Water versus carbohydrate-electrolyte fluid replacement during loaded marching under heat stress

This study compared the effectiveness of carbohydrate-electrolyte (CHO-E) fluid replacement versus water (WAT) on hydration status, physiological and subjective responses, and exercise performance during a 3 × 60-minute loaded (14 kg) treadmill walk in 35°C ambient temperature and 55% humidity. CHO-E did not affect urine loss, plasma volume change (WAT = -3.0 ± 1.6% vs. CHO-E = -1.1 ± 1.6%), dehydration (WAT = 0.4 ± 0.3% vs. CHO-E = 0.4 ± 0.3% of body mass), or core body temperature (T_c) and heart rate (HR) responses. Endurance time was greater but not significantly different with CHO-E (WAT = 134 ± 9 vs. CHO-E = 146 ± 9 minutes). CHO-E increased the frequency of task completion (WAT = 21% vs. CHO-E = 50%), elevated blood glucose, and reduced perceived exertion. CHO-E offers potential to enhance exercise capacity by elevating blood glucose and thereby preventing hypoglycemia, maintaining high rates of carbohydrate oxidation, and/or preventing central fatigue; but provided no additional benefits with regard to hydration status and physiological function during loaded walking under heat stress. Copyright © by Association of Military Surgeons of U.S., 2005.