Critical environmental limits for young, healthy adults (PSU HEAT)

2021 ◽  
Author(s):  
S. Tony Wolf ◽  
Rachel M. Cottle ◽  
Daniel J. Vecellio ◽  
W. Larry Kenney
Keyword(s):  
Heat Stress ◽  
Activities Of Daily Living ◽  
Heat Production ◽  
Daily Living ◽  
Water Vapor Pressure ◽  
Healthy Adults ◽  
Metabolic Heat Production ◽  
Metabolic Heat ◽  
Increased Risk ◽  
Environmental Limits

Critical environmental limits are those combinations of ambient temperature and humidity above which heat balance cannot be maintained for a given metabolic heat production, limiting exposure time and placing individuals at increased risk of heat-related illness. The aim of the present study was to establish those limits in young (18-34 yr) healthy adults during low-intensity activity approximating the metabolic demand of activities of daily living. Twenty-five (12 men/13 women) subjects were exposed to progressive heat stress in an environmental chamber at two rates of metabolic heat production chosen to represent minimal activity (MinAct) or light ambulation (LightAmb). Progressive heat stress was performed with either (1) constant dry-bulb temperature (Tdb) and increasing ambient water vapor pressure (Pa) (Pcrit trials; 36, 38, or 40 °C), or (2) constant Pa and increasing Tdb (Tcrit trials; 12, 16, or 20 mmHg). Each subject was tested during MinAct and LightAmb in 2-3 experimental conditions in random order, for a total of 4-6 trials per participant. Higher metabolic heat production (p < 0.001) during LightAmb compared to MinAct trials resulted in significantly lower critical environmental limits across all Pcrit and Tcrit conditions (all p < 0.001). These data, presented graphically herein on a psychrometric chart, are the first to define critical environmental limits for young adults during activity resembling those of light household tasks or other activities of daily living, and can be used to develop guidelines, policy decisions, and evidence-based alert communications to minimize the deleterious impacts of extreme heat events.

Psychrometric limits and critical evaporative coefficients for unacclimated men and women

2002 ◽  
Vol 92 (6) ◽  
pp. 2256-2263 ◽  
Author(s):  
W. Larry Kenney ◽  
Michael J. Zeman
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Heat Production ◽  
Heat Balance ◽  
Water Vapor Pressure ◽  
Metabolic Heat Production ◽  
Maximal Aerobic Capacity ◽  
Men And Women ◽  
Metabolic Heat ◽  
Environmental Limits

Critical environmental limits, defined as those above which heat balance cannot be maintained for a given metabolic heat production, have not been determined for unacclimated subjects. To characterize critical environmental limits and to derive evaporative heat exchange coefficients ( K e′) for unacclimated young men ( n = 11) and women ( n = 10), subjects of average aerobic fitness walked at 30% maximal aerobic capacity in an environmental chamber. Critical environmental conditions were defined as the psychrometric loci of dry-bulb temperature and water vapor pressure at which core (esophageal) temperature was forced out of equilibrium (heat gain exceeded heat loss). Compared with the men in our study, the women had significantly higher critical environmental limits ( P < 0.001) in warm (34–38°C), humid (>60%) environments, a function of their lower absolute metabolic heat production at the fixed relative exercise intensity. Isotherms constructed from biophysical models closely fit the data in this range of environments but underestimated empirically determined critical limits in hotter, drier environments. Sex-specific values of K e′ were derived by partial calorimetry in the critical water vapor pressure environments, in which full skin wettedness occurred. There were no sex differences for K e′ (men = 17.4, 15.5, and 14.2 W · m−2 · Torr−1 and women = 16.8, 15.5, and 14.2 W · m−2 · Torr−1 at 34, 36, and 38°C, respectively). These K e′ values were lower than those previously published for fully heat-acclimated men (18.4 W · m−2 · Torr−1 at 36°C) and women (17.7 W · m−2 · Torr−1 at 36°C and 15.5 W · m−2 · Torr−1 at 38°C) and may be used to model heat balance responses for unacclimated men and women working in hot environments.

