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PubMed1990

Tracheal blood flow during spontaneous and mechanical ventilation of dry gases in sheep.

Tracheal blood flow increases greater than twofold in response to eucapnic hyperventilation of dry gas in anesthetized sheep. To determine whether this occurs at normal minute ventilation, we studied sheep in which tracheal blood flow was measured in response to humid and dry gas ventilation while 1) awake and spontaneously breathing and 2) anesthetized and intubated during isocapnic mechanical ventilation. In additional sheep, three tracheal mucosal temperatures were measured during humid and dry gas mechanical ventilation to measure airway tissue cooling. Tracheal blood flow was determined by use of a left atrial injection of 15-microns-diam radiolabeled microspheres. Previously implanted flow probes on the pulmonary artery and the common bronchial artery allowed continuous recording of cardiac output and bronchial blood flow. Tracheal blood flow in awake spontaneously breathing sheep was 10.8 +/- 5.6 (SD) ml.min-1.100 g wet wt-1 while humid gas was breathed, and it was unchanged with dry gas. In contrast, isocapnic ventilation of intubated animals with dry gas resulted in a 10-fold increase in blood flow to the most proximal two-ring tracheal segment compared with that seen while humid gases were spontaneously ventilated [101 +/- 75 vs. 11 +/- 6 (SD) ml.min-1.100 g-1, P less than 0.05]. Despite a 10-fold increase in proximal tracheal blood flow, there was no response in distal tracheal and bronchial blood flow, as indicated by no change in the common bronchial artery blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1995

Clothing, assessment and effects on thermophysiological responses of man working in humid heat.

This paper presents the relative importance of the different factors to be taken into account when predicting thermal exchanges when man is wearing garments while being exposed to warm environments. Factors considered are the thermal insulation of clothing (CLO), the thermal efficiency of clothing (Fcl), the clothing area factor (fcl), the pumping coefficient (p), the vapour permeation efficiency factor (Fpcl). As Fpcl depends on CLO, Fcl,fcl and p factors, physiological assessments of this factor appears to be necessary for the calculation of the maximum evaporative capacity (Emax) in clothed subjects. In this paper, comparisons of body temperatures, whole body and local sweating were made from data obtained on both unclothed and then clothed subjects working at 50 watts on a cycloergometer in warm environments (Ta = Tr = Tsk), with increasing ambient humidity levels (Pa). Results showed that clothed subjects sweated more than unclothed man for the same Pa increases and hidromeiosis occurring on the skin of unclothed man seemed to be responsible for this. Sweat accumulation in the clothes confirms that the decrease in the evaporative sweat efficiency for clothed subjects was closely associated with the threshold for occurrence of core temperature drift. However the less important slope in the Tcore vs delta Pa relationship for clothed subjects compared to that for unclothed implies a more efficient body cooling thanks to clothing, which does not lead to as great a physiological disadvantage as expected. Pumping effect and additional concurrent evaporation could account for this phenomenon: the ISO model (Required sweat rate) which includes an additional air velocity as a function of metabolism allows us to consider this beneficial influence of increased Emax in clothed subjects. However this effect should not be considered when the model is used for unclothed subjects.

Adult↗
PubMed1985

An evaluation of the response of some portable, direct-reading 10.2 eV and 11.8 eV photoionization detectors, and a flame ionization gas chromatograph for organic vapors in high humidity atmospheres.

Three portable, direct-reading instruments were tested to evaluate their ability to detect organic vapors in high humidity atmospheres. The instruments included two photoionization detectors (10.2 eV and 11.8 eV), and an organic vapor analyzer with a flame ionization detector. The organic vapors used were hexanes, 1,1-dichloroethane, chloroform, trichloroethylene, perchloroethylene, benzene, toluene and chlorobenzene. Relatively impervious gas bags were used to contain atmospheres of low (zero) and high (90 percent) relative humidities for comparisons. The response of the organic vapor analyzer was practically independent of humidity. The responses of the photoionization detectors were influenced by high humidity even though the 10.2 eV lamp did not detect water vapor itself. The photoionization detectors were adjudged to be unsuitable for quantitative sampling of humid confined spaces since the 11.8 eV lamp was sensitive to water vapor and the 10.2 eV lamp showed unpredictable response factors in high humidity.

