Microclimate Temperature Research Articles

Comparative study of wood betony (Stachys officinalis L) melliferousness in different habitat conditions

Nectar production in wood betony (Stachys officinalis L), grown under differ-microclimatic habitat conditions (forest and experimental field), was analyzed. Study of tar production included determining of the total daily nectar amount (in 24 hours) per flower, the diurnal dynamics of nectar secretion (nectar amount secreted per flower at two hour intervals during the day), and nectar sugar concentration. The aim of this study was to evaluate the influence of microclimatic parameters humidity, air temperature and evaporation) on the secretion process and nectar sugar concentration. Comparative analyses of nectar secretion in Stachys officinalis, grown in two environmentally different habitats, confirmed that this process varied as a function of micro-climatic habitat conditions, and did not reveal a close relationship between these conditions and sugar concentration in nectar. A diurnal model of nectar secretion with two secretion peaks was found. A higher amount of nectar per flower, with an increasing tendency during the first half of the day, and a decreasing tendency during the afternoon was measured in forest conditions (lower temperature, higher relative air humidity and lower evaporation).

Effects of partial humid heat exposure during different segments of sleep on human sleep stages and body temperature

The effects of partial humid heat exposure applied at different segments of sleep on sleep stages and body temperature were examined. In the first experiment, eight male subjects slept under 26 °C 50% (26) and 26 °C for the first 3 h and 45 min followed by a 30-min transition to the conditions of 32 °C 80%, which was maintained for the final 3 h and 45 min (26-32). Wakefulness increased significantly over the last 4 h under 26-32 compared to 26. Mean skin temperature and clothing microclimate temperature (Tcm) were significantly higher during the last 3 h and 45 min, while rectal temperature (Tre) was higher during the last 3 h under 26-32 than in 26. In the second experiment, eight male subjects slept under 26 °C 50% (26) and 32 °C 80% for the first 3 h and 45 min followed by a 30-min transition to 26, which was then maintained for the last 3 h and 45 min (32-26). Wakefulness increased both in first and during the last 4 h, and slow wave sleep (SWS) decreased in the first 4 h under 32-26 compared to 26. Mean Tsk was significantly higher during the first 4:15 h. Tcm decreased in 32-26 compared to 26 just after the 30-min transition due to cooling effects. Tre was higher during the first 5 h under 32-26 compared to 26. These results suggest that humid heat exposure during the initial segment of sleep may be more disruptive to sleep stage distribution, Tre decline, and maintenance of Tcm than the same exposure during the later sleep segments.

Thermal Properties and Physiological Responses of Vapor-Permeable Water-Repellent Fabrics Treated with Microcapsule-Containing PCMs

The purpose of this study is to develop a thermally adaptable, vapor-permeable water-repellent fabric. Vapor-permeable water-repellent fabrics with and without octade cane-containing microcapsules are obtained by a wet porous coating process. The thermal and physical properties of the octadecane-containing water-repellent fabrics (WR-PCM) are compared with the water-repellent fabric without octadecane (WR). The heat of fusion ( ΔHf) of WR-PCM is 13.50 J/g at 29.06°C, and the heat of crystallization ( ΔHf) is 14.02 J/g at 11.45°C. The thermal properties remain relatively high after thirty launderings. WR-PCM shows a lower water vapor transmission value than WR and a lower air permeability. The water repellency of both fabrics is 100%, but the water resistance of WR-PCM decreases dramatically. In wear trials, the mean skin temperature and microclimate temperature of subjects wearing active wear made with WR-PCM are lower than those made with WR. But the microclimate humidity with WR-PCM has a higher rate than WR. Although the subjective sensations of WR and WR-PCM are not significantly different, WR-PCM is cooler and more comfortable than WR. The results of this study indicate that octadecane- containing microcapsules in water-repellent fabrics provide a cooling effect but sacrifice water resistance.

The Effects of Fabric Composition and Design on Thermoregulatory Responses and Comfort During Exercise in the Cold.

