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Purpose: The current study aimed to determine the effect of a synthetic-grass sport surface on core body temperature, skin temperature, heart rate, thermal sensation, thermal comfort, and rating of perceived exertion (RPE) during intermittent exercise in hot conditions. Methods: Using a randomized crossover design, 13 trained/developmental team-sport athletes completed two 50-minute standardized intermittent running protocols on a synthetic and a natural-grass surface, on separate days (control-condition air temperature 32.6 °C [1.3 °C], relative humidity 43.2% [5.3%]). Results: Final skin temperature was significantly higher on synthetic compared with natural grass at the calf (40.1 °C [2.5 °C] vs 33.4 °C [0.6 °C]; P <.001), shoulder (36.6 °C [1.7 °C] vs 33.7 °C [0.7 °C]; P <.001), and chest (33.2 °C [1.1 °C] vs 31.8 °C [1.2 °C]; P =.02). Thermal sensation (median: 2.3; interquartile range [0.5] vs 2.2 [0.5], P =.03) and sweat rate (1.5 [0.4] L·h−1 vs 1.2 [0.3] L·h−1; P =.02) were also significantly higher on synthetic grass. While final core body temperature was significantly higher on the natural than synthetic grass (38.4 °C [0.3 °C] vs 38.2 °C [0.4 °C]), there were no significant differences in delta core temperature, as well as heart rate, thermal comfort, or RPE. Conclusions: Higher skin temperatures, thermal sensation, and sweat rates suggest that exercising on synthetic grass in hot conditions may increase some markers of heat strain during exercise. However, delta core body temperature, heart rate, thermal comfort, and RPE remained unaffected. [ABSTRACT FROM AUTHOR]

Excessive solar radiation negatively affects cognitive performance. Occupational guidelines typically combine environmental components into one value, such as wet-bulb globe temperature (WBGT). Here, we evaluated cognitive performance in two similar 28.6 °C WBGT-effective (WBGTeff) that were designed differently; using high or low levels of solar radiation. Eight soldiers were exposed to a virtual-reality environment in a climate chamber set to high (900 Wm−2) or low solar radiation conditions (300 Wm−2). Soldiers walked 3 x 30 min at 5 kmh−1. Cognitive performance was evaluated using a virtual-reality scenario and a computerised test battery. There was no statistically significant effect of condition on the cognitive tasks (p > 0.05). Associations were found between mean body temperature (Tb) and visual detection (P ≤ 0.01). Differences in solar radiation with similar WBGTeff (28.6 °C) do not cause large systematic differences in cognitive performance. Certain aspects of cognitive performance (i.e. response inhibition) seem to be partly associated with Tb rather than solar radiation. Practitioner summary: Cognitive performance was evaluated in two similar WBGT conditions that were designed differently; using high or low levels of solar radiation. Differences in solar radiation with similar WBGT do not cause systematic differences in cognitive performance. Certain aspects of cognition were partly associated with mean body temperature rather than solar radiation. [ABSTRACT FROM AUTHOR]

The objective of our study was to assess the impact of heat stress on hydration and cognition among outdoor workers in hot environment. Area heat stress assessments were measured using Quest Temp WBGT monitor. Sweat rate for dehydration and reaction time for acute cognitive processing were recorded using standard procedures. Heat stress measurements ranged from 23.8 °C – 42 °C. More than 50 % of the workers had high sweat rate (>1.2 L/h) when exposed to high environmental temperatures. Positive correlation was obtained between WBGT, sweat rate and reaction time which indicates that hyperthermia has an impact on neural network processing. Heart rate and reaction time also increased with rise in WBGT and heavy physical activity. There was impairment of cognitive functions (reaction time) under heat stress conditions. Hence, reaction time can be used to assess the short-term impact of heat stress on neural modulation and will help to plan effective intervention strategies to reduce morbidity and mortality among workers. [ABSTRACT FROM AUTHOR]

Extreme heat events directly impact worker health and cause additional cascading and transitional workplace impacts. However, current investigations on these impacts often rely on specific datasets (e.g., compensation claims, hospitalizations). Thus, to continue to work towards preventing and mitigating the occupational risks posed by extreme heat events, this study aimed to explore the occupational impacts of the 2021 Heat Dome in Canada using a qualitative content analysis method on a news-based dataset. A systematized review of news articles published before, during, and after the 2021 Heat Dome was conducted on academic (n = 8) and news (n = 5) databases, along with targeted grey literature. Two researchers qualitatively coded the articles in NVivo for occupational impacts or references mentioned within the articles. Overall, 52 different occupations were identified as being impacted by the 2021 Heat Dome. Impacts were diverse and ranged from work cancellations or delays to work modifications and reports of heat-related illnesses. The 2021 Heat Dome impacted the health and safety of many occupational groups and provided new insights into the expanding impacts that extreme heat events can have on the Canadian workforce. With climate projections showing a growing trend of more hot days and intense heat waves in Canada, addressing these concerns should be a critical priority. [ABSTRACT FROM AUTHOR]

