Influence Of Daily Step Count On Fluid Intake And Hydration Biomarkers In Underhydrated College Students

PURPOSE: While many college students meet physical activity guidelines, they commonly do not meet fluid intake recommendations. This study aimed to further investigate the relationship between physical activity, total fluid intake, and hydration biomarkers, specifically in underhydrated college students. METHODS: Prospective participants completed an electronic pre-screening fluid intake questionnaire (BEVQ-15) to verify they were consuming less than current fluid intake recommendations for males (< 2.5 L per day) and females (< 2.0 L per day). Eighteen participants (11 female) (mean ± SD; age, 23.1 ± 2.2 y; height, 168.9 ± 10.7 cm; weight, 69.7 ± 13.9 kg; body fat, 27.2 ± 9.0 %) collected 24 h urine samples for 3 consecutive days to assess mean urine volume (UVOL), urine osmolality (UOSMO), and urine specific gravity (USG) and completed a blood draw for assessment of serum osmolality on one day. Daily step counts were monitored with the GARMIN VENU SQ. Daily total fluid intake (TFI) was recorded using the Liq.In7 survey. Repeated-measures correlations were conducted to assess the influence of daily step counts on total fluid intake, 24 h UOSMO, 24 h UVOL, and 24 h USG. RESULTS: Urinary hydration biomarkers among participants suggested underhydration (mean ± SD; TFI, 2239 ± 1358 mL; 24 h UOSMO, 648.9 ± 260.8 mOsm*kg-1; 24 h USG, 1.018 ± 0.007, 24 h UVOL, 1.119 ± 0.688 kg; daily step count, 7844 ± 3820 steps), with serum osmolality within normal limits (291.1 ± 4.1 mOsm*kg-1). Greater daily step count was associated with greater TFI (r(29) = 0.48, 95% CI [0.16, 0.72], p = .006). There were no significant correlations between daily step count and 24 h UVOL (r(31) = 0.25, 95% CI [-0.10, 0.55], p = .157), 24 h UOSMO (r(32) = 0.057, 95% CI [-0.29, 0.39], p = .749), or 24 h USG (r(33) = -0.03, 95% CI [-0.36, 0.31], p = .859). CONCLUSIONS: On days with higher step counts, underhydrated college students increased their fluid intake, although not enough to improve all hydration biomarkers. Physical activity should still be encouraged without concern that this could worsen hydration status. Further investigations should determine what behavioral intervention strategies in this population may promote sufficient additional fluid intake to improve hydration biomarkers. Supported by: This study was supported by an internal grant from the Wellstar College of Health and Human Services at Kennesaw State University.