It is well established that adequate bodily carbohydrate reserves are required for optimal endurance. Based on this fact, it has been hypothesized that consumption of a diet with a high percentage of carbohydrate energy will optimize training adaptations and athletic performance. Scrutiny of the literature, however, does not strongly support the hypothesis that short-term or long-term reductions in dietary carbohydrate energy impairs training or athletic performance. Additional studies with well devised training protocols and performance tests are necessary to prove or disprove the hypothesis that a high carbohydrate energy diet is necessary to optimize training adaptations and performance. Because dietary carbohydrate contributes directly to bodily carbohydrate reserves, and because a high carbohydrate energy diet does not impair athletic performance, it remains prudent to advise athletes to consume a diet with a high carbohydrate energy content.
William M. Sherman and Gregory S. Wimer
Manuel Lugo, William M. Sherman, Gregory S. Wimer, and Keith Garleb
This study examined the effects of consuming the same amount of carbohydrate in solid form, liquid form, or both on metabolic responses during 2 hrs of cycling at 70% peak VO2 and on cycling time-trial performance. Subjects consumed 0.4 g carbohydrate/kg body mass before and every 30 min during exercise. The liquid was a 7% carbohydrate-electrolyte beverage and the solid was a sports bar (1171 kJ) in which 76%, 18%, and 6% of total energy was derived from carbohydrate, fat, and protein, respectively. Blood obtained at baseline, before exercise, and every 30 min was analyzed for glucose, insulin, lactate, hemoglobin, hematocrit, and plasma volume. There were no differences among the treatments for the blood parameters. Total carbohydrate oxidation and time-trial performance were also similar among treatments. Under thermoneutral conditions with equal liquid inges-tion, the metabolic and performance responses are similar when consuming carbohydrate as a liquid, solid, or in combination during prolonged, moderate intensity cycling.