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Exercise by the numbers

Fitness is essential for good health, but for optimal benefits you need to focus on the right exercise duration and intensity.


Any aerobic activity that gets the heart pumping helps you reach the proper intensity.
Image: ConnieTBallash/Thinkstock

The standard guideline for fitness, from both government agencies and health organizations, is 150 minutes of moderate-intensity exercise per week. “It does not matter how you reach those 150 minutes,” says Dr. Elizabeth Matzkin, a sports medicine physician with Harvard-affiliated Brigham and Women’s Hospital. “It could be 50 minutes three times a week, or 30 minutes five times a week, or some other combination. Even a short burst of 10 minutes at one time is beneficial.”

Why 150 minutes per week? Plenty of research has found that this amount is the sweet spot to benefit both brain and heart health. “More is always better, but less than this number tends to be less effective,” says Dr. Matzkin.

However, avoid cramming in more than 50 minutes of exercise at one time, she adds. Spread it out to avoid overexertion, and give yourself plenty of rest between sessions to reduce your risk of injury.

What kind of exercise?

Most of the research that supports the 150-minute mark is based on aerobic exercise—anything that gets the heart pumping and helps you break a sweat. This can cover a range of choices, such as running, cycling, swimming, sports, power walking, elliptical training, or fitness classes.

“Even everyday activities can count toward your 150 minutes, too, such as walking the golf course, mowing the lawn, or walking to the store,” says Dr. Matzkin.

While it is tough to get the same aerobic response from strength training that does not mean you should exclude it. “Strength training can get the heart pumping, too, and it is good for building muscle and improving bone and joint health,” she says.

How to measure intensity

The other part of the 150-minute weekly guideline is intensity: you need to maintain moderate intensity during exercise. But how do you measure that? A lot of factors are in play, especially age and health status.

“A 60-year-old who is diabetic or overweight often cannot do the same level of activity as a healthier 70-year-old,” says Dr. Matzkin. “What is moderate intensity for one person may be too strenuous for someone else.”

There are several ways to measure your exercise intensity. One of the easiest is the talk test. “You should be able to talk and carry on a conversation, but not be able to say multiple sentences in a row, sing a song, or even carry a tune,” says Dr. Matzkin. “This is simple to do and provides immediate feedback.”

Another way is to wear a heart rate monitor. A monitor can help you find that ideal workout intensity and maintain it (see “Getting to the heart of monitors”). It can also teach you to be more in tune with your body, so you can begin to recognize when you are working too hard or not hard enough.

“Heart rate monitors are especially beneficial if you have a cardiac problem and need to make sure you do not overexert yourself,” says Dr. Matzkin. But do not rely on gym machine monitors, she adds, as they are less accurate and only offer an estimate.

Tracking your workouts

Still another method is to keep a daily log of your workouts. Record how long you exercised and how it felt on a 1-to-10 scale, from easy to difficult, and then compare the results from week to week. “As you track your progress, you will begin to see improvement, and you can make adjustments to stay within that moderate-intensity level—often around 5 to 7 on the scale—by increasing either speed, distance, resistance, or time,” says Dr. Matzkin.

If you have trouble maintaining moderate-intensity levels, especially when doing less strenuous daily activities, do not fret. Lower-intensity exercise can still be helpful, but you need to exercise longer than 150 minutes per week.

In fact, a study in the May/June 2015 American Journal of Health Promotion found that adults ages 65 or older who did 300 minutes of light exercise per week were 18% healthier compared with their peers who exercised less. They had lower body mass indexes, smaller waists, and lower risk of chronic disease.

On the other end, you can receive the same benefits of 150 minutes at moderate intensity by exercising for only 75 minutes per week; however, the intensity needs to be much higher. “So you need to be quite fit,” says Dr. Matzkin. (Check with your doctor before embarking on this approach.)

The bottom line is that any type of movement is beneficial, but to tap in to the full rewards of exercise, you need to be diligent about intensity and duration. “Hitting at least 150 minutes per week of moderate-intensity exercise should be your goal,” says Dr. Matzkin.

How you get there is up to you.

Getting to the heart of monitors

Heart rate monitors can help you maintain moderate intensity when you exercise. They can be strapped around your chest or worn on the wrist or head, so choose whatever is the most comfortable for you. Some models only display your heart rate, while others can sound an alarm if your rate gets too low or high. To find your moderate-intensity level based on your heart rate, you need to know your maximum heart rate and then your target heart rate:

  • Maximum heart rate is an estimate of the highest heart rate a person could reach while exercising strenuously. The usual formula for calculating maximum heart rate is 220 minus your age.

  • Target heart rate is between 50% and 85% of your maximum heart rate (see the table at right). Moderate-intensity levels often fall between 50% and 69%, according to the American Heart Association, but again, let your body guide you. “It is ideal to begin at 50% and increase as your fitness level allows,” says Dr. Elizabeth Matzkin, a sports medicine physician with Harvard-affiliated Brigham and Women’s Hospital. Also, be mindful that some medications can affect your target heart rate zone. “And if you have any history of cardiovascular problems, make sure you discuss your target heart rate with your physician,” she says.

Posted by: Dr.Health

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