Heat strain of Japanese firefighters wearing personal protective equipment: a review for developing a test method

The aim of this review was to develop a test method for the evaluation of heat strain for structural firefighters wearing personal protective equipment (PPE) in Japan. We analysed a series of our laboratory's questionnaires and experimental studies and reviewed international standards on test methods. We investigated the actual average working conditions (total firefighting time on one incidence, working time with full PPE, maximum temperature and humidity during firefighting) at structural firefighting site in Japan by conducting a large-scale questionnaire survey of Japanese firefighters. We discussed test subjects (firefighters vs. non-firefighters; body size; physical fitness), exercise intensity (absolutes vs. relative; light vs. heavy) and duration, experimental temperature and relative humidity, experimental clothing items including station uniforms (shorts vs. long), and measurement variables (physiological and subjective responses), and suggested a standard test method to evaluate the heat strain of firefighters in hot and humid environments.Practitioner summary: We reviewed studies on human wear trials of firefighting personal protective equipment (PPE) in hot environments and suggested a standard test method to evaluate the heat strain of firefighters. The test method can be internationally utilised to examine the comfort functions and heat stress of PPE in hot, humid environments.

How humans adapt to hot climates learned from the recent research on tropical indigenes

This review mainly aimed to introduce the findings of research projects comparing the responses of tropical and temperate indigenes to heat. From a questionnaire survey on thermal sensation and comfort of Indonesians and Japanese, we found that the thermal descriptor “cool” in tropical indigenes connotes a thermally comfortable feeling, suggesting that linguistic heat acclimatization exists on a cognitive level. Ten male students born and raised in Malaysia were invited to Fukuoka, Japan, and compared their responses with 10 Japanese male students with matched physical fitness and morphological characteristics. Cutaneous thermal sensitivity: The sensitivities were measured at 28 °C. The forehead warm sensitivity was significantly blunted in Malaysians. The less sensitivity to the warmth of tropical indigenes is advantageous in respect to withstanding heat stress with less discomfort and a greater ability to work in hot climates. Passive heat stress: Thermoregulatory responses, especially sweating, were investigated, during the lower leg hot bathing (42 °C for 60 min). The rectal temperature at rest was higher in Malaysians and increased smaller during immersion. There was no significant difference in the total amount of sweating between the two groups, while the local sweating on the forehead and thighs was lesser in Malaysians, suggesting distribution of sweating was different from Japanese. Exercise: Malaysian showed a significantly smaller increase in their rectal temperature during 55% maximal exercise for 60 min in heat (32 °C 70% relative humidity), even with a similar sweating and skin blood flow response in Japanese. The better heat tolerance in Malaysians could be explained by the greater convective heat transfer from the body core to the skin due to the greater core-to-skin temperature gradient. In addition, when they were hydrated, Malaysian participants showed better body fluid regulation with smaller reduction in plasma volume at the end of the exercise compared to the non-hydrated condition, whereas Japanese showed no difference between hydration conditions. We further investigated the de-acclimatization of heat adaptation by longitudinal observation on the heat tolerance of international students who had moved from tropical areas to Fukuoka for several years.

A review of test methods for evaluating mobility of firefighters wearing personal protective equipment

This review aimed to suggest useful, potential measurements as standard test methods for evaluating the mobility of structural firefighters wearing personal protective equipment (PPE). Based on our previous research on Japanese firefighters' activities related to mobility as well as previous literature results, the findings were categorized (e.g., simulated firefighting activities, test method for mobility assessment, and participants groups), and discussed. We identified four categories that can be used to test and evaluate mobility: (1) simulated firefighting activities consisting of step-ups, obstacle strides, crawling, dragging, and jumping; (2) in terms of balance ability, the postural sway and functional balance tests (functional reach and timed up and go) were useful measurements; (3) range of motion can be used to estimate the mobility associated with the various designs of PPE, as well as the effect of wearing the PPE itself; and (4) subjective evaluations of individuals wearing PPE were available for the mobility assessments. Professional firefighters who were familiar with wearing PPE were suitable for the suggested test method. This review provides useful information for firefighters, researchers, and PPE manufacturers that can be used to develop more comfortable and safer PPE.

A review of Japanese-style bathing: its demerits and merits

Japanese-style bathing (JSB), which involves soaking in hot water up to the shoulders in deep bathtubs for a long time in the evening to night, is unique. Many experimental and epidemiological studies and surveys have shown that JSB improve sleep quality, especially shortens sleep onset latency in winter. In addition, repeated JSB lead the improvement of depressive symptoms. JSB is a simple and low-cost non-pharmacological measure to sleep difficulty in winter and mental disorders, especially for the elderly. On the contrary, drowning, while soaking in a bathtub, is the most common of accidental death at home in Japan. It is estimated that approximately 19,000 Japanese individuals die annually while taking a bath, mostly during winter, and most victims are elderly people. Elderly Japanese people tend to prefer a higher-risk JSB because the temperature inside the house during winter, especially the dressing room/bathroom temperature, is very low. Since the physiological thermal effect of the elderly associated with bathing is relatively lower among the elderly than the young, the elderly prefer to take a long hot bath. This elderly’s favorite style of JSB results in larger increased blood pressure in dressing rooms and larger decreased in blood pressure during hot bathing. A sudden drop in blood pressure while immersed in the bathtub leads to fainting and drowning. Furthermore, elderly people are less sensitive to cold air or hot water, therefore, it is difficult to take appropriate measures to prevent large fluctuations in blood pressure. To ensure a safe and comfortable winter bathing, the dressing room/bathroom temperature needs to be maintained at 20 °C or higher, and several degrees higher would be recommended for the elderly.

Thermoregulatory and cardiovascular responses in the elderly towards a broad range of gradual air temperature changes

This study aimed to determine age-related differences in thermoregulatory and cardiovascular responses to a wide range of gradual ambient temperature (T_a) changes. Morphologically matched normotensive elderly and young males participated. The participants wearing only shorts rested during the 3-h experiment. After 30 min of baseline at 28 °C, T_a increased linearly to 43 °C in 30 min (warming) and then gradually decreased to 13 °C in 60 min (cooling). T_a was rewarmed to 28 °C in 30 min (rewarming), and that temperature was maintained for an additional 30 min (second baseline). During the warming phase, there were no age-related differences in blood pressure (BP) and rectal temperature (T_re), despite a significantly lower cutaneous vascular conductance and heart rate in the elderly (P < 0.05). At the end of the cooling phase, systolic blood pressure (SBP) in the elderly was significantly higher than the young (155.8 ± 16.1 and 125.0 ± 12.5 mmHg, P < 0.01). There was a consistent age group difference in SBP during rewarming. Mean skin temperature was significantly lower in the elderly during rewarming (P < 0.05). T_re decreased more in the elderly and was significantly lower at the end of the experiment than the younger participants (36.78 ± 0.34 and 37.01 ± 0.15 °C, P < 0.05). However, there were no age group differences in thermal sensation. In conclusion, even normotensive elderly participants have a greater and more persistent BP response to cold than younger adults, suggesting that the elderly might be at a higher risk of cardiac events during cooling and subsequent rewarming.

