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O'Rourke N, Dervis S, da Silva DF, Geurts C, Haman F, Adamo KB. Heat production during exercise in pregnancy: discerning the contribution of total body weight. Pflugers Arch 2024; 476:769-778. [PMID: 38433124 DOI: 10.1007/s00424-024-02929-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 12/23/2023] [Accepted: 02/13/2024] [Indexed: 03/05/2024]
Abstract
Studies have reported enhanced thermoregulatory function as pregnancy progresses; however, it is unclear if differences in thermoregulation are attributed to weight gain or other physiological changes. This study aimed to determine if total body weight will influence thermoregulation (heat production (Hprod)), heart rate, and perceptual measurements in response to weight-bearing exercise during early to late pregnancy. A cross-sectional design of healthy pregnant women at different pregnancy time points (early, T1; middle, T2; late, T3) performed a 7-stage weight-bearing incremental exercise protocol. Measurements of Hprod, HR, and RPE were examined. Two experimental groups were studied: (1) weight matched and (2) non-weight matched, in T1, T2, and T3. During exercise, equivalent Hprod at T1 (326 ± 88 kJ), T2 (330 ± 43 kJ), and T3 (352 ± 52 kJ) (p = 0.504); HR (p = 0.830); and RPE (p = 0.195) were observed in the WM group at each time point. In the NWM group, Hprod (from stages 1-6 of the exercise) increased across pregnancy time points, T1 (291 ± 76 kJ) to T2 (347 ± 41 kJ) and T3 (385 ± 47 kJ) (p < 0.001). HR increased from T1 to T3 in the warm-up to stage 6 (p = 0.009). RPE did not change as pregnancy time point progressed (p = 0.309). Total body weight, irrespective of pregnancy time point, modulates Hprod and HR during exercise. Therefore, accounting for total body weight is crucial when comparing thermoregulatory function during exercise across pregnancy.
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Affiliation(s)
- Nicholas O'Rourke
- Faculty of Health Sciences, School of Human Kinetics, University of Ottawa, Lees Campus, 518E, 200 Lees Ave, Ottawa, ON, K1N 6N5, Canada
| | - Sheila Dervis
- Faculty of Health Sciences, School of Human Kinetics, University of Ottawa, Lees Campus, 518E, 200 Lees Ave, Ottawa, ON, K1N 6N5, Canada
| | - Danilo F da Silva
- Sports Studies Department, Faculty of Arts and Science, Bishop's University, Sherbrooke, QC, Canada
| | - Carla Geurts
- Fontys University of Applied Sciences, Venlo, Netherlands
| | - François Haman
- Faculty of Health Sciences, School of Human Kinetics, University of Ottawa, Lees Campus, 518E, 200 Lees Ave, Ottawa, ON, K1N 6N5, Canada
| | - Kristi Bree Adamo
- Faculty of Health Sciences, School of Human Kinetics, University of Ottawa, Lees Campus, 518E, 200 Lees Ave, Ottawa, ON, K1N 6N5, Canada.
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2
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Cowper G, Goodall S, Hicks KM, Burnie L, Fox KT, Keenan A, De Martino E, Briggs MA. Physiological mechanisms associated with the use of a passive heat intervention: positive implications for soccer substitutes. Eur J Appl Physiol 2024; 124:1499-1508. [PMID: 38129698 DOI: 10.1007/s00421-023-05381-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 11/22/2023] [Indexed: 12/23/2023]
Abstract
PURPOSE Soccer substitutes are exposed to periods of limited activity before entering match-play, likely negating benefits of active warm-ups. This study aimed to determine the effects of using a passive heat intervention following a pre-match, and half-time warm-up, on muscle and core temperature in soccer players during ambient (18 °C) and cold (2 °C) conditions. METHODS On four occasions, 8 male players, completed a pre-match warm-up, followed by 45 min of rest. Following this, participants completed a half-time re-warm-up followed by an additional 45 min of rest, simulating a full match for an unplaying substitute. During periods of rest, participants wore either standardised tracksuit bottoms (CON), or heated trousers (HEAT), over typical soccer attire. RESULTS Vastus lateralis temperature declined less in HEAT compared to CON following the 1st half in 2 °C (Δ - 4.39 ± 0.81 vs. - 6.21 ± 1.32 °C, P = 0.002) and 18 °C (Δ - 2.48 ± 0.71 vs. - 3.54 ± 0.88 °C, P = 0.003). These findings were also observed in the 2nd half for the 2 °C (Δ - 4.36 ± 1.03 vs. - 6.26 ± 1.04 °C, P = 0.002) and 18 °C (Δ - 2.85 ± 0.57 vs. - 4.06 ± 1 °C, P = 0.018) conditions. In addition, core temperature declined less in HEAT compared to CON following the 1st (Δ - 0.41 ± 0.25 vs. - 0.84 ± 0.41 °C, P = 0.037) and 2nd (Δ - 0.25 ± 0.33 vs. - 0.64 ± 0.34 °C, P = 0.028) halves of passive rest in 2 °C, with no differences in the 18 °C condition. Perceptual data confirmed that participants were more comfortable in HEAT vs. CON in 2 °C (P < 0.01). CONCLUSIONS Following active warm-ups, heated trousers attenuate the decline in muscle temperature in ambient and cold environments.
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Affiliation(s)
- Gavin Cowper
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK.
| | - Stuart Goodall
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
| | - Kirsty M Hicks
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
| | - Louise Burnie
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
| | - Kai T Fox
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
| | - Ashleigh Keenan
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
| | - Enrico De Martino
- Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Aalborg, Denmark
| | - Marc A Briggs
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
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Beigtan M, Gonçalves M, Weon BM. Heat Transfer by Sweat Droplet Evaporation. Environ Sci Technol 2024; 58:6532-6539. [PMID: 38538556 PMCID: PMC11025549 DOI: 10.1021/acs.est.4c00850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 03/03/2024] [Accepted: 03/12/2024] [Indexed: 04/17/2024]
Abstract
Sweating regulates the body temperature in extreme environments or during exercise. Here, we investigate the evaporative heat transfer of a sweat droplet at the microscale to unveil how the evaporation complexity of a sweat droplet would affect the body's ability to cool under specific environmental conditions. Our findings reveal that, depending on the relative humidity and temperature levels, sweat droplets experience imperfect evaporation dynamics, whereas water droplets evaporate perfectly at equivalent ambient conditions. At low humidity, the sweat droplet fully evaporates and leaves a solid deposit, while at high humidity, the droplet never reaches a solid deposit and maintains a liquid phase residue for both low and high temperatures. This unprecedented evaporation mechanism of a sweat droplet is attributed to the intricate physicochemical properties of sweat as a biofluid. We suppose that the sweat residue deposited on the surface by evaporation is continuously absorbing the surrounding moisture. This route leads to reduced evaporative heat transfer, increased heat index, and potential impairment of the body's thermoregulation capacity. The insights into the evaporative heat transfer dynamics at the microscale would help us to improve the knowledge of the body's natural cooling mechanism with practical applications in healthcare, materials science, and sports science.
