Your Rate of Perceived Exertion, or RPE, is basically how hard you feel you are working during a given workout. The chart below shows how your RPE correlates to our training programs.
RPE is a good place to start if are new to Zone Training. It is something that you will be falling back on again and again because feeling your way in between zones can often at times be the most accurate. This is especially true when it comes to interval training.