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Effects of preexercise feedings on endurance performance

FOSTER C.; COSTILL, D. L.; FINK, W. J.
Medicine & Science in Sports & Exercise: April 1979
Effects of preexercise feedings on endurance performance: PDF Only

ABSTRACT

FOSTER, C., D. L. COSTILL, and W. J. FINK. Effects of Preexercise feedings on endurance performance. Med. Sci. Sports. Vol. 11, No. 1, pp. 1-5, 1979. Eight male and eight female students were studied during exercise to exhaustion on a bicycle ergometer at 80 and 100% of Vo2max following the ingestion of water (W), 75 g of glucose (G) or a liquid meal (M) (10 g protein, 12.5 g fat, 15 g CHO). When compared to the endurance ride (80% Vo2max) in the W treatment, endurance performance time was reduced by 19%, (p<.05) (53.2 to 43.2 min) as a result of the preexercise glucose feeding (Trial G). No difference in performance at 80% Vo2max was found between the W and M trials. The preexercise feedings had no effect on exercise time to exhaustion at 100% Vo2max. During the G and M trials at 80% Vo2max, most of the subjects demonstrated a transient decline in serum glucose (<3.5 m M). After 30-40 min. of exercise, however, serum glucose returned to normal and was seldom low at the time of exhaustion. Serum free fatty acids (FFA) were depressed throughout the G trial. The results of these experiments indicate impaired lipid mobilization following CHO ingestion. The present data support our earlier findings (11) which demonstrate that glucose feedings 30-45 minutes before endurance exercise increase the rate of CHO oxidation and impede the mobilization of FFA, thereby reducing exercise time to exhaustion.

FAT METABOLISM, CARBOHYDRATE METABOLISM, BLOOD GLUCOSE, FFA, PERFORMANCE

Submitted for publication March, 1978.

Accepted for publication October, 1978.

©1979The American College of Sports Medicine