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Affiliation(s)
- Mohadese Beigtan
- Soft
Matter Physics Laboratory, School of Advanced Materials Science and
Engineering, Sungkyunkwan University, Suwon 16419, South Korea
| | - Marta Gonçalves
- Soft
Matter Physics Laboratory, School of Advanced Materials Science and
Engineering, Sungkyunkwan University, Suwon 16419, South Korea
- Research
Center for Advanced Materials Technology, Sungkyunkwan University, Suwon 16419, South Korea
| | - Byung Mook Weon
- Soft
Matter Physics Laboratory, School of Advanced Materials Science and
Engineering, Sungkyunkwan University, Suwon 16419, South Korea
- Research
Center for Advanced Materials Technology, Sungkyunkwan University, Suwon 16419, South Korea
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4
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Bianca E, Dotti F, Orrico F, Ferri A. Thermoregulation of feet in cold environments: A study on alpinism. Appl Ergon 2024; 116:104205. [PMID: 38091693 DOI: 10.1016/j.apergo.2023.104205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 11/20/2023] [Accepted: 12/07/2023] [Indexed: 01/16/2024]
Abstract
Thermal comfort plays a crucial role in the performance and well-being of mountaineers, especially in extreme environments. The aim of this study was to develop a reliable protocol to assess the thermal comfort of mountaineering boots, with a specific focus on temperature variations in different regions of the foot and their correlation with physiological factors. Two different models of mountaineering boots were tested at two different environmental temperature (-15°C and -30°C). The mean skin temperature, measured according to International Standards BS EN ISO 9886:2004, was used as an indicator of overall thermal comfort. Physiological factors such as heart rate (HR), body mass index (BMI) and body surface area (BSA) were also measured to understand their relationship to thermoregulation. Kruskal-Wallis and Pearson's ProductMoment correlation tests were performed to investigate whether there was a statistically significant relationship. The results showed significant differences in foot temperature among the Testers, indicating variations in the perception of thermal comfort. The correlation analysis showed a strong positive relationship between mean skin temperature and HR, highlighting the influence of physiological factors on thermal comfort. In addition, the analysis showed that the dorsum and hallux areas had the largest temperature variations, suggesting the occurrence of vasoconstriction and potential discomfort. This study represents a preliminary approach to establishing a reliable protocol for assessing the thermal performance of cold protective footwear.
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Affiliation(s)
- Eleonora Bianca
- Department of Applied Science and Technology, Polytechnic of Turin, Turin, 10129, Italy.
| | - Francesca Dotti
- Department of Applied Science and Technology, Polytechnic of Turin, Turin, 10129, Italy.
| | | | - Ada Ferri
- Department of Applied Science and Technology, Polytechnic of Turin, Turin, 10129, Italy.
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5
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Xu X, Rioux TP, Welles AP, Jay O, Ely BR, Charkoudian N. Modeling thermoregulatory responses during high-intensity exercise in warm environments. J Appl Physiol (1985) 2024; 136:908-916. [PMID: 38385185 DOI: 10.1152/japplphysiol.00873.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 01/31/2024] [Accepted: 02/19/2024] [Indexed: 02/23/2024] Open
Abstract
The six cylinder thermoregulatory model (SCTM) has been validated thoroughly for resting humans. This type of modeling is helpful to predict and develop guidance for safe performance of work and recreational activities. In the context of a warming global climate, updating the accuracy of the model for intense exercise in warm environments will help a wide range of individuals in athletic, recreational, and military settings. Three sets of previously collected data were used to determine SCTM accuracy. Dataset 1: two groups [large (LG) 91.5 kg and small (SM) 67.7 kg] of individuals performed 60 min of semirecumbent cycling in temperate conditions (25.1°C) at metabolic rates of 570-700 W. Dataset 2: two LG (100 kg) and SM (65.8 kg) groups performed 60 min of semirecumbent cycling in warm/hot environmental conditions (36.2°C) at metabolic rates of 590-680 W. Dataset 3: seven volunteers completed 8-km track trials (∼30 min) in cool (17°C) and warm (30°C) environments. The volunteers' metabolic rates were estimated to be 1,268 W and 1,166 W, respectively. For all datasets, SCTM-predicted core temperatures were found to be similar to the observed core temperatures. The root mean square deviations (RMSDs) ranged from 0.06 to 0.46°C with an average of 0.2°C deviation, which is less than the acceptance threshold of 0.5°C. Thus, the present validation shows that SCTM predicts core temperatures with acceptable accuracy during intense exercise in warm environments and successfully captures core temperature differences between large and small individuals.NEW & NOTEWORTHY The SCTM has been validated thoroughly for resting humans in warm and cold environments and during water immersion. The present study further demonstrated that SCTM predicts core temperatures with acceptable accuracy during intense exercise up to 1,300 W in temperate and warm environments and captures core temperature differences between large and small individuals. SCTM is potentially useful to develop guidance for safe operation in athletic, military, and occupational settings during exposure to warm or hot environments.
