Carb-Protein Sports Drink Research Update
Carbohydrate-protein sports drinks and recovery supplements continue to be intensively researched by exercise scientists. Past research has shown that these products increase time to exhaustion, rehydrate athletes more effectively than carbohydrate-only sports drinks, reduce exercise-induced muscle damage, accelerate post-exercise muscle protein and glycogen synthesis and improve performance in a subsequent workout. Recent studies have now added to this list of benefits. Here are summaries of three such studies:
Carb-Protein Sports Drinks During Resistance Exercise
Everyone knows that ingesting carbohydrate and protein together after resistance exercise reduces muscle protein breakdown and stimulates muscle protein synthesis. But what happens when a carbohydrate-protein supplement is consumed during a weightlifting session?
Researchers from Mastricht University, The Netherlands, recently attempted to answer this question in a study. Ten male subjects completed a two-hour resistance workout on two occasions. During one workout they drank a carbohydrate supplement, and during the other they drank a carb-protein supplement. The rates of muscle protein breakdown and synthesis were measured during each workout. The rate of muscle protein breakdown was 8.4 percent lower, on average, in the carb-protein trial, while the rate of protein oxidation was 77 greater and the rate of muscle protein synthesis was 33 percent greater than in the carbohydrate trial. Whole-body net protein balance was -4.4 micromol phe/kg/h in the carbohydrate trial versus 16.3 micromol phe/kg/h in the carb-protein trial.
The authors of the study, which was published in the American Journal of Physiology, Endocrinology and Metabolism, concluded, "[E]ven in a fed state, protein co-ingestion stimulates whole-body and muscle protein synthesis rates during resistance type exercise."
Another recent study sought to determine whether resistance exercise performance and post-exercise muscle damage were altered when consuming a carb-protein beverage during the workout. Thirty-four male subjects completed three sets of eight repetitions at their eight-repetition maximum in the following exercises: high pull, leg curl, standing overhead press, leg extension, lat pull-down, leg press, and bench press. Subjects consumed 355 ml of either a carb-protein sports drink or placebo 30 minutes prior to exercise, 177 ml immediately prior to exercise, 177 ml halfway through the workout, and 355 ml immediately afterward.
There were no significant differences between groups relative to exercise performance. However, cortisol was significantly elevated in the placebo group compared to the carb-protein group at 24 hours post-exercise. Myoglobin—a biomarker of muscle damage—was significantly elevated at six hours post-exercise compared to the carb-protein group. Creatine kinase—another biomarker of muscle damage—was significantly elevated in the placebo group at 24 hours post-exercise compared to the carb-protein group. The authors of the study concluded that the carb-protein supplement “did not improve performance during a resistance exercise bout, but appeared to reduce muscle damage, as evidenced by the responses of both myoglobin and creatine kinase. These results suggest the use of a [carb-protein] supplement during resistance training to reduce muscle damage and soreness.”
Carb-Protein Drink Enhances Carb Oxidation in Second Workout
Researchers from the University of Bath, England, Loughborough University and Queen's Medical College recently compared the effects of a carbohydrate recovery drink (CHO) and a carbohydrate-protein recovery drink (CHO-PRO) on muscle glycogen resynthesis between two long run workouts undertaken on the same day and on carbohydrate oxidation in the second workout.
Six runners ran for 90 minutes at 70 percent VO2max, rested for four hours, and then ran one hour at the same intensity. During the recovery period they drank either CHO or CHO-PRO. After a 14-day washout period, the runners repeated the protocol, but those who drank CHO the first time drank CHO-PRO instead and vice versa. The researchers found that CHO-PRO produced a greater insulin response during the recovery period, but rates of glycogen resynthesis were the same with the two drinks. Whole-body carbohydrate oxidation was significantly greater in the second run after CHO-PRO was consumed (48.4 vs. 41.7 mg.kg.min), but the rate of muscle glycogen use was the same, indicating that runners relied on blood glucose, liver glycogen and/or exogenous carbohydrate more after drinking CHO-PRO.
These results suggested that if the second run at been a maximal one-hour effort, the runners might have performed better after drinking CHO-PRO, as higher rates of carbohydrate oxidation allow higher rates of muscle work. The authors of this study, which was published in Medicine & Science in Sports & Exercise, did not make this speculation, however, concluding only that "the inclusion of protein in a carbohydrate-recovery supplement can increase the oxidation of extramuscular carbohydrate sources during subsequent exercise without altering the rate of muscle glycogen degradation."