Optimizing muscle glycogen resynthesis postexercise: should protein be added to a carbohydrate drink?

Abstract

During the first few hours of recovery from prolonged exercise, co-ingestion of protein (PRO) with carbohydrate (CHO) will increase the rate of muscle glycogen resynthesis if the rate of CHO intake is sub-optimal and/or when the feeding intervals are > 1 h apart (Burke et al.. 2004). It remains controversial whether the higher rate of glycogen resynthesis is attributable to a PRO-mediated increase in insulin release or simply the result of higher energy intake (Jentjens et al., 2001). The optimal rate of CHO ingestion necessary to maximize glycogen resynthesis remains unknown, although some studies have recommended a peak CHO intake of >1.2 g/kg/h. PURPOSE: We examined whether the addition of PRO or “extra CHO” to a drink that provided 1.2 g CHO/kg/h would increase muscle glycogen resynthesis during recovery from prolonged exercise. METHODS: Six men (22± 1 yr; V02|,eilk= 48±8 ml/kg/min) were studied during a 4-h recovery period on 3 separate occasions after a standardized 2-h exercise protocol designed to substantially lower muscle glycogen. Subjects randomly consumed 1 of 3 drinks during recovery from each trial: 1.2 gCHO/kg/h (CHO), 1.6 gCHO/kg/h (CHO/CHO) or 1.2 gCHO + 0.4 gPRO/kg/h (CHO/PRO). Drinks were consumed immediately post-exercise and at 15 min intervals for 3 hrs. RESULTS: Biopsies obtained at 0 and 4 hrs post-exercise revealed no difference in muscle glycogen resynthesis rates between trials (CHO: 22.7±6.6; CHO/CHO: 25.0±3.0; CHO/PRO: 24.6±4.2 mmol/kg dry wt/h) despite differences in energy intake between trials. The ingestion of additional CHO or PRO did not induce changes in blood [insulin ] and blood [glucose] compared to a 1.2 gCHO/kg/h beverage. Muscle [lactate] increased from immediately post-exercise to 4 hrs into recovery in all 3 trials (main effect for time. P<0.05). All subjects reported some degree of gastro-intestinal(Gl) distress after 3 and 4 hrs of recovery but there were no differences between treatments (main effect for time, P<0.05 vs. 0 hrs). CONCLUSION: Ingesting 1.2 gCHO/kg/h met or exceeded the threshold necessary to optimize muscle glycogen synthesis during the first 4 hrs of recovery from prolonged, strenuous exercise in recreationally active men. The ingestion of >1.2 gCHO/kg/h at a concentration of -20% solution induced GI distress in some individuals and may hamper subsequent same-day performance.