We have all heard the term. But very few fully understand what it means, much less how to implement interval training into our fitness plan. So, here is a primer (though, rather lengthy, I’m afraid) on this very popular exercise program. For one thing, it is not recommended for exercise beginners. For another, great results can still be gained using other exercise programs. PLEASE CONSULT YOUR DOCTOR BEFORE BEGINNING ANY NEW EXERCISE PROGRAM.
Muscle-building does not occur during exercise. Rather, exercise tears down muscles, which then rebuild and adapt during the post-exercise rest and recovery period. That is why, typically, specific muscle groups should not be worked on consecutive days. They should be allowed to recover for at least 48 hours, though 72 hours is generally best. The link below explains the scientific process.