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Affiliation(s)
- Xiaojiang Xu
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States
| | - Timothy P Rioux
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States
| | - Alexander P Welles
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States
| | - Ollie Jay
- Thermal Ergonomics Laboratory, Heat and Health Research Incubator, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
| | - Brett R Ely
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States
- School of Nursing & Health Sciences, Providence College, Providence, Rhode Island, United States
| | - Nisha Charkoudian
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States
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6
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Rodrigues P, Orssatto LBR, Gagnon D, Dahhak A, Hecksteden A, Stewart IB, Minett GM. Passive heat therapy: a promising preventive measure for people at risk of adverse health outcomes during heat extremes. J Appl Physiol (1985) 2024; 136:677-694. [PMID: 38299219 DOI: 10.1152/japplphysiol.00701.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 01/26/2024] [Indexed: 02/02/2024] Open
Abstract
The world is experiencing increased frequency, duration, and severity of life-threatening heat extremes. Most hospitalizations and excess deaths during extreme heat events are associated with preexisting diseases in older adults. As climate change persists, the global population ages and the number of individuals with chronic diseases expands, more people are at risk of adverse health outcomes during extreme heat events. Therefore, proactive preventive measures are urgently needed to mitigate heat-related health risks within these populations. In this context, passive heat therapy (e.g., hot baths, saunas, and water-perfused suits) emerges as a promising countermeasure to improve physiological resilience to a warming planet. Passive heating improves cardiovascular function and overall health in older adults and individuals living with chronic diseases, offering the prospect of reducing cardiovascular strain during hotter days. Moreover, some studies suggest that passive heat therapy can be an effective strategy for heat acclimation (i.e., improved thermoregulation). This review describes the existing literature on the effects of passive heat therapy on cardiovascular and thermoregulatory responses in individuals with higher heat-related health risks and explores the use of passive heating as a strategy for heat acclimation to mitigate health risks during extreme heat events.NEW & NOTEWORTHY Passive heat therapy improves cardiovascular function and health in middle-aged and older adults living with or without chronic diseases. In addition, preliminary studies indicate that passive heat interventions can induce heat acclimation, improving thermoregulatory responses. Thus, passive heat therapy could serve as a preventive measure for people at risk of adverse health outcomes during extreme heat events, improving resilience to ongoing climate change.
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Affiliation(s)
- Patrick Rodrigues
- Institute of Physiology, Medical University of Innsbruck, Innsbruck, Austria
- Institute of Sport Science, Leopold-Franzens-University of Innsbruck, Innsbruck, Austria
- School of Exercise and Nutrition Sciences, Faculty of Health, Queensland University of Technology (QUT), Brisbane, Queensland, Australia
| | - Lucas B R Orssatto
- Institute for Physical Activity and Nutrition (IPAN), School of Exercise and Nutrition Sciences, Faculty of Health, Deakin University, Geelong, Victoria, Australia
| | - Daniel Gagnon
- Montreal Heart Institute, Montréal, Quebec, Canada
- School of Kinesiology and Exercise Science, Université de Montréal, Montréal, Quebec, Canada
| | - Amine Dahhak
- Montreal Heart Institute, Montréal, Quebec, Canada
- School of Kinesiology and Exercise Science, Université de Montréal, Montréal, Quebec, Canada
| | - Anne Hecksteden
- Institute of Physiology, Medical University of Innsbruck, Innsbruck, Austria
- Institute of Sport Science, Leopold-Franzens-University of Innsbruck, Innsbruck, Austria
| | - Ian B Stewart
- School of Exercise and Nutrition Sciences, Faculty of Health, Queensland University of Technology (QUT), Brisbane, Queensland, Australia
| | - Geoffrey M Minett
- School of Exercise and Nutrition Sciences, Faculty of Health, Queensland University of Technology (QUT), Brisbane, Queensland, Australia
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7
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Bernard TE, Wolf ST, Kenney WL. A Novel Conceptual Model for Human Heat Tolerance. Exerc Sport Sci Rev 2024; 52:39-46. [PMID: 38294236 PMCID: PMC10963138 DOI: 10.1249/jes.0000000000000332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Human "heat tolerance" has no accepted definition or physiological underpinnings; rather, it is almost always discussed in relative or comparative terms. We propose to use environmental limits to heat balance accounting for metabolic rate and clothing, that is, the environments for which heat stress becomes uncompensable for a specified metabolic rate and clothing, as a novel metric for quantifying heat tolerance.
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Affiliation(s)
- Thomas E. Bernard
- College of Public Health, University of South Florida, Tampa, FL 33612
| | - S. Tony Wolf
- Department of Kinesiology, University of Georgia, Athens, GA 30602
| | - W. Larry Kenney
- Department of Kinesiology and Integrative and Biomedical Physiology Program, The Pennsylvania State University, University Park, PA 16802
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8
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Zhou S, Ouyang L, Li B, Hodder S, Yao R. A thermoregulation model based on the physical and physiological characteristics of Chinese elderly. Comput Biol Med 2024; 172:108262. [PMID: 38479196 DOI: 10.1016/j.compbiomed.2024.108262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 02/13/2024] [Accepted: 03/06/2024] [Indexed: 03/26/2024]
Abstract
Given the increasing aging population and rising living standards in China, developing an accurate and straightforward thermoregulation model for the elderly has become increasingly essential. To address this need, an existing one-segment four-node thermoregulation model for the young was selected as the base model. This study developed the base model considering age-related physical and physiological changes to predict mean skin temperatures of the elderly. Measured data for model optimization were collected from 24 representative healthy Chinese elderly individuals (average age: 67 years). The subjects underwent temperature step changes between neutral and warm conditions with a temperature range of 25-34 °C. The model's demographic representation was first validated by comparing the subjects' physical characteristics with Chinese census data. Secondly, sensitivity analysis was performed to investigate the influences of passive system parameters on skin and core temperatures, and adjustments were implemented using measurement or literature data specific to the Chinese elderly. Thirdly, the active system was modified by resetting the body temperature set points. The active parameters to control thermoregulation activities were further optimized using the TPE (Tree-structured Parzen Estimator) hyperparameter tuning method. The model's accuracy was further verified using independent experimental data for a temperature range of 18-34 °C for Chinese elderly. By comprehensively considering age-induced thermal response changes, the proposed model has potential applications in designing and optimizing thermal management systems in buildings, as well as informing energy-efficient strategies tailored to the specific needs of the Chinese elderly population.
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Affiliation(s)
- Shan Zhou
- Joint International Research Laboratory of Green Buildings and Built Environments (Ministry of Education), Chongqing University, Chongqing, 400045, China; National Center for International Research of Low-carbon and Green Buildings (Ministry of Science and Technology), Chongqing University, Chongqing, 400045, China
| | - Linyuan Ouyang
- Joint International Research Laboratory of Green Buildings and Built Environments (Ministry of Education), Chongqing University, Chongqing, 400045, China; National Center for International Research of Low-carbon and Green Buildings (Ministry of Science and Technology), Chongqing University, Chongqing, 400045, China
| | - Baizhan Li
- Joint International Research Laboratory of Green Buildings and Built Environments (Ministry of Education), Chongqing University, Chongqing, 400045, China; National Center for International Research of Low-carbon and Green Buildings (Ministry of Science and Technology), Chongqing University, Chongqing, 400045, China
| | - Simon Hodder
- School of Design & Creative Arts, Loughborough University, Loughborough, LE11 3TU, UK
| | - Runming Yao
- Joint International Research Laboratory of Green Buildings and Built Environments (Ministry of Education), Chongqing University, Chongqing, 400045, China; National Center for International Research of Low-carbon and Green Buildings (Ministry of Science and Technology), Chongqing University, Chongqing, 400045, China; School of the Built Environment, University of Reading, Reading, RG6 6DB, UK.
