Liver and muscle glycogen repletion using 13C magnetic resonance spectroscopy following ingestion of maltodextrin, galactose, protein and amino acids

The present study evaluated whether the inclusion of protein (PRO) and amino acids (AA) within a maltodextrin (MD) and galactose (GAL) recovery drink enhanced post-exercise liver and muscle glycogen repletion. A total of seven trained male cyclists completed two trials, separated by 7 d. Each trial involved 2 h of standardised intermittent cycling, followed by 4 h recovery. During recovery, one of two isoenergetic formulations, MD–GAL (0·9 g MD/kg body mass (BM) per h and 0·3 g GAL/kg BM per h) or MD–GAL-PRO+AA (0·5 g MD/kg BM per h, 0·3 g GAL/kg BM per h, 0·4 g whey PRO hydrolysate plus l-leucine and l-phenylalanine/kg BM per h) was ingested at every 30 min. Liver and muscle glycogen were measured after depletion exercise and at the end of recovery using 1H-13C-magnetic resonance spectroscopy. Despite higher postprandial insulin concentations for MD–GAL-PRO+AA compared with MD–GAL (61·3 (se 6·2) v. 29·6 (se 3·0) mU/l, (425·8 (se 43·1) v. 205·6 (se 20·8) pmol/l) P= 0·03), there were no significant differences in post-recovery liver (195·3 (se 2·6) v. 213·8 (se 18·0) mmol/l) or muscle glycogen concentrations (49·7 (se 4·0) v. 51·1 (se 7·9) mmol/l). The rate of muscle glycogen repletion was significantly higher for MD–GAL compared with MD–GAL-PRO+AA (5·8 (se 0·7) v. 3·7 (se 0·6) mmol/l per h, P= 0·04), while there were no significant differences in the rate of liver glycogen repletion (15·0 (se 2·5) v. 13·0 (se 2·7) mmol/l per h). PRO and AA within a MD–GAL recovery drink, compared with an isoenergetic mix of MD–GAL, did not enhance but matched liver and muscle glycogen recovery. This suggests that the increased postprandial insulinaemia only compensated for the lower MD content in the MD–GAL-PRO+AA treatment.