Krystyna M. Kras, Ph.D.
I moved to Davis shortly before summer of last year after accepting a post-doctoral position in the Department of Nutrition at UC Davis. My B.S. degree is in dietetics from Michigan State and I have a M.S. and Ph.D. in nutrition science, both from the University of Georgia. Although my area of expertise is in fat cell development and metabolism, my love for cycling and passion for racing has shifted my interest from the petri dish to direct, real-life application. Nutrition and sports performance are inseparable and I have found myself in several pace lines where I have been asked many nutrition-related questions. In this article I will address the following popular question: Will eating gu or power gel during a race give me an edge? And with hesitation, I give the standard academic nutritionist answer: It depends. First, here's some background information.
Fat and carbohydrates (in the form of glucose) are used as fuel during exercise. In general, carbohydrate use by the body increases with increasing exercise intensity and falls with increasing duration of activity. Carbohydrate fuel can support higher exercise intensity but it is stored in limited amounts as glycogen in liver and muscle, so the challenge is to maintain carbohydrate supply to the muscles while slowing its depletion by relying on fat as a fuel source. Therefore, eating foods with a high glycemic index, such as gus and power gels would be beneficial during and after an event to aid in glycogen restoration.
Before I go further, let me clarify what is meant by "glycemic index." The glycemic index is a relatively new system of carbohydrate classification. This index was originally developed to aid diabetics in making appropriate food choices when balancing blood glucose and insulin levels. The glycemic index represents the magnitude of the increase in blood glucose that occurs shortly after you eat the food. The higher the glycemic index, the faster the rise in blood glucose after eating the food. The less fat, protein, and fructose in the food, the higher the glycemic index. In general, the more processed the food, the higher the glycemic index. And gu certainly has a high glycemic index as do some sports drinks.
Filling glycogen stores before race time is critical with endurance sports. Depending on the duration and intensity of the event, adequate carbohydrate intake occurring days or even hours before the event could eliminate the need to eat during that event. It is a general recommendation that eating low glycemic index foods 30-60 min prior to endurance exercise will help sustain exercise intensity. In fact, as some studies have shown that a low glycemic index pre-race meal promotes utilization of fatty acids, thus aids in prolonging exercise duration.
However, to improve stamina during an event, it is recommended that the rider consumes 100-300 calories of carbohydrates per hour of endurance exercise; or more precisely, 0.5g of carbohydrate per pound of body weight. These carbohydrates can be consumed in various forms: sports drink, sports bar, fruit, and/or gu. If you feel you are going to need extra energy for the final sprint, give yourself about 20 minutes before the end of the race for the carbohydrates to be absorbed and available for use.
Most importantly, experiment with these foods before an event. Too many carbohydrates, especially without proper hydration, can cause diarrhea and cramping. Use training rides as a race simulation to determine which source, how much, and when you need to refuel with carbohydrates during your ride. Also, palatability, cost, portability and accessibility of the food during race events are all factors that need to be considered before the guns go off. Gu or power gel is a compact source of carbohydrates and only requires one hand to consume but the sticky, thick gu is hard to put down in a heated a race without a lot of water. So the best way to decide to gu or not to gu is to try it near the end of your next hard training ride and see if it helps your performance.