Exercise rights--and wrongs
An hour workout or 30 minutes? Walk or run? Does gardening count?
Pushing hard enough. Moderate activity for half an hour, by the way, is somewhere south of huffing and puffing and somewhere north of an easy after-dinner ramble. "Casually strolling around the mall isn't going to produce health benefits," says JoAnn Manson, chief of preventative medicine at Harvard's Brigham & Women's Hospital. Walking should be brisk enough--3 to 4 miles per hour--to raise your heart rate. You can accumulate that exercise, says Blair. So a 10-minute brisk walk after every meal is fine. Physicians also recommend that most people--but particularly women--get two or three days a week of weight training. This has extra benefits, like building bone mass.
Shedding pounds. But wait. Or, weight. About 65 percent of Americans are overweight, and extra pounds raise the risk of disease. That's where the whole hour, as recommended by the Institute of Medicine, comes in. Researchers combed through an international database and found that the people who maintained a healthy weight exercised, on average, the equivalent of a 60-minute brisk walk per day. Bad news: Some people may need to work out even longer than an hour, depending on their diet, muscle mass, and metabolism. "I've run nearly every day for 35 years, and during that time I've gained 30 pounds," says Blair.
Healthier hearts. If you're built like a greyhound but battle high cholesterol, you may need to do something more intense. A study published last month in the New England Journal of Medicine found that walking or jogging the equivalent of 12 miles per week lowered the amount of dangerous LDL (the bad cholesterol) in overweight people. But it took longer and harder workouts--the equivalent of jogging 20 miles per week--to increase the level of HDL (the good cholesterol). Another study, published in the Journal of the American Medical Association in October, suggests that while walking cuts the risk of coronary heart disease, more vigorous activities like running and rowing reduce it even further.
It's a message Randy Devening has taken to heart. After a heart attack, the 60-year-old retired CEO went to the Cooper Institute to learn how to put together a good exercise routine. Back home in Oklahoma City, he now works out as much as 60 to 90 minutes a day, combining cardiovascular exercise, weight lifting, and stretching. "I just feel better," he says.
Dusting doesn't do it. If you can't face 30 or 60 minutes of exercise, do something, because slight workouts do produce slight benefits. Keep in mind, though, that lighter "exercise," like housecleaning, canoeing, or playing golf, helps burn calories and can be a great add-on to your regular routine but is no substitute for that routine. Mild activity, among other things, does nothing to increase bone strength and density, according to a report in last month's Journal of Internal Medicine.
You can do too much as well as too little. Overdoing it can actually suppress the immune system and increase the risk of getting hurt. Warning signs of overtraining include sleeplessness, fatigue, and injuries like stress fractures. Sheila Lynch, a 47-year-old small-business co-owner in Chicago, says she used to push it with aerobics classes, running, and weight lifting in various combinations, five days a week. "I got a lot of knee injuries," she says. Now she hits the gym three times a week, doing both cardio and weight work. And Paffenbarger, having given up marathons a few years ago, still walks daily in the hills near his California home.
If a brisk walk for half an hour isn't for you, other exercises done for these specific times will give you similar benefits. Thirty minutes of walking* is equal to:
Jumping rope 11 min.
Jogging** 13 min.
Swimming 19 min.
Moderate cycling 24 min.
Tennis (doubles) 27 min.
Mowing the lawn 30 min.