Effect of repeated forearm muscle cooling on the adaptation of skeletal muscle metabolism in humans

This study aimed to investigate the effect of repeated cooling of forearm muscle on adaptation in skeletal muscle metabolism. It is hypothesized that repeated decreases of muscle temperature would increase the oxygen consumption in hypothermic skeletal muscle. Sixteen healthy males participated in this study. Their right forearm muscles were locally cooled to 25 °C by cooling pads attached to the skin. This local cooling was repeated eight times on separate days for eight participants (experimental group), whereas eight controls received no cold exposure. To evaluate adaptation in skeletal muscle metabolism, a local cooling test was conducted before and after the repeated cooling period. Change in oxy-hemoglobin content in the flexor digitorum at rest and during a 25-s isometric handgrip (10% maximal voluntary construction) was measured using near-infrared spectroscopy at every 2 °C reduction in forearm muscle temperature. The arterial blood flow was occluded for 15 s by upper arm cuff inflation at rest and during the isometric handgrip. The oxygen consumption in the flexor digitorum muscle was evaluated by a slope of the oxy-hemoglobin change during the arterial occlusion. In the experimental group, resting oxygen consumption in skeletal muscle did not show any difference between pre- and post-intervention, whereas muscle oxygen consumption during the isometric handgrip was significantly higher in post-intervention than in pre-test from thermoneutral baseline to 31 °C muscle temperature (P < 0.05). This result indicated that repeated local muscle cooling might facilitate oxidative metabolism in the skeletal muscle. In summary, skeletal muscle metabolism during submaximal isometric handgrip was facilitated after repeated local muscle cooling.

Effect of water bath temperature on physiological parameters and subjective sensation in older people

AIM

In Japan, the incidence of water bathing-related cardiopulmonary accidents among older people is high in winter. The purpose of the present study was to investigate alterations in physiological characteristics and subjective thermal sensations of older people when bathing in a cool environment.

METHODS

We assessed the skin temperature, rectal temperature, blood pressure, pulse rate, body fluid loss (sweat and urine), and subjective thermal responses of 11 older healthy male and 10 young male volunteers throughout 42°C and 39°C bathing in a room at 20°C with 50% humidity.

RESULTS

At 42°C bathing, the rectal temperature during bathing and in the post-bathing period were significantly lower in the older men than in the young men, and skin temperature during the post-bathing period decreased gradually in the older men. Systolic blood pressure and pulse rate immediately increased just after entering 42°C water and decreased during bathing in the older men. With the activities of dressing, systolic blood pressure increased followed by a decrease during the post-bathing period. Thus, double product (pulse rate × systolic blood pressure) increased during the bathing period. Although there was no significant difference in body fluid loss between the older and younger men in 42°C water, the older men produced significantly less sweat. The older men also reported feeling less warm after 42°C bathing, and feeling less cold during the post-bathing period after 39°C bathing.

CONCLUSIONS

These results suggest that hot water bathing during cold seasons might induce more serious physiological changes in older people. Geriatr Gerontol Int 2017; 17: 2164-2170.

Cognitive performance during passive heat exposure in Japanese males and tropical Asian males from Southeast Asian living in Japan

Background

Heat acclimatization studies have reported that tropical natives have better physiological function to tolerate heat exposure compared to those from temperate natives, in which may result in a better ability to show a better resistance to performance losses during heat stress. In this study, we investigate whether the degree of heat acclimatization affects cognitive abilities during heat exposure by comparing heat acclimatization level of subjects from Southeast Asia and temperate natives from Japan.

Methods

Eleven tropical males from Southeast Asia and ten temperate males from Japan participated in this study and performed two types of cognitive task: short-term memory test and mental arithmetic test, under control and passive heat exposure conditions. Passive heat condition was stimulated through leg immersion protocol by immersing subjects’ lower legs into a hot water maintained at 42 °C in a chamber controlled at 28 °C air temperature and 50% relative humidity.

Results

The results show that the subjects in tropical group, who had smaller increase of rectal temperature, did not show any performance losses in both cognitive tests during heat exposure, while for Japanese group, there was performance decrement in mental arithmetic test during heat exposure (P < 0.05). We also found that the subjects in both tropical and Japanese groups tried to maintain their performance by increasing oxyhemoglobin in their prefrontal cortex area during performing the tasks during heat exposure. In addition, the subjects in the Japanese group showed higher increase of oxyhemoglobin when they performed the tasks during heat exposure than those when they performed the tasks in control condition (P < 0.05), while the subjects in tropical group did not show any differences in oxyhemoglobin during task performance between control and heating conditions.

Conclusions

In addition to a better ability to maintain their homeostasis during heat exposure, tropical natives from Southeast Asia showed better resistance to performance loss during heat exposure in comparison with temperate natives from Japan. The tropical natives also showed smaller increase of oxyhemoglobin indicating less cognitive effort to maintain performance.

Different Physiological and Subjective Responses to the Hyperthermia Between Young and Older Adults: Basic Study for Thermal Therapy in Cardiovascular Diseases

BACKGROUND

Thermal therapy has been used as adjuvant therapy in patients with cardiovascular disease. However, little is known about responses to thermal stress in older adults. We examined the effects of thermal stress in younger and older healthy Japanese individuals.

METHODS

The study included 12 young (mean age, 22 years) and 12 older (mean age, 68 years) healthy adults and was performed under strict temperature and humidity control to minimize confounding. Participants lay supine throughout three consecutive 30-minute phases: Phase I (heating at 70°C in a dome-shaped sauna), Phase II (insulation in the sauna), and Phase III (cool down). Physiological parameters and subjective thermal sensations were compared within and between two age groups.

RESULTS

Mean skin temperature increased significantly in both age groups (Phase I) and after the first 10 minutes was higher among older adults (by 6.8°C vs 6.0°C among younger; p < .01). Mean rectal temperature increased by 0.6°C in both groups (Phase II). Mean heart rate increased significantly in both age groups (Phase II) and was higher among younger adults (by 21.4 vs 11.3 beats/min among older adults; p < .05). Both systolic (by 15.1 mmHg) and diastolic (by 10.5 mmHg) blood pressure dropped significantly among older adults (Phase I), returning to baseline in Phase III; no changes were noted among those younger. There was no between-group difference in fluid loss or thermal sensations.

