Body heat storage during intermittent work in hot–dry and warm–wet environments

2012 ◽  
Vol 37 (5) ◽  
pp. 840-849 ◽  
Author(s):  
Jill M. Stapleton ◽  
Heather E. Wright ◽  
Stephen G. Hardcastle ◽  
Glen P. Kenny
Keyword(s):  
Heat Exchange ◽  
Intermittent Exercise ◽  
Heat Content ◽  
Heat Rate ◽  
High Heat ◽  
Threshold Limit Value ◽  
Whole Body ◽  
Exercise Protocol ◽  
Body Heat ◽  
Intermittent Work

We examined heat balance using an American Conference of Governmental Industrial Hygienists threshold limit value allocated exercise protocol in hot–dry (HD; 46 °C, 10% relative humidity (RH)) and warm–wet (WW; 33 °C, 60% RH) environments of equivalent WBGT (29 °C) for different clothing ensembles. Whole-body heat exchange and changes in body heat content (ΔHb) were measured using simultaneous direct whole-body and indirect calorimetry. Eight males performed six 15-min cycling periods at a constant rate of metabolic heat production (360 W) interspersed by 5-min rest periods for six experimental trials: HD and WW environments for a seminude control (CON), modified work uniform (MWU, moisture permeable top and work pants), and standard work uniform (SWU, work coveralls and cotton undergarments). Whole-body evaporative and dry heat exchange, rectal temperature (Tre), and heart rate were measured continuously. The cumulative ΔHb during the 2 h intermittent exercise protocol was similar between HD and WW environments for each of the clothing ensembles (CON, 387 ± 55 vs. 435 ± 49 kJ; MWU, 485 ± 58 vs. 531 ± 61 kJ; SWU, 585 ± 74 vs. 660 ± 54 kJ, respectively). Similarly, no differences in Tre (CON, 37.67 ± 0.07 vs. 37.48 ± 0.08 °C; MWU, 37.73 ± 0.08 vs. 37.53 ± 0.09 °C; SWU, 38.01 ± 0.09 vs. 37.94 ± 0.05 °C) or heat rate (CON, 93 ± 3 vs. 84 ± 3 beats·min–1; MWU, 102 ± 5 vs. 95 ± 9 beats·min–1; SWU, 119 ± 8 vs. 110 ± 9 beats·min–1) were observed at the end of the 2 h intermittent exercise protocol in HD vs. WW environments, respectively. We showed similar levels of thermal and cardiovascular strain for intermittent work performed in high heat stress conditions of varying environmental conditions but similar WBGT.

scholarly journals Whole body heat loss is reduced in older males during short bouts of intermittent exercise

2013 ◽  
Vol 305 (6) ◽  
pp. R619-R629 ◽  
Author(s):  
Joanie Larose ◽  
Heather E. Wright ◽  
Jill Stapleton ◽  
Ronald J. Sigal ◽  
Pierre Boulay ◽  
...  
Keyword(s):  
Heat Loss ◽  
Heat Storage ◽  
Intermittent Exercise ◽  
Heat Content ◽  
Whole Body ◽  
Evaporative Heat Loss ◽  
Middle Aged ◽  
Young Males ◽  
Body Heat ◽  
Older Males

Studies in young adults show that a greater proportion of heat is gained shortly following the start of exercise and that temporal changes in whole body heat loss during intermittent exercise have a pronounced effect on body heat storage. The consequences of short-duration intermittent exercise on heat storage with aging are unclear. We compared evaporative heat loss (H E) and changes in body heat content (ΔHb) between young (20–30 yr), middle-aged (40–45 yr), and older males (60–70 yr) of similar body mass and surface area, during successive exercise (4 × 15 min) and recovery periods (4 × 15 min) at a fixed rate of heat production (400 W) and under fixed environmental conditions (35°C/20% relative humidity). H E was lower in older males vs. young males during each exercise (Ex1: 283 ± 10 vs. 332 ± 11 kJ, Ex2: 334 ± 10 vs. 379 ± 5 kJ, Ex3: 347 ± 11 vs. 392 ± 5 kJ, and Ex4: 347 ± 10 vs. 387 ± 5 kJ, all P < 0.02), whereas H E in middle-aged males was intermediate to that measured in young and older adults (Ex1: 314 ± 13, Ex2: 355 ± 13, Ex3: 371 ± 13, and Ex4: 365 ± 8 kJ). H E was not significantly different between groups during the recovery periods. The net effect over 2 h was a greater ΔHb in older (267 ± 33 kJ; P = 0.016) and middle-aged adults (245 ± 16 kJ; P = 0.073) relative to younger counterparts (164 ± 20 kJ). As a result of a reduced capacity to dissipate heat during exercise, which was not compensated by a sufficiently greater rate of heat loss during recovery, both older and middle-aged males had a progressively greater rate of heat storage compared with young males over 2 h of intermittent exercise.

