A three-compartment thermometry model for the improved estimation of changes in body heat content

Abstract

Jay, O, Gariépy LM, Reardon FD, Webb P, Ducharme MB, Ramsay T, Kenny GP. A three-compartment thermometry model for the improved estimation of changes in body heat content. Am J Physiol Regul Integr Comp Physiol 292: R167-R175, 2007. First published August 24, 2006; doi:10.1152/ajpregu.00338.2006.-The aim of this study was to use whole body calorimetry to directly measure the change in body heat content (⌬Hb) during steady-state exercise and compare these values with those estimated using thermometry. The thermometry models tested were the traditional twocompartment model of "core" and "shell" temperatures, and a threecompartment model of "core," "muscle," and "shell" temperatures; with individual compartments within each model weighted for their relative influence upon ⌬Hb by coefficients subject to a nonnegative and a sum-to-one constraint. Fifty-two participants performed 90 min of moderate-intensity exercise (40% of V O2 peak) on a cycle ergometer in the Snellen air calorimeter, at regulated air temperatures of 24°C or 30°C and a relative humidity of either 30% or 60%. The "core" compartment was represented by temperatures measured in the esophagus (Tes), rectum (Tre), and aural canal (Tau), while the "muscle" compartment was represented by regional muscle temperature measured in the vastus lateralis (Tvl), triceps brachii (Ttb), and upper trapezius (Tut). The "shell" compartment was represented by the weighted mean of 12 skin temperatures (T sk). The whole body calorimetry data were used to derive optimally fitting two-and three-compartment thermometry models. The traditional two-compartment model was found to be statistically biased, systematically underestimating ⌬Hb by 15.5% (SD 31.3) at 24°C and by 35.5% (SD 21.9) at 30°C. The three-compartment model showed no such bias, yielding a more precise estimate of ⌬Hb as evidenced by a mean estimation error of 1.1% (SD 29.5) at 24°C and 5.4% (SD 30.0) at 30°C with an adjusted R 2 of 0.48 and 0.51, respectively. It is concluded that a major source of error in the estimation of ⌬Hb using the traditional two-compartment thermometry model is the lack of an expression independently representing the heat storage in muscle during exercise. body heat storage; calorimetry; muscle temperature; thermoregulation THE DERIVATION OF THE CHANGE in body heat content (⌬H b ) is of fundamental importance to the physiologist assessing the exposure of the human body to environmental conditions that result in thermal imbalance. In theory, the measurement of body heat exchange using simultaneous measures of direct and indirect calorimetry is the only method whereby ⌬H b can be directly determined. Thus the difference between metabolic heat production using the stoichiometric relationship of the products and reactants of oxidative metabolism (indirect calorimetry) and the total heat lost from the body can be used to estimate ⌬H b . By definition, ⌬H b is the product of the change of the mean temperature of the tissues of the body (⌬T b ), the total body mass (b m ), and the average sp...

Serum from exercising humans suppresses t-cell cytokine production

“…These "candidate" factors include, as noted, catecholamines, growth hormone, and the cytokine IL-6, and the parallel dramatic changes in local muscle and body temperature [29,30], oxygenation and acid-base status [31]. Glucocorticoids also increase with exercise, but usually after much more intense periods of exercise than used in this study [32].…”

Blood temperature and perfusion to exercising and non‐exercising human limbs

“…1999; Jay et al . 2007). The local thermal stimuli modulating thermoregulatory and blood‐flow responses during exercise are therefore weaker in the non‐exercising limbs.…”

“…1999; Jay et al . 2007). To shed light on the mechanisms of temperature and limb blood‐flow regulation, it is timely to investigate the impact of haemodynamic and thermodynamic events in exercising limbs on central and non‐exercising limb perfusion and T B .…”

The Determination of Changes in Body Heat Content during Exercise Using Calorimetry and Thermometry

“…Alternative coefficients have also been suggested for differing levels of clothing insulation (Aoyagi et al, 1996a(Aoyagi et al, , 1996b. However irrespective of the selected weighting coefficients several studies Horstman and Horvath, 1972;Snellen, 2000;Vallerand et al, 1992) have demonstrated that the two-compartmental thermometry model significantly underestimates DT ළ b and therefore DH b by up to ϳ35% (Jay et al, 2007). The thermometry approach is also limited to steady-state body temperatures both at rest and during exercise.…”

“…It is thought that a major source of error in the prediction of DH b using the traditional thermometry approach during steady-state exercise may be due to the thermal influences of a "mid-region", or more specifically muscle tissue, not being considered independently of the "core" and "shell" (Jay et al, 2007;Nadel et al, 1972;Tikuisis, 2003;Webb, 1998). Indeed, this notion was supported by Vallerand et al (Vallerand et al, 1992) who urged that "until more representative measurements of body temperatures at different depths (core, shell and intermediate) are possible, the use of mean body temperature derived heat storage is difficult to justify".…”