title: Hydration assessment among marathoners using urine specific gravity and bioelectrical impedance analysis.
abstract: The present study examined the relationship between urine specific gravity (Usg), body mass (BM) and bioelectrical impedance determined variables [total body water (TBW), per cent TBW and impedance values] before and after a marathon (n = 25 men; 10 women). A significant reduction in BM (pre: 71.2 ± 12.4 kg; post: 69.6 ± 12.0 kg; p < 0.001) and an increase in Usg (pre: 1.009 ± 0.007; post: 1.018 ± 0.009; p < 0.001) was observed post-race. TBW was not significantly decreased (pre: 42.7 ± 8.0 kg; post: 42.4 ± 7.7 kg) while per cent TBW significantly increased post-race (pre: 60.0 ± 3.9%; post: 60.8 ± 3.8%; p < 0.001). Impedance values were significantly greater post-race (pre: 3288 ± 482; post: 3416 ± 492 Ω; p < 0.001). There was no correlation between the change in Usg and the change in BM or any of the bioelectrical impedance determined variables. On average, BM, Usg and impedance values appear to express changes in hydration; however, the observed changes among these variables for a given individual appear to be inconsistent with one another.
authors.affiliation: a Exercise Science and Sport , The University of Scranton , Scranton , PA , USA.
authors.forename: Paul T
authors.initials: PT
authors.lastname: Cutrufello
authors.affiliation: b Health Sciences Dept , Lock Haven University , Lock Haven , PA , USA.
authors.forename: Curt B
authors.initials: CB
authors.lastname: Dixon
authors.affiliation: c Department of Health and Sports Sciences , University of Louisville , Louisville , KY , USA.
authors.forename: Gerald S
authors.initials: GS
authors.lastname: Zavorsky
mesh_terms: D000328:Adult; D001834:Body Water; D001835:Body Weight; D003681:Dehydration / Q000175:diagnosis* / Q000652:urine; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D012420:Running / Q000502:physiology*; D013046:Specific Gravity; D055815:Young Adult
keywords: Dehydration; fluid loss; rehydration; running