KraneXL

1) For building muscle.
2) For preserving muscle.

Its really something you only need during regular anaerobic training -- or when you're trying to get stronger. During period when I'm not going to the gym regularly, I won't supplement protein.

If you're a pure straight and level cyclist, you could very well get all the protein you need just from whole food. Still, its a quick and easy way to replenish your stores especially when you're out or on the go.

Protein drinks are also as healthy as you can get when you want to satisfy your sweet tooth (in a meal); and are recommended when you're dealing with a muscle wasting condition such as after surgery for example.

I use mine when I'm under the weather from a virus and I can't hold down solid food, or just don't have any appetite (people tend to lose muscle when they're sick -- especially the flu).

You are right about the sugar for the boost though. But you really want to avoid using protein as an energy food if you can help it. Sure it will work, but its inefficient, and a very expensive way to fuel a workout. Its like using your home furniture as wood for your fireplace.