CARTER, J. E. and C. V. GISOLFI. Fluid replacement during and after exercise in the heat. Med. Sci. Sports Exerc., Vol. 21, No. 5, pp. 532–539, 1989. This study sought to determine whether ad libitum drinking of a carbohydrate-electrolyte (CE) beverage would minimize the physiological disturbances associated with prolonged (3 h) continuous exercise in the heat (Tdb =31.5 °C, percent RH = 22.3). Seven male subjects performed two bouts of cycle exercise (60% JOURNAL/mespex/04.02/00005768-198910000-00018/ENTITY_OV0312/v/2017-07-20T222223Z/r/image-pngO2max) drinking either a CE beverage (4.85% polycose, 2.65% fructose) or distilled water. Subjects continued to drink ad libitum for 3 h during recovery in the heat. No significant differences were observed between drinks for rectal temperature, heart rate, or sweat rate during exercise. Subjects tended to drink more (P < 0.0565) water than the CE beverage during exercise, but plasma volume (percent PV) decreased less (P < 0.0253) and plasma ([glucose], P < 0.0001 and [K+], P < 0.0047) were higher when subjects drank the CE solution. At the end of exercise, plasma osmolality and [Na+] were also higher (P < 0.05) when subjects drank the CE beverage rather than water. Rating of perceived exertion was higher (P < 0.0001) when drinking water. In recovery, ingesting the CE beverage, 1) subjects drank more (P < 0.0012); 2) plasma volume increased to a higher level (P < 0.0017); 3) plasma osmolality (P < 0.0001), [Na+] (P < 0.0001), glucose (P < 0.0001), and [K+] (P < 0.0015) were greater; and 4) body weight increased more (P < 0.0422) than when water was ingested. Thus, in terms of minimizing physiological disturbances, ad libitum drinking of the CE beverage was as effective as drinking water during exercise but was more effective in recovery.
©1989The American College of Sports Medicine