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Deshayes TA, Hsouna H, Braham MAA, Arvisais D, Pageaux B, Ouellet C, Jay O, Maso FD, Begon M, Saidi A, Gendron P, Gagnon D. Work-rest regimens for work in hot environments: A scoping review. Am J Ind Med 2024; 67:304-320. [PMID: 38345435 DOI: 10.1002/ajim.23569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 01/08/2024] [Accepted: 01/23/2024] [Indexed: 03/16/2024]
Abstract
BACKGROUND To limit exposures to occupational heat stress, leading occupational health and safety organizations recommend work-rest regimens to prevent core temperature from exceeding 38°C or increasing by ≥1°C. This scoping review aims to map existing knowledge of the effects of work-rest regimens in hot environments and to propose recommendations for future research based on identified gaps. METHODS We performed a search of 10 databases to retrieve studies focused on work-rest regimens under hot conditions. RESULTS Forty-nine articles were included, of which 35 were experimental studies. Most studies were conducted in laboratory settings, in North America (71%), on healthy young adults, with 94% of the 642 participants being males. Most studies (66%) employed a protocol duration ≤240 min (222 ± 162 min, range: 37-660) and the time-weighted average wet-bulb globe temperature was 27 ± 4°C (range: 18-34). The work-rest regimens implemented were those proposed by the American Conference of Governmental and Industrial Hygiene (20%), National Institute of Occupational Safety and Health (11%), or the Australian Army (3%). The remaining studies (66%) did not mention how the work-rest regimens were derived. Most studies (89%) focused on physical tasks only. Most studies (94%) reported core temperature, whereas only 22% reported physical and/or mental performance outcomes, respectively. Of the 35 experimental studies included, 77% indicated that core temperature exceeded 38°C. CONCLUSIONS Although work-rest regimens are widely used, few studies have investigated their physiological effectiveness. These studies were mainly short in duration, involved mostly healthy young males, and rarely considered the effect of work-rest regimens beyond heat strain during physical exertion.
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Affiliation(s)
- Thomas A Deshayes
- Montreal Heart Institute, Montréal, Québec, Canada
- École de kinésiologie et des sciences de l'activité physique (EKSAP), Faculté de médecine, Université de Montréal, Montréal, Québec, Canada
| | - Hsen Hsouna
- Montreal Heart Institute, Montréal, Québec, Canada
- École de kinésiologie et des sciences de l'activité physique (EKSAP), Faculté de médecine, Université de Montréal, Montréal, Québec, Canada
| | - Mounir A A Braham
- Département des sciences de l'activité physique, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada
- Département d'anatomie, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada
| | - Denis Arvisais
- Bibliothèque des sciences de la santé, Université de Montréal, Montréal, Québec, Canada
| | - Benjamin Pageaux
- École de kinésiologie et des sciences de l'activité physique (EKSAP), Faculté de médecine, Université de Montréal, Montréal, Québec, Canada
- Centre de recherche de l'Institut universitaire de gériatrie de Montréal (CRIUGM), Montréal, Québec, Canada
- Centre interdisciplinaire de recherche sur le cerveau et l'apprentissage (CIRCA), Montréal, Québec, Canada
| | - Capucine Ouellet
- Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Montréal, Québec, Canada
| | - Ollie Jay
- Heat and Health Research Incubator, University of Sydney, Sydney, New South Wales, Australia
| | - Fabien D Maso
- École de kinésiologie et des sciences de l'activité physique (EKSAP), Faculté de médecine, Université de Montréal, Montréal, Québec, Canada
- Centre interdisciplinaire de recherche sur le cerveau et l'apprentissage (CIRCA), Montréal, Québec, Canada
| | - Mickael Begon
- École de kinésiologie et des sciences de l'activité physique (EKSAP), Faculté de médecine, Université de Montréal, Montréal, Québec, Canada
- Centre de recherche du CHU Sainte-Justine, Montréal, Québec, Canada
| | - Alireza Saidi
- Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Montréal, Québec, Canada
| | - Philippe Gendron
- Département des sciences de l'activité physique, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada
| | - Daniel Gagnon
- Montreal Heart Institute, Montréal, Québec, Canada
- École de kinésiologie et des sciences de l'activité physique (EKSAP), Faculté de médecine, Université de Montréal, Montréal, Québec, Canada