Purpose: To determine if the Physiological Strain Index (PSI), in original or modified form, can evaluate heat strain on a 0-10 scale, in trained and heat-acclimatized men undertaking a competitive half-marathon run in outdoor heat. Methods: Core (intestinal) temperature (TC) and heart rate (HR) were recorded continuously in 24 men (mean [SD] age = 26 [3] y, VO2peak = 59 [5] mL⋅kg⋅min-1). A total of 4 versions of the PSI were computed: original PSI with upper constraints of TC 39.5°C and HR 180 beats⋅min-1 (PSI39.5/180) and 3 modified versions of PSI with each having an age-predicted maximal HR constraint and graded TC constraints of 40.0°C (PSI40.0/PHRmax) 40.5°C (PSI40.5/PHRmax) and 41.0°C (PSI41.0/PHRmax). Results: In a warm (26.1-27.3°C) and humid (79-82%) environment, all runners finished the race asymptomatic in 107 (10) (91-137) min. Peak TC and HR were 39.7°C (0.5°C) (38.5-10.7°C) and 186 (6) (175-196) beats⋅min-1, respectively. In total, 63% exceeded TC 39.5°C, 71% exceeded HR 180 beats⋅min-1, and 50% exceeded both of the original PSI upper TC and HR constraints. The computed heat strain was significantly greater with PSI39.5/180 than all other methods (P <0.003). PSI >10 was observed in 63% of runners with PSI39.5/180, 25% for PSI40.0/PHRmax, 8% for PSI40.5/PHRmax, and 0% for PSI41.0/PHRmax. Conclusions: The PSI was able to quantify heat strain on a 0-10 scale in trained and heat-acclimatized men undertaking a half-marathon race in outdoor heat, but only when the upper TC and HR constraints were modified to 41.0°C and age-predicted maximal HR, respectively. [ABSTRACT FROM AUTHOR]

It is unclear whether men and women perceive thermal stress differently when changes in intestinal temperature (ΔTin) and metabolic heat production (MHprod) are matched between sexes during exercise hyperthermia. This study tested the hypothesis that females have enhanced sensitivity to comfort and perception of thermal stress during exercise hyperthermia in these conditions. We had 22 healthy active adults (11 males, 11 females; M age = 22.4 years, SD = 4.9 ; M height = 169 cm, SD = 7.6; M weight = 68.3 kg, SD = 13) exercise in random order, separated by at least three days at similar MHprod (M = 7.0 W/kg, SD = 1.5; p = 0.32) for 60 minutes on a cycle ergometer in cool (M = 24.00C, SD = 0.0; M = 14.4%Rh, SD = 3.6) and hot (M = 42.3°C, SD = 0.2; M = 10-60%Rh) environments with a progressive increase in humidity conditions. We measured ΔTin, and thermal stress indices for sensation (TS), comfort (TC), pleasantness (TP), and stickiness (S), feeling (FS scale), stress (visual analogue stress scale, VAS), focus (F) and felt arousal (FAS scale). We examined environmental conditions as wet bulb globe temperatures (WBGT). Males and females had similar increases in ΔTin (ME: WBGT; p < 0.0001), and both groups reported increased TS and TC and decreased TP (ME: WBGT, p ≤ 0.01). However, females reported that TS, TC, and TP, felt hotter overall, more uncomfortable, and more unpleasant, compared to males (ME: Sex; p < 0.04). Overall, females felt worse and were more stressed compared to males (ME: Sex; p ≤ 0.05). Females also reported greater internal focus as WBGT increased compared to males (I: WBGT × Sex; p < 0.003). Knowing that females perceive thermal stress during exercise hyperthermia to be hotter, more uncomfortable, more unpleasant, and more stressful compared to males can help coaches/trainers plan different exercise routines for exercisers of both sexes. [ABSTRACT FROM AUTHOR]

Sweating efficiency (SE) is essential for evaluating heat strain. The dripping of sweat off the skin surface of a nude subject occurs locally at an area where the secreted sweat exceeds the local evaporative capacity. However, in clothed subjects, "dripping" sweat is absorbed by clothing. In the present paper, the cooling efficiency of the sweating of a clothed subject is analyzed in relation to SE. First, typical patterns for the regional distribution of the sweat rate (SR) and the capacity of evaporation (CE) of a nude subject were introduced, and the dripping sweat rate was derived as a surplus of the SR over the CE; an equation of SE was derived from combinations of the two typical SR patterns and the uniform CE pattern. Then, the values of SE were calculated numerically, and the results were found to be approximately equal to those obtained experimentally by Alber--Wallerström & Holmér and theoretically from the equation of 1 - 0.5wsw² used in ISO7933. Based on these results, the SE was improved by arranging the distribution of the CE by controlling air velocities over the body surface. Further, the improved SE was found to contribute to the heat strain alleviation of clothed subjects. [ABSTRACT FROM AUTHOR]

Sweating efficiency (SE) is essential for evaluating heat strain. The dripping of sweat off the skin surface of a nude subject occurs locally at an area where the secreted sweat exceeds the local evaporative capacity. However, in clothed subjects, "dripping" sweat is absorbed by clothing. In the present paper, the cooling efficiency of the sweating of a clothed subject is analyzed in relation to SE. First, typical patterns for the regional distribution of the sweat rate (SR) and the capacity of evaporation (CE) of a nude subject were introduced, and the dripping sweat rate was derived as a surplus of the SR over the CE; an equation of SE was derived from combinations of the two typical SR patterns and the uniform CE pattern. Then, the values of SE were calculated numerically, and the results were found to be approximately equal to those obtained experimentally by Alber--Wallerström & Holmér and theoretically from the equation of 1 - 0.5wsw ² used in ISO7933. Based on these results, the SE was improved by arranging the distribution of the CE by controlling air velocities over the body surface. Further, the improved SE was found to contribute to the heat strain alleviation of clothed subjects. [ABSTRACT FROM AUTHOR]

