The Effect of Consuming Carbohydrate With and Without Protein on the Rate of Muscle Glycogen Re-synthesis During Short-Term Post-exercise Recovery: a Systematic Review and Meta-analysis

BackgroundRapid restoration of muscle glycogen stores is imperative for athletes undertaking consecutive strenuous exercise sessions with limited recovery time (e.g. <= 8h). Strategies to optimise muscle glycogen re-synthesis in this situation are essential. This two-part systematic review and meta-analysis investigated the effect of consuming carbohydrate (CHO) with and without protein (PRO) on the rate of muscle glycogen re-synthesis during short-term post-exercise recovery (<= 8h).MethodsStudies were identified via the online databases Web of Science and Scopus. Investigations that measured muscle glycogen via needle biopsy during recovery (with the first measurement taken <= 30min post-exercise and at least one additional measure taken <= 8h post-exercise) following a standardised exercise bout (any type) under the following control vs. intervention conditions were included in the meta-analysis: part 1, water (or non-nutrient beverage) vs. CHO, and part 2, CHO vs. CHO+PRO. Publications were examined for methodological quality using the Rosendal scale. Random-effects meta-analyses and meta-regression analyses were conducted to evaluate intervention efficacy.ResultsOverall, 29 trials (n = 246 participants) derived from 21 publications were included in this review. The quality assessment yielded a Rosendal score of 61 8% (mean standard deviation). Part 1: 10 trials (n = 86) were reviewed. Ingesting CHO during recovery (1.02 +/- 0.4g.kg body mass (BM)(-1) h(-1)) improved the rate of muscle glycogen re-synthesis compared with water; change in muscle glycogen (MG(Delta)) re-synthesis rate = 23.5mmol.kgdm(-1) h(-1), 95% CI 19.0-27.9, p < 0.001; I-2 = 66.8%. A significant positive correlation (R-2 = 0.44, p = 0.027) was observed between interval of CHO administration (<= hourly vs. > hourly) and the mean difference in rate of re-synthesis between treatments. Part 2: 19 trials (n = 160) were reviewed. Ingesting CHO+PRO (CHO: 0.86 +/- 0.2g.kg BM-1 h(-1); PRO: 0.27 +/- 0.1g.kg BM-1 h(-1)) did not improve the rate of muscle glycogen re-synthesis compared to CHO alone (0.95 +/- 0.3g.kg BM-1 h(-1)); MG(Delta) re-synthesis rate = 0.4mmol.kg dm(-1) h(-1), 95% CI -2.7 to 3.4, p = 0.805; I-2 = 56.4%.ConclusionsAthletes with limited time for recovery between consecutive exercise sessions should prioritise regular intake of CHO, while co-ingesting PRO with CHO appears unlikely to enhance (or impede) the rate of muscle glycogen re-synthesis.Trial Registrationegistered at the International Prospective Register of Systematic Reviews (PROSPERO) (identification code CRD42020156841).

Automated summary

This study suggests that athletes with limited recovery time between exercise sessions should prioritize consuming carbohydrates, while simultaneously consuming protein with carbohydrates does not seem to enhance (or impede) the rate of muscle glycogen re-synthesis.