2137 Selection of clothing for exercise in cool and cold weather is complicated by the need to balance heat production with effective heat dissipation. The ability of a fabric or clothing system to provide sufficient insulation while preventing significant increases in total body temperature and skin wetness are vital to ensuring thermal comfort. PURPOSE: This study was designed to assess the impact of fabric design on thermoregulatory responses, clothing moisture management, and comfort during moderate exercise in the cold. METHODS: Eight physically fit men (29.6 ± 4.1 years, 84.02 ± 5.35 kg) performed two identical 54-minute self-paced treadmill runs on separate days in an environmental chamber set to 1.7°C (35°F) and 65% relative humidity. Two different fleece tops were worn in a counterbalanced order with a 100% polyester micro-fiber t-shirt used as the base layer for each run. Both fleeces were made from a 100% polyester micro-fiber brushed fabric. One fleece (N) had a normal inner surface while the other (S) had uniform undulations covering the inside of the garment. Skin temperatures, at seven anatomical sites, and microclimate temperature between layers were monitored continuously. Heart rate was monitored continuously and recorded at 5-minute intervals. Nude and clothed weights were obtained before and after exercise to determine total and evaporative sweat loss. Pre- and post weights of base layer and fleece were measured to assess clothing moisture retention. Following each run subjects filled in a questionnaire, rating thermal and moisture comfort on a nine-point scale. RESULTS: Mean skin temperature was 0.25°C to 0.5°C lower for S during the exercise bout. Mean moisture retention for N (82.7 g.) was higher than S (70.0 g.) (p = 0.06). Mean moisture retention in the base layer when worn under N (88.1 g.) was higher than S (75.0 g.) (p = 0.07). Total sweat loss showed no significant difference between trials. Percentage of sweat evaporated was slightly higher for S. Subjects perceived both the fabric and their skin as remaining significantly dryer during and after exercise in S. Perception scores for overall liking were significantly higher for S (p<0.05). CONCLUSION: Reduced accumulation of moisture in the base layer and the fleece significantly improved thermal comfort when wearing S. Perceptual data indicated that subjects were able to detect the differences in moisture retention between the two garments. Comfort during exercise in this environment was positively affected by fabric composition and design.

The Effects of Fabric Composition and Design on Thermoregulatory Responses and Comfort During Exercise in the Cold.

2137 Selection of clothing for exercise in cool and cold weather is complicated by the need to balance heat production with effective heat dissipation. The ability of a fabric or clothing system to provide sufficient insulation while preventing significant increases in total body temperature and skin wetness are vital to ensuring thermal comfort. PURPOSE: This study was designed to assess the impact of fabric design on thermoregulatory responses, clothing moisture management, and comfort during moderate exercise in the cold. METHODS: Eight physically fit men (29.6 ± 4.1 years, 84.02 ± 5.35 kg) performed two identical 54-minute self-paced treadmill runs on separate days in an environmental chamber set to 1.7°C (35°F) and 65% relative humidity. Two different fleece tops were worn in a counterbalanced order with a 100% polyester micro-fiber t-shirt used as the base layer for each run. Both fleeces were made from a 100% polyester micro-fiber brushed fabric. One fleece (N) had a normal inner surface while the other (S) had uniform undulations covering the inside of the garment. Skin temperatures, at seven anatomical sites, and microclimate temperature between layers were monitored continuously. Heart rate was monitored continuously and recorded at 5-minute intervals. Nude and clothed weights were obtained before and after exercise to determine total and evaporative sweat loss. Pre- and post weights of base layer and fleece were measured to assess clothing moisture retention. Following each run subjects filled in a questionnaire, rating thermal and moisture comfort on a nine-point scale. RESULTS: Mean skin temperature was 0.25°C to 0.5°C lower for S during the exercise bout. Mean moisture retention for N (82.7 g.) was higher than S (70.0 g.) (p = 0.06). Mean moisture retention in the base layer when worn under N (88.1 g.) was higher than S (75.0 g.) (p = 0.07). Total sweat loss showed no significant difference between trials. Percentage of sweat evaporated was slightly higher for S. Subjects perceived both the fabric and their skin as remaining significantly dryer during and after exercise in S. Perception scores for overall liking were significantly higher for S (p<0.05). CONCLUSION: Reduced accumulation of moisture in the base layer and the fleece significantly improved thermal comfort when wearing S. Perceptual data indicated that subjects were able to detect the differences in moisture retention between the two garments. Comfort during exercise in this environment was positively affected by fabric composition and design.

