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King Grub
2009-05-02, 09:36
The Institute of Medicine (IOM) expressed a need for improved sweating rate (msw) prediction models that calculate hourly and daily water needs based on metabolic rate, clothing and environment. More than 25 years ago the Shapiro prediction equation (OSE) was formulated as: msw (g*m(-2)*h-1) = 27.9 * Ereq * (Emax)(-0.455), where Ereq is required evaporative heat loss and Emax is maximum evaporative power of the environment; OSE was developed for a limited set of environments, exposures times, and clothing systems. Recent evidence shows that OSE often over-predicts fluid needs. Our study developed a corrected OSE and a new msw prediction equation, using independent data sets from a wide range of environmental conditions, metabolic rates (rest to </= 450 W*m(-2)), and variable exercise durations. Whole body sweat losses were carefully measured in 101 volunteers (80 males and 21 females; >500 observations) using a variety of metabolic rates over a range of environmental conditions (Ta = 15 degrees C - 46 degrees C, Pw= 0.27 - 4.45 kPa and (V) = 0.4 - 2.5 m*s(-1)), clothing and equipment combinations and durations (2-8h). Data were expressed as (g*m(-2)*h(-1)) and analyzed using fuzzy piecewise regression. OSE over-predicted sweating rates (p<0.003) compared to observed msw. Both the correction equation (OSE,C): msw = 147*exp (0.0012*OSE) and a new equation (PW): msw = 147+1.527*(Ereq) - 0.87*(Emax) were derived, compared to OSE, and then cross-validated against independent data (21 males and 9 females; >200 observations). OSE,C and PW were more accurate predictors of sweating rate (58 and 65% more accurate, p<0.01) and produced minimal error (SEE <100 g*m(-2)*h(-1)) for conditions both within and outside the original OSE domain of validity. The new equations provide for more accurate sweat predictions over a broader range of conditions with applications to public health, military, occupational and sports medicine settings.

J Appl Physiol. 2009 Apr 30. EXPANDED PREDICTION EQUATIONS OF HUMAN SWEAT LOSS AND WATER NEEDS.

http://jap.physiology.org/cgi/reprint/00089.2009v1