Carbohydrates are your body's preferred energy source for exercise. Of course, there are different types of carbs, and a study published in the International Journal of Sports Medicine compared the effects of high and low glycemic index (GI) carbohydrates consumed 3½ hours before intense training. The glycemic index is a measure of how quickly food elevates blood sugar. Rapidly digesting carbs are usually high GI while slowly digested carbs containing fiber typically rate low GI.
Researchers had recreational football players eat a pre-training meal consisting of either high (80) or low (44) GI foods. Aside from measurements of blood glucose, lactate and fatty acid concentrations, there were no differences in performance and metabolic response to 90 minutes of high-intensity training. If you want to cover your bases, the Stacked Carbs found in ABB Performance RTDs are a combination of fast and slower digested carbohydrate sources.