Effects of carbohydrate and protein supplementation during resistance exercise on respiratory exchange ratio, blood glucose, and performance

Introduction Athletes must determine whether they will benefit most from exercise in the fasted or fed state when discussing variables such as substrate oxidation, muscle anabolism, and performance. Objective To determine the effects of a carbohydrate plus protein (C + P) beverage consumed during resistance exercise on respiratory exchange ratio (RER), blood glucose, and performance. Methods Ten resistance trained male subjects completed two bouts of exercise consisting of seven sets of squats and bench presses using 60% of their one repetition maximum (1RM). Subjects consumed C + P during one trial, and a non-caloric placebo (P) in the other. Six sets of each exercise were performed for a predetermined number of repetitions, followed by a seventh set of each exercise for as many repetitions as possible, performed as explosively as possible. Power was measured during the final set of each exercise. Glucose was measured pre, during, and post exercise. RER was measured seven times during each session. Results No significant difference in power was found. C + P resulted in significantly greater work in the bench press (p < 0.05), with no difference in the squat (p = 0.10). Post-exercise glucose was significantly greater (p < 0.05) in C + P vs. placebo. In C + P, post-exercise glucose was significantly greater (p < 0.05) than before or during exercise. For RER, a significant effect was found for time (p < 0.05), with no difference between conditions. Conclusion In active males, C + P ingestion during resistance exercise improved bench press performance and increased blood glucose, but does not appear to affect RER.