Elite sailors compete in a wide-range of environmental conditions. As such, changes in hydration status of 1%-2% measured by lossof body weight can directly lead to reductions in performance. Therefore, determining the optimal composition and rate of ingestionof fluid replacement drinks is essential to attenuate changes in hydration status during training and competition. Two studies were performed using completely random designs to test the composition and rates of consumption of different beverages in cool and warm conditions. In the cool study, participants were provided ad libitumaccess to 3 beverages; water with Crystal Light (control, C); Gatorade (experimental control, ExC); and customized Infinit (experimental,Ex). Wind velocity and wet bulb temperature were 7.1 °C [4.2-11.3] and 23.5 km/h [17.0-37.0] (mean [range]). Athletes lost significant body mass (C, -0.58% ± 0.14%; ExC, -0.49% ± 0.12%; Ex, -0.46% ± 0.11%) (p < 0.01) and plasma potassium (C, -19.4% ± 2.8%; ExC, -13.7% ± 2.6%; Ex, -13.0% ± 3.4%) (p < 0.01) during each condition. Urine specific gravity (USG) showed no differences between conditions or pre- to post-sailing. In the warm condition, participants consumed 11.5 mL/kg·min of C, ExC, or a warmweather Infinit (ExW). Wind velocity and wet bulb temperature were 24.3 km/h [15.0-36.0] and 19.5 °C [17.0-23.3]. Plasma sodium concentrations were reduced 2.6% ± 0.36% in the C and 2.3% ± 0.76% in the ExC condition after training when compared with ExW (p = 0.031, p = 0.069). There was no difference in plasma potassium, chloride, or blood glucose concentration between or within any condition. USG and body mass were not different between or within any drink condition. In summary, participants did not consume enough fluid in any cool condition to attenuate body weight and electrolyte changes. Cool temperatures may cause athletes to underestimate their sweat rate and required fluid intake even in physically demandingconditions. In contrast, consuming 11.5 mL/kg·min of fluid in warm conditions was effective in maintaining hydration status by preventing changes in body mass and USG.
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