Purpose: Current occupational heat stress guidelines rely on time-weighted averaging to quantify the metabolic demands of variable-intensity work. However, variable-intensity work may be associated with impairments in whole-body total heat loss (dry + evaporative heat loss), especially in older workers, which exacerbate heat strain relative to constant-intensity work eliciting the same time-weighted average metabolic rate. We, therefore, used direct calorimetry to evaluate whether variable-intensity work would cause decrements in the average rate of whole-body total heat loss that augment body heat storage and core temperature compared with constant-intensity work in young and older men. Methods: Eight young (19–31 yr) and eight older (54–65 yr) men completed four trials involving 90 min of work (cycling) eliciting an average metabolic heat production of ~200 W·m−2 in dry-heat (40°C, 20% relative humidity). One trial involved constant-intensity work (CON), whereas the others involved 10-min cycles of variable-intensity work: 5-min low-intensity and 5-min high-intensity (VAR 5:5), 6-min low-intensity and 4-min very high-intensity (VAR 6:4), and 7-min low- and 3-min very, very high-intensity (VAR 7:3). Metabolic heat production, total heat loss, body heat storage (heat production minus total heat loss), and core (rectal) temperature were measured throughout. Results: When averaged over each 90-min work period, metabolic heat production, total heat loss, and heat storage were similar between groups and conditions (all P ≥ 0.152). Peak core temperature (average of final 10 min) was also similar between groups and conditions (both P ≥ 0.111). CONCLUSIONS: Whole-body total heat loss, heat storage, and core temperature were not significantly influenced by the partitioning of work intensity in young or older men, indicating that time-weighted averaging appears to be appropriate for quantifying the metabolic demands of variable-intensity work to assess occupational heat stress. [ABSTRACT FROM AUTHOR]

Purpose: Time-weighted averaging is used in occupational heat stress guidelines to estimate the metabolic demands of variable-intensity work. However, compared to constant-intensity work of the same time-weighted average metabolic rate, variable-intensity work may cause decrements in total heat loss (dry + evaporative heat loss) that exacerbate heat storage in women. We therefore used direct calorimetry to assess whole-body total heat loss and heat storage (metabolic heat production minus total heat loss) in women and men during constant- and variable-intensity work of equal average intensity. Methods: Ten women [mean (SD); 31 (11) years] and fourteen men [30 (8) years] completed two trials involving 90-min of constant- and variable-intensity work (cycling) eliciting an average metabolic heat production of ~ 200 W/m2 in dry-heat (40 °C, ~ 15% relative humidity). External work was fixed at ~ 40 W/m2 for constant-intensity work, and alternated between ~ 15 and ~ 60 W/m2 (5-min each) for variable-intensity work. Results: When expressed as a time-weighted average over each work period, total heat loss did not differ between men and women (mean difference [95% CI]; 4 W/m2 [− 11, 20]; p = 0.572) or between constant- and variable-intensity work (1 W/m2 [− 3, 5]; p = 0.642). Consequently, heat storage did not differ significantly between men and women (− 4 W/m2 [− 17, 8]; p = 0.468) or between constant- and variable-intensity work (0 W/m2 [− 3, 3]; p = 0.834). Conclusion: Neither whole-body heat loss nor heat storage was modulated by the partitioning of work intensity, indicating that time-weighted averaging is appropriate for estimating metabolic demand to assess occupational heat stress in women. [ABSTRACT FROM AUTHOR]

Introduction: Research in occupational heat stress and heat strain in developing countries is limited because of several challenges and constraints. Objectives: To describe the prevalence of heat strains of diesel power plant operators and analyze the related factors. Method: Cross-sectional design has been carried out on the diesel power plant operators in the Indonesian state electricity company (N=35). The research variables consisted of heat strain, age, working period, nutritional status, hydration status and heat stress. Measuring instruments used consisted of a heat strain score index (HSSI), heat stress monitor, weight scale, microtoise, and questionnaire. Cramer’s V test and odds ratio were applied to see an association between heat strain prevalence and related factors. Results: 35.8% of diesel power plant operators experienced heat strain in the yellow zone/alarm category, 64.2% was included in the green zone/save category. The heat strain experienced by the operator was significantly related to age (p=0.000), years of service (p=0.000), hydration status (p=0.057) and heat stress (p=0.000). Conclusion: The occurrence of heat strains began to show the alarm stage, this requires efforts to control heat pressure and others variables in order to prevent the heat strain does not get worse. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effects of 60 min daily, short-term (STHA) and medium-term (MTHA) isothermic heat acclimation (HA) on the physiological and perceptual responses to exercise heat stress.Methods: Sixteen, ultra-endurance runners (female = 3) visited the laboratory on 13 occasions. A 45 min sub-maximal (40% Wmax) cycling heat stress test (HST) was completed in the heat (40 °C, 50% relative humidity) on the first (HSTPRE), seventh (HSTSTHA) and thirteenth (HSTMTHA) visit. Participants completed 5 consecutive days of a 60 min isothermic HA protocol (target Tre 38.5 °C) between HSTPRE and HSTSTHA and 5 more between HSTSTHA and HSTMTHA. Heart rate (HR), rectal (Tre), skin (Tsk) and mean body temperature (Tbody), perceived exertion (RPE), thermal comfort (TC) and sensation (TS) were recorded every 5 min. During HSTs, cortisol was measured pre and post and expired air was collected at 15, 30 and 45 min.Results: At rest, Tre and Tbody were lower in HSTSTHA and HSTMTHA compared to HSTPRE, but resting HR was not different between trials. Mean exercising Tre, Tsk, Tbody, and HR were lower in both HSTSTHA and HSTMTHA compared to HSTPRE. There were no differences between HSTSTHA and HSTMTHA. Perceptual measurements were lowered by HA and further reduced during HSTMTHA.Conclusion: A 60 min a day isothermic STHA was successful at reducing physiological and perceptual strain experienced when exercising in the heat; however, MTHA offered a more complete adaptation. [ABSTRACT FROM AUTHOR]

