EFFECT OF CARBOHYDRATE SUBSTRATE AVAILABILITY ON RATINGS OF PERCEIVEDEXERTION DURING PROLONGED EXERCISE OF MODERATE INTENSITY

This investigation examined the effect of carbohydrate substrate avail ability on ratings of perceived exertion (RPE) during cycling at moder ate intensity to exhaustion and the relation between submaximal endura nce performance and RPE obtained following 2 hr. of cycling at moderat e intensity. Seven male cyclists per formed two exercise trials at pow er output corresponding to 70% of their peak oxygen uptake until exhau stion. Subjects ingested either a 6% glucose/sucrose solution at the r ate of 0.6 g . kg(-1) (Body Weight). hr.(-1) or an equal volume of art ificially flavored placebo every 20 min, throughout the exercise trial s. RPE for the legs, chest, and oner-all body, and oxygen consumption, expired ventilation, carbohydrate oxidation rate, and blood concentra tions of glucose, glycerol, and lactate were measured every 20 min, th roughout exercise and at exercise termination. Statistical analysis of these dependent variables indicates that (1) an exercise-induced decr ease in blood-borne carbohydrate substrate intensifies leg and over-al l perceptions of exertion during the later stages of prolonged cycling at 70% VO(2)peak. (2) Factors other than availability of blood-borne carbohydrate substrate may influence perceptual intensity at exhaustio n. (3) Ratings of perceived exertion for the legs and over-all body ob tained after 2 hr. of cycling at moderate intensity may be useful in p redicting submaximal endurance performance.