Psychophysical Load During the Multistage Marathon des Sables: A Case Study

Introduction: This study investigated the impact of the multistage ultra-marathon event ‘‘Marathon des Sables’’ (MdS) performed in the Sahara Desert on the psychophysical capacity of an athlete. Methods: We collected and analyzed environmental, physiological, and behavioral data from a 39-year-old athlete who participated in the MdS. Specifically, we collected environmental temperature (Tenv), upper inguinal skin temperature (Tsk), heart rate, and running speed data. Also, we recorded blood glucose and lactate, thermal comfort, total body water, perceived exertion, and cognitive function at the start, middle, and the end of each race stage. Results: We found significant detrimental impacts on the health and wellbeing of the monitored athlete. The monitored athlete suffered a multi-toe injury during the 3rd stage of MdS. Furthermore, the Tsk (32.6 ¡ 2.6°C) fluctuated considerably between day and night, as the lowest value presented was 29.8°C while the highest was 40.4°C. The Tsk tended to be higher both when the Tenv was higher and when daily running distance was longer. Finally, the athlete’s cognitive and athletic performances tended to be higher when his blood glucose (118.33 ± 19.20mg/dl) levels were higher. Conclusion: The health and wellbeing parameters of the monitored athlete were significantly impacted during the MdS

Influence of Core Temperature Changes During Whole-Body Warming and Cooling on Cutaneous Vascular Reactivity

Objective: Endothelial function, the ability of cells of the vascular endothelial wall to secrete compounds, is linked with metabolic and cardiovascular disease risks. One of the most well-known noninvasive tests used to assess skin vascular reactivity as a measure of endothelial function is the reactive hyperemic response test (RHRT). However, there is lack of consensus regarding the impact of thermoregulation on endothelial (dys)function and the results from the RHRT. Thus, the aim of the present study was to investigate the impact of core temperature on cutaneous vascular reactivity, as assessed via the finger RHRT. Approach: Following a 15-minute baseline period, seven adults entered a water tank maintained at 42°C and passively rested in a semi-supine position. Thereafter, they entered a water tank maintained at 12°C. They were immersed until their rectal temperature (Tre) increased or decreased about 0.5°C above and below the baseline Tre respectively. This procedure was repeated twice and an occlusion was conducted during the baseline period and at the second repetition of water immersions. Main results: During the post-occlusion phase, skin blood flow (SkBF) was greater, comparing to pre- and occlusion phases, across all Tre levels (five levels: baseline, mild hyperthermia 1, mild hypothermia 1, mild hyperthermia 2, mild hypothermia 2). Also, SkBF throughout pre-occlusion, occlusion, and post-occlusion was greater during mild hyperthermia 2. Significance: We found a significant impact of core temperature on SkBF and cutaneous vascular reactivity which affects the diagnostic indicators obtained from the RHRT and can impact the final outcome

Habitual Heat Exposure and Acclimatization Associated with Athletic Performance in the Multistage Marathon des Sables

Introduction The aim of this study was to investigate the impact of heat acclimatization on athletic performance during the 7-day Marathon des Sables (MdS) which takes place in the Sahara Desert. Methods Anonymous data for nationality and average running speed (km/h) of all runners who ran the MdS during the period 2000–2015 were collected from the official website of the race and other related websites. Average maximum temperature for each runner’s country during the month preceding the MdS was collected from www.weatherbase.com. Athletes were divided into two Torigin groups as follows: 25 to 15°C (i.e., cold countries) and 15 to 35°C (i.e., warm countries). Results Overall, 12467 (10828 men; 1639 women) athletes from 78 countries (37 cold; 41 warm) participated in the MdS during the 16-year study period. The ambient temperature of these countries one month prior to the MdS ranged from 24.2 to 34.4°C. Athletes’ average running speed during the MdS ranged from 2.9 to 13.4 km/h. Moreover, athletes who originated from warm countries ran the MdS 10.7% faster compared to athletes from cold countries. Conclusion The natural heat acclimatization achieved by living in warmer countries seems to provide an advantage during the MdS

Workers' health and productivity under occupational heat strain:a systematic review and meta-analysis

This is an Open Access Article. It is published by Elsevier under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/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 13088 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 21721 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

Workers' health and productivity under occupational heat strain: a systematic review and meta-analysis

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 13088 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 21721 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