CONCLUSIONS

Compared with younger adults, older adults are more likely to drop blood pressure in response to thermal stress but had similar fluid loss and subjective responses.

Comparison of firefighters and non-firefighters and the test methods used regarding the effects of personal protective equipment on individual mobility

The aims of this study were 1) to evaluate the current pilot test method and ascertain reliable measurements for a standard test method of mobility with personal protective equipment (PPE), such as physical performance and balance ability tests; 2) to compare two participant groups (firefighters versus non-firefighters) and to investigate whether non-firefighters are appropriate as a standard participant group in the field of PPE or not. Totally, 18 participants (nine professional firefighters and nine untrained males) performed the current pilot test method consisting of a balance test, completed prior to and after a performance test. Significant differences were found between PPE conditions and CON (the control clothing ensemble: T-shirt, shorts, and running shoes) for the functional balance test, physical performance test, heart rate, and subjective evaluations in firefighters group. Therefore, the present pilot test method is valid as a standard test method for assessing mobility while wearing PPE. Moreover, the present result shows that firefighters are more reliable than non-firefighters in testing of PPE with current test methods.

Sex differences in acetylcholine-induced sweating responses due to physical training

Purpose

The present study examined sex differences in the sweat gland response to acetylcholine (ACh) in physically trained and untrained male and female subjects.

Methods

Sweating responses were induced on the forearm and thigh in resting subjects by ACh iontophoresis using a 10% solution at 2 mA for 5 min at 26°C and 50% relative humidity.

Results

The ACh-induced sweating rate (SR) on the forearm and thigh was greater in physically trained male (P < 0.001 for the forearm and thigh, respectively) and female (P = 0.08 for the forearm, P < 0.001 for the thigh) subjects than in untrained subjects of both sexes. The SR was also significantly greater in physically trained males compared to females at both sites (P < 0.001) and in untrained males compared to females on the thigh (P < 0.02) only, although the degree of difference was greater in trained subjects than in untrained subjects. These sex differences can be attributed to the difference in sweat output per gland rather than the number of activated sweat glands.

Conclusion

We conclude that physical training enhances the ACh-induced SR in both sexes but that the degree of enhancement is greater in male than in female subjects. The effects of physical training and sex on the SR may be due to changes in peripheral sensitivity to ACh and/or sweat gland size.

The European, Japanese and US protective helmet, gloves and boots for firefighters: thermoregulatory and psychological evaluations

The purpose of this study was to investigate the physiological and subjective responses of the European, Japanese (JPN) and US firefighters' helmet, gloves and boots for international standardisation. Three experimental conditions were evaluated (clothing mass: 9.4, 8.2 and 10.1 kg for the three conditions, respectively) at the air temperature of 32°C and 60% relative humidity. The results showed that there was no significant difference among the three conditions in oxygen consumption, heart rate, total sweat rate, rectal temperature and mean skin temperature, whereas peripheral temperatures and subjective perceptions were lower in the JPN condition than in the other conditions (P < 0.05). These results indicate that a 0.5-kg reduction in helmet mass and a 1.1-kg reduction in boot mass during exercise resulted in a significant decrease in head and leg temperatures and subjective perceptions, while a 1.9-kg reduction in total clothing mass had insignificant influences on the metabolic burden and overall body temperature.

A comparison of hydration effect on body fluid and temperature regulation between Malaysian and Japanese males exercising at mild dehydration in humid heat

BACKGROUND

This study investigated the effect of hydration differences on body fluid and temperature regulation between tropical and temperate indigenes exercising in the heat.

METHODS

Ten Japanese and ten Malaysian males with matched physical characteristics (height, body weight, and peak oxygen consumption) participated in this study. Participants performed exercise for 60 min at 55% peak oxygen uptake followed by a 30-min recovery at 32°C and 70% relative air humidity with hydration (4 times each, 3 mL per kg body weight, 37°C) or without hydration. Rectal temperature, skin temperature, heart rate, skin blood flow, and blood pressure were measured continuously. The percentage of body weight loss and total sweat loss were calculated from body weight measurements. The percentage change in plasma volume was estimated from hemoglobin concentration and hematocrit.

RESULTS

Malaysian participants had a significantly lower rectal temperature, a smaller reduction in plasma volume, and a lower heart rate in the hydrated condition than in the non-hydrated condition at the end of exercise (P <0.05), whereas Japanese participants showed no difference between the two hydration conditions. Hydration induced a greater total sweat loss in both groups (P <0.05), and the percentage of body weight loss in hydrated Malaysians was significantly less than in hydrated Japanese (P <0.05). A significant interaction between groups and hydration conditions was observed for the percentage of mean cutaneous vascular conductance during exercise relative to baseline (P <0.05).

CONCLUSIONS

The smaller reduction in plasma volume and percentage body weight loss in hydrated Malaysians indicated an advantage in body fluid regulation. This may enable Malaysians to reserve more blood for circulation and heat dissipation and thereby maintain lower rectal temperatures in a hydrated condition.

Effects of 6-h exposure to low relative humidity and low air pressure on body fluid loss and blood viscosity

The purpose of this study was to investigate the effects of 6-h exposure to low relative humidity (RH) and low air pressure in a simulated air cabin environment on body fluid loss (BFL) and blood viscosity. Fourteen young healthy male subjects were exposed to four conditions, which combined RH (10% RH or 60% RH) and air pressure (NP: sea level or LP: equivalent to an altitude of 2000 m). Subjects remained seated on a chair in the chamber for 6 h. Their diet and water intake were restricted before and during the experiment. Insensible water loss (IWL) in LP10% condition was significantly greater than in NP60% condition; thus, combined 10%RH and LP conditions promoted a greater amount of IWL. The BFL under the LP condition was significantly greater than that under the NP condition. Blood viscosity significantly increased under LP conditions. Increases in red blood cell counts (RBCs) and BFL likely contributed to the increased blood viscosity. These findings suggest that hypobaric-induced hypoxia, similar to the conditions in the air cabin environment, may cause increased blood viscosity and that the combined low humidity and hypobaric hypoxia conditions increase IWL.

