fit, we don't see much increase in the risk of dying.

Q: Is that true for more than blood pressure?

A: Yes. Claude Bouchard and his colleagues at Laval University in Quebec had a small group of obese women exercise 90 minutes a day for 14 months--prodigious amounts of exercise. Then he had them continue the exercise and eat a low-fat diet for another 15 months. Although the women lost an average of 24 pounds, they were still obese. Yet metabolically--cholesterol, blood sugar, and so forth--they were normal. So activity is good for you whether you're obese or thin.

Q: But most overweight people are not fit?

A: Right. When we looked at overweight men as a group, they were less physically fit and had the highest death rate. It's only after we looked separately at the overweight men who were fit that we saw a lower death rate. Being fit lessens the harmful effects of obesity.

Q: And the more fit, the better?

A: Yes. We look at low-fit, moderate-fit, and high-fit individuals. Moderate fitness is what you would develop if you followed recommendations to accumulate 30 minutes of moderate-intensity activity most days. That's the advice of the American College of Sports Medicine, the Centers for Disease Control and Prevention, and a National Institutes of Health Consensus Statement. High-fit individuals do more--and probably higher-intensity--exercise.

Q: How can you tell how fit you are?

A: You can get a maximal exercise test at a health club or laboratory or come to the Cooper Clinic, and if the people doing the testing know about our data, they could tell you what category you fall in. But I think we should focus on the activity.

If you accumulate 30 minutes a day of moderate-intensity activity--which is briskly walking a couple of miles a day--that's certainly a sufficient dose of exercise to get almost everybody into the moderate-fit category.

High-fit is more than that--maybe 45 minutes to an hour of brisk walking and some days more vigorous exercise, like jogging or an aerobics class. Low-fit people do somewhere between less than 30 minutes a day and nothing.

Q: Is less than 30 minutes a day better than nothing?

A: Yes. Doing something is better than doing nothing at all and doing more is better still. So for 80 percent of the U.S. population, when they ask: "what should I do?" the answer is one word: more.

Better Bones

Q: Does exercise help prevent osteoporosis?

A: Yes, some clinical trials show that exercise improves bone mineral density. And there is some evidence that people who lead a fit and active life are less likely to develop osteoporosis. Their muscle strength also makes them less likely to fall and get a fracture. It's the fracture more than just the disease that we're concerned about.

Q: So exercise can help people who already have osteoporosis?

A: Right, because they'd be less likely to fall.

Q: And almost any exercise but swimming works?

A: Right. It has to be weight-bearing. Some researchers think it has to be a weight-bearing exercise with changes in direction--like dancing--to provide some stimulus for bone health.

We don't know for sure about cycling. You do have some weight-bearing in the spine and you are exerting the muscles against the pedals, but it's a little unclear.

Q: Can exercise cause arthritis?

A: The evidence suggests that it doesn't, at least in the amount most people are likely to do. People who do prodigious amounts of exercise can get repetitive joint injury. Jackhammer operators get arthritis of the wrist, for example.

And some studies have found an increased risk in young, highly fit, healthy fighting forces, like U.S. Army Rangers or Israeli commandos. But these people get huge amounts of exercise--carrying 50-pound packs across the mountains all day.

Even in runners we don't see an increased risk of arthritis. If anything, we may see a slightly reduced risk, but we can't confirm that.

Q: Can exercise cure arthritis?

A: No, but it seems to improve overall quality of life. A study at Wake Forest University in North Carolina randomly assigned elderly individuals with arthritis of the knee to do aerobic or strength-training exercise or no exercise. After a year, those who did best were in the aerobic group, but those in the strength-training group also got benefit compared to the sedentary group. They reported less pain and less disability than the non-exercise group, and their ability to walk and climb stairs and get in and out of a car improved.

Staying Young

Q: What's the difference between aerobic exercise and strength-training?

A: Aerobic exercises--like brisk walking or running, swimming, and cycling--release energy by using oxygen. They're continuous and rhythmic, and they require more endurance and less power. Strength-training exercises--like weightlifting--are short and intense, and they require more power and coordination and less endurance.

Q: Is aerobic exercise more important than strength-training for seniors?

A: They're both important. I'm convinced that much of the disability, loss of function, and loss of independence that we see in elderly individuals is due to both low muscle and low aerobic fitness.

Studies from Tuffs University make it clear that strength-training builds muscle mass and improves function even in very elderly, quite disabled individuals. Their first study was limited to people in their 90s and older. All of them had chronic disease, and on average they had five or six chronic diseases like stroke, heart attack, or emphysema. Based on the Tufts work, it's never too late to do some muscle-training and put back some muscle mass.

Q: How does low aerobic fitness hurt older people?

A: In our study, people with low aerobic fitness had higher rates of self-reported limitations. We asked people what they were limited in doing. We asked about everything from bathing, dressing, and feeding themselves to strenuous sports, fast walking, and jogging.

At the end of the eight-year follow-up, low-fit women and men in their forties were as likely to report limitations as high-fit men and women in their sixties. And that wasn't related to smoking, obesity, alcohol intake, or chronic disease.