Exercise-rest cycles do not alter local and whole body heat loss responses

2011 ◽  
Vol 300 (4) ◽  
pp. R958-R968 ◽  
Author(s):  
Daniel Gagnon ◽  
Glen P. Kenny
Keyword(s):  
Heat Loss ◽  
Core Temperature ◽  
Intermittent Exercise ◽  
Sweat Rate ◽  
Heat Content ◽  
Whole Body ◽  
Evaporative Heat Loss ◽  
Esophageal Temperature ◽  
Direct Calorimetry ◽  
Body Heat

Previous studies have suggested that greater core temperatures during intermittent exercise (Ex) are due to attenuated sweating [upper back sweat rate (SR)] and skin blood flow (SkBF) responses. We evaluated the hypothesis that heat loss is not altered during exercise-rest cycles (ER). Ten male participants randomly performed four 120-min trials: 1) 60-min Ex and 60-min recovery (60ER); 2) 3 × 20-min Ex separated by 20-min recoveries (20ER); 3) 6 × 10-min Ex separated by 10-min recoveries (10ER), or 4) 12 × 5-min Ex separated by 5-min recoveries (5ER). Exercise was performed at a workload of 130 W at 35°C. Whole body heat exchange was determined by direct calorimetry. Core temperature, SR (by ventilated capsule), and SkBF (by laser-doppler) were measured continuously. Evaporative heat loss (EHL) progressively increased with each ER, such that it was significantly greater ( P ≤ 0.05) at the end of the last compared with the first Ex for 5ER (299 ± 39 vs. 440 ± 41 W), 10ER (425 ± 51 vs. 519 ± 45 W), and 20ER (515 ± 63 vs. 575 ± 74 W). The slope of the EHL response against esophageal temperature significantly increased from the first to the last Ex within the 10ER (376 ± 56 vs. 445 ± 89 W/°C, P ≤ 0.05) and 20ER (535 ± 85 vs. 588 ± 28 W/°C, P ≤ 0.05) conditions, but not during 5ER (296 ± 96 W/°C vs. 278 ± 95 W/°C, P = 0.237). In contrast, the slope of the SkBF response against esophageal temperature did not significantly change from the first to the last Ex (5ER: 51 ± 23 vs. 54 ± 19%/°C, P = 0.848; 10ER: 53 ± 8 vs. 56 ± 21%/°C, P = 0.786; 20ER: 44 ± 20 vs. 50 ± 27%/°C, P = 0.432). Overall, no differences in body heat content and core temperature were observed. These results suggest that altered local and whole body heat loss responses do not explain the previously observed greater core temperatures during intermittent exercise.

Physiological Considerations in the Design of Clothing and Protective Equipment for Extreme Environments and in Modeling Human Heat Exchange

2000 ◽  
Vol 44 (12) ◽  
pp. 2-796-2-799
Author(s):  
Victor S. Koscheyev
Keyword(s):  
Heat Exchange ◽  
Extreme Environments ◽  
Heat Content ◽  
Feedback System ◽  
Physiological Data ◽  
Accurate Information ◽  
Protective Equipment ◽  
New Era ◽  
Terrestrial Environments ◽  
Body Heat

A new era is commencing in which the design of clothing and protective equipment is increasingly taking into account physiological data about human functioning in extreme environments. In these conditions, there is an intensive influence of environmental factors on body systems. Physiological in combination with other types of countermeasures that provide comfort are necessary for stabilizing homeostasis. This approach is extremely important for the design of heavy protective equipment that is widely used in such conditions as space, harsh terrestrial environments, undersea, and in military situations. A physiological overview of the human body for design and modeling purposes is presented, relying on extensive research findings on human thermoregulation and heat exchange using an experimental water circulating plastic tubing garment with the capacity for simultaneous cooling/warming of different body areas. The fingers have great potential as an informative site for providing accurate information about actual body heat status, developing an automatic feedback system between body heat content and the reactivity of the cooling/warming system, and improving modeling approaches.

Temperature gradients in pigs during whole-body hyperthermia at 42 degrees C

1979 ◽  
Vol 47 (4) ◽  
pp. 712-717 ◽  
Author(s):  
J. A. Dickson ◽  
A. McKenzie ◽  
K. McLeod
Keyword(s):  
Core Temperature ◽  
Brain Temperature ◽  
Heat Content ◽  
Temperature Gradients ◽  
Whole Body ◽  
Induction Phase ◽  
Equilibrium Conditions ◽  
Repeated Heating ◽  
Deep Body ◽  
Body Heat

Temperature was simultaneously measured by thermistors in multiple deep-body and peripheral sites in adult pigs heated continuously at 42 degrees C (rectal) and above for 4–24 h. During hyperthermia, the relations between different body temperatures were maintained and up to 1.0 degrees C separated temperature measurements at sites such as liver and bone marrow. These persistent temperature gradients must be borne in mind when evaluating tumor response in patients subjected to whole-body heating for disseminated cancer. Temperatures recorded by rectal, deep esophageal, or tympanic membrane sensors provided a reliable index of core temperature (including brain temperature) under equilibrium conditions at 42 degrees C, but only esophageal and tympanic sensors could safely be used to monitor the induction phase of hyperthermia and the adjustive changes in body-heat content required to stabilize core temperature during sustained hyperthermia. Pigs withstood repeated heating at 42 degrees C for 6 h, and recovered rapidly, but died after 24 h of hyperthermia. Pigs subjected to unrestrained heating died at 45 degrees C (esophagus).

