Hydration Status, Fluid Intake, and Electrolyte Losses in Youth Soccer Players

<jats:p>The purpose of the study was to determine the hydration status, fluid intake, and electrolyte losses of 21 male professional youth soccer players (age 17.1 ± 0.7 y) training in a cool environment. Pretraining and posttraining measurements of body mass, urine (freezing-point osmolality method), and sweat concentration (flame-emission spectroscopy) were collected. Fourteen players were found to be hypohydrated before training. The amount of fluid lost due to exercise equated to a 1.7% loss in body mass, which equated to a gross dehydration loss of 0.5%. Overall, the soccer players replaced 46% ± 88% of sweat loss during training, and only 4 remained hypohydrated after training. No significant correlations between sweat loss and sweat concentrations of Na<jats:sup>+</jats:sup> (<jats:italic>r</jats:italic> = –.11, <jats:italic>P</jats:italic> = .67) or K<jats:sup>+</jats:sup> (<jats:italic>r</jats:italic> = .14, <jats:italic>P</jats:italic> = .58) were found, but there was a significant correlation with Mg<jats:sup>2+</jats:sup> (<jats:italic>r</jats:italic> = –.58, <jats:italic>P</jats:italic> &lt; .009). This study found large variability in pretraining hydration status that the players were able to rehydrate during the training sessions. However, given the numbers starting training in a hypohydrated state, adequate hydration status before training should be considered by youth players, coaches, and sports-science support staff.</jats:p>