Passive heat exposure induced by hot water leg immersion increased oxyhemoglobin in pre-frontal cortex to preserve oxygenation and did not contribute to impaired cognitive functioning

This study investigated the effects of passive heat exposure on pre-frontal cortex oxygenation and cognitive functioning, specifically to examine whether the change in pre-frontal cortex oxygenation coincided with cognitive functioning during heat exposure. Eleven male students who participated in this study immersed their lower legs to the knees in three different water temperatures, 38 °C, 40 °C, and 42 °C water in an air temperature of 28 º C and 50 % relative humidity for 60 min. After 45 min of leg immersion they performed cognitive functioning tasks assessing their short-term memory while immersing their lower legs. There were higher rectal temperature (P < 0.05) and higher increase of oxyhemoglobin in both left (P < 0.05) and right (P < 0.05) pre-frontal cortex at the final stage of 45-min leg immersion in the 42 °C condition with unaltered tissue oxygenation index among the three conditions (P > 0.05). No statistical difference in cognitive functioning among the three conditions was observed with a higher increase of oxyhemoglobin during the cognitive functioning in the 42 °C condition for the left (P = 0.05) and right (P < 0.05) pre-frontal cortex. The findings of this study suggest, first, passive heat exposure increases oxygen delivery in the pre-frontal cortex to maintain pre-frontal cortex oxygenation; second, there is no evidence of passive heat exposure in cognitive functioning in this study; and third, the greater increases of oxyhemoglobin in the pre-frontal cortex during cognitive functioning at the hottest condition suggests a recruitment of available neural resources or greater effort to maintain the same performance at the same level as when they felt thermally comfortable.

The impact of firefighter personal protective equipment and treadmill protocol on maximal oxygen uptake

This study investigated the effects of firefighter personal protective equipment (PPE) on the determination of maximal oxygen uptake (VO(2max)) while using two different treadmill protocols: a progressive incline protocol (PIP) and a progressive speed protocol (PSP), with three clothing conditions (Light-light clothing; Boots-PPE with rubber boots; Shoes-PPE with running shoes). Bruce protocol with Light was performed for a reference test. Results showed there was no difference in VO(2max) between Bruce Light, PIP Light, and PSP Light. However, VO(2max) was reduced in Boots and Shoes with shortened maximal performance time (7 and 6 min reduced for PIP Boots and Shoes, respectively; 11 and 9 min reduced for PSP Boots and Shoes, respectively), whereas the increasing rate of VO(2) in Boots and Shoes during submaximal exercise was greater compared with Light. Wearing firefighter boots compared with wearing running shoes also significantly affected submaximal VO(2) but not VO(2max). These results suggest that firefighters' maximal performance determined from a typical VO(2max) test without wearing PPE may overestimate the actual performance capability of firefighters wearing PPE.

The use of language to express thermal sensation suggests heat acclimatization by Indonesian people

The purpose of this study was to explore whether there is evidence of heat acclimatization in the words used to express thermal sensation. A total of 458 urban Japanese and 601 Indonesians participated in a questionnaire. In addition, in a preliminary survey, 39 native English speakers in the UK participated. Our results showed that (1) for Indonesians, the closest thermal descriptor of a feeling of thermal comfort was 'cool' (75%) followed by 'slightly cool' (7%), 'slightly cold' (5%) and 'cold' (5%), while Japanese responses were distributed uniformly among descriptors 'cool', 'slightly cool', 'neither', 'slightly warm', and 'warm'; (2) the closest thermal descriptors of a feeling of discomfort for Indonesians were less affected by individual thermal susceptibility (vulnerability) than those for Japanese; (3) in the cases where 'cool' and 'slightly cold' were imagined in the mind, the descriptors were cognized as a thermal comfortable feeling by 97% and 57% of Indonesians, respectively; (4) the most frequently voted choice endorsing hot weather was 'higher than 32°C' for Indonesians and 'higher than 29°C' for Japanese respondents; for cold weather, 'lower than 15°C' for Japanese and 'lower than 20°C' for Indonesians. In summary, the descriptor 'cool' in Indonesians connotes a thermally comfortable feeling, but the inter-zone between hot and cold weather that was judged in the mind showed a upward shift when compared to that of Japanese. It is suggested that linguistic heat acclimatization exists on a cognitive level for Indonesians and is preserved in the words of thermal descriptors.

Effects of duration of stay in temperate area on thermoregulatory responses to passive heat exposure in tropical south-east Asian males residing in Japan

BACKGROUND

In this study, we investigated the effects of duration of stay in a temperate area on the thermoregulatory responses to passive heat exposure of residents from tropical areas, particularly to clarify whether they would lose their heat tolerance during passive heat exposure through residence in a temperate country, Japan.

METHODS

We enrolled 12 males (mean ± SE age 25.7 ± 1.3 years) from south-east Asian countries who had resided in Japan for a mean of 24.5 ± 5.04 months, and 12 Japanese males (age 24.1 ± 0.9 years). Passive heat exposure was induced through leg immersion in hot water (42°C) for 60 minutes under conditions of 28°C air temperature and 50% relative humidity.

RESULTS

Compared with the Japanese group, the tropical group displayed a higher pre-exposure rectal temperature (P < 0.01) and a smaller increase in rectal temperature during 60 minutes of leg immersion (P = 0.03). Additionally, the tropical group showed a tendency towards a lower total sweat rate (P = 0.06) and lower local sweat rate on the forehead (P = 0.07). The tropical group also had a significantly longer sweating onset time on the upper back (P = 0.04) compared with the Japanese groups. The tropical group who stayed in Japan for > 23 months sweated earlier on the forehead and upper back than those who stayed in Japan < 11 months (P < 0.01 and P = 0.03 for the forehead and upper back, respectively). There was a positive correlation between duration of stay in Japan and total sweat rate (r = 0.58, P <0.05), and negative correlations between duration of stay and sweating onset time on the forehead (r = -0.73, P = 0.01) and on the upper back (r = -0.66, P = 0.02). Other physiological indices measured in this study did not show any difference between the subjects in the tropical group who had lived in Japan for a shorter time and those who had lived there for a longer time.

CONCLUSIONS

We conclude that the nature of heat acclimatization of the sweating responses to passive heat exposure that are acquired from long-term heat acclimatization is decayed by a stay in a temperate area, as shown by the subjects in our tropical group. We did not find any evidence of a decay in the other physiological indices, indicating that heat tolerance acquired from long-term heat acclimatization is not completely diminished through residence in a temperate area for less than 4 years, although some aspects of this heat tolerance may be decayed.

The effect of repeated mild cold water immersions on the adaptation of the vasomotor responses

There are several types of cold adaptation based on the alteration of thermoregulatory response. It has been thought that the temperature of repeated cold exposures during the adaptation period is one of the factors affecting the type of cold adaptation developed. This study tested the hypothesis that repeated mild cold immersions would induce an insulative cold adaptation but would not alter the metabolic response. Seven healthy male participants were immersed to their xiphoid process level repeatedly in 26°C water for 60 min, 3 days every week, for 4 weeks. During the first and last exposure of this cold acclimation period, the participants underwent body immersion tests measuring their thermoregulatory responses to cold. Separately, they conducted finger immersion into 5°C water for 30 min to assess their cold-induced vasodilation (CIVD) response before and after cold acclimation. During the immersion to xiphoid process, participants showed significantly lower mean skin temperature and skin blood flow in the forearm post-acclimation, while no adaptation was observed in the metabolic response. Additionally, blunted CIVD responses were observed after cold acclimation. From these results, it was considered that the participants showed an insulative-type of cold acclimation after the repeated mild cold immersions. The major finding of this study was the acceptance of the hypothesis that repeated mild cold immersion was sufficient to induce insulative cold adaptation but did not alter the metabolic response. It is suggested that the adaptation in the thermoregulatory response is specific to the response which is repeatedly stimulated during the adaptation process.

