Subjects were not heat acclimatized since the study was conducted in April at ~46°N latitude at the end of the northern hemisphere winter. The two counterbalanced trials for each participant differed by the provision of either a 6% carbohydrate (CHO) or placebo (P) beverage in random order. To achieve a 6% CHO solution, maltodextrin was mixed
with an artificially flavored and sweetened commercially available powder (Crystal Light, Kraft Foods, Glenview, IL). Placebo contained the commercially available selleck products powder with no maltodextrin or other macronutrient energy, both P and CHO included 140 mg sodium per liter. Subjects were instructed to abstain from strenuous exercise for 48 hr, and no exercise for 24 hr before each trial. Subjects recorded diet intake for 24 hr prior to the day of the first trial and were instructed to replicate this exact diet prior to the second trial day. Muscle biopsies were collected pre ride, post ride and at the end of the 3 hr of recovery. On the morning of the trials, immediately prior to the exercise bout (< 5 min) subjects ingested 8 ml•kg-1 of the prescribed beverage, during exercise each beverage was consumed at a rate of 4 ml•kg-1•30 min-1
(~37 g•hr-1 for CHO trial) and 4 ml•kg-1•hr-1 (~18.4 g•hr-1 for CHO trial) during recovery. Body weights were recorded prior to entering the climate Captisol in vivo chamber, post ride, and at the end of the 3 hr recovery. Core temperatures were not measured since the chamber temperature was the
same for both trials. Previously published reports from our lab indicate that a similar exercise protocol in the heat results in rectal temperatures exceeding 39°C . Expired gases and rating of perceived exertion (RPE) were measured at 4, 24, and 54 min during the 1 hr exercise. VO2 and VCO2 were used determine whole-body fuel oxidation using the equation of Péronnet and Massicotte . Body composition Body density was determined using hydrodensitometry and corrected for estimated residual lung volume. Net underwater weights were recorded using load cells (Exertech, Dresbach, MN). Body density was then converted to body composition using Oxalosuccinic acid the Siri equation . Maximal exercise capacity Maximum oxygen consumption (VO2max) and power associated with VO2max was measured for each fasted subject using a graded exercise protocol (starting at 95 W and increasing 35 W every three see more minutes) on an electronically braked cycle ergometer trainer (Velotron, RacerMate Inc., Seattle, WA). Maximum power was calculated as the highest completed stage (in W) plus the proportion of time in the last stage multiplied by the 35 W stage increment. Expired gases were measured and averaged in 15-second intervals during the test using a calibrated metabolic cart (Parvomedics, Inc., Salt Lake City, UT).