The Effect of Physical Activity Levels on Hydration Markers in Non-Athletic Free-Living Individuals
Higher levels of physical activity requires increased fluid intake due to increased water losses via sweating. PURPOSE: To determine the effect of physical activity on hydration status and water intake. METHODS: This study involved 8 visits to the Human Performance Laboratory over 22 days. Body weight and urine measurements were taken every visit. Physical activity was assessed by the International Physical Activity Questionnaire (IPAQ), water intake by the Water Frequency Questionnaire (WFQ), and hydration status by urine osmolality (UOsm), urine specific gravity (USG), and urine color (UC). From the IPAQ subjects were classified as low, moderate and high physical activity levels and the total amount of physical activity was expressed as MET-min∙w-1. All values represent means across 22 days of measurements except physical activity and water intake, which was a mean of two measurements. Participants were excluded if they exercised more than 4 hours a week or if they were on medications that effected fluid balance. One-way analysis of variance was computed to determine differences in hydration status between groups. Additionally, 2-tailed Pearson correlations were computed to determine relationships between all measurements while using physical activity as a continuous variable (i.e., MET-min∙w-1). RESULTS: 95 participants (45 males, 40±13.2 y, 1.76±0.07 m, 27.3±10.8 %BF 25.9±4.6 kg∙m2; 50 females, 41.1±14.8 y, 1.63±.06 m, 35.0±11.0 %BF, 26.6±6.2 kg∙m2) completed the study; n=39 for low activity (822±698 MET-min∙w-1), n=48 for moderate activity (1791±1195 MET-min∙w-1), n=8 for high activity (4,728±1150 MET-min∙w-1). Hydration status and water intake did not differ across all levels of physical activity; UOsm: 587±209, 596±223, 562±290; and TWI: 2.6±.9, 2.9±1.4, 3.0±1.5 L for low, moderate, and high physical activity levels, respectively (P≤0.05). UOsm (589±290) was strongly correlated to Total Water Intake (2.83±1.22 L, P=0.000), and weight (76.4±17.3 kg, P=0.000) at a significance level of P≤0.01 but not strongly correlated to MET∙min∙w-1 (1640±1453). CONCLUSION: No significant differences in hydration or water intake were observed across groups. However, the small numbers of participants in the high physical activity levels may have made this comparison difficult. A wider range of MET-min∙w-1 between groups may need to be studied.
Health and environmental sciences, Education, Hydration markers, Physical activity, Physical activity level, Water intake, Exercise Science, Health and Physical Education, Other Kinesiology
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