Abstract
We examined whether carbohydrate-protein ingestion influences muscle glycogen metabolism during shortterm recovery from exhaustive treadmill running and subsequent exercise. Six endurance-trained individuals underwent two trials in a randomized double-blind design, each involving an initial run-to-exhaustion at 70% VO2max (Run-1) followed by 4-h recovery (REC) and subsequent run-to-exhaustion at 70% VO2max (Run-2). Carbohydrate-protein (CHO-P; 0.8 g carbohydrate.kg body mass [BM-1].h(-1) plus 0.4 g protein.kg BM-1.h(-1)) or isocaloric carbohydrate (CHO; 1.2 g carbohydrate.kg BM-1.h(-1)) beverages were ingested at 30-min intervals during recovery. Muscle biopsies were taken upon cessation of Run-1, postrecovery and fatigue in Run-2. Time-to-exhaustion in Run-1 was similar with CHO and CHO-P (81 +/- 17 and 84 +/- 19 min, respectively). Muscle glycogen concentrations were similar between treatments after Run-1 (99 +/- 3 mmol.kg dry mass [dm(-1)]). During REC, muscle glycogen concentrations increased to 252 45 mmol.kg dm(-1) in CHO and 266 30 mmol.kg dm(-1) in CHO-P (p =.44). Muscle glycogen degradation during Run-2 was similar between trials (3.3 +/- 1.4 versus 3.5 +/- 1.9 mmol.kg dm(-1).min(-1) in CHO and CHO-P, respectively) and no differences were observed at the respective points of exhaustion (93 +/- 21 versus 100 +/- 11 mmol.kg dm(-1); CHO and CHO-P, respectively). Similarly, time-to-exhaustion was not different between treatments in Run-2 (51 +/- 13 and 49 +/- 15 min in CHO and CHO-P, respectively). Carbohydrate-protein ingestion equally accelerates muscle glycogen resynthesis during short-term recovery from exhaustive running as when 1.2 g carbohydrate.kg BM-1.h(-1) are ingested. The addition of protein did not alter muscle glycogen utilization or time to fatigue during repeated exhaustive running.