Air Pollutants, Occupational↗
PubMed1975

Ultrastructural Effects of Water Stress on Chloroplast Development in Jack Bean (Canavalia ensiformis [L.] DC).

An ultrastructural study has been made to determine to what degree chloroplast differentiation is retarded in leaves of young jack bean (Canavalia ensiformis [L.] DC.) seedlings when they are subjected to mild water stress. Rapid chloroplast differentiation occurred when etiolated seedlings were allowed to green at relative humidities above 85% but not at a relative humidity of 25%. Response to a drop in humidity was rapid. Germination and early development in the dark occurred at 100% relative humidity. At the time of exposure to light, the etioplasts contained well formed prolamellar bodies. Under high relative humidity conditions, transformation of the prolamellar body was well advanced within 2 hours. Under low relative humidity conditions, however, prolamellar body differentiation was extremely retarded for more than 24 hours following the beginning of illumination.

Journal Article↗
PubMed2005

Effect of temperature and relative humidity on the cellular defense response of Ephestia kuehniella larvae fed Bacillus thuringiensis.

While maintained under all combinations of three temperatures and two RH, fifth instar larvae of the Mediterranean flour moth, Ephestia kuehniella were fed wheat treated with spores and crystals of Bacillus thuringiensis var. kurstaki. Larvae that had fed on wheat with the bacterial preparation contained higher concentrations of nodules in their haemocoel than did larvae fed on wheat without bacteria. Nodule concentrations in larvae fed untreated wheat were unaffected by temperature or relative humidity. Larvae fed treated wheat had higher nodule concentrations at 32 degrees C than at 15 and 23 degrees C, and higher nodule concentrations at a relative humidity of 85% than at 43%. The percentage of larvae that pupated was lower when larvae were fed the bacterial preparation, and was significantly higher at 23 degrees C than at 15 and 32 degrees C, regardless of whether larvae were fed bacteria or not. Less time was required for larvae to develop to pupation at higher temperatures and at higher humidity. Mean time to pupation was lower for bacteria-fed larvae than for those fed untreated wheat, and this appeared to be a result of truncation of the distribution of times to pupation because only rapidly developing larvae survived to pupation.

Animal Feed↗
PubMed1990

The magnitude of the stomatal response to blue light : modulation by atmospheric humidity.

The effect of leaf-air vapor pressure difference (VPD) on the magnitude of the stomatal response to blue light was investigated in soybean (Glycine max) by administering blue light pulses (22 seconds by 120 micromoles per square meter per second) at different levels of VPD and temperature. At 20 degrees C and 25 degrees C, the magnitude of the integrated conductance response decreased with increasing VPD (0.4 to 2.6 kiloPascals), due to an earlier onset of stomatal closure that terminated the pulse response. In contrast, at 30 degrees C this magnitude increased with rising VPD (0.9 to 3.5 kiloPascals), due to an increasing maximum excursion of the conductance response despite the accelerated onset of stomatal closure. When the feedforward response of stomata to humidity caused steady state transpiration to decrease with increasing VPD, the magnitude of the pulse-induced conductance response correlated with VPD rather than with transpiration. This suggests that water relations or metabolite movements within epidermal rather than bulk leaf tissue interacted with guard cell photobiological properties in regulating the magnitude of the blue light response. VPD modulation of pulse magnitude could reduce water loss during stomatal responses to transient illumination in natural light environments.

Journal Article↗
PubMedDate not supplied

Ocular, airway, and dermal symptoms related to building dampness and odors in dwellings.

The authors examined the relationship between symptoms of Sick Building Syndrome and reports of building dampness and odors. Two hundred thirty-one multifamily buildings built prior to 1961 in Stockholm, Sweden, contained a total of 4,815 dwellings. The authors selected these buildings for study by stratified random sampling. Occupants answered a postal questionnaire that assessed weekly symptoms, personal factors, population density in each apartment, water leakage in the preceding 5 yr, different types of odors, and signs of high indoor air humidity. The response rate was 77%. Independent information on building characteristics was gathered from the building owners and the central building register in Stockholm. Multiple logistic-regression analysis was applied and odds ratios were calculated, with adjustments for age, gender, current smoking, hay fever, population density, type of ventilation, and ownership of the building. In total, 22% reported at least 1 sign of dampness, and 32% reported odor in the dwelling. Condensation on windows, high air humidity in the bathroom, moldy odor, and water leakage were reported from 6.8%, 8.8%, 5.7%, and 13% of the dwellings, respectively. A combination of odor and signs of high humidity was related to an increased occurrence of all symptoms (odds ratios = 2.2-3.6). Similar findings were observed for a combination of odors and a history of water leakage in the past 5 yr (odds ratios = 1.2-4.4). Symptoms increased with the number of signs of dampness. The study indicated that dampness in dwellings, with emissions of odorous compounds, are associated with an increase in symptoms consistent with Sick Building Syndrome.

