Muscles are not built in the gym, per se; they're built by sitting on your behind and resting. It sounds counterintuitive, sure, but it's the truth. Workouts only break down your muscle fibers; it takes rest and proper nutrition to repair the muscles and let them bounce back stronger than before. That's why Back to Fit implements strategic rest days. Plus, not many people can keep up a seven-day workout schedule for long. It's nice to throw in breaks, you know?
Bill Phillip's Back To Fit: Day 21
Smash that rest day!