Search

Introduction: This study examined the impact of different upper-torso sportswear technologies on the performance and physiological heat strain of well-trained and national-level athletes during prolonged running in moderately hot conditions. Methods: A randomized crossover design was employed in which 20 well-trained (n = 16) and national-level (n = 4) athletes completed four experimental trials in moderately hot conditions (35°C, 30% relative humidity). In each trial, participants ran at 70% of their peak oxygen uptake (70% V̇O2peak) for 60 min, while wearing a different upper-body garment: cotton t-shirt, t-shirt with sweat-wicking fabric, compression t-shirt, and t-shirt with aluminum dots lining the inside of the upper back of the garment. Running speed was adjusted to elicit the predetermined oxygen consumption associated with 70% V̇O2peak. Physiological (core and skin temperatures, total body water loss, and urine specific gravity) and perceptual (thermal comfort and sensation, ratings of perceived exertion, and garment cooling functionality) parameters along with running speed at 70% V̇O2peak were continuously recorded. Results: No significant differences were observed between the four garments for running speed at 70% V̇O2peak, physiological heat strain, and perceptual responses (all p > 0.05). The tested athletes reported larger areas of perceived suboptimal cooling functionality in the cotton t-shirt and the t-shirt with aluminum dots relative to the sweat-wicking and compression t-shirts (d: 0.43–0.52). Conclusion: There were not differences among the tested garments regarding running speed at 70% V̇O2peak, physiological heat strain, and perceptual responses in well-trained and national-level endurance athletes exercising in moderate heat.

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.

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.

The present observational study was conducted to uncover potential differences in the risk of experiencing high occupational heat strain during agriculture work between migrants and their native coworkers, as well as to elucidate the factors that may contribute to such differences. The study took place over the period from 2016 through 2019 and involved monitoring 124 experienced and acclimatized individuals from high-income (HICs), upper-middle-income (UMICs), as well as lower-middle- and low-income (LMICs) countries. Baseline self-reported data for age, body stature, and body mass were collected at the start of the study. Second-by-second video recordings throughout the work shifts were captured using a video camera and were used to estimate workers' clothing insulation, covered body surface area, and body posture, as well as to calculate their walking speed, the amount of time they spent on different activities (and their intensity) and unplanned breaks throughout their work shifts. All information derived from the video data was used to calculate the physiological heat strain experienced by the workers. The core temperature of migrant workers from LMICs (37.81 ± 0.38 °C) and UMICs (37.71 ± 0.35 °C) was estimated to be significantly higher compared to the core temperature of native workers from HICs (37.60 ± 0.29 °C) (p < 0.001). Moreover, migrant workers from LMICs faced a 52% and 80% higher risk for experiencing core body temperature above the safety threshold of 38 °C compared to migrant workers from UMICs and native workers from HICs, respectively. Our findings show that migrant workers originating from LMICs experience higher levels of occupational heat strain, as compared to migrant workers from UMICs and native workers from HICs, because they take fewer unplanned breaks during work, they work at a higher intensity, they wear more clothing, and they have a smaller body size.

In a series of three companion papers published in this Journal, we identify and validate the available thermal stress indicators (TSIs). In this first paper of the series, we conducted a systematic review (registration: INPLASY202090088) to identify all TSIs and provide reliable information regarding their use (funded by EU Horizon 2020; HEAT-SHIELD). Eight databases (PubMed, Agricultural and Environmental Science Collection, Web of Science, Scopus, Embase, Russian Science Citation Index, MEDLINE, and Google Scholar) were searched from database inception to 15 April 2020. No restrictions on language or study design were applied. Of the 879 publications identified, 232 records were considered for further analysis. This search identified 340 instruments and indicators developed between 200 BC and 2019 AD. Of these, 153 are nomograms, instruments, and/or require detailed non-meteorological information, while 187 can be mathematically calculated utilizing only meteorological data. Of these meteorology-based TSIs, 127 were developed for people who are physically active, and 61 of those are eligible for use in occupational settings. Information regarding the equation, operating range, interpretation categories, required input data, as well as a free software to calculate all 187 meteorology-based TSIs is provided. The information presented in this systematic review should be adopted by those interested in performing on-site monitoring and/or big data analytics for climate services to ensure appropriate use of the meteorology-based TSIs. Studies two and three in this series of companion papers present guidance on the application and validation of these TSIs, to guide end users of these indicators for more effective use.

Background: Cold-induced vasodilation (CIVD) is a phenomenon that refers to a paradoxical increase in finger temperature that sometimes occurs during cold exposure. The aim of this study was to compare CIVD responses between women and men, during exposure to different environmental conditions. Methods: Seven men and seven women participated in a matched controlled study consisting of a familiarization protocol followed by three experimental sessions (cool (10.8 °C WBGT), thermoneutral (17.2 °C WBGT), and hot (27.2 °C WBGT)). In each session, participants were asked to immerse their left hand and foot in warm water (35 ± 1 °C) for five minutes. Thereafter, the left hand and foot were immersed in cold water (8 ± 1 °C) for 40 min. After that, the left hand and foot were removed from the water and participants remained seated for five minutes. Results: For a matched thermal stress, women experienced an elevated cardiovascular strain (heart rate and in some cases mean arterial pressure) and higher frequency of CIVD reactions (men: 31 vs. women: 60) in comparison to their male counterparts. Conclusions: The present study demonstrated that women experienced elevated cardiovascular strain and higher frequency of CIVD reactions, particularly in the toes, compared to their male counterparts during cold-water immersion.

The present comprehensive review (i) summarizes the current knowledge on the impacts of occupational heat stress on outdoor workers, (ii) provides a historical background on this issue, (iii) presents a meta-analysis of published data, (iv) explores inter-individual and intra-individual factors, (v) discusses the available heat mitigation strategies, (vi) estimates physical work capacity, labour productivity, and metabolic rate for the year 2030, and (vii) provides an overview of existing policy and legal frameworks on occupational heat exposure. Meta-analytic findings from 38 field studies that involved monitoring 2,409 outdoor workers across 41 jobs in 21 countries suggest that occupational heat stress increases the core (r = 0.44) and skin (r = 0.44) temperatures, as well as the heart rate (r = 0.38) and urine specific gravity (r = 0.13) of outdoor workers (all p < 0.05). Moreover, it diminishes the capacity of outdoor workers for manual labour (r = -0.82; p < 0.001) and is responsible for more than two thirds of the reduction in their metabolic rate. Importantly, our analysis shows that physical work capacity is projected to be highly affected by the ongoing anthropogenic global warming. Nevertheless, the metabolic rate and, therefore, labour productivity are projected to remain at levels higher than the workers' physical work capacity, indicating that people will continue to work more intensely than they should to meet their financial obligations for food and shelter. In this respect, complementary measures targeting self-pacing, hydration, work-rest regimes, ventilated garments, and mechanization can be adopted to protect outdoor workers.