Adolescent↗
PubMed1998

Response of turkeys to relative humidity at high ambient temperature.

1. The effects of relative humidity on growth rate and thermoregulation at high ambient temperature were evaluated in turkeys. Male turkeys were exposed to ambient temperature (Ta) of 35 degrees C and relative humidity (RH) of 40% to 75% and 50% to 85%, at ages of 13 to 19 weeks (trial 1) and 10 to 15 weeks (trial 2), respectively. 2. Body weight and food intake in both trials increased as RH increased up to 70% to 75%. When RH increased further to 80% to 85% (Trial 2) both body weight and food intake declined significantly. 3. Blood CO2 partial pressure (pCO2) did not change significantly at different RHs (trial 1). However, in trial 2 it dropped significantly at 80% to 85% RH. This response coincided with an increase in blood pH. 4. The effect of RH on body temperature (Tb) was not significant in either trial. 5. Triiodothyronine (T3) concentrations increased with the increase in RH up to 70% to 75% RH (trials 1 and 2). A significant decrease was observed when RH was further increased to 80% to 85% RH (Trial 2). Positive linear correlations between T3 and food intake or weight gain were observed in both trials. 6. The results indicate that turkeys can thermoregulate efficiently in the face of extreme changes in RH and that only at high RH (above 75%) did the performance of turkeys deteriorate.

Aging↗
PubMed1999

Stomatal behavior of four woody species in relation to leaf-specific hydraulic conductance and threshold water potential.

Midday stomatal closure is mediated by the availability of water in the soil, leaf and atmosphere, but the response to these environmental and internal variables is highly species specific. We tested the hypothesis that species differences in stomatal response to humidity and soil water availability can be explained by two parameters: leaf-specific hydraulic conductance (K(L)) and a threshold leaf water potential (Psi(threshold)). We used a combination of original and published data to estimate characteristic values of K(L) and Psi(threshold) for four common tree species that have distinctly different stomatal behaviors: black cottonwood (Populus trichocarpa Torr. & Gray.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), red alder (Alnus rubra Bong.) and western hemlock (Tsuga heterophylla (Raf.) Sarg.). We used the values to parameterize a simple, nonelastic model that predicts stomatal conductance by linking hydraulic flux to transpirational flux and maintaining Psi(leaf) above Psi(threshold). The model successfully predicted fundamental features of stomatal behavior that have been reported in the literature for these species. We conclude that much of the variation among the species in stomatal response to soil and atmospheric water deficits can be explained by K(L) and Psi(threshold). The relationship between Psi(threshold) and xylem vulnerability to cavitation differed among these species.

Journal Article↗
PubMed1999

Physiological responses of horses to a treadmill simulated speed and endurance test in high heat and humidity before and after humid heat acclimation.

