scholarly journals Physiological tolerance to uncompensated heat stress in soldiers: Effects of various types of body cooling systems

2014 ◽  
Vol 71 (3) ◽  
pp. 259-264 ◽  
Author(s):  
Dalibor Jovanovic ◽  
Radovan Karkalic ◽  
Snjezana Zeba ◽  
Miroslav Pavlovic ◽  
Sonja Radakovic
Keyword(s):  
Heart Rate ◽  
Heat Stress ◽  
Cooling System ◽  
Tympanic Temperature ◽  
Hydration Status ◽  
Physiological Strain ◽  
Cooling Systems ◽  
Physiological Tolerance ◽  
Body Cooling ◽  
Exertional Heat Stress

Background/Aim. In military services, emergency situations when soldiers are exposed to a combination of nuclear, biological and chemical (NBC) contamination combined with heat stress, are frequent and complex. In these specific conditions, usage of personal body cooling systems may be effective in reducing heat stress. The present study was conducted in order to evaluate the efficiency of four various types of contemporary personal body cooling systems based on the ?Phase Change Material? (PCM), and its effects on soldiers? subjective comfort and physiological performance during exertional heat stress in hot environments. Methods. Ten male soldiers were voluntarily subjected to exertional heat stress tests (EHSTs) consisted of walking on a treadmill (5.5 km/h) in hot conditions (40?C) in climatic chamber, wearing NBC isolating impermeable protective suits. One of the tests was performed without any additional cooling solution (NOCOOL), and four tests were performed while using different types of cooling systems: three in a form of vests and one as underwear. Physiological strain was determined by the mean skin temperature (Tsk), tympanic temperature (Tty), and heart rate values (HR), while sweat rates (SwR) indicated changes in hydration status. Results. In all the cases EHST induced physiological response manifested through increasing Tty, HR and SwR. Compared to NOCOOL tests, when using cooling vests, Tty and Tsk were significantly lower (on 35th min, for 0.44 ? 0.03 and 0.49 ? 0.05?C, respectively; p < 0.05), as well as the average SwR (0.17 ? 0.03 L/m2/h). When using underwear, the values of given parameters were not significantly different compared to NOCOOL tests. Conclusions. Using a body cooling system based on PCM in the form of vest under NBC protective clothes during physical activity in hot conditions, reduces sweating and alleviates heat stress manifested by increased core and skin temperatures and heart rate values. These effects directly improve heat tolerance, hydration state, decrease in the risk of heat illness, and extends the duration of soldiers? exposure to extreme conditions.

scholarly journals The influence of the passive evaporative cooling vest on a chemical industry workers and physiological strain level in hot conditions

2015 ◽  
Vol 69 (6) ◽  
pp. 587-594 ◽  
Author(s):  
Radovan Karkalic ◽  
Dalibor Jovanovic ◽  
Sonja Radakovic ◽  
Dusan Rajic ◽  
Biljana Petrovic ◽  
...  
Keyword(s):  
Heat Stress ◽  
Cooling System ◽  
Sweat Rate ◽  
Stress Test ◽  
Tympanic Temperature ◽  
Physiological Strain ◽  
Military Medical Academy ◽  
Hot Environment ◽  
Body Cooling ◽  
Exertional Heat Stress

The present study was conducted in order to evaluate efficiency of a personal body cooling system based on passive evaporative technologies and its effects on test subjects psycho-physiological suitability during exertional heat stress in hot environment. Performed results are based on conducted tests in climatic chamber in the Military Medical Academy Institute of Hygiene in Belgrade. Ten male test subjects were subjected to exertional heat stress test consisted of walking on motorized treadmill at a speed of 5 km/h in hot environment. Tests were performed with and without cooling system. As a physiological strain indicator the following parameters have been determined: mean skin temperature, tympanic temperature, heart rate and sweat rate. Results confirmed that cooling vest worn over the clothes was able to attenuate the physiological strain levels during exercise, when compared to identical exposure without the cooling system.

scholarly journals Efficacy of a novel phase change material for microclimate body cooling

2014 ◽  
Vol 18 (2) ◽  
pp. 657-665 ◽  
Author(s):  
Dalibor Jovanovic ◽  
Radovan Karkalic ◽  
Ljubisa Tomic ◽  
Zlate Velickovic ◽  
Sonja Radakovic
Keyword(s):  
Heat Stress ◽  
Phase Change ◽  
Phase Change Material ◽  
Thermal Imaging ◽  
Cooling System ◽  
Control Group ◽  
Climatic Chamber ◽  
Physiological Strain ◽  
Exertional Heat Stress ◽  
Change Material

The present study was conducted in order to evaluate the efficiency of personal body microclimate cooling systems based on a phase change materials (PCM) and its effects on physiological strain in soldiers during exertional heat stress in hot environment. The results are obtained in the experiment conducted in the climatic chamber in the Institute of Hygiene, Military Medical Academy in Belgrade. Ten male soldiers were voluntarily subjected to exertional heat stress tests (EHST) consisted of walking on treadmill (5.5 km/h) in hot conditions (40?C) in climatic chamber. The subjects performed first test while wearing a field camouflage uniform without any cooling system ("CONTROL" group) and in second test they used additional microclimate cooling system with paraffin wax consist of n-hexadecane (C16H34), in a form of cooling packs ("COOL" group). As indicators of thermal strain, mean skin (Tsk) and tympanic (Tty) temperature were determined. Simultaneously, thermal effects of PCM were measured by thermal imaging camera. The exercise in hot conditions induced a physiological response to heat stress, manifested through increased body core and skin temperatures. The results confirmed that the cooling vest worn over the field uniform was able to attenuate the physiological strain during exercise, compared to the identical exposure in the ''control'' group. The results of thermal imaging also indicate that heat generated inside the body is the main factor that will affect the phase change material melting time.

A Field Evaluation of Construction Workers’ Activity, Hydration Status, and Heat Strain in the Extreme Summer Heat of Saudi Arabia

2020 ◽  
Vol 64 (5) ◽  
pp. 522-535 ◽  
Author(s):  
Mohammed Al-Bouwarthan ◽  
Margaret M Quinn ◽  
David Kriebel ◽  
David H Wegman
Keyword(s):  
Heart Rate ◽  
Saudi Arabia ◽  
Heat Stress ◽  
Heat Exposure ◽  
Heat Strain ◽  
Construction Workers ◽  
Hydration Status ◽  
Summer Heat ◽  
Cardiovascular Strain ◽  
Indoor And Outdoor

Abstract Objectives Assess the impact of summer heat exposure (June–September) on residential construction workers in Al-Ahsa, Saudi Arabia by evaluating (i) heart rate (HR) responses, hydration status, and physical workload among workers in indoor and outdoor construction settings, (ii) factors related to physiological responses to work in hot conditions, and (iii) how well wet-bulb globe temperature-based occupational exposure limits (WBGTOELs) predict measures of heat strain. Methods Twenty-three construction workers (plasterers, tilers, and laborers) contributed 260 person-days of monitoring. Workload energy expenditure, HR, fluid intake, and pre- and postshift urine specific gravity (USG) were measured. Indoor and outdoor heat exposures (WBGT) were measured continuously and a WBGTOEL was calculated. The effects of heat exposure and workload on heart rate reserve (HRR), a measure of cardiovascular strain, were examined with linear mixed models. A metric called ‘heat stress exceedance’ (HSE) was constructed to summarize whether the environmental heat exposure (WBGT) exceeded the heat stress exposure limit (WBGTOEL). The sensitivity and specificity of the HSE as a predictor of cardiovascular strain (HRR ≥30%) were determined. Results The WBGTOEL was exceeded frequently, on 63 person-days indoors (44%) and 91(78%) outdoors. High-risk HRR occurred on 26 and 36 person-days indoors and outdoors, respectively. The HSE metric showed higher sensitivity for HRR ≥30% outdoors (89%) than indoors (58%) and greater specificity indoors (59%) than outdoors (27%). Workload intensity was generally moderate, with light intensity work more common outdoors. The ability to self-pace work was associated with a lower frequency of HRR ≥30%. USG concentrations indicated that workers began and ended their shifts dehydrated (USG ≥1.020). Conclusions Construction work where WBGTOEL is commonly exceeded poses health risks. The ability of workers to self-pace may help reduce risks.

scholarly journals Relationship between heat storage and parameters of thermotolerance and fatigue in exertional-heat stress

2021 ◽  
pp. 99-99
Author(s):  
Sinisa Masic ◽  
Sonja Marjanovic ◽  
Jelena Maric ◽  
Vanja Jovanovic ◽  
Mirjana Joksimovic ◽  
...  
Keyword(s):  
Heat Stress ◽  
Perceived Exertion ◽  
Heat Storage ◽  
Stress Test ◽  
Physiological Strain ◽  
Blood Concentrations ◽  
Fatigue Development ◽  
The Relationship ◽  
Exertional Heat Stress ◽  
Peripheral Markers

Background/Aim. The risk assessment of heat illness and fatigue development is very important in military services. the aim of our study was to investigate the relationship between heat storage and various psychophysiological parameters of heat stress, as well as potential peripheral markers of fatigue in soldiers performing exertional heat stress test. Methods. 15 young, healthy and unacclimatized men underwent exertional heat stress test (EHST) with submaximal work load in warm conditions (WBGT 29 ?C) in climatic chamber. Every 5 minutes following parameters of thermotolerance were measured or calculated: core temperature (Tc), mean skin (Tsk) and body temperature (Tb), heart rate (HR), heat storage (HS), physiological strain index (PSI), as well as peripheral markers of fatigue (blood concentrations of ammonia, urea nitrogen (BUN), lactate dehydrogenase (LDH), cortisol and prolactin) and subjective parameters: thermal sensation (TS) and rate of perceived exertion (RPE). Results. Tolerance time varied from 45-75 minutes (63?7,7 min). Average values of Tc, Tb, and HR constantly increased during EHST, while Tsk after 10 minutes reached the plateau. Concentrations of all investigated peripheral markers of fatigue were significantly higher after EHST compared to baseline levels (31,47?7,29 vs. 11,8?1,11 ?mol/l for ammonia; 5,92?0,73 vs. 4,69?0,74 mmol/l for BUN, 187,27?28,49 vs.152,73?23,39 U/l for LDH, 743,43?206,19 vs. 558,79?113,34 mmol/l for cortisol and 418,08?157,14 vs. 138,79?92,83 ?IU/mL for prolactin). Conclusions. This study demonstrates the relationship between heat storage and Tc, HR, TS and RPE, but also with PSI. Concentrations of cortisol and especially prolactin showed significant correlation with parameters of thermotolerance.

The influence of hydration status on heart rate variability after exercise heat stress

2005 ◽  
Vol 30 (7) ◽  
pp. 495-502 ◽  
Author(s):  
Robert Carter ◽  
Samuel N. Cheuvront ◽  
D.Walter Wray ◽  
Margaret A. Kolka ◽  
Lou A. Stephenson ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Heat Stress ◽  
Hydration Status ◽  
Influence Of Hydration

scholarly journals The influence of an active microclimate liquid-cooled vest on heat strain alleviation

2020 ◽  
pp. 331-331
Author(s):  
Sveta Cvetanovic ◽  
Srdjan Rutic ◽  
Dejan Krstic ◽  
Stanislav Florus ◽  
Pavel Otrisal
Keyword(s):  
Cooling System ◽  
Sweat Rate ◽  
Heat Exposure ◽  
Thermal Strain ◽  
Experimental Results ◽  
Tympanic Temperature ◽  
Body Core Temperature ◽  
Liquid Cooling ◽  
Strain Testing ◽  
Body Cooling

This research was performed to test the effectiveness of the microclimate body cooling system which belongs to the group of active systems with liquid-cooled technology. The liquid cooling vest efficiency was observed concerning the physiological fitness of the standard protective set used in specific environmental conditions which imply increased thermal strain of the test subjects. Experimental results from the research are based on the examinations carried out in a thermo-physiological laboratory. Ten healthy male volunteers - test subjects aged (23.4 ? 2.4 years, weight 74 ? 7 kg, and height 184 ? 9 cm) were exposed to thermal strain testing (40 ?C temperature, 40?3% relative humidity, without wind) and simultaneously to physical effort caused by walking on the treadmill at a speed of 5 km/h, during 45 minutes. Tests were performed in two variants - without any cooling system (NC) and with the KewlFlow Circulatory Cooling Vest with Cooler Kit (LC). Throughout heat exposure, the subject's body core temperature (tympanic temperature - Tty), mean skin temperature (Tsk) and heart rate (HR) were measured. Furthermore, sweat rate (SwR) was calculated in order to determine all changes in the water and electrolyte status. Experimental results confirm that the results of this study have recognized the benefits of a liquid-cooled vest in lowering the thermal strain.

scholarly journals The effects of acclimatization on blood clotting parameters in exertional heat stress

2013 ◽  
Vol 70 (7) ◽  
pp. 670-674 ◽  
Author(s):  
Zoran Vesic ◽  
Milica Vukasinovic-Vesic ◽  
Dragan Dincic ◽  
Maja Surbatovic ◽  
Sonja Radakovic
Keyword(s):  
Heat Stress ◽  
Prothrombin Time ◽  
Blood Clotting ◽  
Stress Test ◽  
Heat Stroke ◽  
Climatic Chamber ◽  
Physiological Strain ◽  
Platelet Counts ◽  
Globe Temperature ◽  
Exertional Heat Stress

Background/Aim. Exertional heat stress is a common problem in military services. Considering the coagulation abnormalities are of major importance in development of severe heat stroke, we wanted to examine changes in hemostatic parameters in soldiers during exertional heat stress test as well as the effects of a 10-day passive or active acclimatization in a climatic chamber. Methods. A total of 40 male soldiers with high aerobic capacity performed exertional heat stress test (EHST) either in cool [20?C, 16?C wet bulb globe temperature (WBGT)], or hot (40?C, 29?C, (WBGT) environment, unacclimatized (U) or after 10 days of passive (P) or active (A) acclimatization. Physiological strain was measured by tympanic temperatures (Tty) and heart rates (HR). Platelet count (PC), antithrombin III (AT), and prothrombin time (PT) were assessed in blood samples collected before and immediately after the EHST. Results. EHST in hot conditions induced physiological heat stress (increase in Tty and HR), with a significant increase in prothrombin time in the groups U and A. Platelet counts were significantly higher after the EHST compared to the basic levels in all the investigated groups, regardless environmental conditions and acclimatization state. Antithrombin levels were not affected by EHST whatsoever. Conclusion. In the trained soldiers, physiological heat stress caused mild changes in some serum parameters of blood clotting such as prothrombin time, while others such as antithrombin levels were not affected. Platelet counts were increased after EHST in all groups. A 10-day passive or active acclimatization in climatic chamber showed no effect on parameters investigated.

scholarly journals Thermotolerance and heat acclimation may share a common mechanism in humans

2011 ◽  
Vol 301 (2) ◽  
pp. R524-R533 ◽  
Author(s):  
Matthew Kuennen ◽  
Trevor Gillum ◽  
Karol Dokladny ◽  
Edward Bedrick ◽  
Suzanne Schneider ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heat Stress ◽  
Heat Shock ◽  
Heat Shock Response ◽  
Heat Acclimation ◽  
Body Temperatures ◽  
Physiological Strain ◽  
Barrier Permeability ◽  
Shock Response ◽  
Gastrointestinal Barrier

