Does perceived exertion depend on glycemic index of foods ingested throughout three hours before a one-hour high-intensity exercise?

The purpose of this study was to assess the relationships between perceived exertion (RPE) and plasma glucose concentrations or hunger feelings during a 1-hr. bicycle submaximal exercise after ingestion of pre-exercise test foods with a different glycemic index. Each of endurance-trained male triathletes ingested three different glycemic index (GI) foods (HighGI: glucose, LowGI: whole-wheat biscuit or water) throughout the 3 hr. before exercise at 80% maximal oxygen uptake (VO2 max). RPE values increased as a logarithmic function of time. This result is opposite to results obtained with longer exercise bouts up to 3 hr. duration. RPE and hunger ratings were not significantly different for the three test foods whatever the time. Moreover, RPE did not correlate with plasma glucose concentrations during exercise. Consequently, RPE did not depend on the GI of the pre-exercise test foods during a 1-hr. exercise at 80% VO2 max. Physiological and psychological factors other than glycemic index may have mediated the perceptual responses during a 1-hr. high-intensity exercise. It is possible that during endurance exercise of longer duration, the level of blood glucose mediates the intensity of peripheral exertional perceptions arising from active skeletal muscle during prolonged exercise.