During physical activity your body requires energy continuously, before using the carbs directly from the food, when it is finished, the body will fetch what it needs from the muscles thus impairing their performance and forcing them moreover to do "extra" work and thus hampering your performance. To avoid this, simply take the right amount of carbohydrates before and during exercise, so as not to restrict muscle performance and to allow the body to work at a 100%. Carbohydrate Energy bars are aimed at helping with this, thanks to their highly energetic composition to make up for the demands of the body it allows you to continue training/racing in the best condition possible.