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Brearley M, Berry R, Hunt AP, Pope R. A Systematic Review of Post-Work Core Temperature Cooling Rates Conferred by Passive Rest. BIOLOGY 2023; 12:biology12050695. [PMID: 37237510 DOI: 10.3390/biology12050695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 05/04/2023] [Accepted: 05/05/2023] [Indexed: 05/28/2023]
Abstract
Physical work increases energy expenditure, requiring a considerable elevation of metabolic rate, which causes body heat production that can cause heat stress, heat strain, and hyperthermia in the absence of adequate cooling. Given that passive rest is often used for cooling, a systematic search of literature databases was conducted to identify studies that reported post-work core temperature cooling rates conferred by passive rest, across a range of environmental conditions. Data regarding cooling rates and environmental conditions were extracted, and the validity of key measures was assessed for each study. Forty-four eligible studies were included, providing 50 datasets. Eight datasets indicated a stable or rising core temperature in participants (range 0.000 to +0.028 °C min-1), and forty-two datasets reported reducing core temperature (-0.002 to -0.070 °C min-1) during passive rest, across a range of Wet-Bulb Globe Temperatures (WBGT). For 13 datasets where occupational or similarly insulative clothing was worn, passive rest resulted in a mean core temperature decrease of -0.004 °C min-1 (-0.032 to +0.013 °C min-1). These findings indicate passive rest does not reverse the elevated core temperatures of heat-exposed workers in a timely manner. Climate projections of higher WBGT are anticipated to further marginalise the passive rest cooling rates of heat-exposed workers, particularly when undertaken in occupational attire.
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Affiliation(s)
- Matt Brearley
- Thermal Hyperformance, Hervey Bay, QLD 4655, Australia
- National Critical Care and Trauma Response Centre, Darwin, NT 0800, Australia
- School of Allied Health, Exercise & Sports Sciences, Charles Sturt University, Albury, NSW 2640, Australia
| | - Rachel Berry
- School of Biomedical Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Andrew P Hunt
- School of Biomedical Sciences, Faculty of Health, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia
| | - Rodney Pope
- School of Allied Health, Exercise & Sports Sciences, Charles Sturt University, Albury, NSW 2640, Australia
- Tactical Research Unit, Bond University, Robina, QLD 4229, Australia
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3
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Smallcombe JW, Foster J, Hodder SG, Jay O, Flouris AD, Havenith G. Quantifying the impact of heat on human physical work capacity; part IV: interactions between work duration and heat stress severity. INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2022; 66:2463-2476. [PMID: 36197554 PMCID: PMC9684271 DOI: 10.1007/s00484-022-02370-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 09/13/2022] [Accepted: 09/15/2022] [Indexed: 06/16/2023]
Abstract
High workplace temperatures negatively impact physical work capacity (PWC). Although PWC loss models with heat based on 1-h exposures are available, it is unclear if further adjustments are required to accommodate repeated work/rest cycles over the course of a full work shift. Therefore, we examined the impact of heat stress exposure on human PWC during a simulated work shift consisting of six 1-h work-rest cycles. Nine healthy males completed six 50-min work bouts, separated by 10-min rest intervals and an extended lunch break, on four separate occasions: once in a cool environment (15 °C/50% RH) and in three different air temperature and relative humidity combinations (moderate, 35 °C/50% RH; hot, 40 °C/50% RH; and very hot, 40 °C/70%). To mimic moderate to heavy workload, work was performed on a treadmill at a fixed heart rate of 130 beats·min-1. During each work bout, PWC was quantified as the kilojoules expended above resting levels. Over the shift, work output per cycle decreased, even in the cool climate, with the biggest decrement after the lunch break and meal consumption. Expressing PWC relative to that achieved in the cool environment for the same work duration, there was an additional 5(± 4)%, 7(± 6)%, and 16(± 7)% decrease in PWC when work was performed across a full work shift for the moderate, hot, and very hot condition respectively, compared with 1-h projections. Empirical models to predict PWC based on the level of heat stress (Wet-Bulb Globe Temperature, Universal Thermal Climate Index, Psychrometric Wet-Bulb Temperature, Humidex, and Heat Index) and the number of work cycles performed are presented.
