Submitted on March 9, 2009
Revised on April 27, 2009
Accepted on May 4, 2009
A simple and valid method to determine thermoregulatory sweating threshold and sensitivity
Samuel N. Cheuvront1*, Shawn E. Bearden2, Robert W. Kenefick1, Brett R. Ely1, David W. DeGroot1, Michael N. Sawka1, and Scott J. Montain1
1 US Army Research Institute of Environmental Medicine
2 Idaho State University
* To whom correspondence should be addressed. E-mail: samuel.n.cheuvront{at}us.army.mil.
Sweating threshold temperature and sweating sensitivity responses are measured to evaluate thermoregulatory control. However, analytical approaches vary and no standardized methodology has been validated. PURPOSE: This study validated a simple and standardized method, segmented linear regression (SReg), for determination of sweating threshold temperature and sensitivity. METHODS: Archived data were extracted for analysis from studies in which local arm sweat rate (Msw, ventilated dew-point temperature sensor) and esophageal temperature (Tes) were measured under a variety of conditions. The relationship Msw/Tes from 16 experiments was analyzed by seven experienced raters (Rater), using a variety of empirical methods, and compared against SReg for the determination of sweating threshold temperature and sweating sensitivity values. Individual inter-rater differences (n= 324 comparisons) and differences between Rater and SReg (n = 110 comparisons) were evaluated within the context of biologically-important limits of magnitude (LOM) via a modified Bland-Altman approach. The average Rater and SReg outputs for threshold temperature and sensitivity were compared (n = 16) using inferential statistics. RESULTS: Rater employed a very diverse set of criteria to determine the sweating threshold temperature and sweating sensitivity for the 16 data sets, but inter-rater differences were within the LOM for 95% (threshold) and 73% (sensitivity) of observations, respectively. Differences between mean Rater and SReg were within the LOM 90% (threshold) and 83% (sensitivity) of the time, respectively. Rater and SReg were not different by conventional t-test (P>0.05). CONCLUSIONS: SReg provides a simple, valid, and standardized way to determine sweating threshold temperature and sweating sensitivity values for thermoregulatory studies.
