Exertional fatigue and cold exposure: mechanisms of hiker's hypothermia

2007 ◽  
Vol 32 (4) ◽  
pp. 793-798 ◽  
Author(s):  
Andrew J. Young ◽  
John W. Castellani
Keyword(s):  
Heat Loss ◽  
Cold Exposure ◽  
Physiological Responses ◽  
Physical Exertion ◽  
The Body ◽  
Cold Weather ◽  
Behavioral Strategies ◽  
Peripheral Vasoconstriction ◽  
Vasoconstrictor Response ◽  
Body Heat

Participants in prolonged, physically demanding activities in cold weather are at risk of a condition known as “hiker's hypothermia”. During exposure to cold weather, the increased gradient favoring body heat loss to the environment must be balanced by physiological responses, clothing, and behavioral strategies that conserve body heat stores, or else body temperature will decline. The primary human physiological responses elicited by cold exposure are shivering and peripheral vasoconstriction. Shivering increases thermogenesis and replaces body heat losses, while peripheral vasoconstriction improves thermal insulation of the body and retards the rate of heat loss. A body of scientific literature supports the concept that prolonged and (or) repeated cold exposure, fatigue induced by sustained physical exertion, or both together can impair shivering and vasoconstrictor response to cold. The mechanisms accounting for this thermoregulatory impairment are not clear, but the possibility that changes in blood glucose availability or sympathetic responsiveness to cold due to exertion and fatigue merit further research.

Impact of electrical heating on effective thermal Insulation of a multi-layered winter clothing system for optimal heating efficiency

2016 ◽  
Vol 28 (2) ◽  
Author(s):  
Huiju Park ◽  
Soo-kyung Hwang ◽  
Joo-Young Lee ◽  
Jintu Fan ◽  
Youngjin Jeong
Keyword(s):  
Ambient Temperature ◽  
Heat Loss ◽  
Thermal Insulation ◽  
Electric Heating ◽  
The Body ◽  
Electrical Heating ◽  
Thermal Manikin ◽  
Heating Unit ◽  
Heating Efficiency ◽  
Body Heat

Purpose This paper investigated the impact of the distance of the heating unit from the body in a multi-layered winter clothing system on effective thermal insulation and heating efficiency. Design/methodology/approach To identify changes in the thermal insulation and heating efficiency of electrical heating in different layers inside a winter clothing ensemble, a series of thermal manikin tests was conducted. A multi-layered winter ensemble with and without activation of a heating unit was tested on the thermal manikin under two different ambient temperature conditions (10°C and -5°C). Findings Results show that the effective thermal insulation of test ensembles increased by 5-7% with the activation of the heating unit compared to that without the activation. The closer the heating unit to the body, the higher the effective thermal insulation was in both ambient temperature conditions. This trend was more significant at lower ambient temperature. Research limitations/implications The results of this study indicate that providing electric heating next to the skin is the most effective in increasing effective thermal insulation and decreasing body heat loss in both ambient temperature (-5°C and 10°C). This trend was more remarkable in colder environment at -5°C of ambient temperature as evidenced by sharp decrease in heating efficiency and effective thermal insulation with an increase in distance between the manikin skin and heating unit at -5°C of ambient temperature compared to at 10°C of ambient temperature. Practical implications Based on the results, it is expected that proximity heating next to the skin, in cold environment, may reduce the weight and size of the battery for the heating unit because of the higher efficiency of electric heating and the potentially immediate perception of warmth supported by the greatest increase in effective thermal insulation, as well as the lowest heat loss that comes with activation of heating on the first layer in cold environment. Originality/value The finding of this study provides guidelines to sportswear designers, textile scientists, sports enthusiasts, and civilians who consider electric heating benefits for improved thermal comfort and safety in cold environments, especially in the areas of outdoor and winter sports and in military service. The results of this study indicate that providing electric heating next to the skin is the most effective in increasing effective thermal insulation and decreasing body heat loss in both ambient temperature (-5°C and 10°C).

