Influence of a carbohydrate-electrolyte solution ingested during running on muscle glycogen utilisation in fed humans

This study investigated whether the ingestion of a carbohydrate-electrolyte solution during running would influence muscle glycogen utilisation in subjects who had consumed a carbohydrate meal 3 hours before exercise. Eight men completed two 60-min treadmill runs at 70% VO(2)max. Before each run they consumed a carbohydrate meal (183 +/- 7 g) 3 hours before exercise and either 1) a carbohydrate-electrolyte solution during the run (46 +/- 1 g) (M+C), or 2) water during the run (M + W). Biopsy samples were obtained from the vastus lateralis muscle at rest and after 60 min of running. Serum insulin concentrations were higher (p < 0.01) in both trials at the start of exercise compared with fasting values, whereas blood glucose concentrations were higher (p < 0.01) after 60 min of running in the M+C trial. Pre-exercise muscle glycogen concentrations were similar in both trials (M+C: 321.9 +/- 27.2 vs M+W: 338.8 +/- 32.8 mmol x kg x dry weight (-1) [dw]; NS). There was no difference in the amount of glycogen used during exercise (M+C: 96.1 +/- 22.1 vs M+W: 77.9 +/- 11.7 mmol x kg x dw (-1); NS). In conclusion, a carbohydrate-electrolyte solution ingested during treadmill running at 70 % VO(2)max does not influence muscle glycogen use during the first hour of exercise when a carbohydrate meal is consumed 3 hours before exercise.