Documents regulation of body temperature 8 results

Protective clothing (PC) results in a micro-environment between itself and the body. Workers are then exposed to a heat stress greater than the ambient environment alone, which is a reflection of micro-environment, metabolic rate and time. Adjustments to the ambient environment to account for the micro-environment have been formulated as a means to predict heat strain for safety and productivity purposes. Measurement of the actual micro-environment was made for a mean of 63.1?7.9 min using a remote sensor at the shoulder, hip and thigh levels on 15 subjects during a continuous work protocol (300 kcal/h) in impermeable PC at an ambient temperature of 30.1°C wet bulb globe temperature (WBGT) (32°C dry, 29°C wet, 33°C globe). Micro-environment temperature increased over the duration of the work period. There was no statistically significant difference ( p >0.05) between the measurements made at the three different body sites for temperature or humidity. The mean micro-environmental WBGT at the end of work was 34.6°C WBGT. Micro-environment WBGT increased rapidly in the first 20 min of work then slowed, rising only 0.5°C WBGT from 40 to 60 min. These results suggest that at this particular high ambient temperature (30.1°C WBGT) an adjustment factor of 5°C WBGT would give a more accurate indication of thermal stress for up to 1 h of continuous moderate work within PC. For shorter work durations, an even smaller adjustment would be appropriate.

"Thermoregulatory and thermal subjective responses were studied in ten male, clothed subjects during continuous (C) and intermittent (I) exercise at the same average level of oxygen consumption. The subjects performed both I and C twice, dressed in two different three-layer cold-protective clothing ensembles of two thermal insulation levels [total clothing insulation = 2.59 clo (L) and 3.20 clo (H)]. Experiments were carried out at an ambient temperature of -10 degrees C. Rectal temperatures increased similarly in both types of exercise. Mean skin temperature (Tsk) was lower in I compared to C with both levels of clothing insulation. Over the last 0.5 h of the experiment Tsk was approximately 1.3 degrees C lower in I than in C for clothing L. The skin evaporation rate was higher in clothing H than L but did not differ between I and C. Subjective ratings for thermal sensations of the whole body (BTS) and hands were close to neutral in I and around slightly warm in C. The BTS was lower in I than in C and was lower in L compared to H. It was concluded that, at equal average energy expenditure, thermal responses to intermittent and continuous exercise in the cold differ in clothed subjects, principally as a result of different patterns of heat exchange."

"Intrinsic thermal clothing insulation and surface air insulation were measured on human subjects by the use of indirect calorimetry. Four male clothing ensembles (0-1-1 -8 clo) and three female clothing ensembles (0-2-1-2 clo) were investigated. Using the standing position as a reference, the influence of sitting, bicycling (40r.p.m., 20 W), walking (3-75 km hour−1) and of light packing work on the thermal insulation was studied. The influence of an air velocity of 11ms−1 on thermal insulation during the standing and walking conditions was investigated. The results showed that: (i) intrinsic clothing insulation was maximal in the standing position. It was reduced by 8-18% in the seated position and by 30-50% during bicycling and walking. An air velocity of 11ms−1 did not influence the intrinsic clothing insulation during walking, but decreased it by 18% in the standing position; (ii) surface air insulation varied with activity and air velocity, but not with clothing. It was increased by up to 25% in the seated position, reduced by 7-26% during bicycling and by 30-50% during walking. An air velocity of 11 ms-1 reduced the surface air insulation by 50% in the standing position and 30% during walking."

"The purpose of this study was to investigate the significance of work level and sweat production for the total amount accumulated and the location of the sweat in a three-layer ensemble as a function of material and textile construction. Furthermore, it was also an aim to investigate how this influenced thermoregulatory responses and thermal comfort during work and during a rest period. Long-legged/long-sleeved underwear manufactured from two different 100% fibre-type materials, polypropylene and wool, was tested as part of a three-layer clothing system. The underwear manufactured from 100% polypropylene was tested in two different knit constructions, a 1 -by-1 rib knit and a fishnet structure, and the woollen underwear in a 1 -by-1 rib knit construction. The test was performed on eight male subjects (Ta= I0°C, RH = 85%, Va <0-lm/s), and comprised a twice-repeated bout of 40-min cycle exercise followed by 20 min rest. Each subject conducted two tests with the work level approximating 30% [Vdot]o2 max and 40% [Vdot]o2 max, respectively. Skin temperatures, rectal temperature, weight loss and humidity near the skin were recorded during the test. Total changes in body and clothing weight were measured separately. Furthermore, subjective ratings on thermal comfort and on sensation of temperature and humidity were collected. The results demonstrated that high heat and sweat production during work periods, leading to increased sweat accumulation, will give higher thermal discomfort ratings for rest periods as well as for work periods compared to intermittent work with lower work intensities. Distribution of accumulated sweat in the clothing ensemble after heavy sweating is dependent on the fibre type in the underwear. Further, it can be concluded that underwear construction clearly has an influence on the evaporation rate in a three-layer ensemble during work at a high activity level."

"Sommaire : La motricité, Postures et mouvements, Dépense énergétique chez l'homme, Besoin énergétiques de l'homme au travail, Adaptations respiratoires et circulatoires du travail musculaire, Régulations végétatives neuro-endocriniennes - L'adaptation, l'agression, Ambiances thermiques, Vie et travail dans les climats chauds, Vie et travail dans les climats froids, Vie travail et altitude, Travail en hyperbarie, Effets des vibrations sur l'homme, Effets physiologiques des accélérations, Eléments de psychophysique acoustique, Audition et effets du bruit sur l'organisme, Vision et éclairage, Travail et prise d'information, Rythmes circadiens - Sommeil veille et travail, Vigilance et travail monotone, Eléments de méthologie ergonomique, Travail et vieillissement, Physiologie du travail et législation."