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9
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Bachraty JP, Qiao J, Powers ES, Vandermark LW, Pryor JL, Pryor RR. Plateau in Core Temperature during Shorter but Not Longer Work/Rest Cycles in Heat. Int J Environ Res Public Health 2024; 21:371. [PMID: 38541370 PMCID: PMC10970706 DOI: 10.3390/ijerph21030371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 03/12/2024] [Accepted: 03/18/2024] [Indexed: 04/09/2024]
Abstract
This study compared physiological responses to two work/rest cycles of a 2:1 work-to-rest ratio in a hot environment. In a randomized crossover design, fourteen participants completed 120 min of walking and rest in the heat (36.3 ± 0.6 °C, 30.2 ± 4.0% relative humidity). Work/rest cycles were (1) 40 min work/20 min rest [40/20], or (2) 20 min work/10 min rest [20/10], both completing identical work. Core temperature (Tc), skin temperature (Tsk), heart rate (HR), nude body mass, and perception of work were collected. Comparisons were made between trials at equal durations of work using three-way mixed model ANOVA. Tc plateaued in [20/10] during the second hour of work (p = 0.93), while Tc increased in [40/20] (p < 0.01). There was no difference in maximum Tc ([40/20]: 38.08 ± 0.35 °C, [20/10]: 37.99 ± 0.27 °C, p = 0.22) or end-of-work Tsk ([40/20]: 36.1 ± 0.8 °C, [20/10]: 36.0 ± 0.7 °C, p = 0.45). End-of-work HR was greater in [40/20] (145 ± 25 b·min-1) compared to [20/10] (141 ± 27 b·min-1, p = 0.04). Shorter work/rest cycles caused a plateau in Tc while longer work/rest cycles resulted in a continued increase in Tc throughout the work, indicating that either work structure could be used during shorter work tasks, while work greater than 2 h in duration may benefit from shorter work/rest cycles to mitigate hyperthermia.
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Affiliation(s)
| | | | | | | | | | - Riana R. Pryor
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY 14214, USA (J.Q.); (E.S.P.)
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10
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Reis J, Buguet A, Radomski M, Stella AB, Vásquez TC, Spencer PS. Neurological patients confronting climate change: A potential role for the glymphatic system and sleep. J Neurol Sci 2024; 458:122900. [PMID: 38310733 DOI: 10.1016/j.jns.2024.122900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 01/18/2024] [Accepted: 01/21/2024] [Indexed: 02/06/2024]
Abstract
Interest in the health consequences of climate change (global warming, heatwaves) has increased in the neurological community. This review addresses the impact of elevated ambient temperatures and heatwaves on patients with neurological and mental health disorders, including multiple sclerosis, synucleinopathies, dementia, epilepsies, mental health, and stroke. Patients with such conditions are highly vulnerable during heatwaves because of functional disorders affecting sleep, thermoregulation, autonomic system reactivity, mood, and cognitive ability. Several medications may also increase the risk of heatstroke. Special attention is devoted to the involvement of common underlying mechanisms, such as sleep and the glymphatic system. Disease prevention and patient care during heatwaves are major issues for caregivers. Beyond the usual recommendations for individuals, we favor artificially induced acclimation to heat, which provides preventive benefits with proven efficacy for healthy adults.
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Affiliation(s)
- Jacques Reis
- Department of Neurology, University Hospital of Strasbourg, 67000 Strasbourg, France; Association RISE, 3 rue du Loir, 67205 Oberhausbergen, France.
| | - Alain Buguet
- Malaria Research Unit, UMR 5246 CNRS, Claude-Bernard Lyon-1 University, 69622 Villeurbanne, France; 21 rue de Champfranc, 38630 Les Avenières Veyrins-Thuellin, France
| | - Manny Radomski
- Emeritus at the University of Toronto, Apt n° 2501, 2010 Islington Avenue, Toronto, ON M9P3S8, Canada
| | - Alex Buoite Stella
- Clinical Unit of Neurology, Department of Medicine, Surgery and Health Sciences, Cattinara University Hospital, University of Trieste, Trieste, Italy
| | - Teresa Corona Vásquez
- División de Estudios de Posgrado, Universidad Nacional Autónoma de México, Mexico City, Mexico; Clinical Neurodegenerative Diseases Laboratory, Instituto Nacional de Neurología y Neurocirugía, Manuel Velasco Suárez, Mexico City, Mexico
| | - Peter S Spencer
- Department of Neurology, School of Medicine, Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239, USA
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11
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Taylor KM, Giersch GEW, Caldwell AR, Epstein Y, Charkoudian N. Relation of body surface area-to-mass ratio to risk of exertional heat stroke in healthy men and women. J Appl Physiol (1985) 2024; 136:549-554. [PMID: 38234291 DOI: 10.1152/japplphysiol.00597.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 12/15/2023] [Accepted: 01/09/2024] [Indexed: 01/19/2024] Open
Abstract
Risk of exertional heat stroke (EHS) is an ongoing challenge for United States military personnel, for athletes and for individuals with occupational stressors that involve prolonged activity in hot environments. Higher body mass index (BMI) is significantly associated with increased risk for EHS in activity duty U.S. Soldiers. During exercise, heat is generated primarily by contracting skeletal muscle (and other metabolically active body mass) and dissipated based on body surface area (BSA). Thus, in compensable environments, a higher BSA·mass-1 may be a benefit to heat dissipation and decrease the risk of EHS. The purpose of the present analysis was to test the hypothesis that BSA·mass-1 ratio is an important biophysical characteristic contributing to the risk of EHS. We employed a matched case-control approach, where each individual with a diagnosis of EHS was matched to five controls who were never diagnosed with EHS but were in the same unit and had the same job title. We used a multivariate conditional logistic regression model including variables of BSA·mass-1, sex, age, military rank, and race. BSA·mass-1 significantly predicted EHS risk (P = 0.006), such that people with higher BSA·mass-1 were at lower risk of developing EHS when controlling for other potential factors such as age and race. This relationship persisted after adjustment for other anthropometric measures of body size including weight, BMI, and BSA. These data suggest that biophysical factors play an important role in EHS risk, particularly in a healthy military-aged cohort of men and women.NEW & NOTEWORTHY With the impacts of climate change yielding higher average ambient temperatures over time, the incidence of EHS for individuals participating in outdoor activities may consequently increase. With the larger sample size in this study compared with prior research in this field, we were able to use various methods that had not been applied before. For example, we were able to mutually adjust for different measurements of body size to understand which metric had the highest association with EHS risk. Understanding factors that may be modifiable may be important for developing interventions to counteract the increased risk of EHS associated with climate change.
