Just like an automobile needs gasoline (fuel) in order to operate at high levels of performance, your body needs the same thing. Glycogen, or sugar, is what your body uses as fuel. The same way that your car uses more fuel when you drive it "harder", so does your body. When you work out really hard your glycogen levels go down. Once it’s gone it needs to be regenerated but your body takes a little time doing so. One of the best ways to replenish your fuel, is with the help of a post-workout recovery drink.
Studies have shown that with the right nutrition during the very first hour after a workout, you can increase your bodies ability to recover dramatically. So a recovery drink is very important. If you don’t replenish your bodies fuel tank after a workout, then your body will need to find some source of fuel for energy and will break down the muscle. Muscle that you have worked long and hard to gain.
Of course it depends also on how hard your workout was. If it’s a light workout like X Stretch or something similar that’s a mild cardio workout then you don’t need a recovery drink because you’re not depleting your glocygen levels. You also need to think about if you really had a tough workout. With all the vitamins and antioxidants you need itll reduce muscle soreness and assist in repair and growth. I’ve been using the P90X recovery formula now for years and I always take one after a tough workout, which seems like an every day thing. :)