Whole‐body heat exchange in black‐African and Caucasian men during exercise eliciting matched heat‐loss requirements in dry heat

2019 ◽  
Vol 105 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Caroline M. Muia ◽  
Sean R. Notley ◽  
Samah Saci ◽  
Andrew W. D'Souza ◽  
Glen P. Kenny
Keyword(s):  
Heat Exchange ◽  
Heat Loss ◽  
Whole Body ◽  
Black African ◽  
Dry Heat ◽  
Caucasian Men ◽  
Body Heat

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

scholarly journals Menstrual cycle phase does not modulate whole body heat loss during exercise in hot, dry conditions

2019 ◽  
Vol 126 (2) ◽  
pp. 286-293 ◽  
Author(s):  
Sean R. Notley ◽  
Sheila Dervis ◽  
Martin P. Poirier ◽  
Glen P. Kenny
Keyword(s):  
Heat Exchange ◽  
Menstrual Cycle ◽  
Heat Loss ◽  
Whole Body ◽  
Cycle Phase ◽  
Menstrual Phase ◽  
Menstrual Cycle Phase ◽  
Dry Conditions ◽  
Exercise Induced ◽  
Body Heat

Menstrual cycle phase has long been thought to modulate thermoregulatory function. However, information pertaining to the effects of menstrual phase on time-dependent changes in whole body dry and evaporative heat exchange during exercise-induced heat stress and the specific heat load at which menstrual phase modulates whole body heat loss remained unavailable. We therefore used direct calorimetry to continuously assess whole body dry and evaporative exchange in 12 habitually active, non-endurance-trained, eumenorrheic women [21 ± 3 (SD) yr] within the early-follicular, late-follicular, and midluteal menstrual phases during three 30-min bouts of cycling at increasing fixed exercise intensities of 40% (Low), 55% (Moderate), and 70% (High) peak oxygen uptake, each followed by a 15-min recovery, in hot, dry conditions (40°C, 15% relative humidity). This model elicited equivalent rates of metabolic heat production among menstrual phases ( P = 0.80) of ~250 (Low), ~340 (Moderate), and ~430 W (High). However, dry and evaporative heat exchange and the resulting changes in net heat loss (dry ± evaporative heat exchange) were similar among phases (all P > 0.05), with net heat loss averaging 216 ± 43 (Low), 287 ± 63 (Moderate), and 331 ± 75 W (High) across phases. Accordingly, cumulative body heat storage (summation of heat production and loss) across all exercise bouts was similar among phases ( P = 0.55), averaging 464 ± 122 kJ. For some time, menstrual cycle phase has been thought to modulate heat dissipation; however, we show that menstrual cycle phase does not influence the contribution of whole body dry and evaporative heat exchange or the resulting changes in net heat loss or body heat storage, irrespective of the heat load. NEW & NOTEWORTHY Menstrual phase has long been thought to modulate thermoregulatory function in eumenorrheic women during exercise-induced heat stress. Contrary to that perception, we show that when assessed in young, non-endurance-trained women within the early-follicular, late-follicular, and midluteal phases during three incremental exercise-induced heat loads in hot, dry conditions, menstrual phase does not modify whole body dry and evaporative heat exchange or the resulting changes in body heat storage, regardless of the heat load employed.

Blunted Effects of Elevated Serum Osmolality on Whole‐body Heat Loss and Rectal Temperature in Middle‐aged‐to‐older Men Exercising in Dry Heat

2020 ◽  
Vol 34 (S1) ◽  
pp. 1-1
Author(s):  
Robert D. Meade ◽  
Sean R. Notley ◽  
Andrew W. D'Souza ◽  
Maura M. Rutherford ◽  
Emileigh R. Binet ◽  
...  
Keyword(s):  
Heat Loss ◽  
Rectal Temperature ◽  
Elevated Serum ◽  
Older Men ◽  
Serum Osmolality ◽  
Whole Body ◽  
Middle Aged ◽  
Dry Heat ◽  
Body Heat

Do older adults experience greater thermal strain during heat waves?

2014 ◽  
Vol 39 (3) ◽  
pp. 292-298 ◽  
Author(s):  
Jill M. Stapleton ◽  
Joanie Larose ◽  
Christina Simpson ◽  
Andreas D. Flouris ◽  
Ronald J. Sigal ◽  
...  
Keyword(s):  
Older Adults ◽  
Heat Loss ◽  
Heat Waves ◽  
Thermal Strain ◽  
Heat Content ◽  
Whole Body ◽  
Evaporative Heat Loss ◽  
Older Individuals ◽  
Dry Heat ◽  
Body Heat

Heat waves are the cause of many preventable deaths around the world, especially among older adults and in countries with more temperate climates. In the present study, we examined the effects of age on whole-body heat loss and heat storage during passive exposure to environmental conditions representative of the upper temperature extremes experienced in Canada. Direct and indirect calorimetry measured whole-body evaporative heat loss and dry heat exchange, as well as the change in body heat content. Twelve younger (21 ± 3 years) and 12 older (65 ± 5 years) adults with similar body weight (younger: 72.0 ± 4.4 kg; older: 80.1 ± 4.2 kg) and body surface area (younger: 1.8 ± 0.1 m2; older: 2.0 ± 0.1 m2) rested for 2 h in a hot–dry [36.5 °C, 20% relative humidity (RH)] or hot–humid (36.5 °C, 60% RH) environment. In both conditions, evaporative heat loss was not significantly different between groups (dry: p = 0.758; humid: p = 0.814). However, the rate of dry heat gain was significantly greater (by approx. 10 W) for older adults relative to younger adults during the hot–dry (p = 0.032) and hot–humid exposure (p = 0.019). Consequently, the cumulative change in body heat content after 2 h of rest was significantly greater in older adults in the hot–dry (older: 212 ± 25 kJ; younger: 131 ± 27 kJ, p = 0.018) as well as the hot–humid condition (older: 426 ± 37 kJ; younger: 317 ± 45 kJ, p = 0.037). These findings demonstrate that older individuals store more heat during short exposures to dry and humid heat, suggesting that they may experience increased levels of thermal strain in such conditions than people of younger age.

scholarly journals Impaired whole-body heat loss in type 1 diabetes during exercise in the heat: a cause for concern?