Q: So an active 65-year-old could function like an inactive 45-year-old?

A: Yes. Unfit people start to develop limitations 20 to 25 years earlier than higher-fit people.

Not Life-or-Death

Q: Does exercise help people sleep better?

A: Yes. Abby King and colleagues at Stanford University Medical School studied middle-aged and older adults with mild sleep disorders. She randomly assigned them to an exercise or non-exercise group. Those who exercised got to sleep faster and stayed asleep longer.

Q: Can exercise reduce stress?

A: I'm not aware of well-controlled studies showing that exercise improves the ability to handle stress. That's partly because stress is difficult to define.

Now, if you asked me about my personal experience, I'd say absolutely yes. If you're having a stressful day, nothing makes you feel better than to go out for a brisk walk or to an aerobics class. I believe it in my gut, but I don't think there's much evidence from controlled studies.

Q: Does exercise prevent constipation?

A: People who are physically active have more bowel movements over the course of a week. It's possible that that's because they eat more food. We have no data on whether exercise helps people who already have constipation, but some researchers believe that it does.

Q: Can exercise help prevent colds?

A: Most researchers agree that exercise makes the immune system work better. And there is some evidence that people who exercise regularly have fewer upper respiratory infections. There's also evidence that you can do too much exercise and depress the immune system. One study found increased rates of upper respiratory infections in marathoners during the week after the marathon.

Q: Does physical activity make people happier?

A: It may. People who are active report a more positive outlook on life. They have a greater sense of well-being. There's also some data that people who are active and fit are less likely to develop depression with the passage of time. And exercise may also help treat depression.

Q: Can exercise improve your sex life?

A: The evidence is largely anecdotal at this point, but I wouldn't be surprised if it were true. Why do I say that? People who exercise regularly feel better. They're more fit. They have more energy. Now, I ask myself, would those things be likely to contribute to a better sex life? Yes.

Q: How much exercise do you do every day?

A: My exercise is running, and I've been doing it nearly every day for 30 years. I'll be 60 on my next birthday, and I'm currently running about 30 miles a week. That's not a huge amount, but it's pretty good for an old geezer like me.

Fitting Fitness In

Q: Do you have any tips for people who have no time to exercise?

A: That's an area of active research for us. I've been talking for years about lifestyle physical activity as opposed to structured exercise--going to the gym or going for a jog or playing a sport.

If modest amounts of exercise accumulated over the course of the day provide benefits, you don't have to dress up in your leotard and go to the gym in order to burn some calories.

Q: You can work it into your everyday life?

A: Yes. Engineers have been very successful, especially since World War II, in cutting the need for energy expenditure. We have energy-saving devices at home, at work, and during leisure: remote controls, self-propelled vacuum cleaners, riding lawn mowers, electric windows in your car, electric doors at the mall, and on and on. A Scottish researcher estimates that in the United Kingdom, average energy expenditures have dropped by 800 calories a day just over the last 25 years.

Q: So we're more sedentary now?

A: Yes. I think sedentary people have three choices. They can remain sedentary and unfit and accept the risks for early death, heart disease, diabetes, etc., that go along with it. They can start what we normally think of as a structured sports program--take up rigorous sports, go to aerobics class, jog, what have you. Or, they can put more activity back into their daily lives.

Now how can you do that? Well it's not for me to say how you can do it, because there's an infinite variety of approaches. At the Cooper Institute, we're trying to give people the skills to become their own exercise advisors. We try to help people think about what they might like or be willing to do and when they could do it.

Q: Like picking a parking place far away from the store?

A: Yes. The most feasible approach is to look for opportunities to be on your feet and moving--to go for short walks and climb the stairs, etc. Remake your image of yourself as the kind of person who does not take elevators unless you have to go up at least five floors. I always take the stairs. It's a habit. It's who I am.

You can take the kids to the park to play. If you don't have kids, find neighbors who do and I assure you they will be delighted to have you take their kids to the park to play. Take your dog for a walk. If you don't have a dog, pretend you have a dog ... or get a dog ... or borrow a dog.

I look for opportunities to walk--down the corridor to talk to my coworkers as opposed to sending an e-mail or getting on the telephone.

Bill Haskell of Stanford University calculated that an office worker who spends two minutes an hour to send e-mail to colleagues in the workplace instead of walking down the hall to speak to them, day after day, would gain the energy equivalent of 11 pounds of fat over a decade. It's a tiny amount each hour and not much each day, but it adds up.

RELATED ARTICLE: WHICH EXERCISE?

Any kind--and any amount--of exercise is better than no exercise. Some studies suggest that as long as you burn 1,000 calories a week, you'll lower your risk of disease. This chart--based on exercise specialist David Nieman's book Exercise Testing and Prescription--shows how many calories a 150-pound person burns by doing any of 30 common physical activities for an hour. (If you weigh more, you'll burn more calories; if you weigh less, you'll burn fewer calories.)

