Date of Award

1-1-2009

Document Type

Campus Access Thesis

Department

Physical Education

First Advisor

Toni Torres-McGehee

Abstract

Context: Importance of maintaining proper electrolyte concentrations is continuously stressed to prevent hypohydration and decreases in performance, but there is no practical method for Certified Athletic Trainers (ATs) to measure sodium concentrations ([Na+]).

Objective: To examine the relationship between plasma [Na+], urine [Na+], and common clinical hydration measures of urine specific gravity (USG), urine color (Ucol), and percent change in body mass (%ΔBM).

Design: Randomized repeated measures design was used to elicit 6 experimental conditions: control(C), sodium depleted(S), hypohydrated(Hh), hypohydrated and sodium depleted(Hh+S), fatigue(F) and hyperthermia and fatigue(Ht+F).

Setting: Exercise Science Research Laboratory.

Participants: Nineteen moderately trained (training 3d/wk for >90min total), healthy volunteers (mean age=28.13+6.82y, height=171.20+12.16cm, mass=73.81+15.21kg) participated in the study.

Main Outcome Measures: Plasma [Na+], urine [Na+], USG, Ucol, and %ΔBM.

Results: We found a significant correlation between USG and Ucol (r=0.831, p<0.001) for all data and within all groups, but no correlation between plasma [Na+] and urine [Na+] or hydration measures overall. For C, urine [Na+] had high correlation to USG (r=0.742, p<0.001). For F, there was a high correlation between plasma [Na+] and %ΔBM (r=0.713, p=0.021). Only USG and Ucol were correlated (r=0.830, p<0.001) for the Ht+F group. Ucol had a high negative correlation with %ΔBM (r=-0.759, p=0.001) in the Hh condition. For S only urine [Na+] highly correlated with USG (r=0.890, p<0.001). Lastly, for Hh+S urine [Na+] highly correlated with both plasma [Na+] (r=0.719, p=0.019) and USG (r 0.884, p=0.001).

Conclusions: Based upon our results there remains no practical method for ATs to estimate [Na+] in athletes potentially at risk for exertional heat illness, exercise associated muscle cramping, and sodium depletion. Our results do support the continued use of USG and Ucol to estimate hydration status in exercising individuals.

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