You go for long walks virtually every day and wear a pedometer to count the steps you take. Most days, you take the 10,000 steps the federal Centers for Disease Control and Prevention says is necessary for an "active" lifestyle. You think you get enough exercise.
You're chained to your desk at the office during the day. But most nights you hit the gym, lifting weights and doing cardio. And most weekends, you play golf or tennis or other active sports. You think you get enough exercise.
Think again, says the American College of Sports Medicine, the professional association of personal trainers and other exercise professionals.
ACSM recently published new guidelines in its journal, Medicine & Science in Sports Exercise, about how much of what kinds of exercise is "enough."
The heavily footnoted journal article refers to dozens of studies that indicate how much exercise is needed to produce significant health benefits. For instance, the recommendations concerning cardio-respiratory fitness are based in large part on the amount of exercise a study indicated can lower mortality rates by 60 percent compared to sedentary people.
"Pedometers are popular and effective for promoting physical activity and modest weight loss," the ACSM acknowledged in the guidelines, "but they provide an inexact index of exercise volume. They are limited in that the 'quality' (e.g., speed, grade, duration) of steps often cannot be determined."
And no matter how long or how briskly you walk, walking alone cannot meet all your fitness needs, according to the ACSM.
Health risks incurred by spending hours sitting at a desk or in front of the television can't be offset with daily visits to the gym, no matter how hard you work out.
"Sedentariness is detrimental even among individuals who meet current physical activity recommendations," the ACSM says. "The evidence suggests it is not enough to consider whether an individual engages in adequate physical activity to attain health benefits, but also that health and fitness professionals should be concerned about the amount of time clients spend in activities such as television watching and sitting at a desk."
To reduce the harm that can be done by prolonged periods of sitting, get up from your desk every hour or so, stretch and take a short walk around the office. If there's no time for that, just stand up for a minute or two. When you're watching TV at home, get up and stretch during the commercials, and take a short walk around the house.
Ron DeAngelo, director of sports-performance training at the University of Pittsburgh Medical Center's Center for Sports Medicine, called the new guidelines a "wake-up call" for some people. "A lot of times people think they are accomplishing a lot more than they really are."
Adults should get four types of exercise each week -- cardiovascular, resistance, flexibility, and neuromotor (exercises to improve balance, agility, coordination and gait), according to the ACSM.
Here are specific recommendations:
-- For cardio, adults should get at least 30 minutes of moderate-intensity exercise five days a week, or at least 20 minutes of vigorous-intensity exercise three days a week. It's OK to meet this requirement through multiple shorter sessions throughout the day.
-- Adults should lift weights or perform other resistance exercises two or three times as week. They should do two to four sets of 8-12 repetitions (to build strength and power) or 15-20 repetitions (to build muscular endurance).
-- Adults should stretch and do other flexibility exercises two or three times a week. Each stretch should be held for 10 to 30 seconds and should be repeated two to four times, for a minimum of 60 seconds per stretch.
Stretching is most effective when the muscle is warm, so it's best to stretch after light aerobic exercise, or -- if your workout is going to consist of stretching only -- take a hot bath beforehand.
-- It's especially important for older Americans to perform neuromotor exercises -- also called functional fitness -- because they help prevent falls. Tai Chi and yoga are good examples.
"The functional standpoint is one of the best parts of these guidelines," said Moira Davenport, who practices sports medicine and emergency medicine at Allegheny (Pa.) General Hospital. "This new emphasis on functional training is going to be very helpful, especially for the aging. It can limit the number of falls and keep them independent for much longer."
If you add up the ACSM's recommendations -- 150 minutes a week for cardio, 40 minutes a week for neuromotor exercises and assume 40 minutes a week for two resistance workouts and 20 minutes for stretching -- that comes out to 4 hours and 10 minutes of exercise a week to meet the minimum guidelines.
The minimum goals can be met by exercising for 45 minutes a day, six days a week. But not many of us exercise that much.
If your exercise routine falls short of ACSM guidelines, don't be too discouraged, said the lead writer, Carol Garber, director of the graduate program in applied physiology at Columbia University.
"We don't really expect that everyone is going to do all the exercises," she said. "That would be the absolute optimum."
The guidelines are the minimum necessary to produce major health and fitness benefits, Garber said, but research makes it clear that any exercise is beneficial.
"A little bit is good," she said. "But a little bit more is even better."