An alternative method of gauging how hard you are working is the Rating of Perceived Exertion (RPE), also called the Borg scale. It has been widely used in both clinical and recreational applications since G. Borg developed it in 1982. If used correctly, it can be very accurate.
The tricky part of using the scale is that it asks you to subjectively rate the amount of effort you are expending by estimating how hard you are working overall. That means that you do not concentrate on how out of breath you are, how much your legs hurt, how much you are sweating or any other indicator of effort — you concentrate on all of them together. How hard do you feel you are working? Of course, if you are working too hard, you may be too out of breath to continue for long. This is best used for true aerobic exercise, where you want to maintain your exercise intensity for 10 or more minutes. The scale is shown below. If you are curious about the numbers, Borg set it up so that it would correspond to the heart rate of a typical 20-year-old individual, if you add a zero to the number. However, to use the scale properly, you ignore any count of heart rate.
6
7 very, very light
8
9 very light
10
11 fairly light
12
13 somewhat hard
14
15 hard
16
17 very hard
18
19 very, very hard
20
You pick the number that corresponds to your overall feeling of effort at that time. If you are lying on the couch contemplating your next snack, that is a 6. Now imagine you are running the 400 meters in the Olympics and you feel your arch rival breathing down your neck as you near the finish.
That’s a 20. So 6 is total rest and 20 is your maximum effort. The 60 to 90 percent range is 12 to 18, and 70 to 75 percent is 14 or 15. You will start breathing heavier around 13 (somewhat hard) and when you reach 17 (very hard) you are pushing so hard you will not be able to maintain it for long unless you’re in good aerobic condition. (For most runners, 5K-pace is around 18.) If you’re very unconditioned or have medical problems, 10 or 11 may be enough for you.
Of course, a beginner running at an RPE of 15 will not be moving nearly as fast as an accomplished runner at 15. If you have a heart rate monitor, it can help you learn faster if you consult it when you feel a certain RPE, and see how you close to that number your heart rate is the next time you are at that RPE.
Practice with RPE and you may find it an excellent tool for gauging your exercise intensity and planning your workouts. Listen to your body.