Fluid balance of elite Brazilian youth soccer players during consecutive days of training


Journal Title (Medline/Pubmed accepted abbreviation): J. Sports Sci.
Year: 2011
Volume: 29
Number:7
Page numbers: 725-732
doi (if applicable): 10.1080/02640414.2011.552189

Summary of Background and Research Design

Background: Dehydration is possible during exercise when the athlete does not consume enough fluid to compensate for fluid losses, mostly due to increased sweating. Dehydration can cause a decrease in performance. Despite access to beverages, adult athletes often do not consume adequate fluid to replenish their losses. It has been shown that younger people have different thermoregulation sensors, but very few studies have been conducted to assess the typical dehydration risk in adolescents.

Research goal: The objective of this study was to measure fluid balance (sweat loss and voluntary fluid intake) in adolescent Brazilian soccer players on 3 consecutive days of outdoor training.

Subjects: Twenty male professional soccer players, age 17.2 ± 0.5 y

Experimental design:no intervention; observational

Treatments and protocol:Data collection occurred during the 3 practices before a qualifying match. Both before and after practice, the boys were weighed and their urine specific gravity was measured to determine hydration status. (Lower urine specific gravity means that the urine is more dilute and implies better hydration.) They also completed a questionnaire assessing thirst. During the 2.5 hr practice, the athletes all drank from a water bottle labeled with their name. The water bottles were weighed before and after practice to calculate the amount of water consumed.

Summary of research findings
  • There was a direct correlation between outside temperature and sweat rate.
  • There was also a direct correlation between sweat rate and amount of fluid consumed.
  • Several players had a urine specific gravity higher than 1.020 before practice, implying slight dehydration. However, there was not a correlation between pre-training urine specific gravity and fluid intake.
  • Athletes lost approximately 0.5-1.2 (±0.5) kg of body weight during the practice. This implies that not enough fluids were consumed to adequately replace what was lost during the practice among most of the players

Interpretation of findings/Key practice applications

Like adults, it is important for adolescents to drink a lot of fluids during exercise, especially when exercising at high heat. Although they may not detect thirst, it is encouraged for them to consume liquids. There was a large variability between individual players, and there are a lot of factors playing into the risk of dehydration: body composition, physical fitness, clothing, tastefulness of the beverage, intensity of exercise, acclimation to heat, outside temperature and humidity, etc. It would be helpful if coaches and event organizers provided a scale so that athletes can assess weight loss during practices and competitions.

Limitations

This study was limited to youth soccer players who played outdoors. Future studies on youth athletes that play different sports, both indoors and outdoors, are needed to assess the factors that contribute to inadequate hydration status in this population.
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