To investigate whether horses were able to acclimate to conditions of high temperature and humidity, 5 horses of different breeds were trained for 80 min on 15 consecutive days on a treadmill at 30 degrees C and 80%RH. Training consisted of a combination of long duration low-intensity exercise, medium duration medium intensity exercise and short duration high intensity exercise. Between training sessions the horses were maintained at 11+/-3 degrees C and 74+/-2%RH. Before (PRE-ACC) and after acclimation (POST-ACC) the horses undertook a simulated Competition Exercise Test (CET), designed to represent the Speed and Endurance Test of a 3-day event, at 30 degrees C/80%RH. Maximal oxygen uptake (VO2PEAK) was not changed following acclimation (PRE-ACC 141+/-8 ml/min/kg bwt vs. POST-ACC 145+/-9 ml/min/kg bwt [STPD], P>0.05). Following acclimation, 4 of the 5 horses were able to complete a significantly greater amount of Phase D in the CET (PRE-ACC 6.3+/-0.3 min vs. POST-ACC 7.3+/-0.3 min, P<0.05; target time = 8 min). Resting body temperatures (pulmonary artery [TPA], rectal [TREC] and tail-skin [TTSK] temperatures) were all significantly lower following acclimation. During exercise, metabolic heat production (M) and heat dissipation (HD), for the same exercise duration, were both significantly lower following acclimation (P<0.05), although heat storage (HS) was significantly higher (P<0.05). The higher heat storage following acclimation was associated with a lower TTSK for a given TPA and a decreased total fluid loss (% bodyweight, P<0.05). Plasma volume was not changed following acclimation. The relationship of sweating rate (SR) to TPA or TTSK on either the neck or the gluteal region was not significantly altered by acclimation, although the onset of sweating occurred at a lower TPA or TTSK following acclimation (P<0.05). The horses in the present study showed a number of physiological adaptations to a period of 15 days of exposure to high heat and humidity consistent with a humid heat acclimation response. These changes were mostly similar to those reported to occur in man and other species and were consistent with thermal acclimation and an increased thermotolerance, leading to an improved exercise tolerance. It is concluded that a 15 day period of acclimation is beneficial for horses from cooler and or drier climates, that have to compete in hot humid conditions and that this may redress, to some extent, the decrement in exercise tolerance seen in nonacclimated horses and reduce the risk of heat related disorders, such as heat exhaustion.

Acid-Base Equilibrium↗
PubMed2002

Co-ordination of vapour and liquid phase water transport properties in plants.

The pathway for water movement from the soil through plants to the atmosphere can be represented by a series of liquid and vapour phase resistances. Stomatal regulation of vapour phase resistance balances transpiration with the efficiency of water supply to the leaves, avoiding leaf desiccation at one extreme, and unnecessary restriction of carbon dioxide uptake at the other. In addition to maintaining a long-term balance between vapour and liquid phase water transport resistances in plants, stomata are exquisitely sensitive to short-term, dynamic perturbations of liquid water transport. In balancing vapour and liquid phase water transport, stomata do not seem to distinguish among potential sources of variation in the apparent efficiency of delivery of water per guard cell complex. Therefore, an apparent soil-to-leaf hydraulic conductance based on relationships between liquid water fluxes and driving forces in situ seems to be the most versatile for interpretation of stomatal regulatory behaviour that achieves relative homeostasis of leaf water status in intact plants. Components of dynamic variation in apparent hydraulic conductance in intact plants include, exchange of water between the transpiration stream and internal storage compartments via capacitive discharge and recharge, cavitation and its reversal, temperature-induced changes in the viscosity of water, direct effects of xylem sap composition on xylem hydraulic properties, and endogenous and environmentally induced variation in the activity of membrane water channels in the hydraulic pathway. Stomatal responses to humidity must also be considered in interpreting co-ordination of vapour and liquid phase water transport because homeostasis of bulk leaf water status can only be achieved through regulation of the actual transpirational flux. Results of studies conducted with multiple species point to considerable convergence with regard to co-ordination of stomatal and hydraulic properties. Because stomata apparently sense and respond to integrated and dynamic soil-to-leaf water transport properties, studies involving intact plants under both natural and controlled conditions are likely to yield the most useful new insights concerning stomatal co-ordination of transpiration with soil and plant hydraulic properties.

Journal Article↗
PubMedDate not supplied

Effects of concentrated ambient particles on airway responsiveness and pulmonary inflammation in pulmonary hypertensive rats.

Epidemiological studies have associated particulate air pollution with exacerbation of lung function in human populations. However, the relationship between ambient particles and lung function in animal studies has been inconsistent. In order to investigate the effects of concentrated ambient particles (CAPs) on airway responsiveness, we exposed pulmonary hypertensive rats to CAPs using particle concentrator at an EPA of Taiwan supersite, located at a traffic busy urban area nearing Taipei city. The exposure group (n = 5) was exposed to CAPs for 6 h each day for 3 consecutive days (mean mass concentration = 371.7 microg/m(3)), while a control group (n = 6) was exposed to HEPA-filtered air. Whole-body barometric plethysmography was used to measure respiratory frequency, tidal volume, and airway responsiveness before and after exposure. Enhanced pause (Penh) was used as an indicator of airway responsiveness. To improve the accuracy of airway responsiveness measurement, we controlled temperature and humidity. Further, airway responsiveness was determined 5 h after particle exposure to overcome the stress effect in nose-only exposure chambers. After CAPs exposure, we found decreased respiratory frequency and increased tidal volume (p < .05). Using the methacholine challenge test, a significant difference of Penh measured before and after experiment was observed in the CAPs group (p < .05), but not in the filtered air group. Further analysis showed that the Penh difference before and after exposure in the CAPs group was significantly greater than that in the filtered air group (p < .05). We conclude that CAPs could induce airway hyperresponsiveness in pulmonary hypertensive rats.

