You can, to some extent, measure your workouts by your sweat. Sweat a lot and you have really worked. Sweat a little, and well, blame it on that late-nighter you pulled in the office the other night.

Although sweat indicates when your body is working to cool itself, it does not always tell you how hard you have worked. For that, you need to turn to 3 common ways of checking your intensity: the talk test, rating of perceived exertion (RPE), and target heart rate (THR).

The Importance of Intensity

Intensity is simply a measure of how hard—or easy—you are working. Monitoring intensity when you exercise is important for many reasons.

First, it lets you know if you are working too hard or not hard enough. Working too hard can cause overtraining which can lead to injuries, decline in fitness performance, mood changes, lack of sleep, and other symptoms. If you are not working hard enough, on the other hand, it may take you longer to meet your fitness goals.

If you are recovering from an injury or illness, monitoring your intensity is a good way to ensure that you are not overdoing it.

Intensity is important for improving your performance as well. For example, if you are training for a faster time in a 10K run, you will need to vary the intensity of your workouts, some days working harder than others.

Testing Your Intensity

How you monitor your intensity is up to you. Here are 3 of the most common ways to check your intensity:

This is the easiest test to do, especially if you are new to exercise. The premise of the talk test is simple: no matter how hard you are exercising, you should still be able to talk.

This does not mean that you have to be able to carry on a whole conversation. Instead, you should be able to speak in broken sentences. If you are too winded to talk and have to gasp for breath between words, you are working too hard. If you feel as if you could talk for hours, you may not be working hard enough.

Another easy way to find out how hard you are exercising is by using RPE, which measures how you feel and how hard you think you are working. Of course, this requires that you be honest with yourself.

One method of RPE lets you rate your exertion on a scale that runs from 0 to 10. For the general population, American Council on Exercise recommends working between a level of 3 and 5. Of course, the toughest part with this intensity check is translating how you are feeling into a number on the scale. Lying in bed, for example, which obviously uses little exertion, would rate a 0. If you run at full speed to catch a bus that is pulling away from the curb, by the time you catch the bus, you may rate yourself a 10.

Another RPE scale, the Borg scale, is a 14-point scale that rates exertion from 6 points (no exertion) to 20 points (maximum exertion). The Borg scale differs in that it may give you a fair estimate of your heart rate during physical activity. All you have to do is take your estimated RPE and multiply it by 10. For example, if you think your activity merits a 12, then multiply by 10, and your heart beats per minute would be 120.

Keep in mind these scales are for your own level of exertion, not how you compare to others.

Perhaps the most popular method of measuring intensity is THR. THR is the number of heartbeats per minute at which your heart should be beating during aerobic exercise. It is a rate that varies with the individual.

Many experts recommend that people in good health work between 50% and 85% of their maximal heart rate—the highest heart rate you can achieve. If you are taking medication, your range may be lower. Talk with your doctor to find out your recommended heart rates.

To find your estimated maximal heart rate, subtract your age from 220. For example, if you are 30, your maximal heart rate is 190 beats per minute (bpm).

Finding your target heart rate is a little different. Multiply your maximal heart rate by 50% (for moderate physical activity) and you come up with 95 bpm. Multiply 190 by 85% (for vigorous physical activity) and you get 162 bpm. This means that after you have warmed up, you should try to keep your heart rate between 95 and 162 bpm, staying toward the lower end if you are just beginning an exercise program.

To find your heart rate, you can use a heart rate monitor. If you do not want to pay for a monitor, you can easily calculate your heart rate using palpation.

Use the fingertips of your first 2 fingers, not your thumb, and with light pressure, locate your pulse at one of the following sites:

  • Carotid pulse—Place your fingers at the carotid artery in the side of your neck toward the front. Never palpate both sides of the carotid artery.
  • Radial pulse—Place your fingers over the radial artery in your wrist. You will find it where the base of your thumb connects to the palm side of your wrist.
  • Temporal pulse—Place your fingers over your left or right temple, located on the side of your head near your eye.

Once you have found your pulse, count the number of beats for 10 seconds. Try to do this within 10 seconds after you have stopped exercising. While you are doing this, move around so that you do not get lightheaded.

Take your 10-second heart rate and multiply it by 6. What you have just found is the number of times your heart is beating per minute. For example, if your 10-second count is 18, then your heart rate is 108 bpm.

Remember, though, that THR is just an estimate. Heart rates can often be affected by stress, medicines, fatigue, caffeine, and other factors.

Intensity Basics

Now that you know how to monitor your intensity, how often should you check it? If you are new to exercise, monitor your intensity frequently during an exercise session, possibly every 10 minutes.

It will also ensure that the level at which you are working is safe for your age, fitness level, and medical status. Once you are familiar with how your body responds to exercise, though, you can monitor your intensity less often.