Water versus carbohydrate-electrolyte fluid replacement during loaded marching under heat stress
Christopher Byrne1, Chin Leong Lim, Serena Ai Neo Chew
1Centre for Human Performance, Defence Medical and Environmental Research Institute, DSO National Laboratories, Republic of Singapore.
Abstract:
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 x 60-minute loaded (14 kg) treadmill walk in 35 degrees 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 (Tc) 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.
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