CARBOHYDRATE INGESTION IMMEDIATELY BEFORE EXERCISE DOES NOT IMPROVE 20 KM TIME TRIAL PERFORMANCE IN WELL TRAINED CYCLISTS

This study examined the effects of carbohydrate ingestion on 20 km cyc le time-trial (TT) performance in 14 well-trained cyclists (11 males, 3 females; peak oxygen uptake [(V) over dot O-2 peak] 4.52 +/- 0.60 l/ min; values are mean +/- SD). All subjects performed two experimental trials on their own bicycles mounted on an air-braked ergometry system (Kingcycle(TM)). Subjects were instructed to maintain the same traini ng and dietary regimens before trials, which were conducted in a rando m 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 ingest ed an 8 ml/kg body mass bolus of either a 6.8 g/100 mi commercial carb ohydrate-electrolyte (CHO) beverage (39 +/- 4 g of CHO), or a co loure d, flavoured placebo. Ten min after finishing the drink, subjects comm enced a 5 min warm-up at 150 W, before commencing the 20 km TT. The av erage power output (312 +/- 40 vs 311 +/- 38 W) and heart-rate (171 +/ - 6 vs 171 +/- 5 beats/min for CHO and placebo, respectively) during t he two rides did not differ between treatments. Accordingly, the perfo rmance times for the two TT's were the same (27:41 +/- 1:39 min:sec, f or both CHO and placebo). We conclude that the ingestion of similar to 40 g of carbohydrate does not improve maximal cycling performance las ting similar to 30 min, and that carbohydrate availability, in the for m of circulating blood glucose, does not limit high-intensity exercise of this duration.