The physiology of heat regulation

1995 ◽  
Vol 268 (4) ◽  
pp. R838-R850 ◽  
Author(s):  
P. Webb
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Heat Content ◽  
The Body ◽  
Temperature Heat ◽  
Calorimetric Studies ◽  
Physiological Method ◽  
Related Level ◽  
Deep Body ◽  
Body Heat

Heat regulation is presented as the physiological method of handling metabolic heat, instead of temperature regulation. Experimental evidence of heat regulation from the literature is reviewed, including more than 20 years of calorimetric studies by the author. Changes in heat production are followed by slow exponential changes in heat loss, which produce changes in body heat storage. Heat balance occurs at many levels of heat production throughout the day and night, and at each level there is a related level of rectal temperature. Heat flow can be sensed by the transcutaneous temperature gradient. The controller for heat loss appears to operate like a servomechanism, with feedback from heat loss and possibly feedforward from heat production. Physiological responses defend the body heat content, but heat content varies over a range that is related to heat load. Changes in body heat content drive deep body temperatures.

Hypohydration and thermoregulation in cold air

1998 ◽  
Vol 84 (1) ◽  
pp. 185-189 ◽  
Author(s):  
Catherine O’Brien ◽  
Andrew J. Young ◽  
Michael N. Sawka
Keyword(s):  
Skin Temperature ◽  
Cold Exposure ◽  
Plasma Osmolality ◽  
Whole Body ◽  
Mean Skin Temperature ◽  
Finger Temperature ◽  
Cold Air ◽  
Vasoconstrictor Response ◽  
Weight Decrease ◽  
Body Heat

O’Brien, Catherine, Andrew J. Young, and Michael N. Sawka.Hypohydration and thermoregulation in cold air. J. Appl. Physiol. 84(1): 185–189, 1998.—This study examined the effects of hypohydration on thermoregulation during cold exposure. In addition, the independent influences of hypohydration-associated hypertonicity and hypovolemia were investigated. Nine male volunteers were monitored for 30 min at 25°C, then for 120 min at 7°C, under three counterbalanced conditions: euhydration (Eu), hypertonic hypohydration (HH), and isotonic hypohydration (IH). Hypohydration was achieved 12 h before cold exposure by inducing sweating (HH) or by ingestion of furosemide (IH). Body weight decrease (4.1 ± 0.2%) caused by hypohydration was similar for HH and IH, but differences ( P < 0.05) were found between HH and IH in plasma osmolality (292 ± 1 vs. 284 ± 1 mosmol/kgH2O) and plasma volume reduction (−8 ± 2 vs. −18 ± 3%). Heat debt (349 ± 14 among) did not differ ( P > 0.05) among trials. Mean skin temperature decreased throughout cold exposure during Eu but plateaued after 90 min during HH and IH. Forearm-finger temperature gradient tended ( P = 0.06) to be greater during Eu (10.0 ± 0.7°C) than during HH or IH (8.9 ± 0.7°C). This suggests weaker vasoconstrictor tone during hypohydration than during Eu. Final mean skin temperature was higher for HH than for Eu or IH (23.5 ± 0.3, 22.6 ± 0.4, and 22.9 ± 0.3°C, respectively), and insulation was lower on HH than on IH (0.13 ± 0.01 vs. 0.15 ± 0.01°C ⋅ W−1 ⋅ m−2, respectively), but not with Eu (0.14 ± 0.01°C ⋅ W−1 ⋅ m−2). This provides some evidence that hypertonicity impairs the vasoconstrictor response to cold. Although mild hypohydration did not affect body heat balance during 2-h whole body exposure to moderate cold, hypohydration-associated hypertonicity may have subtle effects on vasoconstriction that could become important during a more severe cold exposure.