This study investigates indoor heat stress among employees engaged in bakeries in Assiut city. Heat stress is one of the occupational hazards especially in arid climates that impose negative impacts on workers such as heat rashes, heat exhaustion, heat cramps, heat fainting or heat stroke. In this research, 100 subjects were chosen randomly from 20 bakery stations to testify heat stress impacts. Heat stress levels were measured using wet-bulb globe temperature index (WBGT) to evaluate the impacts of environmental factors on the employees. The response of worker's body to this heat stress is expressed as physiological strain index (PSI) that can be estimated by measuring heart rate and core temperature. Results obtained from WBGT index measurements indicated that the average value of heat stress in bakeries reached 31.6 °C that is exceeding than threshold limit value (28 °C) and action limit (25 °C) recommended by American Conference of Government Industrial Hygienists. In addition, WBGT values were compared with the Egyptian Environmental Law 4/1994 and Egyptian Labor Low 12/2003. PSI values fall in the range of 200 < M (metabolic rate) < 260 indicating that workload in bakeries environment lies in the moderate class. According to the questionnaire data, several workers faced heat disorders including heat exhaustion (23 cases), heat cramps (17 cases), and heat stroke (5 cases). Application of control measures such as engineering control, administrative control, and personal protective equipment should be applied. [ABSTRACT FROM AUTHOR]

Introduction The study aimed to investigate how a distortion of perceived exertion in the heat may affect, during a self-paced cycling exercise preceded by prior cognitive task, the thermal perception and the subsequent regulation of power output in high level athletes. Methods Eleven endurance trained male athletes completed four experimental sessions including a 30-min fixed-RPE (15-Hard) cycling exercise in neutral (TMP-22 °C) and hot (HOT-37 °C) conditions, following a 60-min incongruent Stroop task (EXP) or passively watching documentary films (CON). Central and peripheral performances of the knee extensors were assessed before the cognitive task and after the exercise. Results Although mental demand and effort were higher in EXP ( P  < 0.05), no effect of prior cognitive task was observed on subjective feelings of mental fatigue or decline in power output at a fixed RPE. Average exercise intensity was lower in HOT than TMP (3.14 ± 0.09 W⋅kg −1 vs. 3.42 ± 0.10 W⋅kg −1 respectively, P  < 0.05). Skin temperature and warmth sensations were higher in HOT throughout the exercise ( P  < 0.05) but not thermal comfort. Central and peripheral parameters were not affected more in HOT than in TMP. Conclusion Although the effects of combined stressors on the distortion of perceived exertion could not be verified, the greater decline in power output recorded in HOT than TMP suggest a high contribution of both perceptual and cardiovascular responses in the regulation of work rate when the subject is in mild hyperthermia. [ABSTRACT FROM AUTHOR]

Objectives To provide a primer on the physical characteristics of heat from a biometeorological perspective for those interested in the epidemiology of extreme heat. Study design A literature search design was used. Methods A review of the concepts of heat, heat stress and human heat balance was conducted using Web of Sciences, Scopus and PubMed. Results Heat, as recognised in the field of human biometeorology, is a complex phenomenon resulting from the synergistic effects of air temperature, humidity and ventilation levels, radiation loads and metabolic activity. Heat should therefore not be conflated with high temperatures. A range of empirical, direct and rational heat stress indices have been developed to assess heat stress. Conclusion The conceptualisation of heat stress is best described with reference to the human heat balance which describes the various avenues for heat gain to and heat loss from the body. Air temperature alone is seldom the reason for heat stress and thus heat-related health effects. [ABSTRACT FROM AUTHOR]

Purpose: Heat strain is known to be exacerbated on the second of consecutive work days. We therefore evaluated whether prolonged work in the heat would impair whole-body heat loss capacity on the next day. Methods: To evaluate this possibility, we assessed changes in whole-body heat exchange and heat storage in eight young (26 ± 4 yr) men during heat stress tests performed on the same day before (day 1) and on the day after (day 2) a prolonged work simulation. Each heat stress test involved three, 30-min bouts of semirecumbent cycling at fixed rates of metabolic heat production (200 W⋅m-2 (Ex1), 250 W⋅m-2 (Ex2), and 300 W⋅m-2 (Ex3)), each separated by 15-min recovery, under hot, dry conditions (40°C, 20% relative humidity). The work simulation (7.5 h) involved three moderate-intensity intermittent work bouts (2 h), each separated by 30-min rest breaks, under similarly hot, dry conditions (38°C, 34% relative humidity). Total heat loss (evaporative ± dry heat exchange) and metabolic heat production were measured using direct and indirect calorimetry, respectively. Body heat storage was quantified as the temporal summation of heat production and loss. Results: Total heat loss did not differ between days 1 and 2 (P = 0.66) and averaged (mean ± 95% confidence interval) 185 ± 7W(Ex1), 233 ± 7W(Ex2), and 261 ± 5W(Ex3) across test days. Consequently, the change in body heat storage was also similar between days 1 and 2 (P = 0.32), averaging 133 ± 15 kJ (Ex1), 99 ± 16 kJ (Ex2), and 184 ± 15 kJ (Ex3) across test days. Conclusions: When assessed under controlled laboratory conditions in young men, prolonged work in the heat does not seem to impair whole-body heat loss or exacerbate heat storage on the following day. [ABSTRACT FROM AUTHOR]