Effects of firefighters' self-contained breathing apparatus' weight and its harness design on the physiological and subjective responses

To examine the effects of firefighters' self-contained breathing apparatus' (SCBA) weight and its harness design on the physiological and subjective responses, eight male students performed treadmill exercise under four conditions: the 8 kg firefighter protective clothing (PC) (Control), the PC + an 11 kg SCBA with an old harness (Test A), the PC + a 6.4 kg SCBA with an old harness (Test B) and the PC + a 6.4 kg SCBA with a new harness (Test C), at ambient temperatures (T(a)) of 22°C and 32°C. Besides highlighting the fact that a heavy SCBA had a significant effect on the oxygen consumption and metabolic rate, this experiment also found that in a T(a) of 32°C, in particular, the combined effect of 4.7 kg lighter SCBA and new harness design could reduce metabolic rate and improved subjective muscle fatigue and thermal discomfort.

PRACTITIONER SUMMARY

An effort to alleviate the physiological and subjective burden of firefighters by reducing the weight of SCBA and by using the new harness design has provided satisfactory results in reduced oxygen consumption and in improved subjective responses in a hot air environment.

Effects of heated seats in vehicles on thermal comfort during the initial warm-up period

Eight subjects participated in a subjective experiment of eight conditions to investigate the effects of heated seats in vehicles on skin temperature, thermal sensation and thermal comfort during the initial warm-up period. The experimental conditions were designed as a combination of air temperature in the test room (5, 10, 15, or 20 °C) and heated seat (on/off). The heated seat was effective for improving thermal comfort during the initial warm-up period when air temperature was lower than 15 °C. Use of heated seats prevented decreases in or increased toe skin temperature. Heated seats also increased foot thermal sensation at 15 and 20 °C. Optimal thermal sensation in contact with the seat was higher when air temperature was lower. Optimal skin temperature in contact with the seat back was higher than that with the seat cushion. Moreover, these optimal skin temperatures were higher when air temperature was lower.

Validity of infrared tympanic temperature for the evaluation of heat strain while wearing impermeable protective clothing in hot environments

The purpose of this study was to investigate the validity of infrared tympanic temperature (IR T(ty)) as a thermal index to evaluate the heat strain of workers in hot environments, in comparison with rectal temperatures at various depths (T(re-4, -8, and -16) for 4, 8 and 16 cm from the anal sphincter). Eight males underwent twelve experimental conditions: two activities (rest and exercise) × three clothing levels [Control, HDPE (high-density polyethylene coverall) and PVC (polyvinyl chloride coverall) condition] × two air temperatures (25 and 32℃ with 50%RH). The results showed that 1) in the conditions with most heat strain (HDPE or PVC condition at 32℃), IR T(ty) was equal to or even higher than T(re); 2) during exercise, physiological strain index (PSI) using IR T(ty) did not underestimate PSI-values using T(re-16), and overestimated those PSI-values from T(re-16) in HDPE and PVC conditions at 32℃; 3) during exercise, the relationships between IR T(ty) and heart and total sweat rate were stronger than those between T(re-16) and heart and total sweat rate. These results indicated that IR T(ty) is valid as a thermal index to evaluate the heat strain of workers wearing impermeable protective coveralls in hot environments. However, the application of IR T(ty) is limited only for strenuous works wearing encapsulated personal protective clothing with a hood in heat.

Effects of heated seat and foot heater on thermal comfort and heater energy consumption in vehicle

Subjective experiments involving 12 different conditions were conducted to investigate the effects of heated seats and foot heaters in vehicles on thermal sensation and thermal comfort. The experimental conditions involved various combinations of the operative temperature in the test room (10 or 20°C), a heated seat (on/off) and a foot heater (room operative temperature +10 or +20°C). The heated seat and foot heater improved the occupant's thermal sensation and comfort in cool environments. The room operative temperature at which the occupants felt a 'neutral' overall thermal sensation was decreased by about 3°C by using the heated seat or foot heater and by about 6°C when both devices were used. Moreover, the effects of these devices on vehicle heater energy consumption were investigated using simulations. As a result, it was revealed that heated seats and foot heaters can reduce the total heater energy consumption of vehicles. Statement of Relevance: Subjective experiments were conducted to investigate the effects of heated seats and foot heaters in vehicles on thermal comfort. The heated seat and foot heater improved the occupant's thermal sensation and comfort in cool environments. These devices can reduce the total heater energy consumption in vehicles.

Comparison of heat dissipation response between Malaysian and Japanese males during exercise in humid heat stress

This study investigated the differences in heat dissipation response to intense heat stress during exercise in hot and humid environments between tropical and temperate indigenes with matched physical characteristics. Ten Japanese (JP) and ten Malaysian (MY) males participated in this study. Subjects performed exercise for 60 min at 55% peak oxygen uptake in 32°C air with 70% relative humidity, followed by 30 min recovery. The increase in rectal temperature (T(re)) was smaller in MY during exercise compared to JP. The local sweat rate and total body mass loss were similar in both groups. Both skin blood flow and mean skin temperature was lower in MY compared to JP. A significantly greater increase in hand skin temperature was observed in MY during exercise, which is attributable to heat loss due to the greater surface area to mass ratio and large number of arteriovenous anastomoses. Also, the smaller increase in T(re) in MY may be explained by the presence of a significantly greater core-skin temperature gradient in MY than JP. The thermal gradient is also a major factor in increasing the convective heat transfer from core to skin as well as skin blood flow. It is concluded that the greater core-skin temperature gradient observed in MY is responsible for the smaller increase in T(re).

