Effects of preexercise feedings on endurance performance.
Eight male and 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 less than .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 (less than 3.5 mM). 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.
D000328:Adult; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D004040:Dietary Carbohydrates / Q000378:metabolism; D004044:Dietary Proteins; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000097:blood; D006801:Humans; D008297:Male; D008892:Milk; D010101:Oxygen Consumption; D010807:Physical Endurance; D005082:Physical Exertion
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D005230:Fatty Acids, Nonesterified; D005947:Glucose; D005990:Glycerol