The antitoxic and protective effects of Curcuma longa and it`s active agent, Curcumin: оverview

2020 ◽  
pp. 66-72
Author(s):  
A. Khisamova ◽  
O. Gizinger
Keyword(s):  
Curcuma Longa ◽  
Physiological Activity ◽  
Active Agent ◽  
Modern Science ◽  
Physical Exertion ◽  
The Body ◽  
Modern World ◽  
Protective Effects ◽  
Daily Stress ◽  
Anti Cancer

In the modern world, where a person is exposed to daily stress, increased physical exertion, the toxic effect of various substances, including drugs. The task of modern science is to find antioxidants for the body. These can be additives obtained both synthetically and the active substances that we get daily from food. Such a striking example is turmeric, obtained from the plant Curcuma longa. Recently, it has been known that curcumin has an antioxidant, anti-inflammatory, anti-cancer effect and, thanks to these effects, plays an important role in the prevention and treatment of various diseases, in particular, from cancer to autoimmune, neurological, cardiovascular and diabetic diseases. In addition, much attention is paid to increasing the biological activity and physiological effects of curcumin on the body through the synthesis of curcumin analogues. This review discusses the chemical and physical characteristics, analogues, metabolites, the mechanisms of its physiological activity and the effect of curcumin on the body.

ADAPTATION OF WHITE MICE (MUS MUSCULUS) TO REPEATED COOLING

1967 ◽  
Vol 45 (3) ◽  
pp. 321-327 ◽  
Author(s):  
David M. Ogilvie
Keyword(s):  
Body Temperature ◽  
Rectal Temperature ◽  
Cold Exposure ◽  
Mus Musculus ◽  
Room Temperature ◽  
The Body ◽  
Progressive Decrease

The effects, on the body temperature of white mice, of repeated short exposures to cold were investigated using two methods of restraint. Animals held in a flattened posture became hypothermic at room temperature, cooled more than five times as fast at −10 °C as mice that could adopt a heat-conserving posture, and continued to cool for some time after they were removed from the cold. With repeated tests, cooling at room temperature decreased, and an improvement in re warming ability was observed. In addition, with lightly restrained mice, the fall in rectal temperature during cold exposure showed a progressive decrease, a phenomenon not observed with severely restrained animals.

Body Composition Modifications Due to the “Search, Rescue and Survival Training” in Male Military Firefighter Cadets

2021 ◽  
Author(s):  
Thiago Ramos de Barros ◽  
Verônica Pinto Salerno ◽  
Thalita Ponce ◽  
Míriam Raquel Meira Mainenti
Keyword(s):  
Body Composition ◽  
Body Weight ◽  
Repeated Measures ◽  
Food Restriction ◽  
Physical Exertion ◽  
High Energy ◽  
The Body ◽  
Fat Free Mass ◽  
Sleep Restriction ◽  
Fat Percentage

ABSTRACT Introduction To train and prepare cadets for a career as firefighters in Rio de Janeiro, the second-year students of the Officers Training Course are submitted to a Search, Rescue, and Survival Training (SRST) course, which is characterized by long periods of high physical exertion and sleep restriction during a 9-day instruction module, and food restriction during a 7-day survival module. The present study investigated changes in the body composition of 39 male cadets submitted to SRST during training and 4 weeks of recovery with no restrictions in food consumption. Materials and Methods Each cadet was evaluated by anthropometric measurements at six time points: pre-SRST; after the first module; after the second module; and after 1, 2, and 4 weeks of recovery. Measurements included body girths and skinfolds, to estimate trunk (chest and waist) and limbs (arm and thigh) dimensions, as well as body composition. Repeated measures ANOVA and Friedman test were applied (depending on each data distribution). Results Statistically significant decreases in body weight (76.2; 69.8-87.2 to 63.9; 58.9-73.5 kg) and fat free mass (FFM, 69.2; 63.7-77.2 to 60.1; 56.2-68.0 kg) were observed following the second module of SRST. Following a single week of recovery, the FFM returned to pre-SRST values. Body weight returned to pre-training levels in 2 weeks. Body fat percentage and mass also significantly decreased during SRST (9.0; 7.7-12.3 to 6.5; 5.1-9.3% and 6.9; 5.6-10.0 to 6.9; 5.6-10.0 kg, respectively), which showed a slower and more gradual recovery that reached pre-SRST values after 4 weeks. The girths of arm, thigh, chest and waist significantly decreased due to SRST. The girths of the limbs (arm and thigh) returned to pre-training values after one month of recovery, while the girths of the trunk (chest and waist) did not return to pre-SRST values during the study period. Conclusions The findings suggest that men who experience periods of high energy demands and sleep restriction followed by a period of food restriction will endure unavoidable physical consequences that can be mostly reversed by a 1-month recovery.