Purpose We evaluated physiological responses during exercise at a fixed evaporative requirement for heat balance (Ereq) but varying combinations of metabolic and environmental heat load. Methods Nine healthy, physically active males (age: 46±8 years) performed four experimental sessions consisting of 75-min of semi-recumbent cycling at various ambient temperatures. Whole-body dry heat loss (direct calorimetry) was monitored continuously as was heat production (indirect calorimetry), which was adjusted to achieve an Ereq of 400 W. The resultant metabolic heat productions and ambient temperatures for the sessions were: i) 442 W and 30°C (440[30]), ii) 388 W and 35°C (388[35]), iii) 317 W and 40°C (317[40]) and iv) 258 W and 45°C (258[45]). Whole-body evaporative heat loss was determined via direct calorimetry. Esophageal (Tes) and mean skin (Tsk) temperatures as well as heart rate (HR) were monitored continuously. Mean body temperature (Tb) was calculated from Tes and Tsk. Physiological strain index (PSI) was determined from Tes and HR. RESULTS End-exercise evaporative heat loss and Tb were similar between conditions (both P≥0.48). Tes was greater in 440[30] (37.67±0.04°C) and 388[35] (37.58±0.07°C) relative to both 317[40] (37.35±0.06°C) and 258[45] (37.20±0.07°C; all P≤0.05). Further, Tsk was different between each condition (440[30]: 33.85±0.16°C; 388[35], 34.53±0.08°C; 317[40]: 35.67±0.07°C; and 258[45]: 36.54±0.08°C; all P<0.01). In 440[30], HR was elevated by ~13 and ~18 beats•min relative to 317[40] and 258[45], respectively (both P<0.01). Finally, PSI was greater in both 440[30] and 388[35] compared with 317[40] and 258[45] (all P≤0.04). CONCLUSIONS Exercise at a fixed Ereq resulted in similar evaporative heat loss and Tb. However, the Tes, Tsk, HR and PSI responses varied depending on the relative contribution of metabolic and environmental heat load. [ABSTRACT FROM AUTHOR]

BACKGROUND: Many research studies require recruiting heat-acclimatized workers to participate in heat-stress experiments and application fields. A reliable heat acclimatization program for workers in countries with hot environments has not been reported yet. OBJECTIVE: The objective of this studywas to estimate the effects of heat stress and the amount of acclimatization required in hot-climate countries. METHODS: Eighteen male workers from an industrial population participated in this experiment. Nine days of exposure to a hot environment (wet-bulb globe temperature, 30°C) was the independent variable. The participants' cardiac costs and increment aural-canal temperatures were the dependent variables. RESULTS: The study results revealed that 5 days of exposure to heat sessions were sufficient to heat acclimatize the workers based on their physiological responses (i.e., heart rate and aural-canal temperature). CONCLUSIONS: According to the available literature, workers in hot climate countries, similar to the study cohort, can heat acclimatize faster than those in other Western countries. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the effectiveness of a newly designed construction uniform in combating heat stress. Ten male volunteers performed treadmill running in a climatic chamber maintained at 34.5 °C temperature, 75% relative humidity, 0.3 m/s air velocity, and solar radiation of 450 W/m(2) that simulates typical summer working environment of construction sites in Hong Kong. The participants were tested while wearing two kinds of construction uniforms: a commonly worn uniform A, or a newly designed uniform B. It was found during exercise that Tc (38.34 ± 0.14 vs 38.45 ± 0.11 °C, p = 0.03), Tsk (36.01 ± 0.36 vs 36.27 ± 0.34 °C, p = 0.03), HR (162.7 ± 10.1 vs 172.5 ± 9.2 bpm, p < 0.01), PSI (7.0 ± 0.4 vs 7.5 ± 0.5, p = 0.04), thermal sensation (1.7 ± 0.9 vs 2.6 ± 0.7, p = 0.02), and wetness sensation (1.9 ± 0.9 vs 2.6 ± 0.8, p < 0.01) was lower when wearing uniform B than that of uniform A. It was found during recovery that Tc (37.89 ± 0.13 vs 38.06 ± 0.13 °C, p < 0.01), Tsk (35.68 ± 0.37 vs 36.02 ± 0.41 °C, p < 0.01), HR (104.2 ± 10.1 vs 112.6 ± 10.7 bpm, p < 0.01), PSI (3.3 ± 0.7 vs 4.1 ± 1.0, p < 0.01), thermal sensation (0.1 ± 0.9 vs 1.0 ± 0.8, p = 0.02), and wetness sensation (1.1 ± 1.0 vs 2.3 ± 0.8, p = 0.02) was lower when wearing uniform B than that of uniform A. The findings of this study suggested the newly designed construction uniform could reduce thermoregulatory and cardiovascular strain, and improve thermal comfort while exercising in a hot and humid environment. [ABSTRACT FROM AUTHOR]

Motorcycle protective clothing can be uncomfortably hot during summer, and this experiment was designed to evaluate the physiological significance of that burden. Twelve males participated in four, 90-min trials (cycling 30 W) across three environments (25, 30, 35 °C [all 40% relative humidity]). Clothing was modified between full and minimal injury protection. Both ensembles were tested at 25 °C, with only the more protective ensemble investigated at 30 and 35 °C. At 35 °C, auditory canal temperature rose at 0.02 °C min−1(SD 0.005), deviating from all other trials (p < 0.05). The thresholds for moderate (>38.5 °C) and profound hyperthermia (>40.0 °C) were predicted to occur within 105 min (SD 20.6) and 180 min (SD 33.0), respectively. Profound hyperthermia might eventuate in ~10 h at 30 °C, but should not occur at 25 °C. These outcomes demonstrate a need to enhance the heat dissipation capabilities of motorcycle clothing designed for summer use in hot climates, but without compromising impact protection. Practitioner’s Summary: Motorcycle protective clothing can be uncomfortably hot during summer. This experiment was designed to evaluate the physiological significance of this burden across climatic states. In the heat, moderate (>38.5 °C) and profound hyperthermia (>40.0 °C) were predicted to occur within 105 and 180 min, respectively. [ABSTRACT FROM PUBLISHER]

The aim of the study was to identify whether a ventilation cooling shirt was effective in reducing heat strain in a hot climate. Eight female volunteers were exposed to heat (38 °C, 45% relative humidity) for 2 h with simulated office work. In the first hour they were in normal summer clothes (total thermal insulation 0.8 clo); in the second hour a ventilation cooling shirt was worn on top. After the shirt was introduced for 1 h, the skin temperatures at the scapula and the chest were significantly reduced (p < 0.05). The mean skin and core temperatures were not reduced. The subjects felt cooler and more comfortable by wearing the shirt, but the cooling effect was most conspicuous only during the initial 10 min. The cooling efficiency of the ventilation shirt was not very effective under the low physical activity in this hot climate. [ABSTRACT FROM AUTHOR]