Diurnal variation in supercooling points of three species of Collembola from Cape Hallett, Antarctica

Daily changes in microclimate temperature and supercooling point (SCP) of Collembola were measured during summer at Cape Hallett, North Victoria Land, Antarctica. Isotoma klovstadi and Cryptopygus cisantarcticus (Isotomidae) showed bimodal SCP distributions, predominantly in the high group during the day and in the low group during the night. There were no concurrent diurnal changes in water content or haemolymph osmolality. By contrast, Friesea grisea (Neanuridae) had a unimodal distribution of SCPs that was invariant between daytime and nighttime. Isotoma klovstadi collected foraging on moss had uniformly high SCPs, which shifted towards the low group when the animals were starved for 2–8 h. When I. klovstadi was acclimated for five days with lichen or algae, SCPs were higher than if they were supplied with moss, while those that were starved (with free water or 100% relative humidity) displayed a trimodal SCP distribution. A variety of pre-treatments, including cold, heat, desiccation and slow cooling were ineffective at inducing SCP shifts in C. cisantarcticus or I. klovstadi. It is postulated that behavioural avoidance of low temperatures by vertical migration may be key in I. klovstadi’s short-term survival of nighttime temperatures. These data suggest that the full range of thermal responses of Antarctic Collembola is yet to be elucidated.

Nonwoven Protective Garments with Thermo-Regulating Properties

Nonwoven protective garments possess a poor thermo-physiological wearing comfort due to their insufficient breathability. The problem can be solved by applying phase change material (PCM) to the fabrics that the garment consists of PCM is a highly-productive thermal storage medium, which can be used to absorb excessive heat released by the human body under strenuous activities. The heat absorption by the PCM results in a delay in the microclimate temperature increase and hence a substantial decrease of the skin's moisture release. Both lead to an overall enhancement of the thermo-physiological wearing comfort and a prevention of heat stress situations as a serious health risk. Furthermore, the wearing times of nonwoven protective garments can be extended, resulting in an increased productivity.

Microclimate, freezing tolerance, and cold acclimation along an elevation gradient for seedlings of the Great Basin Desert shrub, Artemisia tridentata

Vegetation, microclimate, seedling frequency, freezing tolerance, and cold acclimation were compared for seedlings of Artemisia tridentata collected from 1775, 2175, and 2575 m elevation in the eastern Sierra Nevada, California. Data were used to test the hypothesis that ecotypic differences in stress physiology are important for seedling survival along gradients from desert to montane ecosystems. The vegetation canopy cover and A. tridentata seedling frequency were greatest at 2575 m, compared to 1775 and 2175 m. Snow cover ameliorated temperatures near the soil surface for part of the winter and depth varied across elevations. Freezing tolerance was compared for seedlings maintained in growth chambers at day/night air temperatures of 25°C/15°C. The temperature at which electrolyte leakage and Photosystem II function ( F V/ F M) from leaves were half-maximum was approximately −13·5°C for leaves of seedlings from all three elevations. Shifting day/night air temperatures from 25°C/15°C to 15°C/5°C initiated about 1·5° of acclimation by plants from all three altitudes, with seedlings from the highest elevation exhibiting the greatest acclimation change. Measurements of ambient air and canopy temperatures at the three elevations indicated that wintertime average low temperatures were consistent with the measured degree of freezing tolerance. At small spatial scales used in this study, pollen and seed dispersal between study sites may have precluded resolution of ecotypic differences. Patterns of freezing tolerance and cold acclimation may depend on a combination of mesoclimate and microclimate temperatures, canopy cover, snow depth, and snow melt patterns.

