Hydration assessment among marathoners using urine specific gravity and bioelectrical impedance analysis

Area of Science:

• Exercise Physiology
• Sports Science
• Human Hydration

Background:

• Marathon running leads to significant physiological changes.
• Accurate hydration status assessment is crucial for endurance athletes.
• Urine specific gravity (Usg) and body mass (BM) are common hydration indicators.

Purpose of the Study:

• To investigate the relationship between Usg, BM, and bioelectrical impedance variables (total body water [TBW], %TBW, impedance) before and after a marathon.
• To assess the consistency of these hydration markers in individual athletes.

Main Methods:

• 25 men and 10 women runners were studied.
• Measurements of BM, Usg, and bioelectrical impedance variables were taken pre- and post-marathon.
• Statistical analysis was used to determine changes and correlations.

Main Results:

• Significant decreases in BM and increases in Usg were observed post-race.
• TBW did not significantly decrease, but %TBW significantly increased.
• Impedance values were significantly greater post-race.
• No significant correlation was found between changes in Usg and changes in BM or impedance variables.

Conclusions:

• While BM and Usg generally reflect hydration changes after a marathon, individual variations exist.
• Bioelectrical impedance variables, particularly %TBW, show an increase post-race, contrasting with BM and Usg trends.
• The study highlights potential inconsistencies in hydration status assessment using these combined methods at an individual level.