Effects of preexercise snack feeding on endurance cycle exercise.
We studied the effects of ingesting either a snack food (S) (260 kcal) or placebo (P) 30 min before intermittent cycle exercise at 70% maximal O2 consumption on endurance performance and muscle glycogen depletion in eight healthy human males. Immediately before exercise there were significantly greater increases in plasma glucose (PG) (S +28 +/- 9.7; P +0.1 +/- 0.8 mg/dl) and insulin (S +219 +/- 61.5; P -7 +/- 5.5 pmol/l) (P less than 0.05) following S feeding compared with P. These differences were no longer present by the end of the first exercise period. There were no differences in endurance times (S 52 +/- 6.4; P 48 +/- 5.6 min) or in the extent of muscle glycogen depletion following exercise (S 56 +/- 14.7; P 50 +/- 15.5 micrograms/mg protein) between the two groups. PG was maintained at base-line (prefeeding) concentrations following S, whereas there was a tendency for PG to steadily decrease after P. Total grams of carbohydrate oxidized during exercise did not differ between the two groups (S 120; P 118 g). These results demonstrate that the ingestion of a mixed-macronutrient snack 30 min before exercise does not impair endurance performance nor increase the extent of muscle glycogen depletion during high-intensity cycle exercise in untrained adult male subjects.
D001786:Blood Glucose / Q000032:analysis; D004435:Eating; D004734:Energy Metabolism; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D009132:Muscles / Q000378:metabolism; D010084:Oxidation-Reduction; D010807:Physical Endurance; D005082:Physical Exertion
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D006003:Glycogen