Reliability of Urinary Dehydration Markers in Elite Youth Boxers.

PURPOSE

To determine the reliability and diagnostic accuracy of noninvasive urinary dehydration markers in field-based settings on a day-to-day basis in elite adolescent amateur boxers.

METHODS

Sixty-nine urine samples were collected daily from 23 athletes (17.3 ± 1.9 y) during their weight-stable phase and analyzed by field and laboratory measures of hydration status. Urine osmolality (U), urine specific gravity (U), total protein content (T), and body-mass stability were evaluated to determine fluid balance and hydration status. Overall macronutrient and water intake were determined using dietary records. According to their anthropometric characteristics, athletes were assigned into 2 groups: lightweight (L) and heavyweight (H) boxers.

RESULTS

Data presented on U demonstrated a uniform increment by 11.2% ± 12.8% (L) and 19.9% ± 22.7% (H) (P < .001) over the course of the study, even during the weight-stable phase (body mass, ICC = .99) and ad libitum fluid intake (42 ± 4 mL · kg · d). The intraclass correlation coefficients (ICCs) ranged from .52 to .55 for U and .38 to .52 for U, further indicating inconsistency of the urinary dehydration markers. Poor correlations were found between U and T metabolites (r = .27, P = .211).

CONCLUSIONS

Urinary dehydration markers (both U and U) exhibit high variability and seem to be unreliable diagnostic tools to track actual body-weight loss in real-life settings. The ad libitum fluid intake was apparently inadequate to match acute fluid loss during and after intense preparation. The applicability of a single-time-point hydration-status assessment concept may preclude accurate assessment of actual body-weight deficits in youth boxers.