Our body doesn’t store many carbohydrates.  In fact, you only have something like 100 grams of them in your liver and 300 grams of them in your muscles whenever your carbohydrate stores are full.

If you exercise for a while, you’re going to deplete a lot of those carbohydrate stores.  In addition to that, when you resistance train you create small levels of “micro-trauma” in the muscle fibers themselves.  As a result of those two facts, at the end of your workout you’re somewhat carbohydrate depleted, and you have some muscle fibers that need repair.  You need to eat carbohydrates and protein to fix these two problems.

The main issue with the carb depletion is that your body needs carbs.  If your body has to choose between having carbohydrates for brain function or having extra muscle to be able to bench an extra ten pounds, it will always choose carbs for brain function.  This also means that if you only eat protein after your workout, then your body is going to convert the protein into carbohydrate because it needs carbs more.  The most intelligent way to approach this is to just eat the carbs so your body doesn’t have to waste time and energy converting the protein into carbs.

Once you have your carbs in and your body is happily re-filling its carbohydrate stores, then you can focus on repairing the damaged muscle fibers by eating protein.  In fact, research has shown that around a 3:1 carb to protein ratio is the best for your post-workout meal.  If you’re going to take your 25 grams of protein (what’s in most whey protein powder servings), then you should be getting in around 75 grams of carbohydrate.

Also, as a fun sidenote, chocolate milk has been shown to be just as effective for post-workout recovery as any brand-name recovery drink or powder.  It’s a lot cheaper, too.  🙂