EFFECT OF CHO INGESTION ON EXERCISE METABOLISM AND PERFORMANCE IN DIFFERENT AMBIENT-TEMPERATURES

Two series of experiments were conducted to examine the effect of inge sting beverages with differing carbohydrate (CHO) concentrations and o smolalities on metabolism and performance during prolonged exercise in different environmental conditions. Ln series 1, 12 subjects performe d three cycling exercise trials to fatigue at 70% VO2peak in either 33 degrees C (N = 6) (HT1) or 5 degrees C (N = 6) (CT). Subjects ingeste d either a 14% CHO solution (osmolality = 390 mosmol . l(-1)) (HCHO); a 7% CHO solution (330 mosmol . l(-1)) (NCHO) or a placebo (90 mosmol . l(-1)) (CON1). In series 2, six subjects performed the same three tr ials at 33 degrees C (HT2), while ingesting either NCHO, a 4.2% CHO so lution (240 mosmol . l(-1)) (LCHO) or a placebo) (240 mosmol . l(-1)) (CON2). Plasma glucose was higher (P < 0.05) in HCHO than NCHO, which in rum was higher (P < 0.05) than CONI in both CT and HT1. Plasma gluc ose was lower (P < 0.05) in CON2 compared with NCHO and LCHO in HT2. T he fall in plasma volume was greater (P < 0.05) in HCHO than other tri als in both CT and HT1 but was not different when comparing the three trials in HT2. Exercise time was not different when comparing the tria ls in either HT1 or HT2 but was longer (P < 0.05) in NCHO compared wit h HCHO, which, in rum, was longer (P < 0.05) than CON1 in CT. These da ta demonstrate that, during prolonged exercise in the heat, fatigue is related to factors other than CHO availability. In addition, during e xercise in 5 degrees C a 7% CHO solution is more beneficial for exerci se performance than a 14% CHO solution.