Effects of thermal underwear on thermal and subjective responses in winter.

This study was conducted to obtain basic data in improving the health of Koreans, saving energy and protecting environments. This study investigated the effects of wearing thermal underwear for keeping warm in the office in winter where temperature is not as low as affecting work efficiency, on thermoregulatory responses and subjective sensations. In order to create an environment where every subject feels the same thermal sensation, two experimental conditions were selected through preliminary experiments: wearing thermal underwear in 18 degrees C air (18-condition) and not wearing thermal underwear in 23 degrees C air (23-condition). Six healthy male students participated in this study as experiment subjects. Measurement items included rectal temperature (T(re)), skin temperature (T(sk)), clothing microclimate temperature (T(cm)), thermal sensation and thermal comfort. The results are as follows: (1) T(re) of all subjects was maintained constant at 37.1 degrees C under both conditions, indicating no significant differences. (2) (T)(sk) under the 18-condition and the 23-condition were 32.9 degrees C and 33.7 degrees C, respectively, indicating a significant level of difference (p<0.05). (3) Among local skin temperature, trunk part (forehead and abdomen) did not show significant differences. After 90-min exposure, the skin temperature of hands and feet under the 18-condition was significantly lower than that under the 23-condition (p<0.001). (4) More than 80% of all the respondents felt comfortable under both conditions. It was found (T)(sk) decreased due to a drop in the skin temperature of hands and feet, and the subjects felt cooler wearing only one layer of normal thermal underwear at 18 degrees C. Yet, the thermal comfort level, T(re) and T(cm) of chest part under the 18-condition were the same as those under the 23-condition. These results show that the same level of comfort, T(re) and T(cm) can be maintained as that of an environment about 5 degrees C higher in the office in winter, by wearing one layer of thermal underwear. In this regard, this study suggests that lowering indoor temperature by wearing thermal underwear in winter can contribute to saving energy and improving health.

Thermal Storage/Release, Durability, and Temperature Sensing Properties of Thermostatic Fabrics Treated with Octadecane-Containing Microcapsules

To develop a thermostatic fabric, a 100% polyester fabric is treated with octadecane- containing microcapsules by a knife-over-roll coating process. The amount of heat content increases as the concentration of microcapsules increases. and it decreases as the temper ature and time increase. The surfactant treatment at a given microcapsule concentration increases the heat content of the treated fabrics about 56-94%. The durability of the coated microcapsules lasts for about ten launderings. The treated fabric becomes stiffer and less smooth, soft, and full than the untreated fabric, as shown by KES measurements. Wear trials with the untreated and treated garments in a conditioned environment confirm the temperature sensing properties of treated garments. The cooling effect from thermal storage of the octadecane-containing microcapsules is revealed by results showing that the changes in the mean skin and microclimate temperature with the treated garment are less than for those wearing the untreated garment.

On the cold hardiness of Stereotydeus mollis (Acari: Prostigmata) from Ross Island, Antarctica

Summary Cold hardiness of the prostigmatid mite Stereotydeus mollis from Ross Island, Antarctica was investigated, and two years of microclimate temperatures recorded. There was no correlation between supercooling points and several microclimate parameters. Supercooling points changed significantly during the course of two summers, with highest median SCPs near the end of both summers. Osmolality was similar to what has been found in other Antarctic mites, however no thermal hysteresis activity was detectable in haemolymph samples. Preliminary investigations revealed that the main carbohydrates in the mite were glucose, trehalose and myo-inositol, with trace amounts of glycerol.

