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1.
Looking ahead of 2021 Tokyo Summer Olympic Games: How Does Humid Heat Affect Endurance Performance? Insight into physiological mechanism and heat-related illness prevention strategies.
Lei, TH, Wang, F
Journal of thermal biology. 2021;:102975
Abstract
The combination of high humidity and ambient temperature of the 2021 Tokyo Summer Olympic Game will undoubtfully result in greater physiological strains and thereby downregulates the endurance performance of athletes. Although many research studies have highlighted that the thermoregulatory strain is greater when the environment is hot and humid, no review articles have addressed the thermoregulatory and performance differences between dry and humid heat and such lack of consensuses in this area will lead to increase the risk of heat-related injuries as well as suboptimal preparation. Furthermore, specific strategies to counteract this stressful environment has not been outlined in the current literature. Therefore, the purposes of this review are: 1) to provide a clear evidence that humid heat is more stressful than dry heat for both male and female athletes and therefore the preparation for the Tokyo Summer Olympic should be environmental specific instead of a one size fits all approach; 2) to highlight why female athletes may be facing a disadvantage when performing a prolonged endurance event under high humidity environment and 3) to highlight the potential interventional strategies to reduce thermal strain in hot-humid environment. The summaries of this review are: both male and female should be aware of the environmental condition in Tokyo as humid heat is more stressful than dry heat; Short-term heat acclimation may not elicit proper thermoregulatory adaptations in hot-humid environment; cold water immersion with proper hydration and some potential per-cooling modalities may be beneficial for both male and female athletes in hot-humid environment.
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2.
Roundtable on Preseason Heat Safety in Secondary School Athletics: Heat Acclimatization.
Adams, WM, Hosokawa, Y, Casa, DJ, Périard, JD, Racinais, S, Wingo, JE, Yeargin, SW, Scarneo-Miller, SE, Kerr, ZY, Belval, LN, et al
Journal of athletic training. 2021;(4):352-361
Abstract
OBJECTIVE To provide best-practice recommendations for developing and implementing heat-acclimatization strategies in secondary school athletics. DATA SOURCES An extensive literature review on topics related to heat acclimatization and heat acclimation was conducted by a group of content experts. Using the Delphi method, action-oriented recommendations were developed. CONCLUSIONS A period of heat acclimatization consisting of ≥14 consecutive days should be implemented at the start of fall preseason training or practices for all secondary school athletes to mitigate the risk of exertional heat illness. The heat-acclimatization guidelines should outline specific actions for secondary school athletics personnel to use, including the duration of training, the number of training sessions permitted per day, and adequate rest periods in a cool environment. Further, these guidelines should include sport-specific and athlete-specific recommendations, such as phasing in protective equipment and reintroducing heat acclimatization after periods of inactivity. Heat-acclimatization guidelines should be clearly detailed in the secondary school's policy and procedures manual and disseminated to all stakeholders. Heat-acclimatization guidelines, when used in conjunction with current best practices surrounding the prevention, management, and care of secondary school student-athletes with exertional heat stroke, will optimize their health and safety.
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3.
From theory to practice: operationalizing a climate vulnerability for sport organizations framework for heat hazards among US High schools.
Grundstein, AJ, Scarneo-Miller, SE, Adams, WM, Casa, DJ
Journal of science and medicine in sport. 2021;(8):718-722
Abstract
BACKGROUND Sport organizations must comprehensively assess the degree to which their athletes are susceptible to exertional heat illnesses (i.e. vulnerable) to appropriately plan and adapt for heat-related hazards. Yet, no heat vulnerability framework has been applied in practice to guide decision making. OBJECTIVES We quantify heat vulnerability of state-level requirements for health and safety standards affecting United States (US) high school athletes as a case study. DESIGN Observational. METHODS We utilize a newly developed climate vulnerability to sports organizations framework (CVSO), which considers the heat hazard of each state using summer maximum wet bulb globe temperature (WBGT) in combination with an 18-point heat safety scoring system (18 = best policy). Heat vulnerability is categorized as "problem" [higher heat (>27.9°C) and lower policy score (≤9)], "fortified" [higher heat (>27.9°C) and higher policy score (>9)], "responsive" [lower heat (<27.9°C) and lower policy score (≤9)], and "proactive" [lower heat (<27.9°C) and higher policy score (>9)]. RESULTS Across the US, the mean WBGT was 28.4±2.4°C and policy score was 6.9±4.7. In combination, we observed organizations within each of the four vulnerability categories with 16% (n=8) in fortified, 16% (n=8) in proactive, 29% (n=15) in problem, and 39% (n=20) in responsive. CONCLUSIONS The CSVO framework allowed us to identify different degrees of vulnerability among the state's and to highlight the 29% (n=15) of states with immediate needs for policy revisions. We found the CSVO framework to be highly adaptable in our application, suggesting feasibility for use with other sports governing bodies.
