Ask any professional body builder what they do when they're not working out, and you'll quickly find out it has nothing to do with exercise. In fact, it's quite the opposite. Fitness buffs use their downtime to relax -- as in, their muscles.

The reason for this is that the truth behind building muscle has a lot less to do with "building" than many people think. When we work out, we may feel that our muscles are growing larger and harder as we work, but in truth this is just a temporary expansion due to the current stress on the muscle.

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Part of the reason for this expansion is that when we work out, we are actually causing our muscles to tear. That might sound bad, but it surprisingly isn't. Believe it or not, in order to "build" muscle, it has to first broken down.

Real muscle building doesn't occur until after the workout. In a similar fashion to a tear in your skin healing and scarring over, the tears in your muscles scar over, causing the muscle to become thicker, larger, and stronger. This is why it is so important to body builders that they get plenty of rest; the more rest time they have, the more time is dedicated to their muscles actually building and properly healing before the next workout and tearing-rebuilding cycle.