In order to investigate the effect of sucrose or caffeine ingestion on the performance of prolonged running, five male middle and long distance runners attending senior high school carried out running on a treadmill at an intensity corresponding to individuals' 80% of VO₂max until they could not continue to run at the intensity. Sixty minutes before, immediately before and forty five minutes after onset of the exercise, subjects were given either placebo (Con.), placebo and sucrose (90g) (Su.), caffeine (420mg) (Caf.) or sucrose (90g) and caffeine (420mg) (Su. +Caf.) solution. Duration of the exercise become significantly longer in Su., Caf. and Su. +Caf. than in Con. The duration in four of five subjects was longest in Su. +Caf., though it was not significantly different from Su. and Caf. During exercise, plasma glucose and CHO combustion were higher in Su. than in Con. Plasma free fatty acid (FFA) and fat combustion were higher in Caf. than in Con. but they were not significantly different between two trials. Plasma glucose and lactate were higher in Su. +Caf. than in Con., while plasma FFA and CHO and fat combustion in Su. +Caf. were same as those in Con. In conclusion, ingestion of sucrose, caffeine or sucrose and caffeine solution was effective to improve the performance of prolonged running carried out at 80% VO₂max. It was suggested that ingestion of each solution altered way of supplying and using energy, which spared glycogen consumption in the working muscle.

DESCENTE SPORTS SCIENCE Vol.7/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE