-
1.
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.
-
2.
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.
-
3.
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.
-
4.
On the use of wearable physiological monitors to assess heat strain during occupational heat stress.
Notley, SR, Flouris, AD, Kenny, GP
Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme. 2018;(9):869-881
Abstract
Workers in many industries are required to perform arduous work in high heat-stress conditions, which can lead to rapid increases in body temperature that elevate the risk of heat-related illness and even death. Traditionally, effort to mitigate work-related heat injury has been directed toward the assessment of environmental heat stress (e.g., wet-bulb globe temperature), rather than toward the associated physiological strain responses (e.g., heart rate and skin and core temperatures). However, because a worker's physiological response to a given heat stress is modified independently by inter-individual factors (e.g., age, sex, chronic disease, others) and intra-individual factors both within (e.g., medication use, fitness, acclimation and hydration state, others) and beyond (e.g., shift duration, illness, others) the worker's control, it becomes challenging to protect workers on an individual basis from heat-related injury without assessing those physiological responses. Recent advancements in wearable technology have made it possible to monitor one or more physiological indices of heat strain. Nonetheless, information on the utility of the wearable systems available for assessing occupational heat strain is unavailable. This communication is therefore directed toward identifying the physiological indices of heat strain that may be quantified in the workplace and evaluating the wearable monitoring systems available for assessing those responses. Finally, emphasis is placed on the barriers associated with implementing these devices to assist in mitigating work-related heat injury. This information is fundamental for protecting worker health and could also be utilized to prevent heat illnesses in vulnerable people during leisure or athletic activities.
-
5.
Cooling During Exercise: An Overlooked Strategy for Enhancing Endurance Performance in the Heat.
Stevens, CJ, Taylor, L, Dascombe, BJ
Sports medicine (Auckland, N.Z.). 2017;(5):829-841
Abstract
It is well established that endurance performance is negatively affected by environmental heat stress due to a complex interaction of physical, physiological and psychological alterations. Numerous scientific investigations have attempted to improve performance in the heat with pre-cooling (cooling prior to an exercise test), and as such this has become a well-established ergogenic practice for endurance athletes. However, the use of mid-cooling (cooling during an exercise test) has received considerably less research attention in comparison, despite recent evidence to suggest that the advantage gained from mid-cooling may outweigh that of pre-cooling. A range of mid-cooling strategies are beneficial for endurance performance in the heat, including the ingestion of cold fluids and ice slurry, both with and without menthol, as well as cooling of the neck and face region via a cooling collar or water poured on the head and face. The combination of pre-cooling and mid-cooling has also been effective, but few comparisons exist between the timing and type of such interventions. Therefore, athletes should experiment with a range of suitable mid-cooling strategies for their event during mock competition scenarios, with the aim to determine their individual tolerable limits and performance benefits. Based on current evidence, the effect of mid-cooling on core temperature appears largely irrelevant to any subsequent performance improvements, while cardiovascular, skin temperature, central nervous system function and psychophysiological factors are likely involved. Research is lacking on elite athletes, and as such it is currently unclear how this population may benefit from mid-cooling.
-
6.
Farmworker Vulnerability to Heat Hazards: A Conceptual Framework.
Mac, VVT, McCauley, LA
Journal of nursing scholarship : an official publication of Sigma Theta Tau International Honor Society of Nursing. 2017;(6):617-624
-
-
Free full text
-
Abstract
PURPOSE To review factors that impact the effect of hot environments on the human body in order to develop a conceptual model of human biological response. METHODS The organizing concept for the model development was the multilevel integration of three major factors, exposure to heat, sensitivity and adaptive capacity, and the heat stress response. Exposure of a vulnerable occupational group was used to illustrate the components of the model. FINDINGS Components of this framework include the hazard (environmental heat stress), vulnerability factors (workplace exposure, sensitivity and adaptive capacity), and the heat stress response. The combination of the vulnerability factors of workplace exposure (work intensity, duration), sensitivity (age, gender, etc.), and adaptive capacity (hydration, clothing, work hygiene) mediate a worker's heat stress response to the hazard. A worker's heat stress response can be classified as progressing towards two outcomes: physiologic equilibrium or physiologic disequilibrium. CONCLUSIONS This framework provides a starting point for the design and development of studies of heat-related illness (HRI) in farmworker and other vulnerable populations exposed to rising global temperatures. CLINICAL RELEVANCE Identification of vulnerability factors to HRI, informs research designs which will lead to the development of public health interventions.
-
7.
Mitigating Exertional Heat Illness in Military Personnel: The Science Behind a Rice-Based Electrolyte and Rehydration Drink.
Moore, B, O'Hara, R
Journal of special operations medicine : a peer reviewed journal for SOF medical professionals. 2016;(4):49-53
Abstract
BACKGROUND Exertional heat illness continues to be prevalent among members of active duty personnel, especially those in specific military occupational specialties such as loadmasters, flight crew, flight maintainers, and Special Operations Forces. Therefore, the primary objective of this article was to elucidate the various oral rehydration solutions (ORSs) on the market that are used to mitigate exertional heat illness (EHI) in military personnel, and to focus on the science behind a ricebased electrolyte drink, CeraSport®, currently used by US military personnel in mitigating EHI during sustained training operations in high-heat environments. METHODS A search of the literature (through March 2016) was performed using PubMed and ProQuest, in addition to searching bibliographies and text books. We reviewed 63 articles and three texts. Articles were limited to those published in English and to studies that used only carbohydrates (e.g., no amino acids) and drinks reported to be used by the military in field training and deployment. CONCLUSION Heat illness is prevalent among military personnel operating in high-heat environments and a variety of ORSs and sports drinks are available to help mitigate this. However, CeraSport, compared with other ORSs and sports drinks, may offer benefits such as faster gastric emptying rates and improved absorption from the gastrointestinal tract, which can provide rapidly available carbohydrate substrates for energy needs, and increased water retention for maintenance of blood plasma volume.
