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Body heat storage during dynamic exercise – A Comparison of direct calorimetry and thermometry
Author(s) -
Kenny Glen Patrick,
Gariepy Louise M,
Webb Paul,
Ducharme Michel B,
Reardon Francis D
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a828-c
Subject(s) - calorimetry , calorimeter (particle physics) , chemistry , heat capacity , thermal energy storage , lean tissue , thermoregulation , lean body mass , core (optical fiber) , zoology , thermodynamics , analytical chemistry (journal) , materials science , medicine , body weight , biochemistry , adipose tissue , physics , chromatography , detector , biology , optics , composite material
Heat storage is commonly estimated from body temperature derived from a weighted sum of mean skin and core temperatures, body mass, and the body specific heat value of 3.47 kJ·kg −1 . This model assumes uniformity of heat distribution throughout the body space and similar relative mass and composition of the body. We evaluated whether there are differences in the heat storage calculated by direct calorimetry compared to the heat storage obtained by thermometry measured during exercise. 41 subjects exercised in a Snellen air calorimeter on a cycle ergometer at 40% of VO 2peak until steady state rectal temperature was achieved. Oxygen consumption, sensible and insensible heat loss and core, muscle and skin temperatures were measured continuously. Body heat content (ΔH b ) was calculated as follows: ΔH b = Δ((0.80·T re )+(0.20·T sk )) · body mass · C p (Burton,, Nutr 9:261, 1935). Specific heat capacity (C p ) for each subject was calculated by partitioning body weight into fat, lean and bone by dual energy x‐ray absorptiometry. Changes in H b were 203 ± 78 W and 148 ± 58 W as measured by calorimetry and thermometry respectively (P<0.05). We proposed a new model incorporating muscle tissue temperature to estimate ΔH b which significantly improved the estimate of ΔH b as compared to conventional thermometry (212 ± 55 W vs. 148 ± 58 W, P<0.05). In summary, changes in ΔH b measured by thermometry are significantly underestimated when compared to those values measured by direct calorimetry. Funded by U.S. Army Medical Research Acquisition Activity and Natural Sciences and Engineering Research Council of Canada.