Longitudinal analysis of body composition in Italian national U17 male handball players using bioelectrical impedance vector analysis

Background: Monitoring body composition is crucial for optimizing performance and preventing injuries in young athletes during a competitive season. This study evaluated changes in body composition and bioelectrical impedance vector analysis (BIVA) in 15 male U17 Italian national handball players (age: 16.44±0.60 years). Methods: Bioelectrical parameters were analyzed across four time points: end of the season (T0), pre-season (T1), season onset (T2), and winter break (T3), using repeated measures mixed models, while Mahalanobis' tests track vector shifts and ellipse distances (D). Statistical significance was set at P<0.05. Results: The vector significantly lengthened from T0 to T1 (D=1.95), then shortened from T1 to T2 (D=1.63) and T2 to T3 (D=0.88). Stature-adjusted resistance significantly decreased at T2 (262.9 Ω/m±26.1) compared to T1 (275.6 Ω/m±27.8) and at T3 (249.7 Ω/m±21.4) compared to T0 (269.7 Ω/m±27.9), T1, and T2. Stature-adjusted reactance significantly increased at T1 (39.00 Ω/m±3.7) compared to T0 (35.3 Ω/m±3.6) then decreased at T2 (36.2 Ω/m±3.2) and T3 (35.7 Ω/m±3.4) compared to T1. From T0 to T3, phase angle, total body water, and fat-free mass increased significantly from 7.4°±0.5 to 8.1±0.6°, 59.9±3.6% to 61.1±3.7%, and 82.0±4.5% to 84.0±5.1%, respectively. Conclusions: Bioelectrical analysis effectively tracks hydration indices and training adaptations in young athletes, representing a valuable tool for managing performance and recovery.