Nutritional Ergogenic Aids: The Influences of Carbohydrate-Protein Supplementation During Endurance Exercise

Mixed results, in terms of performance benefits, have been found when comparing carbohydrate (CHO) and carbohydrate-protein (CHO-P) supplementation during endurance exercise. Thus this study assessed performance from three different supplements (CHO-P, CHO, double carbohydrate [CHO-CHO]) as compared to a placebo (PLA) during a time trial (TT) run. Twelve male recreational runners (age = 32.4 ± 9.5 yrs; body mass index [BMI] = 22.7 ± 1.5 kg/m2; VO2max = 59.68 ± 7.53 mL/kg body weight; 100% white) individually completed four, 12-mile TT runs, 7-10 days apart, at about 75% of the their race pace. Dietary and physical activity consistency within the 24-hour time period prior to each run was controlled via individualized diet and activity prescriptions based off of the diet consumed and the physical activity engaged in prior to TT 1. Throughout each TT run, participants consumed a 600 mL load of one of the four aforementioned supplements. Supplement order was counterbalanced with a latin-square design. Endurance performance was measured by time to complete the 12-mile run, and time to complete the last 1.2 miles of the run, where participants were instructed to run at maximal effort, 100% race pace. A main effect of time occurred during the TTs for perceived exertion (RPE) and heart rate (HR). RPE (Borge 10-point scale) significantly increased from the mid-point of the TT to completion of the run (4.7 ± 0.7, 9.7 ± 0.9, p < 0.001); HR significantly increased from the start of the run to the start of the maximal effort, and was significantly higher at completion of the effort (84.4 ± 14.5 bpm, 166.0 ± 8.3 bpm, 178.8 ± 7.4 bpm, p < 0.001). No significant difference was found in overall time to complete the 12-mile run or maximal effort between the supplements (PLA = 88.6 ± 11.6 min, CHO = 89.1 ± 11.3 min, CHO-P = 89.1 ± 11.8 min, CHO-CHO = 89.6 ± 11.9 min; PLA = 8.3 ± 1.2 min, CHO = 8.2 ± 1.2 min, CHO-P = 8.2 ± 1.2 min, CHO-CHO = 8.4 ± 1.5 min). These findings suggest that type of supplementation (CHO, CHO-CHO, CHO-P) consumed during an endurance exercise bout has no influence on enhancing endurance performance in male recreational runners during TT runs less than 100 minutes in length.