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Affiliation(s)
- James W Smallcombe
- Environmental Ergonomics Research Centre, Loughborough University, Loughborough, LE11 3TU, Leicestershire, UK
- Thermal Ergonomics Laboratory, University of Sydney, Sydney, NSW, Australia
| | - Josh Foster
- Environmental Ergonomics Research Centre, Loughborough University, Loughborough, LE11 3TU, Leicestershire, UK
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital and University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Simon G Hodder
- Environmental Ergonomics Research Centre, Loughborough University, Loughborough, LE11 3TU, Leicestershire, UK
| | - Ollie Jay
- Thermal Ergonomics Laboratory, University of Sydney, Sydney, NSW, Australia
| | - Andreas D Flouris
- FAME Laboratory, Department of Physical Education and Sport Science, University of Thessaly, Trikala, Greece
| | - George Havenith
- Environmental Ergonomics Research Centre, Loughborough University, Loughborough, LE11 3TU, Leicestershire, UK.
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Notley SR, Akerman AP, Friesen BJ, Poirier MP, McCourt E, Flouris A, Kenny GP. Heat tolerance and the validity of occupational heat exposure limits in women during moderate-intensity work. Appl Physiol Nutr Metab 2022; 47:711-724. [PMID: 35259026 DOI: 10.1139/apnm-2022-0003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To mitigate excessive rises in core temperature (>1°C) in non heat-acclimatized workers, the American Conference of Governmental Industrial Hygienists (ACGIH) provide heat stress limits (Action Limit Values; ALV), defined by the wet-bulb globe temperature (WBGT) and a worker's metabolic rate. However, since these limits are based on data from men, their suitability for women remains unclear. We therefore assessed core temperature and heart rate in men (n=19; body surface area-to-mass ratio: 250 (SD 17) cm2/kg) and women (n=15; body surface area-to-mass ratio: 268 (SD 24) cm2/kg) aged 18-45 years during 180-min walking at a moderate metabolic rate (200 W/m2) in WBGTs below (16 and 24°C) and above (28 and 32°C) ACGIH ALV. Sex did not significantly influence (i) rises in core temperature, irrespective of WBGT, (ii) the proportion of participants with rises in core temperature >1°C in environments below ACGIH limits, and (iii) work duration before rises in core temperature exceeded 1°C or volitional termination in environments above ACGIH limits. Although further studies are needed, these findings indicate that for the purpose of mitigating rises in core temperature exceeding recommended limits (>1°C), ACGIH guidelines have comparable effectiveness in non heat-acclimatized men and women when working at a moderate metabolic rate. Novelty points • Sex did not appreciably influence thermal strain nor the proportion of participants with core temperatures exceeding recommended limits. • Sex did not significantly influence tolerance to uncompensable heat stress • Despite originating from data obtained in only men, current occupational heat stress guidance offered comparable effectiveness in men and women.
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Affiliation(s)
| | | | - Brian J Friesen
- University of Ottawa, Human Kinetics, Ottawa, Ontario, Canada;
| | - Martin P Poirier
- University of Ottawa, School of Human Kinetics, Faculty of Health Sciences, Ottawa, Ontario, Canada;
| | | | - Andreas Flouris
- FAME Laboratory, Institute of Human Performance and Rehabilitation, Centre for Research and Technology Thessaly, Trikala, Thessaly, Greece.,Department of Research and Technology Development, Biomnic Ltd., Trikala, Thessaly, Greece;
| | - Glen P Kenny
- University of Ottawa, 6363, Ottawa, Canada, K1N 6N5.,Ottawa Hospital Research Institute, 10055, Ottawa, Canada, K1Y 4E9;
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