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How Much Moderate-Intensity Physical Activity Is Enough?
This is an excerpt from Fitness for Life Canada With Web Resources by Guy Le Masurier,Charles B. Corbin,Kellie Baker & John Byl.
National physical activity guidelines in Canada recommend 60 minutes of moderate- to vigorous-intensity daily activity for teens to gain health benefits. Vigorous activity (e.g., running, in-line skating, soccer) should be performed at least three days a week. Moderate-intensity activity (e.g., walking, skating, bike riding) that promotes muscle fitness and bone building should be performed at least three days a week as well. For adults to achieve health benefits, the recommendation is 150 minutes of moderate to vigorous aerobic activity per week, in bouts of 10 minutes or more. At least two days should be devoted to bone and strengthening activities using major muscle groups. This translates to 30 minutes per day on five days a week. For this reason, many experts recommend that teens get at least 30 minutes of moderate-intensity activity each day so that they develop the habit of meeting the adult activity guideline.
You need to be familiar with the FIT formulas for moderate physical activity for both teens and adults (see table 7.2). The teen guidelines apply, of course, while you're in school, and the adult guidelines will apply for the rest of your life after school.
For teens, the goal is to accumulate at least 60 minutes each day, but more is better. Moderate-intensity activities can be combined with other activities from the pyramid to meet the goal. Experts now agree that it is best to get your 60 minutes in bouts or activity sessions lasting at least 10 minutes each. In other words, you could do six 10-minute bouts, three 20-minute bouts, two 30-minute bouts, or other combinations that total 60 minutes a day. Accumulating 60 minutes in bouts shorter than 10 minutes each is better than doing nothing, but it does not give you optimal benefits.
Recreational biking is an example of a moderate-intensity physical activity. It's one of many activities you can choose to accumulate your 60 minutes of daily physical activity.
For adults, the recommendation is 150 minutes per week because this amount provides many health benefits with a minimum of effort. As with teens, moderate-intensity exercise is best done on several days a week (see table 7.2) and in bouts of at least 10 minutes each. Doing more than 30 minutes at a time gives additional benefits and is recommended for maintaining a healthy weight and for achieving good fitness, health, and wellness. Adults can substitute 75 minutes per week of vigorous exercise for the 150 minutes of moderate-intensity activity; they can also meet the guidelines by combining moderate- and vigorous-intensity activity.
Fitness Technology: Pedometers and Accelerometers
A pedometer is a small, battery-powered device that can be worn on your belt. It counts each step you take and displays the running count on a meter. You simply open the face of the pedometer or push a button to see how many steps you've taken. Some pedometers also contain a small computer that allows you to enter the length of your step (your stride length) and your body weight so that the computer can estimate the distance you walk and the number of calories you expend. More expensive pedometers can also track the total time you spend in activity during the day and the number of bouts of activity that you perform lasting 10 minutes or longer. Less expensive pedometers must be reset at the end of the day, but some more expensive ones can store steps for several days. There are also numerous free or inexpensive apps for Apple and Android devices.
Accelerometers are similar to pedometers but measure physical activity in more detail. Specifically, accelerometers can record the intensity of your movements (for more about intensity, see the discussion of METs and recall the "I" in the FITT formula), as well as the amount of time (the first "T" in the FITT formula) you spend at different intensities. Like a pedometer, an accelerometer is worn on your belt and contains a small computer and a device (the accelerometer itself) that measures the intensity of your movements. Most accelerometers can count your steps taken per day and estimate the calories you expend in activity. There are also numerous free or inexpensive apps for Apple and Android devices. Be sure to check the customer reviews when searching for apps.
A pedometer counts steps and is a good way to self-monitor moderate activity.
Using Technology
Estimate the number of steps you take on a typical weekday and a typical weekend day. Then wear a pedometer to see how many steps you actually take (weekday and weekend day). See if you're as active as you think you are!
Counting Steps and Movement
Another way to determine how much moderate-intensity physical activity you perform is to count the steps you take each day. You can do so by using a pedometer (see the Fitness Technology feature), which automatically tracks your step count; the disadvantage is that a pedometer counts all steps that you take, regardless of whether they come in very light, light, or even vigorous-intensity activity. Still, wearing a pedometer can help you see how active you really are; you may have the opportunity to wear one in school. The American College of Sports Medicine states that moderate-intensity physical activity requires a step rate of 100 steps per minute.
For adults, some experts believe that taking 10,000 steps each day is necessary to be in the target zone for moderate physical activity. Other experts are concerned about this advice because you can reach 10,000 steps without doing any sustained activity (bouts of 10 minutes or more). On the other hand, some people can do 60 minutes of moderate-intensity activity each day and still not reach a 10,000-step count. Rather than setting an absolute daily step count, most experts recommend monitoring your activity for a full week and then determining your average daily step count. People who want to increase their activity level can then establish a realistic step goal that is 500 to 1,000 steps per day higher than their average step count. Once they reach this goal, they can, if desired, gradually increase their step count to higher levels.
Studies show that Canadian children take between 10,779 and 13,103 steps a day. The national average is 11,607 steps a day; to meet the national physical activity guidelines of 60 minutes a day, most teens would require 12,000 steps. However, if you're just beginning, remember the principle of progression. Instead of starting with a high goal such as 12,000 steps per day, work gradually toward a realistic step goal.
Fit Fact
The average person in Canada accumulates 3,500 to 5,000 steps per day. This is considerably less than the averages in some other countries - for example, 9,000 or more in Australia and Switzerland and 7,000 or more in Japan - where obesity rates are much lower.
As mentioned previously, you can monitor moderate-intensity physical activity by using devices such as an accelerometer (see the Fitness Technology feature). Heart rate monitors can also be used, and as with the accelerometer, there are heart rate monitor apps. An accelerometer both counts your steps and gives you a better idea of your exercise intensity than a pedometer can. You can determine the distance you've walked by finding out the length of your step (your stride length), then multiplying it by the number of steps you take.
Counting Physical Activity Calories
We know that moderate-intensity activity should be done according to the FIT formula summarized in table 7.2. Another way to determine whether you perform enough moderate-intensity activity is to count the calories you expend in activity. For example, a teen who weighs 68 kilograms (150 pounds) would expend 300 to 400 calories during 60 minutes of moderate-intensity activity, such as brisk walking. Therefore, this number of calories expended per day would be a good goal for moderate activity. You can learn more about counting calories in chapter 14.
Moderate-intensity sports like curling can help you reach your daily goal for calorie expenditure.
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