PSII-6 Electronically controlled cooling pads improve litter growth and thermoregulatory measures and increase total heat production in heat stressed lactating sows

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 312-312
Author(s):  
Taylor L Jansen ◽  
Michaiah J Galvin ◽  
Tyler C Field ◽  
Jason R Graham ◽  
Robert M Stwalley ◽  
...  
Keyword(s):  
Heat Stress ◽  
Growth Performance ◽  
Heat Production ◽  
Total Heat ◽  
Metabolic Heat Production ◽  
Controlled Cooling ◽  
Study Objective ◽  
Metabolic Heat ◽  
Indirect Measures ◽  
Lactating Sows

Abstract Heat stress (HS) decreases lactation output in sows due to an attempt to reduce metabolic heat production; however, this negatively affects litter growth performance. Therefore, the study objective was to determine whether electronically controlled cooling pads (ECP) would improve indirect measures of lactation output (e.g., metabolic heat production) and litter growth performance in HS exposed sows. Over two repetitions, 12 multiparous (2.69 ± 0.85) lactating sows (265.4 ± 26.1 kg) and litters were assigned to either an ECP (n = 6) or a non-functional ECP (NECP; n = 6) and placed into farrowing crates within indirect calorimeters from d 3.7 ± 0.5 to d 18.7 ± 0.5 of lactation. Litters were standardized across all sows (11.4 ± 0.7 piglets/litter), and sows were provided ad libitum feed and water. All sows were exposed to cyclical HS (28.27 ± 1.42°C nighttime to 35.14 ± 0.70°C daytime). On d 4, 8, 14, and 18 of lactation, indirect calorimetry was performed on each individual sow and litter to determine total heat production (THP). Body temperature (TB), was measured hourly using vaginal implants, and respiration rate (RR) was measured daily at 0700, 1100, 1300, 1500, and 1900 h. Litter weights were obtained at birth and weaning. An overall decrease (P &lt; 0.01; 25 bpm) in RR and maximum daily TB (P = 0.02; 0.40°C) was observed in ECP versus NECP sows. An increase in THP (P &lt; 0.01; 20.4%) and THP/kg0.75 (P &lt; 0.01; 23.1%) was observed for ECP when compared to NECP sows and litters. Litter growth rate was increased (P &lt; 0.01; 20.8%) in ECP versus NECP sows. In summary, the use of ECP improves litter growth, thermoregulatory measures, and bioenergetic parameters associated with greater milk production in lactating sows exposed to cyclical heat stress.

Effect of dual feeding program and heat stress on broiler performance

2003 ◽  
Vol 2003 ◽  
pp. 179-179
Author(s):  
H. Hossain Zadeh ◽  
A. M. Tahmasbi ◽  
Gh. Moghadam ◽  
S. Alijani
Keyword(s):  
Genetic Variation ◽  
Heat Stress ◽  
Heat Production ◽  
Feed Intake ◽  
Metabolic Heat Production ◽  
Broiler Performance ◽  
Metabolic Heat ◽  
Broiler Industry ◽  
Feeding Program

Heat stress is a major concern of the broiler industry due to the resulting decreased growth, feed intake and increased FCR ratio and mortality (Cooper and Washburn, 1998). Heat exposed birds decrees feed intake in order to reduce metabolic heat production and maintain hometheremy, resulting in slower growth. Genetic variation in responses to heat stress has been shown to exist between breeds (Yalcin, et al., 1997). The dual feeding program may have transitory effects on heat production during the heat stress (De Basilio et al., 2001). The aim of this research was to evaluate the response of broiler performance when a two different type of diet were offered during the heat stress.

scholarly journals Association of self-perceived income sufficiency with cognitive impairment among older adults: a population-based study in India

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
T. Muhammad ◽  
Shobhit Srivastava ◽  
T. V. Sekher
Keyword(s):  
Risk Factors ◽  
Older Adults ◽  
Cognitive Impairment ◽  
Activities Of Daily Living ◽  
Psychological Health ◽  
Daily Living ◽  
Basic Needs ◽  
Well Being ◽  
Asset Ownership ◽  
Increased Risk