Diabetologia ◽  
2019 ◽  
Vol 62 (6) ◽  
pp. 1087-1089 ◽  
Author(s):  
Sean R. Notley ◽  
Martin P. Poirier ◽  
Jane E. Yardley ◽  
Ronald J. Sigal ◽  
Glen P. Kenny
Keyword(s):  
Type 1 Diabetes ◽  
Heat Loss ◽  
Whole Body ◽  
Body Heat

Intermittent sequential pneumatic compression does not enhance whole-body heat loss in elderly adults during extreme heat exposure

2019 ◽  
Vol 44 (12) ◽  
pp. 1383-1386
Author(s):  
Andrew W. D’Souza ◽  
Sean R. Notley ◽  
Robert D. Meade ◽  
Glen P. Kenny
Keyword(s):  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Heat Loss ◽  
Lower Limb ◽  
Vascular Function ◽  
Heat Exposure ◽  
Extreme Heat ◽  
Whole Body ◽  
Elderly Adults ◽  
Body Heat

Lower-limb intermittent sequential pneumatic compression (ISPC) improves circulation and vascular function in elderly adults. We evaluated the hypothesis that ISPC would also augment whole-body heat loss (WBHL) in elderly adults (aged 69 ± 4 years) resting in extreme heat (40 °C). While ISPC increased mean arterial pressure (91 ± 9 mm Hg) relative to no-ISPC (83 ± 5 mm Hg; P = 0.013) at the end of the exposure, no influence on WBHL was observed (81 ± 7 and 86 ± 11 W for ISPC and no-ISPC, respectively, P = 0.310). Novelty When assessed in elderly adults during an extreme heat exposure, intermittent sequential pneumatic compression augmented mean arterial pressure but did not enhance whole-body heat loss.

Light masking of circadian rhythms of heat production, heat loss, and body temperature in squirrel monkeys

1999 ◽  
Vol 276 (2) ◽  
pp. R298-R307 ◽  
Author(s):  
Edward L. Robinson ◽  
Charles A. Fuller
Keyword(s):  
Body Temperature ◽  
Heat Loss ◽  
Heat Production ◽  
Whole Body ◽  
Direct Calorimetry ◽  
Set Point ◽  
Subjective Night ◽  
Timing System ◽  
Circadian Timing System ◽  
Body Heat

Whole body heat production (HP) and heat loss (HL) were examined to determine their relative contributions to light masking of the circadian rhythm in body temperature (Tb). Squirrel monkey metabolism ( n = 6) was monitored by both indirect and direct calorimetry, with telemetered measurement of body temperature and activity. Feeding was also measured. Responses to an entraining light-dark (LD) cycle (LD 12:12) and a masking LD cycle (LD 2:2) were compared. HP and HL contributed to both the daily rhythm and the masking changes in Tb. All variables showed phase-dependent masking responses. Masking transients at L or D transitions were generally greater during subjective day; however, L masking resulted in sustained elevation of Tb, HP, and HL during subjective night. Parallel, apparently compensatory, changes of HL and HP suggest action by both the circadian timing system and light masking on Tb set point. Furthermore, transient HL increases during subjective night suggest that gain change may supplement set point regulation of Tb.

Effect of heating rate on evaporative heat loss in the microwave-exposed mouse

1982 ◽  
Vol 53 (2) ◽  
pp. 316-323 ◽  
Author(s):  
C. J. Gordon
Keyword(s):  
Body Temperature ◽  
Heat Loss ◽  
Heat Dissipation ◽  
Dew Point ◽  
Whole Body ◽  
Evaporative Heat Loss ◽  
Heat Absorption ◽  
Deep Body Temperature ◽  
The Difference ◽  
Body Heat

Male CBA/J mice were administered heat loads of 0–28 J X g-1 at specific absorption rates (SARs) of either 47 or 93 W X kg-1 by exposure to 2,450-MHz microwave radiation at an ambient temperature of 30 degrees C while evaporative heat loss (EHL) was continuously monitored with dew-point hygrometry. At an SAR of 47 W X kg-1 a threshold heat load of 10.5 J X g-1 had to be exceeded before EHL increased. An approximate doubling of SAR to 93 W X kg-1 reduced the threshold to 5.2 J X g-1. Above threshold the slopes of the regression lines were 1.15 and 0.929 for the low- and high-SAR groups, respectively. Thus the difference in threshold and not slope attributes to the significant increase in EHL when mice are exposed at a high SAR (P less than 0.02). In separate experiments a SAR of 47 W X kg-1 raised the deep body temperature of anesthetized mice at a rate of 0.026 degrees C X s-1, whereas 93 W X kg-1 raised temperature at 0.049 degrees C X s-1. Hence the sensitivity of the EHL mode of heat dissipation is directly proportional to the rate of heat absorption and to the rate of rise in body temperature. These data contradict the notion that mammals have control over whole-body heat exchange only (i.e., thermoregulation) but instead indicate that the EHL system is highly responsive to the rate of heat absorption (i.e., temperature regulation).

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