Cold tolerance of the Antarctic springtail Gomphiocephalus hodgsoni (Collembola, Hypogastruridae)

Cold tolerance of the springtail Gomphiocephalus hodgsoni Carpenter (Collembola: Hypogastruridae) was studied at Cape Bird, Ross Island, Antarctica (77°13′S, 166°26′E). Microclimate temperatures indicate a highly seasonal thermal environment, with winter minima &lt;–39°C. Snow cover significantly buffers both minimum temperatures and cooling rates. Gomphiocephalus hodgsoni survives low temperatures by avoiding freezing. Mean low group supercooling points (SCPs) ranged from –35.4°C in October to –28.3°C in January. The lowest SCP measured was –38.0°C. The high SCP group was very small, making up only 18% of the population in January. In October, G. hodgsoni had a very high glycerol content (&gt;80 μg mg−1 dry weight), although this declined rapidly to low levels (c. 7–10 μg mg−1 dry weight) in January. Quantities of glucose and trehalose were low during October, but steadily increased throughout the summer. Haemolymph osmolality was exceptionally high (up to 1755 mOsm kg−1) at the end of November, but this rapidly declined to c. 500 mOsm kg−1 by late December. The presence of thermal hystersis proteins was indicated by both osmometry on haemolymph samples and recrystallization inhibition studies of springtail homogenates. There was a strong relationship between glycerol content and SCP, but the relationship between haemolymph osmolality, SCP and carbohydrates is uncertain.

Field ecology of freeze tolerance: interannual variation in cooling rates, freeze‐thaw and thermal stress in the microhabitat of the alpine cockroach Celatoblatta quinquemaculata

Microclimate recordings were made over four years on the Rock and Pillar Range, New Zealand. These are used in conjunction with mortality and freezing data derived in the laboratory to make inferences about the winter thermal ecology of the freeze‐tolerant alpine cockroach Celatoblatta quinquemaculata (Dictyoptera: Blattidae). Threshold temperatures are identified through laboratory experiments at ecologically relevant cooling rates: 0°C; −3.1°C (FP5: the temperature at which 5% of cockroaches are expected to be frozen); and −4.5°C (FP50). The maximum cooling rate in the microhabitat across any of the thresholds was 0.06°C min−1, considerably slower than the 1°C min−1 normally used in laboratory studies. Freeze‐thaw events occurred regularly in the field, and temperature minima occasionally fell to temperatures lethal to C. quinquemaculata. Variability in snow cover contributed to interannual variation in microclimate temperatures. Decreased snow cover is predicted with climate change scenarios, and this will probably result in more freeze‐thaw cycles and more extreme minimum temperatures in this environment. It is concluded that the limited environmental tolerances of the animals living in this habitat make the few degrees of interannual variation ecologically relevant.

Heat of sorption induced by sweating affects thermoregulatory responses during heat load.

To investigate the effects of heat of sorption per se induced by sweating on thermoregulatory responses in clothed subjects, two experiments were carried out. In experiment 1 [ambient temperature (Ta) 27.2 degrees C, 50% relative humidity (r.h.)], seven female subjects immersed their lower-legs in a water bath at a temperature raised between 35-41 degrees C during 70 min wearing garments made for the experiment of either 100% cotton (C) or 100% polyester (P). Skin blood flow at the forearm was significantly greater in C than in P (P < 0.05). The increase of mean skin temperature (Tsk) and clothing surface and clothing microclimate temperatures were significantly higher in C than that of P after the onset of sweating (P < 0.05). Furthermore, these responses were accompanied by warmer and more uncomfortable sensations in C than in P despite a lower rectal temperature in C compared with P and identical mean body temperature in both sets of garments. In experiment 2, to simulate the clothing microclimate after the onset of sweating, C and P garments were exposed in the climate chamber to r.h. raised from 50% to 95% at a constant Ta of 27.2 degrees C. The clothing surface temperature rose by 2.2 degrees C for C and by 0.5 degree C for P after the increase of r.h. These results clearly showed a more marked increase in heat of sorption in C than in P. These results indicated that the heat of sorption per se after the onset of an increasing clothing microclimate vapour pressure, mimicking the onset of sweating, enhanced thermoregulatory responses such as skin blood flow, (Tsk) and subjective voting in C.

