This is a good summary, and also how HIIT (High Intensity Interval Training) works its magic when you're trying to lose weight. You basically exercise at maxim

This is a good summary, and also how HIIT (High Intensity Interval Training) works its magic when you're trying to lose weight. You basically exercise at maximum safe heart rate (mostly determined by age) for a period of time (usually 2 minutes) and then slow down to recuperate. Of course, during recuperation you are still burning calories since you've merely slowed down to a more comfortable rate. It's basically only "relaxing" in comparison to the higher intensity. Psychologically you are putting in serious physical oomph, but not noticing it very much until you hit the scales a week later. By switching back and forth, you get in the maximum calorie burn without passing out or harming yourself. After a few of days of getting used to it, you don't even get much muscle burn or achiness anymore. You definitely sweat a lot more using HIIT. It's pretty ingenious.