# What Is Strenuous Exercise?

If you prefer to sleep in during the morning versus getting up to exercise, you’re in luck. That’s because according to new recommendations from American College of Sports Medicine, you can exercise for fewer days each week -- so long as you exercise vigorously.

## Maximal Heart Rate

Before you put away your workout shoes and slink back into bed, understand what the American College of Sports Medicine means by vigorous exercise. For an exercise to count as vigorous, it must raise your heart rate to at least 70 percent of your maximal heart rate. This is the point at which exercise transitions from moderate- to vigorous-intensity exercise according to the ACSM. It is also the moment when every drop of sweat means more to your heart.

You can estimate your maximal heart rate quickly by subtracting your age from 220, which will give you your heart rate maximum in beats per minute. For example, a 40-year-old woman would subtract 40 from 220, giving her an estimated maximal heart rate of 180 beats per minute. To determine the heart rate for vigorous exercise, she would then multiply 180 by 70 percent. This would give her a minimal heart rate target of 126 beats per minute.

## Exercise Efficiently

The ACSM recommends that healthy adults should get at least 30 to 60 minutes of moderate intensity exercise five times per week. But if you exchange the time you spend doing moderate-intensity exercise for vigorous-intensity exercise, you only need to exercise for a minimum of 20 to 60 minutes -- and only on three days per week.

## Tips

If you do not have a heart rate monitor, use the Rating of Perceived Exertion. Health care professionals use this scale to estimate the intensity level of an activity by asking an exerciser how she feels. This method yields surprisingly accurate results because how an exercise feels highly correlates with your heart rate. For example, most people select the descriptive words of “somewhat hard” or “hard” from the Rating of Perceived Exertion list to describe how they feel as they reach 70 percent of their maximal heart rate. Knowing this, you can estimate when an aerobic exercise is vigorous by asking yourself, “How does this exercise feel?” If you choose the words “somewhat hard” or “hard” to describe the exercise, you are probably doing a vigorous exercise.