Comparison of thermoregulatory responses to heat between Malaysian and Japanese males during leg immersion

The objective of this study was to investigate thermoregulatory responses to heat in tropical (Malaysian) and temperate (Japanese) natives, during 60 min of passive heating. Ten Japanese (mean ages: 20.8 ± 0.9 years) and ten Malaysian males (mean ages: 22.3 ± 1.6 years) with matched morphological characteristics and physical fitness participated in this study. Passive heating was induced through leg immersion in hot water (42°C) for 60 min under conditions of 28°C air temperature and 50% RH. Local sweat rate on the forehead and thigh were significantly lower in Malaysians during leg immersion, but no significant differences in total sweat rate were observed between Malaysians (86.3 ± 11.8 g m(-2) h(-1)) and Japanese (83.2 ± 6.4 g m(-2) h(-1)) after leg immersion. In addition, Malaysians displayed a smaller rise in rectal temperature (0.3 ± 0.1°C) than Japanese (0.7 ± 0.1°C) during leg immersion, with a greater increase in hand skin temperature. Skin blood flow was significantly lower on the forehead and forearm in Malaysians during leg immersion. No significant different in mean skin temperature during leg immersion was observed between the two groups. These findings indicated that regional differences in body sweating distribution might exist between Malaysians and Japanese during heat exposure, with more uniform distribution of local sweat rate over the whole body among tropical Malaysians. Altogether, Malaysians appear to display enhanced efficiency of thermal sweating and thermoregulatory responses in dissipating heat loss during heat loading. Thermoregulatory differences between tropical and temperate natives in this study can be interpreted as a result of heat adaptations to physiological function.

Physiological strains of wearing aluminized and non-aluminized firefighters' protective clothing during exercise in radiant heat

This study examined the influences of aluminized (Type A) and non-aluminized firefighters' protective clothing (Type B, C, D and CON) on physiological and subjective responses in radiant heat. Total clothing weight was 6.24, 6.38, 6.06, 5.76 and 3.82 kg for Type A, B, C, D and CON, respectively. Eight firefighters performed exercise at an air temperature of 30°C with 50%RH. Three bouts of 10 min-bicycle exercise in radiant heat (a globe temperature of 70°C) was spaced by a 10 min rest with no radiant heat. Results showed that rectal temperature, mean skin temperature, heart rate, and body weight loss were significantly greater in Type A than in other types (p<0.05). For Type A, thermal gradient of the body reached 0.0 ± 0.7°C, heart rate showed a maximum level of 183 ± 11 bpm and 1.9% of body weight was lost due to sweat secretion. Firefighters felt the hottest and most discomfort in Type A. It appeared that firefighters' thermoregulatory mechanism was severely challenged by wearing aluminized protective clothing during exercise in strong radiant heat. Therefore, it is suggested that the safe upper limits while wearing aluminized firefighters' clothing should be distinguished from those for typical firefighters' protective clothing.

Linguistic dimensions in descriptors expressing thermal sensation in Korean: 'warm' projects thermal comfort

The present study was triggered by the inconsistency in verbal descriptors in English and Korean describing 'warm' and 'hot' in the thermal sensation scale. The purpose of this study was to examine the linguistic dimensions of the terms expressing 'ttatteuhada (warm)' and 'yakkan duptta (slightly hot)' in Korean. A total of 988 urban Koreans (479 males and 509 females) participated in a questionnaire survey consisting of six questions. The one-to-one survey was conducted indoors in December 2008. Our results showed that (1) 'warm' and 'slightly hot' in Korean are distinctive thermal descriptors; (2) 'warm' projects thermal comfort (80.4% of 988 respondents), but 'slightly hot' projects some thermal discomfort (54.3% of 988 respondents); (3) a slight thermally comfortable feeling was expressed as 'warm' (83.9% of 988 respondents), while a slight thermally uncomfortable feeling was seldom expressed as 'warm' (6.2% of 988 respondents) in mild heat environments; (4) the linguistic dimension within the term 'warm' was less affected by individual thermal susceptibility (vulnerability) than that of the term 'slightly hot'. In summary, 'warm' in Korean connotes a thermally comfortable feeling. In the case of being a little thermally uncomfortable, Koreans project their thermal sensation through the term 'slightly hot', rather than 'warm'. In conclusion, thermal descriptors in the ISO 10551/ASHRAE scale, i.e., 'very cold-cold-cool-slightly cool-neutral-slightly warm-warm-hot-very hot', are not valid for the evaluation of mild hot environments in Korea. A new categorical scale is required in Korean considering the descriptors 'warm' and 'slightly hot'.

Combined factors effect of menstrual cycle and background noise on visual inspection task performance: a simulation-based task

It is well known that women are physiologically and psychologically influenced by the menstrual cycle. In addition, the presence of background noise may affect task performance. So far, it has proven difficult to describe how the menstrual cycle and background noise affect task performance; some researchers have found an increment of performance during menstruation or during the presence of noise, others found performance deterioration, while other still have reported no dominant effect either of the menstrual cycle in performance or of the presence of noise. However, no study to date has investigated the combinational effect between the menstrual cycle and the presence of background noise in task performance. Therefore, the purpose of this study was to examine the combined factor effect of menstrual cycle and background noise on visual inspection task performance indices by Signal Detection Theory (SDT) metrics: sensitivity index (d') and response criteria index (beta). For this purpose, ten healthy female students (21.5+/-1.08 years) with a regular menstrual cycle participated in this study. A VDT-based visual inspection task was used for the experiment in 3x2 factorial designs. Two factors, menstrual phase, pre-menstruation (PMS), menstruation (M), and post-menstruation (PM) and background noise, with 80 dB(A) background noise and without noise, were analyzed as the main factors in this study. The results concluded that the sensitivity index (d') of SDT was affected in all the menstrual cycle conditions (p<0.01) and the presence of background noise (p<0.05) but no combinational effect of menstrual cycle and background noise was found in this study. On the other hand, no significant effect was observed in the subject's tendency in visual inspection, shown by beta along the menstrual cycle and the presence of background noise. According to the response criteria for each individual subject, the presence of noise affected the tendency of some subjects in detecting the object and making decision during the visual inspection task.

Issues in combining the categorical and visual analog scale for the assessment of perceived thermal sensation: methodological and conceptual considerations

Typically, the scales for the measurement of thermal sensation have been formatted as categorical scales (CS). Emerging is the use of CS combined with visual analog scale (VAS) for the measurement of thermal sensation to improve the sensitivity of scales. However, reports are rare comparing the typical CS, standard VAS, and combined CS with VAS. Methodological and conceptual issues are arising with the combining of scales, but there are insufficient reports about the advantages and limitations of different scales. The present study compared 9-points categorical scale (9pts CS), VAS, and CS combined with VAS (graphic CS) through a questionnaire survey (n=988) and a controlled experiment during exercise (17 male subjects). Our results showed that graphic CS was more closely related to indoor air temperature for resting residents rather than VAS or 9pts CS. Around thermal neutral zone indoor environments, sensitivity to discriminate thermal sensation was the greatest for graphic CS. In particular, questionnaire responses to VAS showed a remarkable clustering around the thermal neutral zone. For dynamic exercising subjects, mean skin temperature was more closely related to graphic CS than 9pts CS. Our results indicated that graphic CS seemed to be more valid and sensitive than 9pts CS or VAS for the measurement of thermal sensation, but there are many issues to be considered when combining CS and VAS from the methodological and conceptual view points: definitions of terms, verbalizing with descriptors, number of category, scoring length, unipolar/bipolar construction, language translation, central terms, both anchor terms, orientation, color, etc. The above methodological and conceptual issues were discussed.

