Abstract des Autors

This study examined the effects of carbohydrate ingestion on 20 km cycle time-trial (TT) performance in 14 well-trained cyclists (11 males, 3 females, peak oxygen uptake (VO2peak) 4.52+/-0.60 l/min; values are mean+/-SD). All subjects performed two experimental trials on their own bicycles mounted on an airbraked ergometry system (Kingcycle). Subjects were instructed to maintain the same training and dietary regimens before trials, which were conducted in a random order, 3-7 days apart, and at the same time of day for each subject. On the day of a trial, subjects reported to the laboratory and ingested an 8 ml/kg body mass bolus of either a 6.8 g/100 ml commercial carbohydrate-electrolyte (CHO) beverage (39+/-4 g of CHO), or a coloured, flavoured placebo. Ten min after finishing the drink, subjects commenced a 5 min warm-up at 150 W, before commencing the 20 km TT. The average power output (312+/-40 vs 311+/-38 W) and heart-rate (171+/-6 vs 171+/-5 beats/min for CHO and placebo, respectively) during the two rides did not differ between treatments. Accordingly, the performance times for the two TT's were the same (27:41+/-1:39 min:sec, for both CHO and placebo). We conclude that the ingestion of ca. 40 g of carbohydrate does not improve maximal cycling performance lasting ca. 30 min, and that carbohydrate availability, in the form of circulating blood glucose, does not limit high-intensity exercise of this duration. Verf.-Referat