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4.
The HEAT-SHIELD project - Perspectives from an inter-sectoral approach to occupational heat stress.
Morris, NB, Piil, JF, Morabito, M, Messeri, A, Levi, M, Ioannou, LG, Ciuha, U, Pogačar, T, Kajfež Bogataj, L, Kingma, B, et al
Journal of science and medicine in sport. 2021;(8):747-755
Abstract
OBJECTIVES To provide perspectives from the HEAT-SHIELD project (www.heat-shield.eu): a multi-national, inter-sectoral, and cross-disciplinary initiative, incorporating twenty European research institutions, as well as occupational health and industrial partners, on solutions to combat negative health and productivity effects caused by working on a warmer world. METHODS In this invited review, we focus on the theoretical and methodological advancements developed to combat occupational heat stress during the last five years of operation. RESULTS We outline how we created climate forecast models to incorporate humidity, wind and solar radiation to the traditional temperature-based climate projections, providing the basis for timely, policy-relevant, industry-specific and individualized information. Further, we summarise the industry-specific guidelines we developed regarding technical and biophysical cooling solutions considering effectiveness, cost, sustainability, and the practical implementation potential in outdoor and indoor settings, in addition to field-testing of selected solutions with time-motion analyses and biophysical evaluations. All recommendations were adjusted following feedback from workshops with employers, employees, safety officers, and adjacent stakeholders such as local or national health policy makers. The cross-scientific approach was also used for providing policy-relevant information based on socioeconomic analyses and identification of vulnerable regions considered to be more relevant for political actions than average continental recommendations and interventions. DISCUSSION From the HEAT-SHIELD experiences developed within European settings, we discuss how this inter-sectoral approach may be adopted or translated into actionable knowledge across continents where workers and societies are affected by escalating environmental temperatures.
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5.
Comparison of two different cooling systems in alleviating thermal and physiological strain during prolonged exercise in the heat.
Keller, S, Kohne, S, Bloch, W, Schumann, M
Ergonomics. 2021;(1):129-138
Abstract
This study compared the efficacy of an ice vest comprising of water (WATER) or a water-carbon (CARBON) emulsion on thermophysiological responses to strenuous exercise in the heat. Twelve male cyclists completed three 50-minute constant workload trials (55% of peak power output, ambient temperature 30.4 ± 0.6°C) with WATER, CARBON, and without ice vest (CONTROL), respectively. The increase in core body temperature (Tcore) was lower in WATER at 40 (-0.49 ± 0.34 °C) and 50 minutes (-0.48 ± 0.48 °C) and in CARBON at 30 (-0.41 ± 0.48 °C), 40 (-0.54 ± 0.51 °C), and 50 minutes (-0.67 ± 0.62 °C) as compared to CONTROL (p < 0.05, ES > 0.8). While heart rate and blood lactate kinetics did not differ between the conditions, statistical main effects in favour of both WATER and CARBON were found for thermal sensation (condition p < 0.001 and interaction p < 0.01) and rating of perceived exertion (condition p < 0.05). Per-cooling with CARBON and WATER similarly reduced Tcore but not physiological strain during prolonged exercise in the heat. Practitioner Summary: Exercise in the heat is characterised by increases in thermophysiological strain. Both per-cooling with a novel carbon-based and a conventional water-based ice vest were shown to reduce core temperature significantly. However, due to its lower mass, the carbon-based system may be recommended especially for weight-bearing sports.
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6.
Impact of 24-h high and low fermentable oligo-, di-, monosaccharide, and polyol diets on markers of exercise-induced gastrointestinal syndrome in response to exertional heat stress.