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Affiliation(s)
- Kathryn M Taylor
- Military Performance Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States
| | - Gabrielle E W Giersch
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States
| | - Aaron R Caldwell
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States
| | - Yoram Epstein
- School of Public Health, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Nisha Charkoudian
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States
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12
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Mota CMD, Madden CJ. Neural circuits of long-term thermoregulatory adaptations to cold temperatures and metabolic demands. Nat Rev Neurosci 2024; 25:143-158. [PMID: 38316956 DOI: 10.1038/s41583-023-00785-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/15/2023] [Indexed: 02/07/2024]
Abstract
The mammalian brain controls heat generation and heat loss mechanisms that regulate body temperature and energy metabolism. Thermoeffectors include brown adipose tissue, cutaneous blood flow and skeletal muscle, and metabolic energy sources include white adipose tissue. Neural and metabolic pathways modulating the activity and functional plasticity of these mechanisms contribute not only to the optimization of function during acute challenges, such as ambient temperature changes, infection and stress, but also to longitudinal adaptations to environmental and internal changes. Exposure of humans to repeated and seasonal cold ambient conditions leads to adaptations in thermoeffectors such as habituation of cutaneous vasoconstriction and shivering. In animals that undergo hibernation and torpor, neurally regulated metabolic and thermoregulatory adaptations enable survival during periods of significant reduction in metabolic rate. In addition, changes in diet can activate accessory neural pathways that alter thermoeffector activity. This knowledge may be harnessed for therapeutic purposes, including treatments for obesity and improved means of therapeutic hypothermia.
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Affiliation(s)
- Clarissa M D Mota
- Department of Neurological Surgery, Oregon Health and Science University, Portland, OR, USA
| | - Christopher J Madden
- Department of Neurological Surgery, Oregon Health and Science University, Portland, OR, USA.
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13
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Deshayes TA, Sodabi DGA, Dubord M, Gagnon D. Shifting focus: Time to look beyond the classic physiological adaptations associated with human heat acclimation. Exp Physiol 2024; 109:335-349. [PMID: 37885125 PMCID: PMC10988689 DOI: 10.1113/ep091207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Accepted: 10/12/2023] [Indexed: 10/28/2023]
Abstract
Planet Earth is warming at an unprecedented rate and our future is now assured to be shaped by the consequences of more frequent hot days and extreme heat. Humans will need to adapt both behaviorally and physiologically to thrive in a hotter climate. From a physiological perspective, countless studies have shown that human heat acclimation increases thermoeffector output (i.e., sweating and skin blood flow) and lowers cardiovascular strain (i.e., heart rate) during heat stress. However, the mechanisms mediating these adaptations remain understudied. Furthermore, several possible benefits of heat acclimation for other systems and functions involved in maintaining health and performance during heat stress remain to be elucidated. This review summarizes recent advances in human heat acclimation, with emphasis on recent studies that (1) advanced our understanding of the mechanisms mediating improved thermoeffector output and (2) investigated adaptations that go beyond those classically associated with heat acclimation. We highlight that these studies have contributed to a better understanding of the integrated physiological responses underlying human heat acclimation while leaving key unanswered questions that will need to be addressed in the future.
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Affiliation(s)
- Thomas A. Deshayes
- Montreal Heart InstituteMontréalCanada
- School of Kinesiology and Exercise ScienceUniversité de MontréalMontréalCanada
| | - Dèwanou Gilles Arnaud Sodabi
- Montreal Heart InstituteMontréalCanada
- School of Kinesiology and Exercise ScienceUniversité de MontréalMontréalCanada
| | - Marianne Dubord
- Montreal Heart InstituteMontréalCanada
- School of Kinesiology and Exercise ScienceUniversité de MontréalMontréalCanada
| | - Daniel Gagnon
- Montreal Heart InstituteMontréalCanada
- School of Kinesiology and Exercise ScienceUniversité de MontréalMontréalCanada
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14
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Kirby NV, Meade RD, Richards BJ, Notley SR, Kenny GP. Hormonal intrauterine devices and heat exchange during exercise. J Physiol 2024; 602:875-890. [PMID: 38367251 DOI: 10.1113/jp285977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Accepted: 01/22/2024] [Indexed: 02/19/2024] Open
Abstract
Synthetic progestins in oral contraceptives are thought to blunt heat dissipation by reducing skin blood flow and sweating. However, whether progestin-releasing intrauterine devices (IUDs) modulate heat loss during exercise-heat stress is unknown. We used direct calorimetry to measure whole-body total (dry + evaporative) heat loss in young, physically active women (mean (SD); aged 24 (4) years,V ̇ O 2 peak ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{peak}}}}$ 39.3 (5.3) ml/kg/min) with (IUD; n = 19) and without (Control; n = 17) IUDs in the follicular and luteal phases of the menstrual cycle during light- and moderate-intensity exercise at fixed rates of heat production (∼175 and ∼275 W/m2 ) in 30°C, ∼21% relative humidity. Between-group and -phase differences were evaluated using traditional hypothesis testing and statistical equivalence testing within pre-determined bounds (±11 W/m2 ; difference required to elicit a ±0.3°C difference in core temperature over 1 h) in each exercise bout. Whole-body total heat loss was statistically equivalent between groups within ±11 W m-2 (IUD-Control [90% CIs]; Light: -2 [-8, 5] W/m2 , P = 0.007; Moderate: 0 [-6, 6] W/m2 , P = 0.002), as were dry and evaporative heat loss (P ≤ 0.023), except for evaporative heat loss during moderate-intensity exercise (equivalence: P = 0.063, difference: P = 0.647). Whole-body total and evaporative heat loss were not different between phases (P ≥ 0.267), but dry heat loss was 3 [95% CIs: 1, 5] W/m2 greater in the luteal phase (P ≤ 0.022). Despite this, all whole-body heat loss outcomes were equivalent between phases (P ≤ 0.003). These findings expand our understanding of the factors that modulate heat exchange in women and provide valuable mechanistic insight of the role of endogenous and exogenous female sex hormones in thermoregulation. KEY POINTS: Progestin released by hormonal intrauterine devices (IUDs) may negatively impact heat dissipation during exercise by blunting skin blood flow and sweating. However, the influence of IUDs on thermoregulation has not previously been assessed. We used direct calorimetry to show that IUD users and non-users display statistically equivalent whole-body dry and evaporative heat loss, body heat storage and oesophageal temperature during moderate- and high-intensity exercise in a warm, dry environment, indicating that IUDs do not appear to compromise exercise thermoregulation. However, within IUD users and non-users, dry heat loss was increased and body heat storage and oesophageal temperature were reduced in the luteal compared to the follicular phase of the menstrual cycle, though these effects were small and unlikely to be practically meaningful. Together, these findings expand our understanding of the factors that modulate heat exchange in women and have important practical implications for the design of future studies of exercise thermoregulation.