Effects of saliva collection using cotton swab on cortisol enzyme immunoassay

Cotton swabs are among the most commonly used devices for collecting saliva, but various studies have reported that their use impacts the results of salivary cortisol assays. These studies, however, estimated this impact by comparing the average of the concentration and/or scatter plots. In the present study, we estimated the impact of cotton swabs on the results of salivary cortisol enzyme immunoassay (EIA) by Bland-Altman plot. Eight healthy males (aged 20-23 years) provided four saliva samples on different days to yield a total of 32 samples. Saliva samples were collected directly in plastic tubes using plastic straws and then pipetted onto cotton swabs (cotton saliva collection) and into clear sterile tubes (passive saliva collection). There was a lower correlation between cotton and passive saliva collection. Individually, four subjects showed a negative correlation between passive and cotton saliva collection. A Bland-Altman plot indicated that cotton swabs causes a proportional bias on the EIA assay result. Our findings indicate a considerable effect of using cotton swabs for saliva collection, and subject-specific variability in the impact. A Bland-Altman plot further suggests possible reasons for this effect.

Effects of setting up of humidifiers on thermal conditions and subjective responses of patients and staff in a hospital during winter

The purpose of this survey was to measure the thermal environment in a hospital during winter, and to investigate the subjective responses of patients and staff via a questionnaire. The air temperature and humidity in the sickrooms and nurse stations were measured for 3 months during winter. After 2 months, we introduced humidifiers into about half of the rooms and nurse stations as a method of improving the environment, and evaluated the effects of the installed humidifiers on the thermal conditions. In all, 36 patients and 45 staff members were asked once a week about subjective symptoms (dry and itchy skin, thirst, etc.). Before setting up the humidifiers, the existence of a low-humidity environment in the hospital during winter was confirmed, with the levels of relative humidity and humidity ratio reaching under 50% and 5g/kg DA, respectively, which is known to promote the spread of influenza viruses. However, the introduction of the humidifiers increased the relative humidity in sickrooms from 32.8% to 43.9% on average, and the air humidity in sickrooms thus almost reached the optimum range suggested by the Hospital Engineering Association of Japan (HEAJ). Additionally, complaints of thermal discomfort and dryness of air decreased among the staff, though not among the patients, after the humidifiers were installed. These results suggest that introducing humidifiers into a hospital during winter is an effective method of improving the low-humidity environment and relieving the discomfort of staff members.

Effects of worn-out soles on lower limb stability, shock absorption and energy cost during prolonged walking

This study investigated the effects of worn-out shoes on lower leg stability, shock absorption and energy cost during prolonged walking. Seven male subjects (23.4 +/- 0.5 yr) walked at 4.8 km/h for 60 minutes wearing three different pairs of shoes: two of these pairs had severely and moderately worn soles (EASC: Excessive Attrite Shoe Condition and MASC: Moderate Attrite Shoe Condition, respectively) and the other pair had no wear (NASC: No Attrite Shoe Condition). Impact acceleration at the subtalar at heel strike, rearfoot angles (the subtalar joint and the lower leg) during stance phase, and oxygen uptake (VO2) were measured throughout the 60-minute walk. At the 10th minute of walking, worn-out shoes increased the supination of the subtalar joint and extortion of the lower leg. In addition, VO2 was significant larger in EASC (808.3 ml x min(-1)) than in NASC (749.5 ml x min(-1)). During the 60-minute walk, however, there were no time effects of shoe condition on the rearfoot angles and on VO2. In contrast, impact acceleration at the subtalar joint in EASC remained almost constant until the 30th minute of walking, and then began to elevate. In conclusion, worn-out shoes increased the energy cost and reduced lower leg stability during walking, although these changes were not influenced by walking duration within 60 minutes. However, prolonged walking showed the potential negative effect of worn-out shoe on shock absorption.

Environmental and behavioral conditions of bathing among elderly Japanese

This study investigated the bathing conditions of elderly Japanese, and sought to find factors relating to regional differences in death rates from bathtub accidents. A questionnaire survey was carried out in 11 areas of Japan. Questionnaires including questions regarding the length of time since houses had been built, types of facilities, and subjects' indoor thermal sensations and behavior while bathing were distributed to detached houses in each area twice, once in summer and once in winter. Completed questionnaires were collected from approximately 160 elderly people over 65 years old. Information regarding thermal sensations of rooms in winter revealed that a prefabricated bath and insulating window glass eased the cold in the bathroom. Unexpectedly, more subjects in the southern region than in the northern region reported being cold or a little cold while bathing in winter. In the present study, thermal sensations and behaviors while bathing seemed to be more affected by facilities and the location of houses than by the sex and age of the subjects.

Physiological and Subjective Responses to Low Relative Humidity in Young and Elderly Men

In order to compare the physiological and the subjective responses to low relative humidity of elderly and young men, we measured saccharin clearance time (SCT), frequency of blinking, hydration state of the skin, transepidermal water loss (TEWL), sebum level recovery and skin temperatures as physiological responses. We asked subjects to evaluate thermal, dryness and comfort sensations as subjective responses using a rating scale. Eight non-smoking healthy male students (21.7+/-0.8 yr) and eight non-smoking healthy elderly men (71.1+/-4.1 yr) were selected. The pre-room conditions were maintained at an air temperature (Ta) of 25 degrees C and a relative humidity (RH) of 50%. The test-room conditions were adjusted to provide 25 degrees C Ta and RH levels of 10%, 30% and 50%. RH had no effect on the activity of the sebaceous gland or change of mean skin temperature. SCT of the elderly group under 10% RH was significantly longer than that of the young group. In particular, considering the SCT change, the nasal mucous membrane seems to be affected more in the elderly than in the young in low RH. Under 30% RH, the eyes and skin become dry, and under 10% RH the nasal mucous membrane becomes dry as well as the eyes and skin. These findings suggested that to avoid dryness of the eyes and skin, it is necessary to maintain greater than 30% RH, and to avoid dryness of the nasal mucous membrane, it is necessary to maintain greater than 10% RH. On the thermal sensation of the legs, at the lower humidity level, the elderly group felt cooler than the young group. On the dry sensation of the eyes and throat, the young group felt drier than the elderly group at the lower humidity levels. From the above results, the elderly group had difficulty in feeling dryness in the nasal mucous membrane despite being easily affected by low humidity. On the other hand, the young group felt the change of humidity sensitively despite not being severely affected by low humidity. Ocular mucosa and physiology of skin by dryness showed no difference by age. In the effect of longer exposure (180 min.) to low RH, only TEWL showed a slight decrease after 120 minutes in 30% RH, and all the measured results showed no noticeable differences compared with the result at 120 minutes.

