You choose a value between 1 and 10 based on muscular tiredness, higher heart rate, and increased pace of breathing to get your RPE. The greater the number, the more strenuous the workout. An RPE of 1 is considered to be slightly above rest, with little exertion, whereas an RPE of 10 is considered to be peak effort. Most people can maintain an RPE between 6 and 9. The best way to establish the rate of perceived exertion is by using a scale that measures how hard you are working out. There are many different scales available, but the most common one is called the Borg Scale. It works by measuring your maximum heart rate (which can be found by taking your age times 0.65 if you are over 40). Then you measure how hard you are working out by comparing it to this maximum heart rate. If you are working at a lower intensity than this maximum level, then you should feel exhausted and need to slow down or stop exercising. When you reach this maximum heart rate, you will not be able to maintain this pace for more than 10 minutes, so you should start reducing your exercise load gradually until you return to a lower intensity. On the Borg Scale, 1 is equivalent to very light activity, while 10 is equivalent to maximal effort. So, the harder you work, the higher number you will see on the scale. You can also estimate the amount of effort you are putting in by comparing your own performance to others who have done similar exercises before you.