May 29, 2003 -- When it comes to exercise, couch potatoes like to cut corners. In fact, most people gravitate toward a pretty moderate workout routine -- walking a little after work or on weekends. Question is, is that enough?
It's an issue addressed in a new study, presented at the annual meeting of the American College of Sports Medicine held in San Francisco this week.
In the study, 87 overweight adults were randomly assigned to a low, moderate, or high supervised program based on exercise time and intensity. The workout involved stationary bicycles, treadmills, and elliptical trainers (a cross between a treadmill and a bicycle).
- The low workout routine involved about 187 minutes of exercise per week at 40%-55% of maximal oxygen capacity (a measure used in fitness studies).
- The moderate workout routine involved about 123 minutes per week at 65%-80% of maximal oxygen capacity.
- The high workout routine involved about 180 minutes per week at 65%-80% of maximal oxygen capacity.
After the study had ended, follow-up phone calls showed that people in the high-intensity program tended to downgrade their exercise into the more moderate range. And many of the low intensity exercisers tended to upgrade to the more moderate range.
Americans' known love of the couch may make it obvious why the high-intensity exercises reduced their workout routine. But why did so many low exercisers decide to kick it up a notch? Researchers say it may be due to the fact that the exercise program was supervised for nine months -- making exercise more of a habit by that point.
Researchers also found that most people -- 84% -- had switched to walking as their "most comfortable and convenient" form of exercise, reports lead researcher Lori Aiken, with Duke University Medical Center, in a news release. Very few stuck with the workout equipment, she says.
Virtually everyone was fighting a busy schedule to find time for walking -- which translated into briefer workouts, about two hours a week. Also, most people adjusted their workout intensity to a more moderate level -- about 11 miles during a week's time.
Were they reaping any benefits from a ratcheted-down, moderate workout routine?
"Sure they're getting benefits, but in general, more is better," says Joe Miller, MD, a preventive cardiologist at Emory University School of Medicine. He agreed to discuss the findings with WebMD.
In fact, 25 minutes a day is the minimum anyone should get for heart protection, Miller says. "Most data indicates that people do better if they get moderate, sustained exercise like moderate-intensity walking for 25 minutes, four to five times week."
He encourages people to make little changes in their daily routine -- walk between terminals at the airport, park the car at the far end of a parking lot, that kind of thing. Exercise accumulated during the day can equal a moderate workout routine, Miller says.
But if you're trying to lose weight, aim higher -- make moderate workout routines longer than 20 minutes a day, says Andrew Sherman, MD, a physiatrist at the University of Miami School of Medicine.
"Obviously, some exercise is better than no exercise," Sherman tells WebMD. "But if you're ever going to get significant fat-burning benefits from aerobic exercise, the magic number is more than 20 minutes per session."
In the first 20 minutes, your body burns carbohydrates; after that, you begin burning more fat than carbohydrates, Sherman explains. "By exercising for a too-little period of time, you may get some benefits from not being totally sedentary, but you're not necessarily going to gain any fat-burning potential."
"We all would like exercise in pill," Miller tells WebMD. "The American mentality is to get more for less. It's the American dream. But when it comes to preventing heart disease, hypertension, diabetes, it just doesn't work that way." A moderate workout routine -- over the long haul -- can keep fat and disease at bay.