Everyone's pretty much in agreement that carbohydrates help power physical performance. The challenge comes with knowing how much and when to use them. To give you a benchmark for endurance training, a study published in the journal Applied Physiology, Nutrition, and Metabolism examined the time trial performance of 6 male and 4 female amateur triathletes engaged in a simulated Olympic distance event.
Two minutes before completing each quarter of the cycle, subjects drank 200 mL of a solution containing either 1.2 grams of maltodextrin and 0.6 grams of fructose or a sugar free fruit flavored beverage. Finishing a time trial after the swimming and cycling legs of the triathlon went about 4% faster for the subjects who had carbs instead of the placebo drink. Dial this data into your next endurance training session.