Background: Explosive ordnance disposal (EOD) technicians are often required to wear specialized clothing combinations that not only protect against the risk of explosion but also potential chemical contamination. This heavy (>35kg) and encapsulating ensemble is likely to increase physiological strain by increasing metabolic heat production and impairing heat dissipation. This study investigated the physiological tolerance times of two different chemical protective undergarments, commonly worn with EOD personal protective clothing, in a range of simulated environmental extremes and work intensities Methods: Seven males performed 18 trials wearing 2 ensembles. The trials involved walking on a treadmill at 2.5, 4, and 5.5 km h-1 at each of the following environmental conditions, 21, 30, and 37°C wet bulb globe temperature. The trials were ceased if the participants' core temperature reached 39°C, if heart rate exceeded 90% of maximum, if walking time reached 60min or due to volitional fatigue. Results: Physiological tolerance times ranged from 8 to 60min and the duration (mean difference: 2.78min, P > 0.05) were similar in both ensembles. A significant effect for environment (21 > 30 > 37°C wet bulb globe temperature, P < 0.05) and work intensity (2.5 > 4 > 5.5 km h-1, P < 0.05) was observed in tolerance time. The majority of trials across both ensembles (101/126; 80.1%) were terminated due to participants achieving a heart rate equivalent to greater than 90% of their maximum. Conclusions: Physiological tolerance times wearing these two chemical protective undergarments, worn underneath EOD personal protective clothing, were similar and predominantly limited by cardiovascular strain. [ABSTRACT FROM AUTHOR]

Elderly indoors can be subject to considerable heat strain during heat waves. We investigated if a short indoor acclimation (HA) program leads to improved resilience to heat. Although full HA takes about ten days, the main changes occur in the first days, leading to reduced heat strain with similar stress. This study investigates changes after 3 days HA in 8 elderly (>75 y) and 8 young (20–30 y) females. The pre-test (Monday) and post-test (Friday) was a 20-min 50 W cycle exercise test in 35 °C/40% relative humidity (RH); the indoor preparation program or HA consisting of one hour exercise in the same climate aimed at reaching a gastrointestinal temperature ( T gi ) of 38 °C. HA did not result in any changes in T gi , mean skin temperature, heart rate, weight loss or thermal sensation. The elderly felt more fatigued but evaporated 28% less sweat than the young group during the tests. We conclude that 3-day HA for one hour daily is insufficient to cause physiological benefits in young and elderly females. [ABSTRACT FROM AUTHOR]

The purpose of this study was to develop a body characteristic index (BCI) based on the distribution of maximal oxygen uptake per body mass (VO2max/mass), body surface area per body mass (BSA/mass), and percentage of body fat (Fat%) to evaluate the relative level of individual physiological responses to heat strain in a group of workers. BCI was based upon the data obtained from 10 males and 10 females exercising for 60 min on a treadmill at 2 relative exercise intensities of 25% and 45% VO2max in mild, warm wet, and hot dry climate condition, separately. BCI was developed into 2 formulas, which were proved to be better predictors for heat strain responses than each individual characteristic, and more sensitive than body type to describe the distributions of individual characteristics and distinguish the differences in physiological responses to heat. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the components contributions of personal protective equipment on physiological strain in firefighters during exercise and recovery. Eight firefighters participated in trials in which various combinations of personal protective equipment components weighing from 1.3 to 15.1 kg were worn. The results showed that rectal temperature, changes in rectal temperature, mean skin temperature, heart rate, oxygen consumption and blood lactate concentration were smaller in conditions without boots (no-boots) than in other conditions with no helmet, gloves or self-contained breathing apparatus (P < 0.05). Increases in rectal temperature per unit mass of personal protective equipment were approximately twice as small in no-boots condition as the other conditions. These results suggest that the reduction of the boots' mass might be more efficient to alleviate heat strain of firefighters wearing personal protective equipment, rather than the reduction of the mass of self-contained breathing apparatus, helmet or gloves. Practitioner Summary:As firefighters' protective boots induce greater physiological burden when compared with a helmet, gloves or self-contained breathing apparatus, personal protective equipment designers need to consider the improvement of boots in terms of mass reduction, improvement of thermal comfort and ease of doffing during recovery to alleviate physiological strain on firefighters. [ABSTRACT FROM PUBLISHER]

The article reports on research which was conducted to investigate thermoregulatory, cardiovascular and perceptual response to intermittent cooling during exercise in a hot, humid outdoor environment. Researchers evaluated intermittent cooling with 10 healthy male subjects. They found that intermittent cooling was effective in reducing skin temperature but did not sufficiently reduce core body temperature or cardiovascular strain.

The article discusses the impact of climate change to the productivity of the workers in harvesting rice in India. It highlights the effect of heat exposure to the workers including high risk of heat stroke and limit work productivity. It notes that heat exposure contributes to the impairment of human physiological function and health.

