The standard high-carb bars, such as the well known PowerBar and Clif Bar, are great for fueling before, during and after an activity because, as with sports drinks and gels, they introduce a quick release of carbs into the blood stream. About 70 percent of their carbohydrate calories come from grains (oats and rice crisps) and sugars (brown-rice syrup and sucrose), with some bars containing fruit and nuts, which are the most natural and one of the easiest carb sources to digest quickly.
