Football Practices in Hot Environments Impact Subsequent Days' Hydration

Area of Science:

• Sports Medicine
• Environmental Physiology
• Exercise Science

Background:

• Exertional heat illness is a risk in American football, particularly during preseason practices in hot environments.
• The impact of hydration status on subsequent practice performance and health in this population is not well understood.
• High school football athletes face unique hydration challenges due to practice intensity and environmental conditions.

Purpose of the Study:

• To evaluate the accuracy of urinary hydration markers (urine color and urine-specific gravity) in assessing body mass changes in high school football players.
• To investigate the carryover effects of consecutive football practices on hydration status in a hot environment.
• To determine the impact of multiple daily practices on athlete hydration levels.

Main Methods:

• 31 male high school football players participated in 7 outdoor practices in a hot environment (wet-bulb globe temperature = 31.3 ± 1.8° C).
• Urine samples and body mass were measured before and after each practice to assess hydration and body mass changes.
• Receiver operating characteristic (ROC) analysis was used to determine the sensitivity and specificity of urine color (Ucol) and urine-specific gravity (USG).
• Paired samples t-tests and repeated-measures ANOVA assessed carryover effects between and across practices.

Main Results:

• Urine color and urine-specific gravity showed no significant accuracy in determining body mass changes.
• Significant carryover effects on hydration status were observed between consecutive practices, particularly with less than 24 hours between sessions.
• Percentage of body mass loss was significantly greater after two-a-day practices, indicating cumulative dehydration.
• Dehydration effects, evidenced by higher urine color and body mass loss, were more pronounced after two-a-day practices on later training days.

Conclusions:

• Urinary hydration markers (urine color, urine-specific gravity) may not be sufficiently accurate for assessing acute body mass changes in this setting.
• Consecutive practices, especially those conducted twice daily, lead to cumulative dehydration and increased risk of heat-related issues.
• Athletes must prioritize consistent fluid replenishment during and between practices to maintain euhydration and mitigate heat illness risks.