I never ran with a heart rate monitor because I don't need it. But even with my good feeling for my body and my long experience as a runner, I cannot say from the way I feel if I covered the kilometer in 2:40 or 2:45. Therefore, I check the speed in the workouts where it matters on a measured route with a stopwatch Even if you don't have this sense for your body, you should never become a slave of your heart rate monitor. If you don't have a problem with your health, meaning you are not allowed to exceed a certain heart rate, leave your heart rate monitor at home more often and try to run by listening inside you. It gives you graeter joy when you run in harmony with nature. - Paul Tergat, from his book " Running to the limit"