Air Pollutants↗
PubMed1993

Comparison of chemiluminescence and ultraviolet ozone monitor responses in the presence of humidity and photochemical pollutants.

The effect of water vapor and other pollutants on ozone monitoring instruments was investigated. Five UV-type and two chemiluminescence-type monitors were employed in this study. The results of the study indicate that in systems containing ozone, water vapor and zero air only, the UV-based monitors showed negligible effects due to humidity. On average, the UV monitors were within 0.5 percent of independently determined ozone values judged to be extremely accurate. The chemiluminescence-based monitors showed systematically higher readings than the UV monitors with added water vapor. The effect was found to be linear with water vapor concentration with an average positive deviation of 3.0 percent per percent H2O at 25 degrees C. For these measurement, ozone concentrations ranged from 85 to 320 ppbv and water concentrations from 1 to 3 percent (i.e., dew point temperatures from 9 to 24 degrees C). These results are largely in agreement with previous studies conducted to measure this interference, although the present study extends the range of water concentrations tested. Studies were also performed with a smog chamber with simulated polluted air (containing paraffinic, olefinic and aromatic hydrocarbon precursors) and varying relative humidities. Although the presence of water vapor did not appear to represent a substantial interference in these systems, a positive interference was observed with the UV monitors. This interference was likely a result of the presence of toluene and some of its aromatic photooxidation products (e.g., benzaldehyde), which can be partially removed from the reference stream by the ozone scrubber within the UV monitor. If the compound absorbs radiation at 254 nm, it is detected as ozone. However, when the results are scaled back to ambient concentrations of toluene and NO(x), the effect appears to be very minor (ca. 3 percent under the study conditions). It is concluded that under atmospheric conditions at moderate pollution and relative humidity levels, both types of instruments can give accurate measurements of the ozone concentration. These potential effects should be recognized when conducting ambient ozone measurements.

Journal Article↗
PubMed2005

Thermoregulation responses of broiler chickens to humidity at different ambient temperatures. II. Four weeks of age.

Two experiments were conducted to investigate the effect of RH (35, 60, and 85%) on thermoregulation of broiler chickens at high (35 degrees C) and mild (30 degrees C) temperatures at the age of 4 wk. The effects of humidity on rectal temperature (RT) and plumage temperature at back (PBAT) and skin temperature at breast (SBRT) were determined at 1, 4, 8, 16, and 24 h after exposure. The RT, PBAT, and SBRT were all significantly increased by high temperature (35 degrees C). Humidity had a significant influence on RT at 35 degrees C but not at 30 degrees C. The peripheral temperatures (PBAT and SBRT) were significantly affected by humidity but responded differently at high (35 degrees C) compared with mild temperature (30 degrees C). In conclusion, high humidity above 60% impaired the heat transmission from body core to the periphery at 35 degrees C but facilitated it at 30 degrees C in 4-wk-old broiler chickens. The effect of humidity on nonevaporative heat loss was depended on air temperature, as nonevaporative heat loss was suppressed by high humidity (>60% RH) at high temperature but enhanced at the mild temperature. The effect of humidity on the relationship between peripheral and core temperature depends on ambient temperature as well as on the age of the broiler chicken. The disturbance of thermal balance could not be determined only by changes in RT or peripheral temperature at a single time point but could be determined by mean body temperature within a certain time frame.

Aging↗
PubMed1996

Growth indices and stomatal control of transpiration in Acacia koa stands planted at different densities.

