Human Metabolic Heat in the Cold

This study examined how time of day affects thermoregulation during cold-water immersion (CWI). It was hypothesized that the shivering and vasoconstrictor responses to CWI would differ at 0700 vs. 1500 because of lower initial core temperatures (Tcore) at 0700. Nine men were immersed (20°C, 2 h) at 0700 and 1500 on 2 days. No differences ( P > 0.05) between times were observed for metabolic heat production (M˙, 150 W ⋅ m−2), heat flow (250 W ⋅ m−2), mean skin temperature (T sk, 21°C), and the mean body temperature-change in M˙(ΔM˙) relationship. Rectal temperature (Tre) was higher ( P < 0.05) before (Δ = 0.4°C) and throughout CWI during 1500. The change in Tre was greater ( P < 0.05) at 1500 (−1.4°C) vs. 0700 (−1.2°C), likely because of the higher Tre-T skgradient (0.3°C) at 1500. These data indicate that shivering and vasoconstriction are not affected by time of day. These observations raise the possibility that CWI may increase the risk of hypothermia in the early morning because of a lower initial Tcore.

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Infrared thermography can detect pre‐visual bacterial growth in a laboratory setting via metabolic heat detection

Journal of Applied Microbiology ◽

10.1111/jam.15218 ◽

2021 ◽

Author(s):

Ben Hunt ◽

Reza Saatchi ◽

Melissa M Lacey

Keyword(s):

Infrared Thermography ◽

Bacterial Growth ◽

Laboratory Setting ◽

Metabolic Heat

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Human thermoregulatory responses during serial cold-water immersions

Journal of Applied Physiology ◽

10.1152/jappl.1998.85.1.204 ◽

1998 ◽

Vol 85 (1) ◽

pp. 204-209 ◽

Cited By ~ 27

Author(s):

John W. Castellani ◽

Andrew J. Young ◽

Michael N. Sawka ◽

Kent B. Pandolf

Keyword(s):

Body Temperature ◽

Rectal Temperature ◽

Heat Production ◽

Alternative Explanation ◽

Cold Water ◽

Metabolic Heat Production ◽

Normal Body Temperature ◽

Repeat Trial ◽

Metabolic Heat ◽

Made In

This study examined whether serial cold-water immersions over a 10-h period would lead to fatigue of shivering and vasoconstriction. Eight men were immersed (2 h) in 20°C water three times (0700, 1100, and 1500) in 1 day (Repeat). This trial was compared with single immersions (Control) conducted at the same times of day. Before Repeat exposures at 1100 and 1500, rewarming was employed to standardize initial rectal temperature. The following observations were made in the Repeat relative to the Control trial: 1) rectal temperature was lower and heat debt was higher ( P < 0.05) at 1100; 2) metabolic heat production was lower ( P < 0.05) at 1100 and 1500; 3) subjects perceived the Repeat trial as warmer at 1100. These data suggest that repeated cold exposures may impair the ability to maintain normal body temperature because of a blunting of metabolic heat production, perhaps reflecting a fatigue mechanism. An alternative explanation is that shivering habituation develops rapidly during serially repeated cold exposures.

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Changes in serotonin contents in brain affect metabolic heat production of rabbits in cold

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1978.235.1.r41 ◽

1978 ◽

Vol 235 (1) ◽

pp. R41-R47

Author(s):

M. T. Lin ◽

I. H. Pang ◽

S. I. Chern ◽

W. Y. Chia

Keyword(s):

Blood Flow ◽

Amino Acid ◽

Heat Loss ◽

Acid Decarboxylase ◽

Evaporative Heat Loss ◽

Decarboxylase Inhibitor ◽

Ambient Temperatures ◽

Amino Acid Decarboxylase ◽

Metabolic Heat ◽

Normal Limits

Elevating serotonin (5-HT) contents in brain with 5-hydroxytryptophan (5-HTP) reduced rectal temperature (Tre) in rabbits after peripheral decarboxylase inhibition with the aromatic-L-amino-acid decarboxylase inhibitor R04-4602 at two ambient temperatures (Ta), 2 and 22 degrees C. The hypothermia was brought about by both an increase in respiratory evaporative heat loss (Eres) and a decrease in metabolic rate (MR) in the cold. At a Ta of 22 degrees C, the hypothermia was achieved solely due to an increase in heat loss. Depleting brain contents of 5-HT with intraventricular, 5,7-dihydroxytryptamine (5,7-DHT) produced an increased Eres and ear blood flow even at Ta of 2 degrees C. Also, MR increased at all but the Ta of 32 degrees C. However, depleting the central and peripheral contents of 5-HT with p-chlorophenylalanine (pCPA) produced lower MR accompanied by lower Eres in the cold compared to the untreated control. Both groups of pCPA-treated and 5,7-DHT-treated animals maintained their Tre within normal limits. The data suggest that changes in 5-HT content in brain affects the MR of rabbits in the cold. Elevating brain content of 5-HT tends to depress the MR response to cold, while depleting brain content of 5-HT tends to enhance the MR response to cold.

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Recent advances of microcalorimetry for studying cellular metabolic heat

TrAC Trends in Analytical Chemistry ◽

10.1016/j.trac.2021.116353 ◽

2021 ◽

pp. 116353

Author(s):

Ye Wang ◽

Hanliang Zhu ◽

Jianguo Feng ◽

Pavel Neuzil

Keyword(s):

Metabolic Heat ◽

Recent Advances

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Selection for biomass production based on respiration parameters in eucalypts: effects of origin and growth climates on growth rates

Canadian Journal of Forest Research ◽

10.1139/x26-175 ◽

1996 ◽

Vol 26 (9) ◽

pp. 1556-1568 ◽

Cited By ~ 10

Author(s):

Thimmappa S. Anekonda ◽

Richard S. Criddle ◽

Lee D. Hansen ◽

Mike Bacca

Keyword(s):

Temperature Dependence ◽

Growth Rates ◽

Heat Rate ◽

Eucalyptus Species ◽

Relative Growth ◽

Relative Growth Rates ◽

Metabolic Heat ◽

Respiratory Parameters ◽

Metabolic Heat Rate ◽

Different Climates

Seventeen Eucalyptus species and 30 rapid-growing Eucalyptuscamaldulensis trees (referred to as plus trees), growing in a plantation were studied to examine relationships among measured plant growth and respiratory parameters, geographical origins, and growth climate. The respiratory parameters measured at two different temperatures by isothermal calorimetry were metabolic heat rate, rate of CO2 production, and the ratio of heat rate to CO2 rate. Metabolic heat rate was also measured as a continuous function of temperature by differential scanning calorimetry in the range of 10 to 40 °C. Tree growth was measured as rates of height and stem volume growth. The values of respiratory and growth variables of Eucalyptus species are significantly correlated with latitude and altitude of origin of their seed sources. The maximum metabolic heat rate, the temperature of the maximum heat rate, the temperature coefficients of metabolic rate, and the temperatures at which the slopes of Arrhenius plots change are all genetically determined parameters that vary both within and among species. Measurement of growth rate–respiration rate–temperature relationships guide understanding of why relative growth rates of Eucalyptus species and individual genotypes differ with climate, making it possible to identify genotypes best suited for rapid growth in different climates. The temperature dependence of respiration rates is an important factor determining relative growth rates of eucalypts in different climates. To achieve optimum biomass production the temperature dependence of individual plants must be matched to growth climate.

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