Background: Heat exposure among construction workers in the Persian Gulf region is a serious hazard for health. The aim of this study was to evaluate the performance of wet bulb globe temperature (WBGT) Index for estimation of heat strain in hot/humid conditions by the use of Physiological Strain Index (PSI) as the gold standard. Material and Methods: This cross‑sectional study was carried out on 71 workers of two Petrochemical Companies in South of Iran in 2010 summer. The WBGT index, heart rate, and aural temperature were measured by Heat Stress Monitor (Casella Microtherm WBGT), Heart Rate Monitor (Polar RS100), and Personal Heat Strain Monitor (Questemp II), respectively. The obtained data were analyzed with descriptive statistics and Pearson correlation analysis. Results: The mean (SD) of WBGT values was 33.1 (2.7). The WBGT values exceed from American Conference of Governmental Industrial Hygienists (ACGIH) standard (30°C) in 96% work stations, whereas the PSI values were more than 5.0 (moderate strain) in 11% of workstations. The correlation between WBGT and PSI values was 0.61 (P = 0.001). When WBGT values were less and more than 34°C, the mean of PSI was 2.6 (low strain) and 5.2 (moderate strain), respectively. Conclusion: In the Persian Gulf weather, especially hot and humid in the summer months, due to the WBGT values exceeding 30°C (in 96% of cases) and weak correlation between WBGT and PSI, the work/rest cycles of WBGT Index is not suitable for heat stress management. Therefore, in Persian Gulf weather, heat stress evaluation based on physiologic variables may have higher validity than WBGT index. [ABSTRACT FROM AUTHOR]

Body ventilation systems (BVS) are effective in reducing heat strain, but the amount of heat that a BVS removes from a human body is unclear. The purpose of this study was to propose a method for quantifying BVS cooling capacity using manikin evaluation and modeling. Cooling capacity was calculated as the product of maximum cooling potential and cooling efficiency. The maximum cooling potential is calculated as the difference in enthalpy between the air entering and exiting the BVS where the outlet air temperature is equal to skin temperature with a relative humidity of 100%. The cooling efficiency, defined as a ratio of the cooling capacity to the maximum cooling potential, can be determined through measurements on sweating thermal manikins. A BVS system was evaluated on a manikin with the ventilation fan ON (flow rate 4.7 L/s) or OFF under eleven ambient conditions. The measured cooling efficiencies were 0.31 ± 0.02 and almost constant. Using this cooling efficiency, the BVS cooling capacities at various skin temperature and ambient conditions were estimated. This two-step approach can be used to quantify BVS cooling effectiveness during physiology studies. First, the cooling efficiency is determined on sweating thermal manikins. Second, the cooling capacity is calculated from the skin temperature, ambient temperature and relative humidity. However, various factors may reduce the actual cooling provided by the BVS, and the calculated cooling capacity should be considered the upper limit for cooling. [ABSTRACT FROM AUTHOR]

Heat acclimation (HA) often starts in a moderately hot environment to prevent thermal overload and stops immediately prior to athletic activities. The aims of this study were 1) to establish whether acclimation to a moderately hot climate is sufficient to provide full acclimation for extreme heat and 2) to investigate the physiological responses to heat stress during the HA decay period. 15 male subjects exercised for 9 consecutive days at 26°C Wet Bulb Globe Temperature (WBGT) and 3 days at 32°C WBGT on a cycle ergometer for up to 2 h per day and repeated the exercise 3, 7 and 18 days later in 26°C WBGT. Rectal temperature (Tre) and heart rate (HR) were measured during 60 min of steady state exercise (~45% of maximum oxygen uptake). During days 1-9, end-exercise Tre was reduced from 38.7 ± 0.1 to a plateau of 38.2 ± 0.1°C (p < 0.05), HR was reduced from 156 ± 10 to 131 ± 11 bpm (p < 0.05). No changes in HR and Tre occurred during the 3 days in the very hot environment. However, Tre during rest and exercise were significantly lower by 0.4 - 0.5°C after HA compared with day 9, suggesting that heat acclimation did not decay but resulted in further favourable adaptations. [ABSTRACT FROM AUTHOR]

A previous study by the authors using a heated thermal manikin showed that the cooling rates of phase change material (PCM) are dependent on temperature gradient, mass, and covering area. The objective of this study was to investigate if the cooling effects of the temperature gradient observed on a thermal manikin could be validated on human subjects in extreme heat. The subjects wore cooling vests with PCMs at two melting temperatures (24 and 28°C) and fire-fighting clothing and equipment, thus forming three test groups (vest24, vest28 and control group without the vest). They walked on a treadmill at a speed of 5 km/h in a climatic chamber (air temperature = 55°C, relative humidity = 30%, vapour pressure = 4,725 Pa, and air velocity = 0.4 m/s). The results showed that the PCM vest with a lower melting temperature (24°C) has a stronger cooling effect on the torso and mean skin temperatures than that with a higher melting temperature (28°C). Both PCM vests mitigate peak core temperature increase during the resting recovery period. The two PCM vests tested, however, had no significant effect on the alleviation of core temperature increase during exercise in the heat. To study the possibility of effective cooling of core temperature, cooling garments with PCMs at even lower melting temperatures (e.g. 15°C) and a larger covering area should be investigated. [ABSTRACT FROM AUTHOR]

Heat strain in chemical protective clothing is an important factor in industrial and military practice. Various improvements to the clothing to alleviate strain while maintaining protection have been attempted. More recently, selectively permeable membranes have been introduced to improve protection, but questions are raised regarding their effect on heat strain. In this paper the use of selectively permeable membranes with low vapour resistance was compared to textile-based outer layers with similar ensemble vapour resistance. For textile-based outer layers, the effect of increasing air permeability was investigated. When comparing ensembles with a textile vs. a membrane outer layer that have similar heat and vapour resistances measured for the sum of fabric samples, a higher heat strain is observed in the membrane ensemble, as in actual wear, and the air permeability of the textile version improves ventilation and allows better cooling by sweat evaporation. For garments with identical thickness and static dry heat resistance, but differing levels of air permeability, a strong correlation of microclimate ventilation due to wind and movement with air permeability was observed. This was reflected in lower values of core and skin temperatures and heart rate for garments with higher air permeability. For heart rate and core temperature the two lowest and the two highest air permeabilities formed two distinct groups, but they did not differ within these groups. Based on protection requirements, it is concluded that air permeability increases can reduce heat strain levels allowing optimisation of chemical protective clothing. Statement of Relevance: In this study on chemical, biological, radiological and nuclear (CBRN) protective clothing, heat strain is shown to be significantly higher with selectively permeable membranes compared to air permeable ensembles. Optimisation of CBRN personal protective equipment needs to balance sufficient protection with reduced heat strain. Using selectively permeable membranes may optimise protection but requires thorough consideration of the wearer's heat strain. [ABSTRACT FROM AUTHOR]