Patterns of arthropod abundance, vegetation, and microclimate at boreal forest edge and interior in two landscapes: Implications for forest birds

The effects of anthropogenic edges on leaf-litter and shrub arthropods were examined in both agriculture and forestry-dominated landscapes in central Saskatchewan, Canada. Microclimate, vegetation, and shrub and leaf-litter arthropods were sampled at south-facing forest edges and interiors of three sites within each landscape. Forest edges in the agricultural landscape were older and had vegetation structures that differed from those in the forestry landscape. This resulted in a sharper contrast in microclimate (temperature and humidity) between edge and interior in forests abutting agriculture than in stands abutting recent clearcuts. Arthropods from the leaf-litter and shrub-layer samples exhibited different responses to edges. In both landscapes, total shrub-arthropod abundance was not significantly affected by edges, while total leaf-litter arthropod abundance was lower at edges than in forest interiors. This reduced abundance of leaf-litter arthropods could negatively affect birds and other insectivorous vertebrates or could have been caused by greater vertebrate predation there. Forest edges in agriculture and forestry landscapes represent relative extremes in edge maturity, demonstrating that age of edges cannot completely mitigate edge effects on microclimate and abundance of arthropods. We discuss the implications of our findings for influences of forest fragmentation and landscape change on forest birds.

Effect of Grapevine Training Systems on Development of Powdery Mildew

The effects of two training systems and row spacing on development of powdery mildew caused by Uncinula necator on clusters of 'Chardonnay' and 'Cabernet Sauvignon' grapevines were examined. Disease development was monitored in blocks with two different row spacing (2 and 3 m) in vertical shoot positioned vines (VSP) and in free-positioned, topped vines (FC) with no foliage support wires. The FC vines were hedged to about one meter shoot length. No fungicides were applied and disease powdery mildew level was recorded four to seven days after appearance of the first disease symptoms. During five consecutive years (1994–1998), disease incidence was higher in the VSP system than the FC vines. The difference was high when disease level was low (30% of the clusters in VSP vines infected, compared to 5% in the FC vines) and decreased when disease pressure was high (79% in VSP compared to 46% in FC vines). In the 'Cabernet Sauvignon', in four of the years, disease incidence was higher in the narrow spacing of 2 m between the rows than that in the wider 3 m spacing. Microclimate (temperature, relative humidity and light intensity) was monitored in the cluster zone near the spurs of 'Chardonnay' vines during three weeks in the 1998 season. In VSP vines light intensity was lower then that in FC vines both four and one week before disease symptoms appeared (72% and 18% respectively). The differences in temperature and relative humidity were less than 1°C and 3%, respectively, and most likely did not affect disease development. The results suggested that high light intensity is the primary factor, which limits powdery mildew growth development on field-grown grapevines in the Golan region of Israel. The use of the FC system might be useful in reducing the need of fungicides.

EVALUACION ECOLOGICA DEL ANTIGUO BASURAL DE OVEJERIA (OSORNO, CHILE)

An ecological evaluation of the plant associations that were developed spontaneously in the old dump of Ovejeria (Osorno, Chile), using the ecological indicator values of species was made.For each species,the ecological indicator value of the microclimatic variables light and temperature and of the soil variables pH, nitrogen and humidily, were taken from the literature. the evaluation of the associations of the dump and a comparison with an anthropogenic prairie typical of this region, was made using ecological indicator values averages for each association calculated by presence and by cover of the species. The results confirm that the use of the ecological indicator values is a good tool to evaluate and to compare biotops of dumps and prairies, in its microclimate and soil characteristics. According to the ecological indicators values averages the vegetation of the dump is heliophyllous, termophyllous and nitrophyllous and very diff'erent to the vegetation of the adjacent prairie. It was proven a great variation of the ecological indicator values for the soil humidity factor between the different associations of the dump. The foregoing permits to characterize the flora and the vegetation of the studied dump as azonal.

Microclimatic parameters influencing nitrogen fixation in the phyllosphere in a Costa Rican premontane rain forest.

