Check out this great article on fructose:
The farther you have to go, the more you’ll want to consider pure crystalline fructose. Because fructose, compared to glucose, helps the energy store in the muscles last longer.
Endurance and Muscle Glycogen. Carbohydrates stored in the body’s muscles are referred to as muscle glycogen. The more muscle glycogen available during sustained exercise, the greater the potential for improved endurance.
Sugars and Glycogen Storage. The various sugars have different effects on muscle glycogen depletion rates. Glucose, for example, provides a quick spurt of energy, but also triggers the release of insulin. This actually increases the depletion of muscle glycogen and also suppresses the conversion of fat to energy.
Fructose and Glycogen Storage. Taking fructose before exercise, compared to glucose, results in a much lower rate of muscle glycogen depletion. Because fructose does not cause a rapid rise in either blood sugar or insulin. It provides a steadier supply of blood sugar and helps the store in the muscles last longer. This carries the potential for greater endurance during exercise.
The Glycemic Edge. In recent years, emphases has been placed on the glycemic index in the evaluation of dietary carbohydrates. Glucose, which creates the greatest rise in blood sugar and insulin, has been assigned a glycemic index of 100. Foods which behave most like glucose have high index numbers. Fructose, however, has an index of 20, one of the lowest of the 63 carbohydrates on the list, and in this regard can be said to offer a “glycemic edge.”
FroCup.com