-
8.
What are the Physiological Mechanisms for Post-Exercise Cold Water Immersion in the Recovery from Prolonged Endurance and Intermittent Exercise?
Ihsan, M, Watson, G, Abbiss, CR
Sports medicine (Auckland, N.Z.). 2016;(8):1095-109
Abstract
Intense training results in numerous physiological perturbations such as muscle damage, hyperthermia, dehydration and glycogen depletion. Insufficient/untimely restoration of these physiological alterations might result in sub-optimal performance during subsequent training sessions, while chronic imbalance between training stress and recovery might lead to overreaching or overtraining syndrome. The use of post-exercise cold water immersion (CWI) is gaining considerable popularity among athletes to minimize fatigue and accelerate post-exercise recovery. CWI, through its primary ability to decrease tissue temperature and blood flow, is purported to facilitate recovery by ameliorating hyperthermia and subsequent alterations to the central nervous system (CNS), reducing cardiovascular strain, removing accumulated muscle metabolic by-products, attenuating exercise-induced muscle damage (EIMD) and improving autonomic nervous system function. The current review aims to provide a comprehensive and detailed examination of the mechanisms underpinning acute and longer term recovery of exercise performance following post-exercise CWI. Understanding the mechanisms will aid practitioners in the application and optimisation of CWI strategies to suit specific recovery needs and consequently improve athletic performance. Much of the literature indicates that the dominant mechanism by which CWI facilitates short term recovery is via ameliorating hyperthermia and consequently CNS mediated fatigue and by reducing cardiovascular strain. In contrast, there is limited evidence to support that CWI might improve acute recovery by facilitating the removal of muscle metabolites. CWI has been shown to augment parasympathetic reactivation following exercise. While CWI-mediated parasympathetic reactivation seems detrimental to high-intensity exercise performance when performed shortly after, it has been shown to be associated with improved longer term physiological recovery and day to day training performances. The efficacy of CWI for attenuating the secondary effects of EIMD seems dependent on the mode of exercise utilised. For instance, CWI application seems to demonstrate limited recovery benefits when EIMD was induced by single-joint eccentrically biased contractions. In contrast, CWI seems more effective in ameliorating effects of EIMD induced by whole body prolonged endurance/intermittent based exercise modalities.
-
9.
Novel Cooling Strategies for Military Training and Operations.
Lee, JK, Kenefick, RW, Cheuvront, SN
Journal of strength and conditioning research. 2015;:S77-81
Abstract
The deleterious effects of environmental heat stress, combined with high metabolic loads and protective clothing and equipment of the modern Warfighter, impose severe heat strain, impair task performance, and increase risk of heat illness, thereby reducing the chance for mission success. Despite the implementation of heat-risk mitigation procedures over the past decades, task performance still suffers and exertional heat illness remains a major military problem. We review 3 novel heat mitigation strategies that may be implemented in the training or operational environment to reduce heat strain and the risk of exertional heat illness. These strategies include ingestion of ice slurry, arm immersion cooling, and microclimate cooling. Each of these strategies is suitable for use in different scenarios and the choice of cooling strategy is contingent on the requirements, circumstances, and constraints of the training and operational scenario. Ingestion of ice slurry and arm immersion cooling are practical strategies that may be implemented during training scenarios; ice slurry can be ingested before and during exercise, whereas arm immersion cooling can be administered after exercise-heat exposure. In the operational environment, existing microclimate cooling can be implemented with retrofitted vehicles and as an unmounted system, and it has the potential for use in many military occupational scenarios. This review will discuss the efficacy, limitations, and practical considerations for field implementation of each strategy.
-
10.
The relationship between exertional heat illness, exertional rhabdomyolysis, and malignant hyperthermia.
Capacchione, JF, Muldoon, SM
Anesthesia and analgesia. 2009;(4):1065-9
Abstract
Exertional heat illness, exertional rhabdomyolysis, and malignant hyperthermia (MH) are complex syndromes with similar pathophysiology. All three are hypermetabolic states that include high demand for adenosine triphosphate, accelerated oxidative, chemical, and mechanical stress of muscle, and uncontrolled increase in intracellular calcium. Although there are no controlled clinical studies to support a relationship, there is evidence to suggest an association between unexpected heat/exercise intolerance and MH susceptibility. There are multiple case reports and a small number of clinical studies that have used in vitro muscle contracture testing and/or genetic testing to make the association. However, such methodology is problematic in that these tests are validated for clinical MH in association with anesthesia, and not for exertional heat illness or exertional rhabdomyolysis. Nevertheless, these relationships may have implications for some MH-susceptible patients and their capacity to exercise, as well as for clinicians treating and anesthetizing patients with histories of unexplained exertional heat and exercise illnesses.