We compared the effects of an ice-slush beverage (ISB) and a cool liquid beverage (CLB) on cycling performance, changes in rectal temperature (T (re)) and stress responses in hot, humid conditions. Ten trained male cyclists/triathletes completed two exercise trials (75 min cycling at ~60% peak power output + 50 min seated recovery + 75% peak power output × 30 min performance trial) on separate occasions in 34°C, 60% relative humidity. During the recovery phase before the performance trial, the athletes consumed either the ISB (mean ± SD -0.8 ± 0.1°C) or the CLB (18.4 ± 0.5°C). Performance time was not significantly different after consuming the ISB compared with the CLB (29.42 ± 2.07 min for ISB vs. 29.98 ± 3.07 min for CLB, P = 0.263). T (re) (37.0 ± 0.3°C for ISB vs. 37.4 ± 0.2°C for CLB, P = 0.001) and physiological strain index (0.2 ± 0.6 for ISB vs. 1.1 ± 0.9 for CLB, P = 0.009) were lower at the end of recovery and before the performance trial after ingestion of the ISB compared with the CLB. Mean thermal sensation was lower (P < 0.001) during recovery with the ISB compared with the CLB. Changes in plasma volume and the concentrations of blood variables (i.e., glucose, lactate, electrolytes, cortisol and catecholamines) were similar between the two trials. In conclusion, ingestion of ISB did not significantly alter exercise performance even though it significantly reduced pre-exercise T(re) compared with CLB. Irrespective of exercise performance outcomes, ingestion of ISB during recovery from exercise in hot humid environments is a practical and effective method for cooling athletes following exercise in hot environments. [ABSTRACT FROM AUTHOR]

This study tested a new portable cooling device for fire fighting recovery. Participants (N = 8) walked and did arm curls (time-weighted VO2: 1.6 L· min-1 on a treadmill for 40 min in a heated chamber (wet bulb globe temperature: 33.7°C; relative humidity: 40-45%) while wearing firefighter turn-out gear and self-contained breathing apparatus (SCBA). Immediately on finishing exercise, participants recovered for 40 min with either a hand-cooling device or seated passive recovery at an ambient temperature of 22°C, 35% RH in a repeated-measures counterbalanced design. The cooling device had little impact on recovery during the first 30 min; however, compared with passive cooling, the cooling device resulted in significantly lower rectal temperature (Tre) during the last 10 min. Relative to starting Tre of the recovery period, ΔTre at 35 min had fallen 0.51 ± 0.19°C (passive) and 0.76 ± 0.30°C (active) (p = 0.03); and at 40 min ΔTre had fallen 0.63 ± 0.17°C (passive) and 0.88 ± 0.31°C (active) (p = 0.03). Cooling capacity of the device calculated from ΔTre over the whole recovery period averaged about 144% of passive. Reductions in heat storage enhance worker safety and performance in hot environments. [ABSTRACT FROM AUTHOR]

• A hybrid cooling system HYB incorporated with dry ice and ventilation was developed. • HYB's cooling performance was examined and compared with a water-cooling suit WCS. • Both HYB and WCS prevented core temperature from rising >38.0 °C throughout 60-min trials. • HYB and WCS significantly improved thermophysiological and perceptual responses. • HYB's total weight gradually reduced due to dry ice sublimation, thereby it helped mascot actors to alleviate heat strain. Mascot actors have to wear bulky, heavy and low permeability costumes during a performance. Documented work and headline news have consistently demonstrated that severe heat illnesses associated with mascot costumes are the major health problem among mascot actors. Though various personal cooling systems (PCSs) have been developed to mitigate the heat stress of people wearing protective clothing, no research has been reported on the actual cooling benefit of using PCSs under mascot costumes. Thus, in this work, a newly developed hybrid personal cooling suit based with dry ice and ventilation fans (HYB), and a water-cooling suit (WCS) were chosen to examine their actual cooling performances on mascot actors while performing a moderate activity in a hot and humid condition (i.e., 34 ± 0.5°C, RH = 78 ± 5%, wet-bulb globe temperature [WBGT] = 31.8°C). The total trial duration was 60 min, which comprised 40-min walking at 4.0 km/h followed by 20-min resting at room temperature (i.e., 24 ± 1 °C, RH = 55 ± 5%, WBGT = 20.1 °C). The present study showed that both HYB and WCS successfully prevented the core temperature of mascot wearers from rising above 38.0 °C throughout the 60-min trials. In contrast, the wearers' core temperature reached 38.0°C in about 35 min in CON (i.e., CONTROL, no cooling). HYB and WCS could also bring remarkable cooling to the body surface so that mean skin temperatures stayed <36.5 °C. Moreover, both HYB and WCS decreased the total sweat production by over 34.2–46.0% compared to CON. Heart rates in HYB and WCS were also decreased by 12 and 20 beats/min compared to that of CON. Therefore, physiological strain index and perceptual responses have been greatly improved by using HYB and WCS. It is thus concluded that the two cooling suits can be used to mitigate heat stress on mascot wearers during a one-hour performance in the studied condition. It was noted that the cooling performance of WCS was greatly deteriorated approaching the end of the trials. Thus, mascot actors are advised to replace cooling sources during the resting period in order to ensure the WCS suit could still bring pronounced body cooling benefits for upcoming work-rest cycles. [ABSTRACT FROM AUTHOR]