When your heart rate varies, the readings alter. Some treadmills can detect the signal from the strap and show your heart rate on the dashboard. Fitness bands or activity trackers, which have been selling in large quantities, are the latest technique to assess your heart rate. These devices measure your pulse continuously and report it to the software when you reach a certain level of exercise. The body's response to stress is determined by two things: the intensity of the exercise and the frequency with which it is repeated. The more intense the exercise, the faster your heart rate will be. If you start out at a low intensity and increase the pace over time, your heart rate will also rise. However, if you keep the speed constant and increase the intensity of the exercise, your heart rate will go up too. People often think that since they are only exercising for half as long, the intensity of their workout is not as high as those who stay on the machine for an hour. This is not true; you are still putting out the same amount of energy per minute as those who stay on the machine for longer. It's just that you're able to work out at a lower intensity because there's less of a risk of injury. Your heart rate increases as a result of different activities. At rest, it usually ranges between 60 and 100 beats per minute. During moderate exercise, this number may go up to 150 or more.