During exercise, your body does use stored sugar for energy. Any food that is broken down into sugar can be stored for energy. Sugar, in the form of glycogen and glucose is stored in three places – your muscles, liver, and blood, with your muscles storing the highest amount. Unfortunately, these three systems do not have an unlimited capacity. Once your glycogen and glucose stores are full, no further amount of ingested sugar can be saved. Additional ingested sugar will actually be stored as fat, which is the main theory behind using low carbohydrate diets to trigger weight loss. With the rise in popularity of ultra, endurance events such as marathons, triathlons and bike races, there has been a lot of research on the performance effects of high carbohydrate diets. Research out of the Department of Physiology at the University of Cape Town Medical School in South Africa, studied the effects of carbo-loading before a one hour cycling time trial. The study showed no performance increase in the tested subjects, and also showed that after the event was complete there was still a reserve of carbohydrate in the subjects’ muscles. This would indicate that muscle glycogen stores are not a determining factor of fatigue in a race of this duration. Additional research out of the Department of Biology at The University of Colorado showed that when subjects participated in a 45-minute bout of exercise at 85% of maximal effort, a high versus low carbohydrate diet had no effect on performance when the low carbohydrate diet had a sufficient amount of total calories. So what about taking in carbs during long bouts of exercise or between multiple games in one day? Muscle glycogen stores take too long to restore during exercise, but ingested carbohydrate can boost blood glucose very quickly. This is why many serious endurance athletes fuel up with carbohydrate during their races or long training sessions, usually with drinks or sports gels. Research from The Australian Institute of Sport in Canberra showed that while carbo-loading had no effect on performance during a 100 kilometer cycling time trial, boosting blood glucose during exercise with ingested carbs did offset any depletion of stored muscle and liver glycogen. So the night before a game or race, stick to a balanced meal with plenty of lean protein and vegetables that are high in fiber, and anti-oxidants. If you are an endurance athlete looking for a performance edge, try eating a higher fat diet for a couple of months while training for a big race. Your body will get better at using fat for energy during exercise, and when you go back to eating more carbs, you’ll be able to better utilize both types of stored energy.The parents of our high school athletes usually ask us as many questions as the athletes themselves. A common question has to do with what their kids should eat the night before the game. Team pasta dinners are still pretty popular, and the idea of “carbo-loading” before a competition or race is still considered by most people to be a good idea. The theory behind carbo-loading is to eat a high carbohydrate meal (usually pasta) the night before a race or competition, so that you will have extra energy (in the form of sugar in your body) for the next day.
March 18, 2009
Carbo-loading won’t help you as much as you may think