Seasonal Heat Acclimatisation in Healthy Adults:A Systematic Review

BACKGROUND: Physiological heat adaptations can be induced following various protocols that use either artificially controlled (i.e. acclimation) or naturally occurring (i.e. acclimatisation) environments. During the summer months in seasonal climates, adequate exposure to outdoor environmental heat stress should lead to transient seasonal heat acclimatisation. OBJECTIVES: The aim of the systematic review was to assess the available literature and characterise seasonal heat acclimatisation during the summer months and identify key factors that influence the magnitude of adaptation. ELIGIBILITY CRITERIA: English language, full-text articles that assessed seasonal heat acclimatisation on the same sample of healthy adults a minimum of 3 months apart were included. DATA SOURCES: Studies were identified using first- and second-order search terms in the databases MEDLINE, SPORTDiscus, CINAHL Plus with Full Text, Scopus and Cochrane, with the last search taking place on 15 July 2021. RISK OF BIAS: Studies were independently assessed by two authors for the risk of bias using a modified version of the McMaster critical review form. DATA EXTRACTION: Data for the following outcome variables were extracted: participant age, sex, body mass, height, body fat percentage, maximal oxygen uptake, time spent exercising outdoors (i.e. intensity, duration, environmental conditions), heat response test (i.e. protocol, time between tests), core temperature, skin temperature, heart rate, whole-body sweat loss, whole-body and local sweat rate, sweat sodium concentration, skin blood flow and plasma volume changes. RESULTS: Twenty-nine studies were included in this systematic review, including 561 participants across eight countries with a mean summer daytime wet-bulb globe temperature (WBGT) of 24.9 °C (range: 19.5–29.8 °C). Two studies reported a reduction in resting core temperature (0.16 °C; p < 0.05), 11 reported an increased sweat rate (range: 0.03–0.53 L·h(−1); p < 0.05), two observed a reduced heart rate during a heat response test (range: 3–8 beats·min(−1); p < 0.05), and six noted a reduced sweat sodium concentration (range: − 22 to − 59%; p < 0.05) following summer. The adaptations were associated with a mean summer WBGT of 25.2 °C (range: 19.6–28.7 °C). LIMITATIONS: The available studies primarily focussed on healthy male adults and demonstrated large differences in the reporting of factors that influence the development of seasonal heat acclimatisation, namely, exposure time and duration, exercise task and environmental conditions. CONCLUSIONS: Seasonal heat acclimatisation is induced across various climates in healthy adults. The magnitude of adaptation is dependent on a combination of environmental and physical activity characteristics. Providing environmental conditions are conducive to adaptation, the duration and intensity of outdoor physical activity, along with the timing of exposures, can influence seasonal heat acclimatisation. Future research should ensure the documentation of these factors to allow for a better characterisation of seasonal heat acclimatisation. PROSPERO REGISTRATION: CRD42020201883. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40279-022-01677-0

The HEAT-SHIELD project - Perspectives from an inter-sectoral approach to occupational heat stress

Objectives: To provide perspectives from the HEAT-SHIELD project (www.heat-shield.eu): a multinational, 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.The study has received funding from the European Union’s Horizon 2020 research and innovation program under the grant agreement No 66878

Thermogenic capacity of human white-fat: the actual picture

Presented at the 9th Greek Conference of Biochemistry and Physiology of Exercise, Thessaloniki, Greece, 18–20 October 2019Cold exposure and exercise may increase thermogenic capacity of white adipose tissue (WAT), which could subsequently enhance energy expenditure and body weight loss. We aimed to identify possible alterations in uncoupling protein 1 (UCP1)—the main biomarker of thermogenic activation—in human WAT due to both cold exposure and exercise, as well as the link between environmental temperature and thermogenic capacity of human WAT. MATERIAL &amp; METHOD: We conducted four human experimental studies and two systematic reviews and meta-analyses—PROSPERO registration CRD42019120116, CRD42019120213. RESULTS: UCP1 mRNA was higher in winter than in summer [t(30) = 2.232, p = 0.03] in human WAT and our meta-analysis showed a main effect of cold exposure on human UCP1 mRNA [standard mean difference (Std-md) = 1.81, confidence interval (CI) = 0.50–3.13, p = 0.007]. However, UCP1 mRNA/protein expressions displayed no associations with %fat mass or BMI (p &gt; 0.05, Cohen’s f2 &lt; 0.20). Both a 2-hour cooling and a non-cooling protocol preceding the positron emission tomography/computed tomography (PET/CT) measurements revealed no association between environmental temperature and standardised uptake value (SUVmax) of human WAT, as well as no mean differences in SUVmax-WAT-activity between winter and summer. An 8-week exercise program had no effect on UCP1 of human WAT or on body composition. Our meta-analysis also revealed: (a) no effect of chronic exercise on human UCP1 mRNA, (b) a main effect of chronic exercise on UCP1 protein concentrations (Std-md = 0.59, CI = 0.03–1.16, p = 0.04) and UCP1 mRNA (Std-md = 1.76, CI = 0.48–3.04, p = 0.007) in WAT of normal diet animals, c) a main effect of chronic exercise on UCP1 mRNA (Std-md = 2.94, CI = 0.24–5.65, p = 0.03) and UCP1 protein concentrations (Std-md = 2.06, CI = 0.07–4.05, p = 0.04) of high-fat diet animals. CONCLUSIONS: Cold exposure represents a main stimulus for increased thermogenic capacity in human white adipocytes; however, this may have no impact on body weight loss. Chronic exercise may represent no major stimulus for UCP1 induced in human white adipocytes, while in animals it increases UCP1 gene independently of their diet. Therefore, evidence from animal studies regarding UCP1 gene activation in white adipocytes may not be applicable in humans. Finally, the identification of human WAT thermogenic capacity via PET/CT examination may be optimal with both a cooling and a non-cooling protocol.Published onlin