Gaskell, SK, Taylor, B, Muir, J, Costa, RJS
Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme. 2020;(6):569-580
Abstract
The study aimed to determine the effects of 24-h high (HFOD) and low (LFOD) fermentable oligo-, di-, monosaccharide, and polyol (FODMAP) diets before exertional heat stress on gastrointestinal integrity, function, and symptoms. Eighteen endurance runners consumed a HFOD and a LFOD (double-blind crossover design) before completing 2 h of running at 60% maximal oxygen uptake in 35 °C ambient temperature. Blood samples were collected before and after exercise to determine plasma cortisol and intestinal fatty acid binding protein (I-FABP) concentrations, and bacterial endotoxin and cytokine profiles. Breath hydrogen (H2) and gastrointestinal symptoms (GIS) were determined pre-exercise, every 15 min during, and in recovery. No differences were observed for plasma cortisol concentration between diets. Plasma I-FABP concentration was lower on HFOD compared with LFOD (p = 0.033). A trend for lower lipopolysaccharide binding protein (p = 0.088), but not plasma soluble CD14 (p = 0.478) and cytokine profile (p > 0.05), responses on HFOD was observed. A greater area under the curve breath H2 concentration (p = 0.031) was observed throughout HFOD (mean and 95% confidence interval: HFOD 2525 (1452-3597) ppm·4 h-1) compared with LFOD (1505 (1031-1978) ppm·4 h-1). HFOD resulted in greater severity of GIS compared with LFOD (pre-exercise, p = 0.017; during, p = 0.035; and total, p = 0.014). A 24-h HFOD before exertional heat stress ameliorates disturbances to epithelial integrity but exacerbates carbohydrate malabsorption and GIS severity in comparison with a LFOD. Novelty Twenty-four-hour high FODMAP diet ameliorated disturbances to gastrointestinal integrity. Twenty-four-hour high FODMAP diet results in greater carbohydrate malabsorption compared with low FODMAP diet. Incidence of GIS during exertional heat stress were pronounced on both low and high FODMAP diets, but greater GIS severity was observed with high FODMAP diet.
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7.
Sustainable solutions to mitigate occupational heat strain - an umbrella review of physiological effects and global health perspectives.
Morris, NB, Jay, O, Flouris, AD, Casanueva, A, Gao, C, Foster, J, Havenith, G, Nybo, L
Environmental health : a global access science source. 2020;(1):95
Abstract
BACKGROUND Climate change is set to exacerbate occupational heat strain, the combined effect of environmental and internal heat stress on the body, threatening human health and wellbeing. Therefore, identifying effective, affordable, feasible and sustainable solutions to mitigate the negative effects on worker health and productivity, is an increasingly urgent need. OBJECTIVES To systematically identify and evaluate methods that mitigate occupational heat strain in order to provide scientific-based guidance for practitioners. METHODS An umbrella review was conducted in biomedical databases employing the following eligibility criteria: 1) ambient temperatures > 28 °C or hypohydrated participants, 2) healthy adults, 3) reported psychophysiological (thermal comfort, heart rate or core temperature) and/or performance (physical or cognitive) outcomes, 4) written in English, and 5) published before November 6, 2019. A second search for original research articles was performed to identify interventions of relevance but lacking systematic reviews. All identified interventions were independently evaluated by all co-authors on four point scales for effectiveness, cost, feasibility and environmental impact. RESULTS Following screening, 36 systematic reviews fulfilled the inclusion criteria. The most effective solutions at mitigating occupational heat strain were wearing specialized cooling garments, (physiological) heat acclimation, improving aerobic fitness, cold water immersion, and applying ventilation. Although air-conditioning and cooling garments in ideal settings provide best scores for effectiveness, the limited applicability in certain industrial settings, high economic cost and high environmental impact are drawbacks for these solutions. However, (physiological) acclimatization, planned breaks, shading and optimized clothing properties are attractive alternative solutions when economic and ecological sustainability aspects are included in the overall evaluation. DISCUSSION Choosing the most effective solution or combinations of methods to mitigate occupational heat strain will be scenario-specific. However, this paper provides a framework for integrating effectiveness, cost, feasibility (indoors and outdoor) and ecologic sustainability to provide occupational health and safety professionals with evidence-based guidelines.
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8.
Exertional heat stress-induced gastrointestinal perturbations: prevention and management strategies.
Snipe, RMJ
British journal of sports medicine. 2019;(20):1312-1313
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9.
Brief in-play cooling breaks reduce thermal strain during football in hot conditions.
