Effects of pre-exercise ingestion of differing amounts of carbohydrate on subsequent metabolism and cycling performance

Studies on the effect of the pre-exercise ingestion of carbohydrate on metabolism and performance have produced conflicting results, perhaps because of differences in the designs of the studies. The purpose of the present study was to examine the effects of ingesting differing amounts of glucose pre-exercise on the glucose and insulin responses during exercise and on time-trial (TT) performance. Nine well-trained male cyclists completed four exercise trials separated by at least 3 days. At 45 min before the start of exercise subjects consumed 500 ml of a beverage containing either 0 g (PLAC), 25 g (LOW), 75 g (MED) or 200 g (HIGH) of glucose. The exercise trials consisted of 20 min of submaximal steady-state exercise (SS) at 65% of maximal power output immediately followed by a [mean (SEM)] 691 (12) kJ TT. Plasma insulin concentrations at the onset of exercise were significantly higher ( P