“Cardio” is derived from the Greek word “kardia”, which means heart. This means that cardio training is the the training of the heart and we must assume that motivation to train the heart comes from the need or desire to get better so when performing cardio training we want to improve the function of the heart. However, many people are under the assumtion that all you need to do cardio is an elevated heart rate but that is very wrong. If all it takes to “do cardio” is an elevated heart rate, I could just scare you into better shape. The physiology of the heart does not work that way and most trainers and coaches are blind to this fact!