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HARGREAVES M.; COSTILL, DAVID L.; KATZ, A.; FINK, W. J.
Medicine & Science in Sports & Exercise: June 1985
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ABSTRACT

Eight healthy males were studied to compare the effects of preexercise fructose and glucose ingestion on muscle glycogen usage during exercise. Subjects performed three randomly assigned trials, each involving 30 min of cycling exercise at 75% VO2max. Forty-five min prior to commencing each trial, subjects ingested either 50 g of glucose (G), 50 g of fructose (F), or sweet placebo (C). No differences in JOURNAL/mespex/04.02/00005768-198506000-00010/ENTITY_OV0312/v/2017-07-20T222118Z/r/image-pngO2 or respiratory exchange ratio were observed between the trials. Blood glucose was elevated (P < 0.05) as a result of the glucose feeding. With the onset of exercise, blood glucose declined rapidly during G, reaching a nadir of 3.18 ± 0.15 (SE) mmol.1-1 at 20 min of exercise. This value was lower (P < 0.05) than the corresponding values in F (3.79 ± 0.20) and C (3.99 ± 0.18). No differences in exercise blood glucose levels were observed between F and C. Muscle glycogen utilization was greater (P < 0.05) during G (55.4 ± 3.3 mmol.kg-1 w.w.) than C (42.8 ± 4.2). No difference was observed between F (45.6 ± 4.3) and C. There was a trend (P = 0.07) for muscle glycogen usage to be lower during F than G. These results suggest that the adverse effects of preexercise glucose ingestion are, in general, not observed with either fructose or sweet placebo.

©1985The American College of Sports Medicine