Physiological and Subjective Responses to Low Relative Humidity

In order to investigate the influence of low relative humidity, we measured saccharin clearance time (SCT), frequency of blinking, heart rate (HR), blood pressure, hydration state of skin, transepidermal water loss (TEWL), recovery sebum level and skin temperature as physiological responses. We asked subjects to judge thermal, dryness and comfort sensations as subjective responses using a rating scale. Sixteen non-smoking healthy male students were selected. The pre-room conditions were maintained at an air temperature (Ta) of 25 degrees C and a relative humidity (RH) of 50%. The test room conditions were adjusted to provide a Ta of 25 degrees C and RH levels of 10%, 30% and 50%.RH had no effect on the activity of the sebaceous gland and on cardiovascular reactions like blood pressure and HR. However, it was obvious that low RH affects SCT, the dryness of the ocular mucosa and the stratum corneum of the skin and causes a decrease in mean skin temperature. Under 30% RH, the eyes and skin become dry, and under 10% RH the nasal mucous membrane becomes dry as well as the eyes and skin, and the mean skin temperature decreases. These findings suggested that to avoid dryness of the eyes and skin, it is necessary to maintain an RH greater than 30%, and to avoid dryness of the nasal mucous membrane, it is necessary to maintain an RH greater than 10%. Subjects felt cold immediately after a change in RH while they had only a slight perception of dryness at the change of humidity.

Decay of heat acclimation during exercise in cold and exposure to cold environment

Sixteen male students exercised for 14 days (1 h/day) in the heat for heat acclimation (HA). During deacclimation (DA) one group exercised in the cold (EXG, n=8) for 60 min/day (morning) and was exposed to the cold for another hour (afternoon) for 14 days. The other group was exposed to the cold (EPG, n=8) for 1 h each in the morning and afternoon (Ta: 18.0 degrees C, RH: 58%) over the same period. All returned to exercise in the heat for reacclimation (RA) for 10 days. Subjects were tested on days 1, 16, 21, 32, 36 and 44 on a bicycle ergometer for 60 min at 60% of VO(2max) in the heat (Ta: 31.1 degrees C, RH: 70%). Rectal temperature (T (re)) and heart rate (HR) at 40 min of exercise were used to determine the decay/gain of HA, which was calculated using the formula described by Pandolf et al. (Ergonomics, 20:399-408, 1977). After HA (day 16) T (re) and HR decreased significantly. During DA, EXG showed decay in T (re) of 24 and 35% and HR of 29 and 35% on days 21 and 32, respectively. For EPG the corresponding decay was of 2 and 9% for T (re) and 17 and 17% for HR. After 10 days of RA, EXG showed gains of 11% in T (re) and 12% in HR, while EPG showed gains of 47% in T (re) and 38% in HR. In conclusion, EXG had greater decay during DA and lower gains in RA compared to EPG. However, the differences between groups were significant only for T (re) after 4 days of DA.

Effects of ambient temperature steps on thermal comfort requirements

The purpose of this study was to determine the thermal comfort requirements for steps in temperature. Thirty male subjects were exposed for 50 min to a 34 or 37 degrees C condition, and then quickly transferred to a cooler environment of 31, 28, 25, and 22 degrees C for 50 min. Mean skin temperature was continuously measured, and the subjects reported their thermal sensation and comfort sensation every 2 min. Just after the step changes, the mean skin temperature immediately decreased, while the thermal sensation overshot and gradually rose again. Both the skin temperature and the thermal sensation seemed to reach a constant level within about 20 min. However, there were differences in the mean skin temperature and the neutral temperature derived from the correlation between the ambient temperature and the thermal sensation even 50 min after the steps, due to the thermal environmental condition before the changes of temperature. The change in the neutral temperature with time was expressed as two attenuating equations. These equations indicate that there is an obvious difference between the neutral temperatures due to the thermal condition before step changes, and that it takes >50 min after the step changes to reach the steady state. It is expected that these equations predict in quantitative terms the thermal comfort requirements within a given experimental condition.

Thermal environment and subjective responses of patients and staff in a hospital during winter

The purpose of this study was to ascertain the actual conditions of the thermal environment and the symptoms of patient and staff (nurses and nurses' aides) during winter in a hospital. We measured the ambient temperature and humidity in sickrooms, nurse stations, and corridors. The subjects included 36 patients and 45 staff members. The existence of low humidity environments (relative humidity was less than 40%) in a hospital during winter was confirmed, and the levels of low humidity reached those known to promote the spread of influenza viruses. Thermal comfort of patients was not directly connected to the low humidity in sickrooms. However, 54.9% and 73.4% of patients were conscious of itchy skin and thirst, respectively. The majority of the staff members were working with itchy skin and thirst. These results suggested that extreme low humidity in a hospital during winter presents problem that should be solved quickly.

Thermal sensation and comfort during exposure to local airflow to face or legs

The present study examined the contribution of local airflow temperature to thermal sensation and comfort in humans. Eight healthy male students were exposed to local airflow to their faces (summer condition) or legs (winter condition) for 30 minutes. Local airflow temperature (Tf) was maintained at 18 degrees C to 36 degrees C, and ambient temperature (Ta) was maintained at 17.4 degrees C to 31.4 degrees C. Each subject was exposed to 16 conditions chosen from the combination of Tf and Ta. Based on the results of multiple regression analysis, the standardized partial regression coefficient of Tf and Ta were determined to be 0.93 and 0.13 in the summer condition, and 0.71 and 0.36 in the winter condition at the end of the exposure. Also, thermal comfort was observed to depend closely on the interrelation between Tf and Ta. The present data suggested that local airflow temperature is an important thermal factor regarding thermal sensation and comfort.

Work in Artificial Cold Environments

The physiological characteristics of work in cold stores, as a typical artificial cold environment, are reviewed mainly from our various field and experimental studies. There are about 4,000 cold stores in Japan, and 85% of them are kept at temperatures below -20 degrees C. Although the duration of cold exposure per stay in a cold store was very short, forklift workers entered the cold stores very frequently. Cold stress and the decrease in workers' performance were the same as for continuous exposure to cold. Since the peripheral skin temperature of subjects at night is higher than that in the afternoon, they are less likely to feel cold or pain sensation at night. However, there was a marked decrease in rectal temperature and in manual performance. There is an increased risk of both hypothermia and accidents for those who work at night. The cold store workers, however, had adapted to cold through daily repeated cold exposures.