The effect of a low carbohydrate-protein beverage on endurance performance
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Introduction: The performance benefit of ingesting carbohydrate (CHO) plus protein (PRO) beverages during prolonged endurance exercise vs. the ingestion of traditional CHO-only beverages is still controversial. Purpose: To investigate the aerobic endurance characteristics of an isocaloric CHO plus PRO drink and a low caloric CHO plus PRO drink against a traditional 6% CHO sports beverage. Methods: Eleven male and female trained cyclists exercised on four separate occasions at intensities that varied between 55% and 75% VO2max for 2.5 h and then at 80% VO2max until fatigued. Supplements (250.1 [plus or minus] 8.1 mL) were provided every 20 min and consisted of a 4.5% carbohydrate plus 1.15% protein complex (CHO/PRO H), a 3% carbohydrate plus 0.75% protein complex (CHO/PRO L), a 6% carbohydrate supplement (CHO), or a placebo (PLA). Treatments were administered using a double-blind randomized design. Results: Time to fatigue at 80% VO2max was significantly longer (P < 0.05) during the CHO (29.3 [plus or minus] 6.3 min; mean [plus or minus] SE), the CHO/PRO H (32.4 [plus or minus] 6.2), and the CHO/PRO L (31.2 [plus or minus] 6.6) trials compared to the PLA trial (16.0 [plus or minus] 3.5), with no significant differences among the CHO, CHO/PRO H, and CHO/PRO L treatments. In general, blood glucose, plasma insulin, CHO and fat oxidation, and RER, were elevated above PLA during the CHO, CHO/PRO H, and CHO/PRO L trials. With the exception of blood glucose and plasma insulin, no differences in the above measurements occurred among the CHO, CHO/PRO H, and CHO/PRO L treatments. Only minor differences in blood glucose and plasma insulin responses occurred among the CHO, CHO/PRO H and CHO/PRO L treatments, and there were no differences noted in heart rate, energy expenditure, blood lactate, or plasma myoglobin among these treatments. Conclusion: A low-caloric CHO plus PRO sports drink was as effective in improving endurance performance as a traditional 6% CHO sports drink or an isocaloric CHO plus PRO sports drink despite containing significantly less CHO and fewer calories. These results suggested that a small amount of PRO can replace CHO in a traditional sports drink without a loss of efficacy. This could be an important consideration for individuals who are concerned about caloric intake and body weight.