Chalmers, S, Siegler, J, Lovell, R, Lynch, G, Gregson, W, Marshall, P, Jay, O
Journal of science and medicine in sport. 2019;(8):912-917
Abstract
OBJECTIVES The study examined if three feasible strategies involving additional in-play cooling periods attenuate the core (rectal) temperature rise during simulated football matches. DESIGN Four counterbalanced experimental trials in an environmental chamber set to 35 °C ambient temperature, 55% relative humidity, and 30 °C WBGT. METHODS Twelve healthy well-trained football players completed a regular simulated match (REG), regular simulated match with additional 3-min cooling periods at the 30-min mark of each half inclusive of chilled water consumption (COOLwater), regular simulated match with additional 3-min cooling periods at the 30-min mark of each half inclusive of chilled water consumption and the application of an ice towel around the neck (COOLtowel), regular simulated match with an extended (+5 min; total of 20-min) half-time break (HTextended). RESULTS The difference in rectal temperature change was significantly lower in the COOLwater (-0.25 °C), COOLtowel (-0.28 °C), and HTextended (-0.21 °C) trials in comparison to the REG (all p < 0.05). Exercising heart rate and session rating of perceived exertion was lower in the COOLwater (-13 bpm; -1.4 au), COOLtowel (-10 bpm; -1.3 au), and HTextended (-8 bpm; -0.9 au) trials in comparison to the REG trial (all p < 0.05). The cooling interventions did not significantly change skin temperature or thermal sensation in comparison to the REG (all p > 0.05). CONCLUSIONS All three cooling interventions attenuated core body thermal strain during simulated matches. The laboratory-based study supports the use of brief in-play cooling periods as a means to attenuate the rise in core temperature during matches in hot and humid conditions.
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10.
Workers' health and productivity under occupational heat strain: a systematic review and meta-analysis.
Flouris, AD, Dinas, PC, Ioannou, LG, Nybo, L, Havenith, G, Kenny, GP, Kjellstrom, T
The Lancet. Planetary health. 2018;(12):e521-e531
Abstract
BACKGROUND Occupational heat strain (ie, the effect of environmental heat stress on the body) directly threatens workers' ability to live healthy and productive lives. We estimated the effects of occupational heat strain on workers' health and productivity outcomes. METHODS Following PRISMA guidelines for this systematic review and meta-analysis, we searched PubMed and Embase from database inception to Feb 5, 2018, for relevant studies in any labour environment and at any level of occupational heat strain. No restrictions on language, workers' health status, or study design were applied. Occupational heat strain was defined using international health and safety guidelines and standards. We excluded studies that calculated effects using simulations or statistical models instead of actual measurements, and any grey literature. Risk of bias, data extraction, and sensitivity analysis were performed by two independent investigators. Six random-effects meta-analyses estimated the prevalence of occupational heat strain, kidney disease or acute kidney injury, productivity loss, core temperature, change in urine specific gravity, and odds of occupational heat strain occurring during or at the end of a work shift in heat stress conditions. The review protocol is available on PROSPERO, registration number CRD42017083271. FINDINGS Of 958 reports identified through our systematic search, 111 studies done in 30 countries, including 447 million workers from more than 40 different occupations, were eligible for analysis. Our meta-analyses showed that individuals working a single work shift under heat stress (defined as wet-bulb globe temperature beyond 22·0 or 24·8°C depending on work intensity) were 4·01 times (95% CI 2·45-6·58; nine studies with 11 582 workers) more likely to experience occupational heat strain than an individual working in thermoneutral conditions, while their core temperature was increased by 0·7°C (0·4-1·0; 17 studies with 1090 workers) and their urine specific gravity was increased by 14·5% (0·0031, 0·0014-0·0048; 14 studies with 691 workers). During or at the end of a work shift under heat stress, 35% (31-39; 33 studies with 13 088 workers) of workers experienced occupational heat strain, while 30% (21-39; 11 studies with 8076 workers) reported productivity losses. Finally, 15% (11-19; ten studies with 21 721 workers) of individuals who typically or frequently worked under heat stress (minimum of 6 h per day, 5 days per week, for 2 months of the year) experienced kidney disease or acute kidney injury. Overall, this analysis include a variety of populations, exposures, and occupations to comply with a wider adoption of evidence synthesis, but resulted in large heterogeneity in our meta-analyses. Grading of Recommendations, Assessment, Development and Evaluation analysis revealed moderate confidence for most results and very low confidence in two cases (average core temperature and change in urine specific gravity) due to studies being funded by industry. INTERPRETATION Occupational heat strain has important health and productivity outcomes and should be recognised as a public health problem. Concerted international action is needed to mitigate its effects in light of climate change and the anticipated rise in heat stress. FUNDING EU Horizon 2020 research and innovation programme.