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Affiliation(s)
- Nathalie V Kirby
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Robert D Meade
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Brodie J Richards
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Sean R Notley
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
- Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
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15
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Lobo JM. Hotter-is-not-better: A study on the thermal response of a winter active and nocturnal beetle. J Insect Physiol 2024; 153:104602. [PMID: 38142956 DOI: 10.1016/j.jinsphys.2023.104602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 12/12/2023] [Accepted: 12/19/2023] [Indexed: 12/26/2023]
Abstract
While there are numerous examples of thermogenesis processes in poikilothermic insects that maintain a stable temperature for a certain time and in certain parts of the body, there is a lack of information on ectothermic insect species capable of remaining active under "cold" conditions that would be challenging for other species. Such a thermal strategy would imply the existence of a metabolism that can operate at different temperatures without the need to increase body temperature when experiencing cold environmental conditions. This "hotter-is-not-better" thermal strategy is considered ancestral and conjectured to be linked to the origin and evolution of endothermy. In this study, we examined the thermal performance of a large-bodied dung beetle species (Chelotrupes momus) capable of being active during the winter nights in the Iberian Mediterranean region. Field and laboratory results were obtained using thermocamera records, thermocouples, data loggers and spectrometers that measured ultraviolet, visible and near-infrared wavelengths. The thermal data clearly indicated that this species can remain active at a body temperature of approximately 6 °C without the need to warm its body above ambient temperature. Comparing the spectrophotometric data of the species under study with that from other previously examined dung beetle species indicated that the exoskeleton of this particular species likely enhances the absorption of infrared radiation, thereby implying a dual role of the exoskeleton in both heat acquisition and heat dissipation. Taken together, these results suggest that this species has morphological and metabolic adaptations that enable life processes at temperatures that are typically unsuitable for most insect species in the region.
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Affiliation(s)
- Jorge M Lobo
- Departamento de Biogeografía y Cambio Global, Museo Nacional de Ciencias Naturales-CSIC, Spain.
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16
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Dawson TJ, Maloney SK. Functional interactions between coat structure and colour in the determination of solar heat load on arid living kangaroos in summer: balancing crypsis and thermoregulation. J Comp Physiol B 2024; 194:53-64. [PMID: 38336838 PMCID: PMC10940446 DOI: 10.1007/s00360-024-01534-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 01/01/2024] [Accepted: 01/08/2024] [Indexed: 02/12/2024]
Abstract
Interactions of solar radiation with mammal fur are complex. Reflection of radiation in the visible spectrum provides colour that has various roles, including sexual display and crypsis, i.e., camouflage. Radiation that is absorbed by a fur coat is converted to heat, a proportion of which impacts on the skin. Not all absorption occurs at the coat surface, and some radiation penetrates the coat before being absorbed, particularly in lighter coats. In studies on this phenomenon in kangaroos, we found that two arid zone species with the thinnest coats had similar effective heat load, despite markedly different solar reflectances. These kangaroos were Red Kangaroos (Osphranter rufus) and Western Grey Kangaroos (Macropus fuliginosus).Here we examine the connections between heat flow patterns associated with solar radiation, and the physical structure of these coats. Also noted are the impacts of changing wind speed. The modulation of solar radiation and resultant heat flows in these coats were measured at wind speeds from 1 to 10 m s-1 by mounting them on a heat flux transducer/temperature-controlled plate apparatus in a wind tunnel. A lamp with a spectrum like solar radiation was used as a proxy for the sun. The integrated reflectance across the solar spectrum was higher in the red kangaroos (40 ± 2%) than in the grey kangaroos (28 ± 1%). Fur depth and insulation were not different between the two species, but differences occurred in fibre structure, notably in fibre length, fibre density and fibre shape. Patterns of heat flux within the species' coats occurred despite no overall difference in effective solar heat load. We consider that an overarching need for crypsis, particularly for the more open desert-adapted red kangaroo, has led to the complex adaptations that retard the penetrance of solar radiation into its more reflective fur.
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Affiliation(s)
- Terence J Dawson
- School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Shane K Maloney
- School of Human Sciences, University of Western Australia, Crawley, WA, 6009, Australia.
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17
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Rodríguez H, Arriaza C, Sarabia L, Espinoza-Navarro O. Anatomical and physiological adaptation of the scrotal artery with muscular reinforcement in the middle layer and connective reinforcement of the adventitia. Microsc Res Tech 2024; 87:403-407. [PMID: 37877624 DOI: 10.1002/jemt.24440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 09/25/2023] [Accepted: 10/05/2023] [Indexed: 10/26/2023]
Abstract
The histology of blood vessels shows they are structured in three layers or tunics: tunica intima, which includes the internal limiting lamina with high elastin content; tunica media of smooth muscles fibers of circular disposition, which includes the external limiting lamina; and tunica adventitia of connective tissue. The vascular system is essential in regulating body temperature, especially in the scrotum and testis. This study aimed to analyze the histology of the scrotal arteries and their possible relationship to testicular temperature homeostasis. This study used scrotal samples from human adults, anonymized and obtained from the University of Chile's teaching bank. The control group corresponds to an arteriole of muscle tissue. The results show that the middle layer of the scrotal artery is made up of smooth muscle fibers distributed in two layers: a longitudinal inner sublayer and a circular outer sublayer, different from the findings in muscle tissue arteries, with a single, circularly arranged muscle layer. This arrangement could be related to testicular temperature homeostasis by reducing the temperature of the testis and seminiferous tubules. The results described in this work suggest that these anatomical adaptations may be very significant in the face of the constant increase in global temperature. Further and better research is required to understand the mechanisms of thermoregulation in human reproduction and the histological particularities of the tissues that form the scrotum. RESEARCH HIGHLIGHTS: The human scrotal artery has a histological composition adapted for regulation of testicular temperature. The muscular double middle layer of the scrotal artery retains intravascular temperature.