The chart also shows how well each activity builds cardiovascular health, burns fat, or builds muscle strength (1 = not at all, 2 = a little, 3 = moderately, 4 = strongly, and 5 = very strongly). For muscle strength, the activity is rated high if both upper and lower body muscles are strengthened.

Activity                              Calories
                                      per Hour
                                      (150-lb. person)

aerobic dance (vigorous)                   475
basketball (competitive)                   545
canoeing or rowing (fast pace)             815
cross country skiing machine               645
cycling (fast pace)                        680
cycling (leisurely pace)                   375
cycling (stationary, moderate)             475
dancing                                    305
gardening                                  340
golf (walking and carrying bag)            375
handball (casual)                          475
lawn mowing (power mower)                  305
racquetball or squash (casual)             475
raking leaves                              270
rope jumping (moderate to hard)            680
running (brisk pace, 8 mph)                920
running (moderate pace, 6 mph)             680
shoveling dirt or digging                  580
skating (in-line or ice)                   475
skiing (cross country, brisk speed)        610
skiing (downhill)                          340
soccer (casual)                            475
splitting wood                             410
stair climbing                             610
swimming (laps, vigorous)                  680
swimming (moderate)                        545
tennis (competitive)                       475
volleyball (competitive)                   270
walking (brisk pace, 4 mph)                270
walking (slow pace, 2 mph)                 170
weight training                            205
yoga                                       170

Activity                              Builds Cardiovascular
                                      Health & Burns Fat

aerobic dance (vigorous)                    4
basketball (competitive)                    4
canoeing or rowing (fast pace)              5
cross country skiing machine                5
cycling (fast pace)                         5
cycling (leisurely pace)                    3
cycling (stationary, moderate)              4
dancing                                     3
gardening                                   3
golf (walking and carrying bag)             3
handball (casual)                           4
lawn mowing (power mower)                   3
racquetball or squash (casual)              4
raking leaves                               3
rope jumping (moderate to hard)             5
running (brisk pace, 8 mph)                 5
running (moderate pace, 6 mph)              5
shoveling dirt or digging                   4
skating (in-line or ice)                    4
skiing (cross country, brisk speed)         5
skiing (downhill)                           3
soccer (casual)                             4
splitting wood                              4
stair climbing                              5
swimming (laps, vigorous)                   5
swimming (moderate)                         4
tennis (competitive)                        4
volleyball (competitive)                    3
walking (brisk pace, 4 mph)                 3
walking (slow pace, 2 mph)                  2
weight training                             2
yoga                                        1

Activity                              Builds Muscle
                                      Strength

aerobic dance (vigorous)                    4
basketball (competitive)                    2
canoeing or rowing (fast pace)              4
cross country skiing machine                4
cycling (fast pace)                         3
cycling (leisurely pace)                    2
cycling (stationary, moderate)              3
dancing                                     2
gardening                                   3
golf (walking and carrying bag)             3
handball (casual)                           3
lawn mowing (power mower)                   3
racquetball or squash (casual)              3
raking leaves                               3
rope jumping (moderate to hard)             3
running (brisk pace, 8 mph)                 2
running (moderate pace, 6 mph)              2
shoveling dirt or digging                   4
skating (in-line or ice)                    3
skiing (cross country, brisk speed)         4
skiing (downhill)                           3
soccer (casual)                             3
splitting wood                              4
stair climbing                              3
swimming (laps, vigorous)                   4
swimming (moderate)                         3
tennis (competitive)                        3
volleyball (competitive)                    3
walking (brisk pace, 4 mph)                 2
walking (slow pace, 2 mph)                  2
weight training                             5
yoga                                        2

Sources: David Nieman (personal communication) and Exercise Testing and Prescription: A Health-Related Approach, by David Nieman (Mountain View, California: Mayfield Publishing, 1999). To order, call 800-433-1279.

RELATED ARTICLE: Fitness After 50

Talk about a how-to. How to stretch, how to start strength-training at home, how to pick an exercise, how to choose a bicycle, a pair of athletic shoes, or a health club. And, perhaps most important, how to get started and stick with it.

Fitness After 50--co-authored by Steven Blair--can motivate you to get moving. It answers dozens of questions about what, when, where, and why to do it. For instance:

* How physically active are you? Count the number of minutes you spend walking and climbing stairs. Buy an inexpensive (less than $20) pedometer to see how far you walk each day.

* Is your response to exercise normal? Sweating and breathing deeply and faster are okay. Light-headedness, pain, numbness, and nausea are not.

* What should you wear if it's cold outdoors? Layers. Layer I shouldn't be cotton or wool, which absorb perspiration. Polypropylene is best. Layer 2 should be wool or synthetic fabric for warmth. Layer 3 should be an outer shell to keep away wind and water.

Fitness After 50, by Walter Ettinger, Jr., Brenda Mitchell, and Steven Blair, 1996, Beverly Cracom Publications, St. Louis, Missouri, $24.95. To order, call 800-341-0880.

Steven Blair is director of research and director of epidemiology and clinical applications at the Cooper Institute of Aerobics Research in Dallas. He spoke to Nutrition Action's Bonnie Liebman by telephone.