Abstract Background Greater cognitive performance has been shown to be associated with better mental and physical health and lower mortality. The present study contributes to the existing literature on the linkages of self-perceived income sufficiency and cognitive impairment. Study also provides additional insights on other socioeconomic and health-related variables that are associated with cognitive impairment in older ages. Methods Data for this study is derived from the 'Building Knowledge Base on Population Ageing in India'. The final sample size for the analysis after removing missing cases was 9176 older adults. Descriptive along with bivariate analyses were presented to show the plausible associations of cognitive impairment with potential risk factors using the chi-square test. Also, binary logistic regression analysis was performed to provide the relationship between cognitive impairment and risk factors. The software used was STATA 14. Results About 43% of older adults reported that they had no source of income and 7.2% had income but not sufficient to fulfil their basic needs. Older adults with income but partially sufficient to fulfil their basic needs had 39% significantly higher likelihood to suffer from cognitive impairment than older adults who had sufficient income [OR: 1.39; OR: 1.21–1.59]. Likelihood of cognitive impairment was low among older adults with asset ownership than older adults with no asset ownership [OR: 0.83; CI: 0.72–0.95]. Again, older adults who work by compulsion (73.3%) or felt mental or physical stress due to work (57.6%) had highest percentage of cognitive impairment. Moreover, older adults with poor self-rated health, low instrumental activities of daily living, low activities of daily living, low subjective well-being and low psychological health were at increased risk for cognitive impairment. Conclusion The study highlights the pressing need for care and support and especially financial incentives in the old age to preserve cognitive health. Further, while planning geriatric health care for older adults in India, priority must be given to financially backward, with no asset ownership, with poor health status, older-older, widowed, and illiterate older individuals, as they are more vulnerable to cognitive impairment.

scholarly journals Human thermoregulatory responses during serial cold-water immersions

1998 ◽  
Vol 85 (1) ◽  
pp. 204-209 ◽  
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.

Physical fitness and thermoregulatory reactions in a cold environment in men

1988 ◽  
Vol 65 (5) ◽  
pp. 1984-1989 ◽  
Author(s):  
J. H. Bittel ◽  
C. Nonotte-Varly ◽  
G. H. Livecchi-Gonnot ◽  
G. L. Savourey ◽  
A. M. Hanniquet
Keyword(s):  
Physical Fitness ◽  
Cold Stress ◽  
Heat Production ◽  
Ambient Air ◽  
Metabolic Heat Production ◽  
Adult Males ◽  
Fitness Level ◽  
Metabolic Heat ◽  
Air Temperatures ◽  
Thermoregulatory Reactions

The relationship between the physical fitness level (maximal O2 consumption, VO2max) and thermoregulatory reactions was studied in 17 adult males submitted to an acute cold exposure. Standard cold tests were performed in nude subjects, lying for 2 h in a climatic chamber at three ambient air temperatures (10, 5, and 1 degrees C). The level of physical fitness conditioned the intensity of thermoregulatory reactions to cold. For all subjects, there was a direct relationship between physical fitness and 1) metabolic heat production, 2) level of mean skin temperature (Tsk), 3) level of skin conductance, and 4) level of Tsk at the onset of shivering. The predominance of thermogenic or insulative reactions depended on the intensity of the cold stress: insulative reactions were preferential at 10 degrees C, or even at 5 degrees C, whereas colder ambient temperature (1 degree C) triggered metabolic heat production abilities, which were closely related to the subject's physical fitness level. Fit subjects have more efficient thermoregulatory abilities against cold stress than unfit subjects, certainly because of an improved sensitivity of the thermoregulatory system.

Acclimatization of calves to a hot dry environment

1959 ◽  
Vol 52 (3) ◽  
pp. 296-304 ◽  
Author(s):  
W. Bianca
Keyword(s):  
Heart Rate ◽  
Respiratory Rate ◽  
Rectal Temperature ◽  
Heat Production ◽  
Metabolic Heat Production ◽  
Metabolic Heat ◽  
Physiological Reactions

1. Three calves were individually exposed in a climatic room to an environment of 45° C. dry-bulb and 28° C. wet-bulb temperature for 21 successive days up to 5 hr. each day.2. In the 21-day period, mostly during the first half of it, the following changes in the physiological reactions of the animals were observed: progressive reductions in rectal temperature, in heart rate and in respiratory rate with a change of breathing from a laboured to a less laboured type.3. It was suggested that a decrease in metabolic heat production might play a part in the observed acclimatization.

Effects of solar radiation and wind speed on metabolic heat production by two mammals with contrasting coat colours.