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Affiliation(s)
- Héctor Rodríguez
- Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Facultad de Medicina, Universidad de Atacama, Copiapó, Chile
| | - Camilo Arriaza
- Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Luis Sarabia
- Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Omar Espinoza-Navarro
- Departamento de Biología, Facultad de Ciencias, Universidad de Tarapacá, Arica, Chile
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18
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Valenza A, Blount H, Bianco A, Worsley PR, Filingeri D. Biophysical, thermo-physiological and perceptual determinants of cool-seeking behaviour during exercise in younger and older women. Exp Physiol 2024; 109:255-270. [PMID: 37975151 PMCID: PMC10988754 DOI: 10.1113/ep091533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 10/27/2023] [Indexed: 11/19/2023]
Abstract
Women continue to be under-represented in thermoregulatory research despite their undergoing unique physiological changes across the lifespan. This study investigated the biophysical, thermo-physiological, and perceptual determinants of cool-seeking behaviour during exercise in younger and older women. Eleven younger (25 ± 5 years; 1.7 ± 0.1 m; 63.1 ± 5.2 kg) and 11 older women (53 ± 6 years; 1.7 ± 0.1 m; 65.4 ± 13.9 kg) performed a 40-min incremental cycling test in a thermoneutral environment (22 ± 1.7°C; 36 ± 4% relative humidity). Throughout the test, participants freely adjusted the temperature of a cooling probe applied to their wrists to offset their thermal discomfort. We continuously recorded the probe-wrist interface temperature to quantify participants' cool-seeking behaviour. We also measured changes in participants' rate of metabolic heat production, core and mean skin temperatures, and skin wetness. Finally, we body-mapped participants' skin heat, cold and wetness sensitivity. Our results indicated that: (1) older and younger women exhibited similar onset and magnitude of cool-seeking behaviour, despite older women presented reduced autonomic heat-dissipation responses (i.e., whole-body sweat losses); (2) older women's thermal behaviour was less determined by changes in core temperature (this being a key driver in younger women), and more by changes in multiple thermo-physiological and biophysical parameters (i.e., physical skin wetness, temperature and heat production); (3) older women did not present lower regional skin thermal and wetness sensitivity than younger women. We conclude that predictions of female cool-seeking behaviours based on thermo-physiological variables should consider the effects of ageing. These findings are relevant for the design of wearable cooling systems and sports garments that meet the thermal needs of women across the lifespan.
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Affiliation(s)
- Alessandro Valenza
- ThermosenseLab, Skin Sensing Research Group, School of Health SciencesThe University of SouthamptonSouthamptonUK
- Sport and Exercise Sciences Research Unit, SPPEFF DepartmentUniversity of PalermoPalermoItaly
| | - Hannah Blount
- ThermosenseLab, Skin Sensing Research Group, School of Health SciencesThe University of SouthamptonSouthamptonUK
| | - Antonino Bianco
- Sport and Exercise Sciences Research Unit, SPPEFF DepartmentUniversity of PalermoPalermoItaly
| | - Peter R. Worsley
- PRESSURELAB, Skin Sensing Research Group, School of Health SciencesThe University of SouthamptonSouthamptonUK
| | - Davide Filingeri
- ThermosenseLab, Skin Sensing Research Group, School of Health SciencesThe University of SouthamptonSouthamptonUK
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19
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Fisher KG, Cottle RM, Kenney WL, Wolf ST. Sunscreen does not alter sweating responses or critical environmental limits in young adults (PSU HEAT project). J Appl Physiol (1985) 2024; 136:322-329. [PMID: 38126091 DOI: 10.1152/japplphysiol.00756.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 11/27/2023] [Accepted: 12/13/2023] [Indexed: 12/23/2023] Open
Abstract
Outdoor athletes often eschew using sunscreen due to perceived performance impairments, which many attribute in part to the potential for reduced thermoregulatory heat loss. Past studies examining the impact of sunscreen on thermoregulation are equivocal. The purpose of this study was to determine the effects of mineral and chemical-based sunscreens on sweating responses and critical environmental limits in hot-dry (HD) and warm-humid (WH) environments. Nine subjects (3 M/6 F; 25 ± 2 yr) were tested with 1) no sunscreen (control), 2) chemical-, and 3) mineral-based sunscreen. Subjects were exposed to progressive heat stress with either 1) constant dry-bulb temperature (Tdb) at 34°C and increasing water vapor pressure (Pa) (WH trials) or 2) constant Pa at 12 mmHg and increasing Tdb (HD trials). Subjects walked at 4.9 ± 0.5 metabolic equivalents (METs) until an upward inflection in gastrointestinal temperature was observed (i.e., the critical environmental limit). Compared with control (39.9 ± 3.0°C), critical Tdb was not different in mineral (39.2 ± 3.5°C, P = 0.39) or chemical (39.7 ± 3.0°C, P = 0.98) sunscreen trials in HD environments. Compared with control (18.8 ± 4.0 mmHg), critical Pa was not different in mineral (18.9 ± 4.8 mmHg, P = 0.81) or chemical (19.5 ± 4.6 mmHg, P = 0.81) sunscreen trials in WH environments. Sweating rates, evaporative heat loss, skin wettedness, and sweating efficiency were not different among the three trials in the WH (all P ≥ 0.48) or HD (all P ≥ 0.87) environments. Critical environmental limits are unaffected by sunscreen application, suggesting sunscreen does not alter integrative thermoregulatory responses during exercise in the heat.NEW & NOTEWORTHY Our findings demonstrate that neither sweating nor critical environmental limits were affected by mineral-based and chemical-based sunscreen applications. The rates of change in core temperature during compensable and uncompensable heat stress were not changed by wearing sunscreen. Evaporative heat loss, efficiency of sweat evaporation, skin wettedness, and sweating rates were unaffected by sunscreen. Sunscreen did not alter integrative thermoregulatory responses during exercise in the heat.
