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Health and Safety
Published in Kenneth F. Cherry, Asbestos, 2020
The degree to which a worker’s body has physiologically adjusted or acclimatized to working under hot conditions affects his or her ability to work. Acclimatized individuals generally have lower heart rates and body temperatures than unacclimatized individuals, and sweat sooner and more profusely. This enables them to maintain lower skin and body temperatures at a given level of environmental heat and work loads than unacclimatized workers. Sweat composition also becomes more dilute with acclimatization, which reduces salt loss. Acclimatization can occur after just a few days of exposure to a hot environment. The National Institute of Occupational Safety and Health recommends a progressive six-day acclimatization period for the unacclimatized worker before allowing him/her to do full work on a hot job. Under this regimen, the first day of work on site is begun using only 50% of the anticipated work load and exposure time, and 10% is added each day through day six. With fit or trained individuals, the acclimatization period may be shortened two or three days. However, workers can lose acclimatization in a matter of days, and work regimens should be adjusted to account for this.
How we experience indoor and outside climates
Published in Karl H.E. Kroemer, Fitting the Human, 2017
Acclimatization is the status of adjustment of an individual’s body (and mind) to changed environmental conditions. The process of getting there is called acclimation. Acclimation of the body to a hot environment mostly improves the control of blood flow to the skin, facilitates sweating, and increases the stroke volume of the heart without increase in heart rate. Healthy and fit persons achieve heat acclimatization in one or two weeks but can lose it just as quickly. In contrast, in a moderately cold environment usually very little physiological acclimation of the whole body takes place since most of the adjustment made concerns proper clothing, beneath which the body performs in its usual microclimate. However, the blood flow to exposed surfaces of the face and the neck and to the hands and the feet can adapt to cold conditions.
Hypobaric Hypoxia: Adaptation and Acclimatization
Published in Anthony N. Nicholson, The Neurosciences and the Practice of Aviation Medicine, 2017
John H. Coote, James S. Milledge
With acute systemic hypoxia, as occurs on ascent to high altitude, the high gradient of oxygen tension from arteriole and capillary to tissue will inevitably decrease and so oxygen delivery is compromised. There are several changes that attempt to limit the effect on brain function, some of which have been referred to earlier. Acutely, cerebral vessel dilatation increases cerebral blood flow and the carotid chemoreceptor-induced hyperventilation reduces the magnitude of decrease in oxygen tension in the blood supplying the brain. During acclimatization, oxygen delivery is further improved by an increase in the number of red blood cells due to hypoxia-induced release of erythropoietin which stimulates erythropoiesis. Perhaps most importantly, the oxygen environment close to neurons is improved by a lessening of the diffusion distance by angiogenesis leading to an increase in the number of capillaries and small arterioles (Figure 7.9). According to studies on experimental animals exposed to hypobaric hypoxia for three weeks, the number of capillaries in the cortex may double (LaManna et al., 2004; LaManna, 2007). The target genes for erythropoiesis and for angiogenesis are activated by the hypoxia-sensitive transcription factor HIF-1α, as described in a previous section.
Concurrent validity of the CORE wearable sensor with BodyCap temperature pill to assess core body temperature during an elite women’s field hockey heat training camp
Published in European Journal of Sport Science, 2023
Paul S. R. Goods, Peta Maloney, Joanna Miller, Denise Jennings, Jack Fahey-Gilmour, Peter Peeling, Brook Galna
The most well accepted method for combatting the physiological stress associated with exercise in the heat is to undergo a heat acclimation or acclimatisation intervention (Racinais et al., 2015). While individual rates and magnitudes of physiological adaptations to heat exposure may vary, it is well accepted that interventions should illicit increases in sweating and core body temperature (Tc) (Racinais et al., 2015). Traditionally, exercise-based heat exposures resulting in Tc increases to ≥38.5°C have been recommended to induce optimal physiological adaptations (Fox et al., 1963), and while several new methods have now been developed, it remains important that the stimulus induces increases in Tc (Daanen et al., 2018). To confirm the Tc stimulus applied, the measurement of Tc during heat acclimation interventions is vital, usually performed in laboratory trials using esophageal (Maloney et al., 2021) or rectal (Dennis et al., 2021) thermometers. However, these invasive procedures are not possible to employ during field-based interventions, and therefore, non-invasive methods for assessing Tc in the sporting environment have received recent attention (Racinais et al., 2019; Verdel et al., 2021).
Effects of heat load and hypobaric hypoxia on cognitive performance: a combined stressor approach
Published in Ergonomics, 2023
Charelle Bottenheft, Eric L. Groen, Douwe Mol, Pierre J. L. Valk, Mark M. J. Houben, Boris R. M. Kingma, Jan B. F. van Erp
Furthermore, this study showed that cognitive performance significantly declines under heat load. Thus, attention should be paid to the consequences of the rise of temperature in the cockpit during flight preparations. However, the participants in our study were not acclimatised to heat before the test days. Acclimatisation to heat results in various changes in physiological responses that can make it easier for the body, and therefore probably also for the cognitive state, to cope with warm climates. Therefore it is reasonable to assume that the results obtained in this study are not applicable to heat acclimatised people. Nevertheless, it is possible that personnel acclimatised to a hot climate can temporarily encounter even higher temperatures. For example, during the pre-takeoff check on the ground, the temperature inside a helicopter cockpit can increase significantly above the air temperature to which the aircrew has been acclimatised. The results of our study apply to such situations.
Continuous forearm cooling attenuates gastrointestinal temperature increase during cycling
Published in Journal of Sports Sciences, 2021
Eric T. Hedge, Kathryn A. Zuj, Alexander G. Stothart, Erica H. Gavel, Len S. Goodman, Andrew J.M. Buckrell, Sean D. Peterson
Exercise results in increased metabolic heat production which is mitigated through thermoregulatory heat dissipation pathways (Gisolfi & Wenger, 1984). While these pathways are usually efficient in maintaining core body temperature (Tc), environmental conditions, such as high ambient temperature and humidity, can reduce heat dissipation leading to heat accumulation and exacerbated heat strain. The combination of metabolic heat production and environmental factors can correspond with an increase of Tc, rating of perceived exertion (RPE), and thermal comfort (Maw et al., 1993). Furthermore, the combination can result in diminished exercise performance (Nybo & Nielsen, 2001; Peiffer & Abbiss, 2011; Periard et al., 2011) and lead to heat exhaustion, heat stroke, and irreversible cellular damage (Harker & Gibson, 1995). Consensus guidelines suggest using a combination of heat acclimatization, hydration, and cooling strategies to combat heat stress (Racinais et al., 2015). While it is not uncommon for the Tc of elite level cyclists to be greater than 40°C without developing heat illness (Racinais et al., 2019), the highest rates of exertional heat injury are observed in endurance sports, including cycling, with studies reporting 0.67–5.96% of athletes experiencing heat illness at a given competition (Gamage et al., 2020). Therefore, development of a practical cooling device that attenuates the accumulation of heat in the body while cycling would be beneficial, and possibly lead to reduced risk of injury and improved performance.