We examined the influences of selected environmental variables on stomatal behavior and regulation of transpiration in 26-month-old Acacia koa Gray (koa) stands planted at spacings of 1 x 1 m or 2.5 x 2.5 m and grown without irrigation. Field measurements were made during recovery from an extended 60-day dry period with only 38 mm of precipitation. Biomass and leaf area were also measured at 3-month intervals over the first 24 months after planting and again following completion of the transpiration (T) and stomatal conductance (g(s)) measurements at about 26 months after planting. Transpiration was measured as sap flow through intact branches by a heat balance method. After a 22-day period during which 130 mm of rain were recorded, average T was substantially higher in the 2.5 x 2.5 m stand on both a leaf area and ground area basis even though leaf area index was about 3.5 times higher in the 1 x 1 m stand. After an additional 25 mm of rain during an 8-day period, T was still slightly higher on a leaf area basis in the 2.5 x 2.5 m stand but was about 3 times higher on a ground area basis in the 1 x 1 m stand. A strong stomatal response to humidity limited the increase in T with increasing evaporative demand. Values of g(s) in koa phyllodes were comparable to those reported for leaves of other mesic tropical forest trees, but were several times higher than those reported for Acacia species native to arid and semi-arid regions. The 1 x 1 m planting yielded three times more biomass per unit ground area than the 2.5 x 2.5 m planting. However, greater stand density, which resulted in more rapid depletion of soil water between rainfall inputs, was associated with lower growth efficiency and lower radiation conversion efficiency.

Journal Article↗
PubMed1974

Efficiency and regulation of water transport in some woody and herbaceous species.

The efficiency with which plants transport water is related to the water potential differences required to drive water fluxes from the soil to the leaf. A comparative study of two woody and three herbaceous species (Citrus sinensis L. cv. Koethen, Pyrus kawakami L., Helianthus annuus L. cv. Mammoth Russian, Capsicum frutescens L. cv. Yolo Wonder, and Sesamum indicum L. cv. Glauca) indicated contrasts in water transport efficiency. Depression of leaf water potential in response to transpiration increases was found in the woody species; the herbaceous species, however, had more efficient water transport systems and presented no measurable response of leaf water potential to transpiration changes. Different maximum transpiration rates under the same climatic conditions were observed with different species and may be accounted for by stomatal response to humidity gradients between leaf and air. Leaf diffusion resistance in sesame increased markedly as the humidity gradient was increased, while leaf resistance of sunflower responded less to humidity. Stomata appeared to respond directly to the humidity gradient because changes in leaf water potential were not detected when leaf resistance increased or decreased.

Journal Article↗
PubMed1986

Effect of mesomorphy on hyperthermia during exercise in a warm, humid environment.

The hyperthermic response to exercise in a warm (30 degrees C), humid (80% relative humidity) environment was obtained for 27 men who exhibited a wide range of body physique in terms of the mesomorphy component of somatotype. Increase in tympanic temperature (Yty) was significantly dependent on mesomorphy rating (X) according to the regression equation Yty = -0.390 + 0.088X. Increase in rectal temperature (Yre) was also significantly dependent on mesomorphy rating according to the equation Yre = -0.100 + 0.066X. The hyperthermic response was significantly correlated with other measures of physique, including ectomorphy, surface area/weight ratio, and body weight, but was not correlated with fatness or fitness. The results support the generalization that during exercise in a warm, humid environment individual differences in heat strain can be highly dependent on physique, especially if fitness and fatness are similar. In this context, mesomorphy appears to provide the optimum description of physique variation. Individuals with a mesomorphy rating greater than 7 warrant designation as being at high risk for heat intolerance during exercise in environments that significantly impair the rate of body heat loss.

Adolescent↗
PubMed1986

Physique and thermoregulation in prepubertal males during exercise in a warm, humid environment.

The hyperthermic response to exercise in a warm (30 degrees C), humid (80% relative humidity) environment was obtained for 23 prepubertal males. After the initial increase of core temperatures (tympanic and rectal) to elevated set points, further hyperthermia was minimal and was unrelated to any physique variable except for the case of endomorphy, which was weakly correlated with hyperthermia at the rectal site. This result for boys is attributed to the combination of small body size (relative to adults) and absence of pronounced, age-dependent muscular development as evidenced by low rating and small variation of the mesomorphy component of somatotype. Both of these factors were associated with a high surface area to weight ratio compared to adults, which facilitated heat loss. It is concluded that prepubertal males thermoregulate efficiently during moderate exercise in a warm, humid environment. Other than cases of obesity, variation in physique is not an important consideration for assessing the risk of heat strain.

Adolescent↗