The acetylene reduction method was used to measure nitrogen fixation in the phyllosphere of attached leaves of different phorophytes under natural conditions in a premontane rain forest in Costa Rica. Maximum rates of nitrogen fixation (26 ng N · cm-2 leaf area · h-1) - mainly due to the activity of two species of Scytonema (Cyanobacteria) - were measured in the rainy season in bright sunlight. Rates of nitrogen fixation were correlated with the leaf area covered by Scytonema. In periods without precipitation the fixation activity decreased to zero within 2-3 days. As long as the epiphylls were sufficiently supplied with water, other microclimatic factors like temperature and light intensity also influenced nitrogen fixation rates, but to a lesser extent. Relative humidity and species of phorophyte showed no direct influence. It was concluded that the most important factor for nitrogen fixation in the phyllosphere was the availability of liquid water. Linking these results to meteorological data, the input of nitrogen by biological nitrogen fixation in the phyllosphere in the investigation area was estimated to be as much as 1.6 ± 0.8 kg N · ha-1 · year-1 per unit of leaf area index (LAI). For an LAI of 2 for the understory the nitrogen input would vary between 2 and 5 kg N · ha-1 · year-1. This work also demonstrates the importance of detailed knowledge of variation in microclimate throughout the year as a basis for extrapolation of the annual nitrogen input.

Physiological significance of hydrophilic and hydrophobic textile materials during intermittent exercise in humans under the influence of warm ambient temperature with and without wind.

The purpose of this present study was to compare the physiological effects of the hydrophilic and hydrophobic properties of the fabrics investigated in exercising and resting subjects at an ambient temperature of 30 degrees C and a relative humidity of 50% with and without wind. Three kinds of clothing ensemble were tested: wool and cotton blend with high moisture regain (A), 100% cotton with intermediate moisture regain (B), 100% polyester clothing with low moisture regain (C). The experiments were performed using seven young adult women as subjects. They comprised six repeated periods of 10-min exercise on a cycle ergometer at an intensity of 40% maximal oxygen uptake followed by 5 min of rest (20 min for the last rest). The experiments comprised two sessions. During session I (first three repetitions of exercise and rest) the subjects were exposed to an indifferent wind velocity and during session II (last three repetitions of exercise and rest) they were exposed to a wind velocity of 1.5 m x s(-1). Rectal temperature and skin temperatures at eight sites, pulse rate and clothing microclimate were recorded throughout the whole period. The main findings can be summarized as follows: rectal temperature during session II was kept at a significantly lower level in A than in B and C. Clothing microclimate humidity at the chest was significantly lower in A than in B and C during session II. Skin and clothing microclimate temperatures at the chest were significantly lower in A than in B and C during session II. Pulse rate was significantly higher in C than in A and B during sessions I and II. It was concluded that the hydrophilic properties of the fabrics studied were of physiological significance for reducing heat strain during exercise and rest especially when influenced by wind.

Efficacy of a water-cooled garment for auxiliary body cooling in heat

The efficacy of a water-cooled jacket for auxiliary body cooling was examined under a simulated hot environment. The personal garment comprised of a water re-circulating three-layered vest of cotton fabric lined with 2 mm diameter latex tubing and inter-spaced coating of rubberized solution. Four subjects wearing the water-cooled jacket were tested in the environment chamber (30, 35 and 40°C DB, 50–60% RH, air velocity 0·3, 0·6 and 0·9 m/s, with corresponding average effective temperature of 26±2·3, 33±1·1 and 36±1·5 C). The inlet water temperature was maintained at 10–12°C, with flow rates of 2·6±0·3, 4·3±0·3 and 5·1±0·3 l/h). At 30°C DB, variation in water flow had marginal effect on microclimate, while at higher temperatures (35 and 40°C DB), the re-circulating cooled water had noticeable effects in lowering microclimate, trunk and other skin temperatures, and maintaining the body core within 36·7±0·2 to 37·5±0·2°C, over 2 h exposure at 35 and 40°C DB. The observation indicates that the watercooled jacket provided auxiliary cooling to maintain comfortable microclimate, skin and body core temperatures. This enabled subjects to sustain comfortable heat balance over 2 h heat exposure without any noticeable heat strain.