A simple and valid method to determine thermoregulatory sweating threshold and sensitivity

• Published in: Journal of applied physiology (1985) Vol. 107; no. 1; pp. 69 - 75
• Main Authors: Cheuvront, Samuel N, Bearden, Shawn E, Kenefick, Robert W, Ely, Brett R, DeGroot, David W, Sawka, Michael N, Montain, Scott J
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01-07-2009; American Physiological Society
• Subjects: Anaerobic Threshold - physiology; Biological and medical sciences; Body fluids; Body temperature; Body Temperature - physiology; Body Temperature Regulation - physiology; Exercise Test; Fundamental and applied biological sciences. Psychology; Humans; Male; Oxygen Consumption - physiology; Regression analysis; Reproducibility of Results; Sensitivity; Sweating - physiology; Validation studies; Young Adult; Physical exercise; Temperature; Linear regression; Thermoregulation; Environmental factor; exercise; Stress; heat stress; Vertebrata; Heat; Sensitivity; Mammalia; segmented linear regression; Threshold
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00250.2009

1 United States Army Research Institute of Environmental Medicine, Natick, Massachusetts; and 2 Department of Biological Sciences, Idaho State University, Pocatello, Idaho
Submitted 9 March 2009
; accepted in final form 4 May 2009
Sweating threshold temperature and sweating sensitivity responses are measured to evaluate thermoregulatory control. However, analytic approaches vary, and no standardized methodology has been validated. This study validated a simple and standardized method, segmented linear regression (SReg), for determination of sweating threshold temperature and sensitivity. Archived data were extracted for analysis from studies in which local arm sweat rate ( sw ; ventilated dew-point temperature sensor) and esophageal temperature (T es ) were measured under a variety of conditions. The relationship sw /T es 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 interrater 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. Rater employed a very diverse set of criteria to determine the sweating threshold temperature and sweating sensitivity for the 16 data sets, but interrater 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). SReg provides a simple, valid, and standardized way to determine sweating threshold temperature and sweating sensitivity values for thermoregulatory studies.
thermoregulation; heat stress; exercise; segmented linear regression
Address for reprint requests and other correspondence: S. N. Cheuvront, US Army Research Institute of Environmental Medicine, Thermal and Mountain Medicine Division, Kansas St., Natick, MA 01760-5007 (e-mail: samuel.n.cheuvront{at}us.army.mil )