Thermotolerance and heat acclimation are key adaptation processes that have been hitherto viewed as separate phenomena. Here, we provide evidence that these processes may share a common basis, as both may potentially be governed by the heat shock response. We evaluated the effects of a heat shock response-inhibitor (quercetin; 2,000 mg/day) on established markers of thermotolerance [gastrointestinal barrier permeability, plasma TNF-α, IL-6, and IL-10 concentrations, and leukocyte heat shock protein 70 (HSP70) content]. Heat acclimation reduced body temperatures, heart rate, and physiological strain during exercise/heat stress) in male subjects ( n = 8) completing a 7-day heat acclimation protocol. These same subjects completed an identical protocol under placebo supplementation (placebo). Gastrointestinal barrier permeability and TNF-α were increased on the 1st day of exercise/heat stress in quercetin; no differences in these variables were reported in placebo. Exercise HSP70 responses were increased, and plasma cytokines (IL-6, IL-10) were decreased on the 7th day of heat acclimation in placebo; with concomitant reductions in exercise body temperatures, heart rate, and physiological strain. In contrast, gastrointestinal barrier permeability remained elevated, HSP70 was not increased, and IL-6, IL-10, and exercise body temperatures were not reduced on the 7th day of heat acclimation in quercetin. While exercise heart rate and physiological strain were reduced in quercetin, this occurred later in exercise than with placebo. Consistent with the concept that thermotolerance and heat acclimation are related through the heat shock response, repeated exercise/heat stress increases cytoprotective HSP70 and reduces circulating cytokines, contributing to reductions in cellular and systemic markers of heat strain. Exercising under a heat shock response-inhibitor prevents both cellular and systemic heat adaptations.

Thermal and circulatory responses during exercise: effects of hypohydration, dehydration, and water intake

1997 ◽  
Vol 82 (6) ◽  
pp. 2028-2035 ◽  
Author(s):  
Lawrence E. Armstrong ◽  
Carl M. Maresh ◽  
Catherine V. Gabaree ◽  
Jay R. Hoffman ◽  
Stavros A. Kavouras ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heat Stress ◽  
Water Intake ◽  
Rectal Temperature ◽  
Stress Test ◽  
Plasma Osmolality ◽  
Interactive Effects ◽  
Stress Tests ◽  
Physiological Strain ◽  
Exercise Induced

Armstrong, Lawrence E., Carl M. Maresh, Catherine V. Gabaree, Jay R. Hoffman, Stavros A. Kavouras, Robert W. Kenefick, John W. Castellani, and Lynn E. Ahlquist. Thermal and circulatory responses during exercise: effects of hypohydration, dehydration, and water intake. J. Appl. Physiol. 82(6): 2028–2035, 1997.—This investigation examined the distinct and interactive effects of initial hydration state, exercise-induced dehydration, and water rehydration in a hot environment. On four occasions, 10 men performed a 90-min heat stress test (treadmill walking at 5.6 km/h, 5% grade, 33°C, 56% relative humidity). These heat stress tests differed in pretest hydration [2 euhydrated (EU) and 2 hypohydrated (HY) trials] and water intake during exercise [2 water ad libitum (W) and 2 no water (NW) trials]. HY + NW indicated greater physiological strain than all other trials ( P < 0.05–0.001) in heart rate, plasma osmolality (Posm), sweat sensitivity (g / °C ⋅ min), and rectal temperature. Unexpectedly, final HY + W and EU + W responses for rectal temperature, heart rate, and Posm were similar, despite the initial 3.9 ± 0.2% hypohydration in HY + W. We concluded that differences in pretest Posm (295 ± 7 and 287 ± 5 mosmol/kg for HY + W and EU + W, respectively) resulted in greater water consumption (1.65 and 0.31 liter for HY + W and EU + W, respectively), no voluntary dehydration (0.9% body mass increase), and attenuated thermal and circulatory strain during HY + W.

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