INFLUENCE OF CAFFEINE AND CARBOHYDRATE FEEDINGS ON ENDURANCE PERFORMANCE

Abstract

Trained cyclists (9) were studied to determine the effects of caffeine (CAF), and glucose polymer (GP) feedings on work production (kpm [kilopound meter]) during 2 h of isokinetic cycling exercise (80 rpm). Ingestion of 250 mg of CAF 60 min prior to the ride was followed by ingestion of an additional 250 mg fed at 15 min intervals over the first 90 min of the exercise. This treatment significantly increased work production by 7.4% and .ovrhdot.VO2 [O2 uptake] by 7.3% as compared to control (C) while the subjects'' perception of exertion remained unchanged. Ingestion of approximately 90 g of GP during the first 90 min (12.8 g/15 min) of the exercise had no effect on total work production or .ovrhdot.VO2. It was effective in reducing the rate of fatigue over the last 30 min of cycling. Although GP maintained blood glucose and insulin levels (P .ltoreq. 0.05) above those of the C and CAF trials, total CHO [carbohydrate] utilization did not differ between treatments. During the last 70 min of the CAF trial, fat oxidation was elevated 31% and appeared to provide the substrate needed for the increased work production during this period of exercise. An enhanced rate of lipid catabolism and work production following the ingestion of CAF was demonstrated.