Whole‐body Heat Exchange in Young and Middle‐Aged Men during Constant‐ and Variable‐Intensity Work of Equivalent Metabolic Demand in Dry Heat

2020 ◽  
Vol 34 (S1) ◽  
pp. 1-1
Author(s):  
Sean R. Notley ◽  
Robert D. Meade ◽  
Andrew W. D’Souza ◽  
Maura M. Rutherford ◽  
Jung-Hyun Kim ◽  
...  
Keyword(s):  
Heat Exchange ◽  
Whole Body ◽  
Metabolic Demand ◽  
Middle Aged ◽  
Variable Intensity ◽  
Dry Heat ◽  
Body Heat

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

2007 ◽  
Vol 292 (1) ◽  
pp. R167-R175 ◽  
Author(s):  
Ollie Jay ◽  
Louise M. Gariépy ◽  
Francis D. Reardon ◽  
Paul Webb ◽  
Michel B. Ducharme ◽  
...  
Keyword(s):  
Vastus Lateralis ◽  
Estimation Error ◽  
Heat Content ◽  
Compartment Model ◽  
Whole Body ◽  
Moderate Intensity ◽  
Upper Trapezius ◽  
Two Compartment Model ◽  
Three Compartment Model ◽  
Body Heat

The aim of this study was to use whole body calorimetry to directly measure the change in body heat content (ΔHb) during steady-state exercise and compare these values with those estimated using thermometry. The thermometry models tested were the traditional two-compartment model of “core” and “shell” temperatures, and a three-compartment model of “core,” “muscle,” and “shell” temperatures; with individual compartments within each model weighted for their relative influence upon ΔHb by coefficients subject to a nonnegative and a sum-to-one constraint. Fifty-two participants performed 90 min of moderate-intensity exercise (40% of V̇o2 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 (T̄sk). 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 ΔHb 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 ΔHb 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 R2 of 0.48 and 0.51, respectively. It is concluded that a major source of error in the estimation of ΔHb using the traditional two-compartment thermometry model is the lack of an expression independently representing the heat storage in muscle during exercise.

Whole-Body Heat Exchange during Heat Acclimation and Its Decay

2015 ◽  
Vol 47 (2) ◽  
pp. 390-400 ◽  
Author(s):  
MARTIN P. POIRIER ◽  
DANIEL GAGNON ◽  
BRIAN J. FRIESEN ◽  
STEPHEN G. HARDCASTLE ◽  
GLEN P. KENNY
Keyword(s):  
Heat Exchange ◽  
Heat Acclimation ◽  
Whole Body ◽  
Body Heat

Increasing Exercise Duration Does Not Affect the Postexercise Elevation in Esophageal Temperature

1999 ◽  
Vol 24 (4) ◽  
pp. 377-386 ◽  
Author(s):  
Glen P. Kenny ◽  
Paul M. Denis ◽  
Normand G. Boulé ◽  
Carolyn E. Proulx ◽  
James S. Thoden ◽  
...  
Keyword(s):  
Heat Content ◽  
Exercise Bout ◽  
Exercise Duration ◽  
Whole Body ◽  
Temperature Threshold ◽  
Esophageal Temperature ◽  
Cutaneous Vasodilation ◽  
The Relationship ◽  
Recovery Cycles ◽  
Body Heat

It has previously been observed that (a) following 15 min of intense exercise, esophageal temperature (Tes), remains elevated at a plateau value equal to that at which active vasodilation had occurred during exercise (i.e., esophageal temperature threshold for cutaneous vasodilation [ThVD]); and (b) exercise/recovery cycles of identical intensity and duration, when sequential, result in progressively higher Tes at the beginning and end of exercise. In the latter case, parallel increases in both the exercise ThVD and postexercise plateau of Tes were noted. This study was conducted to determine if the elevated postexercise Tes is related to increases in whole-body heat content. On separate occasions, 9 subjects completed 3 bouts of treadmill exercise at 70% [Formula: see text] max, 29 °C ambient temperature. Each exercise bout lasted either 15, 30, or 45 min and was followed by 60 min of inactive recovery. Esophageal temperatures were similar at the start of each exercise bout, but the rise in Tes during exercise nearly doubled from 1.0 °C after 15 min of exercise to 1.9 °C after 45 min of exercise. There were no intercondition differences among the exercise ThVD (∼0.36 °C above baseline) or postexercise plateau values for Tes (∼0.40 °C above baseline). Thus the relationship between the ThVD during exercise and the postexercise Tes did not appear to be dependent on changes in whole-body heat content as produced by endogenous heating during exercise of different duration. Key words: cutaneous vasodilation threshold, exercise hyperthermia. temperature elevation

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