Carbohydrate-electrolyte ingestion during intermittent high-intensity running

Purpose: The purpose of this study was to examine the effects of ingesting a carbohydrate-electrolyte beverage or a noncarbohydrate placebo on muscle glycogen utilization during 90 min of intermittent high-intensity running. Methods: Six trained games players (age 24.6 +/- 2.2 yr; height 179.6 +/- 1 .9 cm; body mass 74.5 +/- 2.0 kg; (V) over dot O-2max 56.3 +/- 1.3 mL.kg(-1 ).min(-1); mean +/- SEM) performed two exercise trials, 7 d apart. The subj ects were university soccer, hockey, or rugby players. On each occasion, th ey completed six 15-min periods of intermittent running, consisting of maxi mal sprinting, interspersed with less intense periods of running and walkin g. During each trial, subjects consumed either a 6.9% carbohydrate-electrol yte solution (CHO-E: the CHO trial) or a noncarbohydrate placebo (the CON t rial) immediately before exercise (5 mL.kg(-1) BM) and after every 15 min o f exercise thereafter (2 mL.kg(-1) BM). Drinks were administered in a doubl e-blind, counter-balanced order, and the total volume of fluid consumed dur ing each trial was 1114 +/- 30 mt. Needle biopsy samples were obtained from the vastus lateralis muscle before and after 90 min of exercise. Venous bl ood samples were collected from an antecubital vein at rest and every 30 mi n during exercise. Results: Muscle glycogen utilization in mixed muscle sam ples was lower (P < 0.05) during CHO [192.5 +/- 26.3 mmol glucosyl units (k g.DM-1)] than CON [245.3 +/- 22.9 mmol glucosyl units (kg.DM-1)]. Single fi ber analysis on the biopsy samples of the subjects during the CON trial sho wed a greater glycogen utilization in the Type II fibers compared with Type I fibers during this type of exercise [Type I: 182.2 +/- 34.5 vs Type II: 287.4 +/- 41.2 mmol glucosyl units (kg.DM-1); P < 0.05). After 30 min of ex ercise, blood lactate was significantly greater (P < 0.05) and serum insuli n concentration lower (P < 0.05) in CON. Conclusions: In summary, when trai ned games players ingested a carbohydrate-electrolyte beverage, muscle glyc ogen utilization was reduced by 22% when compared with a control condition.