RESUMEN
The purpose of this study was to examine the effect of fructose ingestion on maximal exercise performance capacity following prolonged steady-state exercise compared with glucose or placebo ingestion, in 7 male college students (age 23.3±0.7 yr, height 171.3±1.9 cm, weight 68.4±1.4 kg, Vo2max 3.5±0.2 L/min, mean ± SEM) . The subjects cycled constantly on an ergometer at 59± 2 % Vo2max for 100 min divided in the middle by a 5-min rest, and then performed 10 min of all-out self-paced cycling. They ingested either 8 % fructose solution (F), 8 % glucose solution (G) or artifi-cially sweetened placebo (P) before and during exercise (at 20, 40, 65, 85 mm) . Before exercise and at 50 and 100 min of exercise and 5 min after the performance ride, blood samples were collected for determination of the concentrations of blood lactate, serum glucose and serum FFA. In the G trial, the serum FFA level was significantly lower than in the P and F trials at any of the time points dur-ing and after exercise (vs. P ; p<0.01, vs. F ; p<0.05) . However, glucose ingestion maintained serum glucose at a significantly higher level during and after exercise than placebo ingestion (p< 0.01) and improved the total work output in the 10-min performance ride (G vs. P ; 135± 8 KJ vs. 128± 8 KJ, p<0.05) . Although in the F trial, the serum FFA level was elevated during exercise compared to that in the G trial and the serum glucose level was significantly higher than in the P trial (vs. P ; p<0.01), the blood lactate level after exercise was lower than in the G trial and total work output was similar to that in the P trial (123± 8 KJ, vs. G ; p<0.01) . These results indicate that fructose ingestion before and during exercise cannot improve the ability to perform high-intensity exercise late in prolonged exercise despite maintaining the serum glucose level.