Accidental Hypothermia

PEDIATRICS ◽  
1979 ◽  
Vol 63 (6) ◽  
pp. 926-928
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Weather Conditions ◽  
Accidental Hypothermia ◽  
Good Judgment ◽  
Hand Coordination ◽  
Body Heat ◽  
Unfavorable Weather

Pediatricians may be able to bring the dangers of accidental hypothermia to the attention of their patients at the time of a sports, camp, or college "physical." People who spend time outdoors must learn to recognize hypothermia-producing weather and water; to know that shivering indicates heat loss exceeding available insulation and body heat production; and to understand that loss of good judgment and hand coordination soon follow uncontrollable shivering. They must not go into areas in which, without proper gear, unfavorable weather conditions or dangerous water may develop, and they must understand that most tragedies from cold result from failure to make camp or to return to safety when weather conditions become unfavorable.

Rancang Bangun Pengukur Suhu Tubuh Dengan Multi Sensor Untuk Mencegah Penyebaran Covid-19

2021 ◽  
Vol 5 (3) ◽  
pp. 543-549
Author(s):  
Helmy Yudhistira Putra ◽  
Utomo Budiyanto
Keyword(s):  
Body Temperature ◽  
Temperature Measurement ◽  
Temperature Sensor ◽  
The Body ◽  
Body Temperatures ◽  
Heat Measurement ◽  
Turn On ◽  
Measurement Results ◽  
Door Lock ◽  
Body Heat

During the COVID-19 pandemic, the price of preventive equipment such as masks and hand sanitizers has increased significantly. Likewise, thermometers are experiencing an increase and scarcity, this tool is also sought after by many companies for screening employees and guests before entering the building to detect body temperatures that are suspected of being positive for COVID-19. The use of a thermometer operated by humans is very risky because dealing directly with people who could be ODP (People Under Monitoring/Suscpected ) or even positive for COVID-19, therefore we need tools for automatic body temperature screening and do not involve humans for the examination. This research uses the MLX-90614 body temperature sensor equipped with an ultrasonic support sensor to detect movement and measure the distance between the forehead and the temperature sensor so that the body heat measurement works optimally, and a 16x2 LCD to display the temperature measurement results. If the measured body temperature is more than 37.5 ° C degrees Celsius then the buzzer will turn on and the selenoid door lock will not open and will send a notification to the Telegram messaging application. The final result obtained is the formation of a prototype device for measuring body temperature automatically without the need to involve humans in measuring body temperature to control people who want to enter the building so as to reduce the risk of COVID-19 transmission

External work in level and grade walking on a motor-driven treadmill

1960 ◽  
Vol 15 (5) ◽  
pp. 759-763 ◽  
Author(s):  
J. W. Snellen
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Total Energy Expenditure ◽  
The Body ◽  
External Work ◽  
Thermal Exchange ◽  
Level Walking ◽  
The Subject ◽  
Set Up ◽  
Physical Laws

When studying a walking subject's thermal exchange with the environment, it is essential to know whether in level walking any part of the total energy expenditure is converted into external mechanical work and whether in grade walking the amount of the external work is predictable from physical laws. For this purpose an experiment was set up in which a subject walked on a motor-driven treadmill in a climatic room. In each series of measurements a subject walked uphill for 3 hours and on the level for another hour. Metabolism was kept equal in both situations. Air and wall temperatures were adjusted to the observed weighted skin temperature in order to avoid any heat exchange by radiation and convection. Heat loss by evaporation was derived from the weight loss of the subject. All measurements were carried out in a state of thermal equilibrium. In grade walking there was a difference between heat production and heat loss by evaporation. This difference equaled the caloric equivalent of the product of body weight and gained height. In level walking the heat production equaled heat loss. Hence it was concluded that in level walking all the energy is converted into heat inside the body. Submitted on April 26, 1960

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