The Validity of Multi-Frequency Bioelectrical Impedance Measures To Detect Changes In The Hydration Status Of Wrestlers During Acute Dehydration And Rehydration

PURPOSE: To examine the validity of multi-frequency bioelectrical impedance spectroscopy (MFBIA) measures to detect changes in the hydration status of wrestlers after undergoing 3.5% acute dehydration and a 2-h rehydration period. METHODS: 56 NCAA wrestlers: (mean ± SEE); age 19.5 ± 0.2, height 1.73 ± 0.01 m, body mass (BM) 82.5 ± 2.3 kg were tested in euhydrated, dehydrated (- 3.5%), and a 2-h rehydration conditions using MFBIA to detect changes in hydration status. Hydration status was quantified by measuring changes in plasma osmolality (Posm), urine osmolality (Uosm), urine specific gravity (Usg), BM and MFBIA at 5, 20, 50, 100, and 500 Khz. RESULTS: A new prediction equation provided by the manufacturer to estimate Hydration Index (HI) was able to detect a significant change in hydration status after a 3.5% reduction in body weight. All frequencies significantly increased for HI at the post-dehydration time point, but did not return to baseline at 2-h rehydration. Posm (303 ± 0.6 mOsm.L-1) Uosm (617 ± 47 mOsm.L-1) and Usg (1.017 ± 0.001) significantly increased at post-dehydration, but did not return to below baseline until 2-h rehydration. Estimations of extracellular water (ECW) were significantly different throughout the trial, but there were there was no significant change in estimations of total body water (TBW) or intracellular water (ICW). CONCLUSIONN: Results of the present study demonstrate the potential use of MFBIA as a field measure to assess the hydration status of wrestlers for the purpose of minimal weight certification. When employing MFBIA, results indicate that changes in HI at the frequencies evaluated are sensitive to acute changes in dehydration, but lag behind changes in the standard physiological (plasma and urinary) markers of hydration status after a 2-h rehydration.