For a few years now, fitness experts—including those at AMERICAN HEALTH—have been touting the life-enhancing benefits of even minimal physical activity. Last February, for instance, the Centers for Disease Control and Prevention and the American College of Sports Medicine (ACSM) issued exercise guidelines urging sedentary people (some 60% of Americans) to accumulate a mere 30 minutes of any kind of moderate physical activity (say, walking, gardening or climbing stairs) over the course of a day. Now a major new study suggests that when it comes to extending life, only vigorous exercise will do the trick. What’s going on here?
Harvard University researchers tracked the workout habits of 17,321 healthy men for over 20 years and found that those who burned at least 1,500 calories a week in activities such as running, walking briskly, cycling or swimming had a 25% lower death rate than men who sweated off a meager 150 calories a week through exercise. That’s the equivalent of the difference in mortality between nonsmokers and men who smoke a pack of cigarettes a day.
What does intense exercise do for the body that more moderate pursuits do not? Epidemiologist and study author I-Min Lee believes regular, vigorous workouts may boost good HDL cholesterol levels more dramatically than less taxing regimens. Some examples of vigorous activities: walking for 45 minutes five times a week at four to five miles an hour, jogging for three hours a week at six to seven miles an hour or cycling hard for an hour four times a week.
“Vigorous exercise is more effective than nonvigorous exercise for cardiorespiratory conditioning,” Dr. Lee writes in The Journal of the American Medical Association. In other words, the harder you work, the stronger your heart and lungs become—and the less likely you are to succumb to cardiovascular disease.
So should less ambitious exercisers throw in the towel? Not at all, says study coauthor and Stanford epidemiologist Ralph Paffenbarger, who emphasizes that it’s “not necessary to be so intense about exercise to enjoy a better quality of life.” All you need do is “push hard enough to work up a fine sheen of sweat and raise your heart rate above its usual level.” And even the most active men in the Harvard study were likely to have exercised less vigorously as they aged, a factor not taken into account by the researchers.
Dr. Russell Pate, an exercise physiologist at the University of South Carolina in Columbia and former president of the ACSM, says the new findings have to be put into a broader context: “While it’s not surprising that different levels of activity, including vigorous activity, have different health effects,” he explains, “there is still a mass of evidence pointing to the benefits of moderate exercise.” When done on a regular basis, for instance, even nonstrenuous pursuits such as brisk walking have been shown to lower blood pressure, shore up bones and reduce the risk of diabetes, heart disease and certain cancers. The message, then, remains essentially the same: Almost any kind (or amount) of moderate physical activity will keep you feeling better longer, no matter how long you happen to be around. —PAULA DERROW
And Decreases Colon Cancer Risk
A second Harvard study, even larger than the one above, suggests that both moderate and vigorous exercise protect against colon cancer, which kills 48,000 Americans each year.
Researchers followed more than 47,000 men between the ages of 40 and 75 for six years, questioning them on the state of their health and their exercise habits. After adjusting for factors like diet and family history, they found that compared with the sedentary men, those who worked out at least three times a week were significantly less likely to develop colon cancer or polyps, timorous growths that can be a precursor to cancer.
Avid exercisers fared best: The most active men in the study—those who ran for an average of four hours a week or played eight hours of tennis a week—had about half as much risk of colon cancer as sedentary subjects. But even casual exercisers—those who ran two hours or walked six hours a week—had a one-third lower colon cancer risk than the inactive men. “You don’t have to go out and run a marathon to reap the effects,” says epidemiologist and study author Edward Giovannucci. “While more activity is better, men in their 70s benefited greatly from just walking.” Although the study involved only men, Dr. Giovannucci says, “The evidence strongly suggests that women would benefit too.”
Being overweight, on the other hand, increases colon cancer risk: In the Harvard study, obese men had a 50% higher risk overall than normal-weight men, and those who carried their extra weight primarily in the abdominal region were 3% times as likely to develop the disease as lean subjects. It’s possible, says Giovannucci, that the high level of insulin typically found in obese people stimulates the growth of cancerous tumors.
Researchers believe exercise reduces the risk of colon cancer by lowering insulin levels (which also tend to be high in normal-weight people who are sedentary). It’s also likely that physical activity is beneficial because it keeps weight down. Finally, exercise promotes bowel activity, which means cancer-causing substances don’t linger as long in the body.
Exercise During Pregnancy
For decades, pregnant women were advised by their doctors to take it easy, if not take to their beds. There’s new evidence, however, not only that it’s safe to stay active during pregnancy, but also that doing so may help prevent excess weight gain and make labor and delivery easier.
Researchers at Case Western Reserve School of Medicine in Cleveland followed 79 women between the ages of 28 and 34 who’d been working out moderately for 30 minutes at least three times a week. Nearly half chose to stop exercising when they became pregnant; the others continued running, swimming, cycling, and stair climbing or taking aerobic dance classes.
Although there was no difference between the two groups at first, after 15 weeks the exercisers gained weight at a slower rate than the sedentary group (114 pounds a week vs. I pounds). At the time of delivery, the exercisers had gained less weight overall (31 to 33 pounds vs. 39 to 42 pounds), and had, on average, 4% pounds less body fat. All the women gave birth to healthy, normal-weight babies. And a second, larger study at Case Western Reserve found that exercisers spent a third less time in labor and were less likely to need a cesarean section or delivery with forceps than sedentary women.
There’s no need for expectant mothers to push themselves to their physical limit, however. “Women who exercised six times a week gained the same amount of weight as those who worked out three times a week,” says obstetrician and study author James Clapp.
Of course, it makes sense to check with your doctor before embarking on any fitness regimen. And if you haven’t been active, don’t start working out vigorously when you become pregnant; stick with the general level of activity you’re accustomed to. Finally, avoid sports that can result in a hard fall and abdominal trauma, such as horseback riding, downhill skiing, mountain climbing and in-line skating.