Legs are the foundation of a structurally sound body. When training legs properly, your entire body will change for the better. Strength in other lifts will increase due to increased levels of testosterone which you will recruit by training your legs. Also when doing movements like squats, you recruit muscle fibers from your entire body: back, abs, shoulders, and of course your legs.

Training legs properly and consistently will also help you maintain a lower level of body fat due to the number of calories you will burn. If anyone asks me what's the most important body part to train, I will always tell them legs...

So, apply this program and enjoy!