1995 ◽  
Vol 198 (7) ◽  
pp. 1499-1507 ◽  
Author(s):  
G E Walsberg ◽  
B O Wolf
Keyword(s):  
Wind Speed ◽  
Solar Radiation ◽  
Heat Production ◽  
Metabolic Heat Production ◽  
Heat Gain ◽  
Solar Heat ◽  
Wind Speeds ◽  
Convective Heat Loss ◽  
Metabolic Heat ◽  
Solar Heat Gain

We report the first empirical data describing the interactive effects of simultaneous changes in irradiance and convection on energy expenditure by live mammals. Whole-animal rates of solar heat gain and convective heat loss were measured for representatives of two ground squirrel species, Spermophilus lateralis and Spermophilus saturatus, that contrast in coloration. Radiative heat gain was quantified as the decrease in metabolic heat production caused by the animal's exposure to simulated solar radiation. Changes in convective heat loss were quantified as the variation in metabolic heat production caused by changes in wind speed. For both species, exposure to 780 W m-2 of simulated solar radiation significantly reduced metabolic heat production at all wind speeds measured. Reductions were greatest at lower wind speeds, reaching 42% in S. lateralis and 29% in S. saturatus. Solar heat gain, expressed per unit body surface area, did not differ significantly between the two species. This heat gain equalled 14-21% of the radiant energy intercepted by S. lateralis and 18-22% of that intercepted by S. saturatus. Body resistance, an index of animal insulation, declined by only 10% in S. saturatus and 13% in S. lateralis as wind speed increased from 0.5 to 4.0 ms-1. These data demonstrate that solar heat gain can be essentially constant, despite marked differences in animal coloration, and that variable exposure to wind and sunlight can have important consequences for both thermoregulatory stress experienced by animals and their patterns of energy allocation.

Mechanisms of thermal stability during flight in the honeybee apis mellifera

1999 ◽  
Vol 202 (11) ◽  
pp. 1523-1533 ◽  
Author(s):  
S.P. Roberts ◽  
J.F. Harrison
Keyword(s):  
Thermal Stability ◽  
Heat Loss ◽  
Heat Production ◽  
Radiative Heat ◽  
Carbon Dioxide Production ◽  
Metabolic Heat Production ◽  
Evaporative Heat Loss ◽  
Radiative Heat Loss ◽  
Convective Heat Loss ◽  
Metabolic Heat

Thermoregulation of the thorax allows honeybees (Apis mellifera) to maintain the flight muscle temperatures necessary to meet the power requirements for flight and to remain active outside the hive across a wide range of air temperatures (Ta). To determine the heat-exchange pathways through which flying honeybees achieve thermal stability, we measured body temperatures and rates of carbon dioxide production and water vapor loss between Ta values of 21 and 45 degrees C for honeybees flying in a respirometry chamber. Body temperatures were not significantly affected by continuous flight duration in the respirometer, indicating that flying bees were at thermal equilibrium. Thorax temperatures (Tth) during flight were relatively stable, with a slope of Tth on Ta of 0.39. Metabolic heat production, calculated from rates of carbon dioxide production, decreased linearly by 43 % as Ta rose from 21 to 45 degrees C. Evaporative heat loss increased nonlinearly by over sevenfold, with evaporation rising rapidly at Ta values above 33 degrees C. At Ta values above 43 degrees C, head temperature dropped below Ta by approximately 1–2 degrees C, indicating that substantial evaporation from the head was occurring at very high Ta values. The water flux of flying honeybees was positive at Ta values below 31 degrees C, but increasingly negative at higher Ta values. At all Ta values, flying honeybees experienced a net radiative heat loss. Since the honeybees were in thermal equilibrium, convective heat loss was calculated as the amount of heat necessary to balance metabolic heat gain against evaporative and radiative heat loss. Convective heat loss decreased strongly as Ta rose because of the decrease in the elevation of body temperature above Ta rather than the variation in the convection coefficient. In conclusion, variation in metabolic heat production is the dominant mechanism of maintaining thermal stability during flight between Ta values of 21 and 33 degrees C, but variations in metabolic heat production and evaporative heat loss are equally important to the prevention of overheating during flight at Ta values between 33 and 45 degrees C.

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