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Affiliation(s)
- Kat G Fisher
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
| | - Rachel M Cottle
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
- Center for Healthy Aging, The Pennsylvania State University, University Park, Pennsylvania, United States
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
- Center for Healthy Aging, The Pennsylvania State University, University Park, Pennsylvania, United States
- Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania, United States
| | - S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
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20
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Iwata R, Kawamura T, Okabe F, Fujita Z. Effects of palm cooling on thermoregulatory-related and subjective indicators during exercise in a hot environment. J Therm Biol 2024; 120:103803. [PMID: 38382413 DOI: 10.1016/j.jtherbio.2024.103803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 12/03/2023] [Accepted: 01/19/2024] [Indexed: 02/23/2024]
Abstract
Palm cooling is a simple and easily implemented intervention strategy during exercise. We aimed to examine the effects of bilateral palm cooling before and during exercise on thermoregulatory-related and subjective indicators in a hot environment. Ten active men (age: 21 ± 1 years; height 172.2 ± 5.7 cm; weight 67.4 ± 7.2 kg) underwent three experimental trials at the same time of the day, consisting of palm cooling with 12°C (ICE12°C), palm cooling with 0°C (ICE0°C) where vasoconstriction is supposed to occur, and control (CON) trials. After 30 min rest at ambient temperature, participants performed 20 min exercise at 33°C, 60% relative humidity. Rectal temperature, skin temperature, rate of perceived exertion, heart rate, local sweat rate, oxygen uptake, carbon dioxide production, and respiratory exchange ratio did not differ between the trials. Thermal sensation and comfort were lower in the ICE12°C and ICE0°C trials than in the CON trial, but the ICE0°C trial showed a longer duration of cold sensation than the ICE12°C trial. Palm cooling at 12°C and 0°C improved thermal sensation and thermal comfort during exercise in a hot environment, although there was no effect on core body temperature, sweating, and cardiorespiratory function. Bilateral palm cooling at 12°C and 0°C improve subjective indicators during exercise in a hot environment and these effects are slightly greater at 0°C than at 12°C cooling, while having no effect on thermoregulatory-related indicators. These results suggest that bilateral palm cooling at lower temperatures may safely reduce the perception of warmth during exercise in a hot environment.
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Affiliation(s)
- Risa Iwata
- Japan Institute of Sport Sciences, 3-15-1 Nishigaoka, Kita-ku, Tokyo, 115-0056, Japan; Waseda Institute for Sport Sciences, 2-579-15 Mikajima, Tokorozawa City, Saitama, 359-1192, Japan.
| | - Takuji Kawamura
- Waseda Institute for Sport Sciences, 2-579-15 Mikajima, Tokorozawa City, Saitama, 359-1192, Japan
| | - Fumitake Okabe
- Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, 359-1192, Japan
| | - Zenya Fujita
- Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, 359-1192, Japan
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21
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Wijffels G, Sullivan ML, Stockwell S, Briscoe S, Pearson R, Li Y, Macs AM, Sejian V, McCulloch R, Olm JCW, Cawdell-Smith J, Gaughan JB. Comparing the responses of grain-fed feedlot cattle under moderate heat load and during subsequent recovery with those of feed-restricted thermoneutral counterparts: blood cells and inflammatory markers. Int J Biometeorol 2024; 68:211-227. [PMID: 38092991 PMCID: PMC10794350 DOI: 10.1007/s00484-023-02584-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 11/15/2023] [Accepted: 11/19/2023] [Indexed: 01/18/2024]
Abstract
Given the climate projections for livestock rearing regions globally, understanding the inflammatory status of livestock under various heat loads will be informative to animal welfare and management. A survey of plasma inflammatory markers was conducted, and blood leucocyte counts followed to investigate the capacity of the ~ 500 kg grain fed Black Angus steer to respond to and recover from a moderate heat load challenge. Two sequential cohorts of 12 steers were housed in climate-controlled rooms (CCR) for 18 days. A thermally challenged (TC) group (n = 2 × 6) experienced five consecutive periods: PreChallenge, Challenge, and Recovery within the CCR, and 40 days in outdoor pens (PENS and Late PENS). PreChallenge (5 days) and Recovery (7 days) delivered thermoneutral conditions, whereas in Challenge the TC steers experienced a diurnal temperature range of 28-35 °C. A feed-restricted thermoneutral (FRTN) treatment (n = 2 × 6) was run concurrently to differentiate between responses to reduced feed intake alone and moderate heat stress. Blood neutrophil counts were particularly sensitive to moderate heat load with higher numbers during Challlenge and in PENs. The plasma concentrations of TNFα and IL-1β were depressed in the TC group compared to the FRTN counterparts and remained so for 40 days after Challenge. Linear relationships of the concentrations of IL-1β, IL-10, and haptoglobin with rumen temperature or dry matter intake detected in the FRTN group were altered or absent in the TC group. The findings suggest significant impacts of moderate heat load on the inflammatory status of feedlot cattle.
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Affiliation(s)
- G Wijffels
- CSIRO Agriculture and Food, Queensland Bioscience Precinct, St Lucia, Qld, 4067, Australia.
| | - M L Sullivan
- School of Agriculture and Food, The University of Queensland, Gatton, Qld, 4343, Australia
| | - S Stockwell
- CSIRO Agriculture and Food, Queensland Bioscience Precinct, St Lucia, Qld, 4067, Australia
| | - S Briscoe
- CSIRO Agriculture and Food, Queensland Bioscience Precinct, St Lucia, Qld, 4067, Australia
| | - R Pearson
- CSIRO Agriculture and Food, Queensland Bioscience Precinct, St Lucia, Qld, 4067, Australia
| | - Y Li
- CSIRO Agriculture and Food, Queensland Bioscience Precinct, St Lucia, Qld, 4067, Australia
| | - A M Macs
- CSIRO Agriculture and Food, Queensland Bioscience Precinct, St Lucia, Qld, 4067, Australia
| | - V Sejian
- Rajiv Gandhi Institute of Veterinary Education and Research, Kurumbapet, Puducherry, 605009, India
| | - R McCulloch
- CSIRO Agriculture and Food, Queensland Bioscience Precinct, St Lucia, Qld, 4067, Australia
| | - J C W Olm
- School of Veterinary Science, The University of Queensland, Gatton, Qld, 4343, Australia
| | - J Cawdell-Smith
- School of Agriculture and Food, The University of Queensland, Gatton, Qld, 4343, Australia
| | - J B Gaughan
- School of Agriculture and Food, The University of Queensland, Gatton, Qld, 4343, Australia
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22
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Barratt A, Turbill C. Nightly reductions in body temperature and effect of transmitter attachment method in free-living welcome swallows (Hirundoneoxena). J Therm Biol 2024; 120:103792. [PMID: 38403496 DOI: 10.1016/j.jtherbio.2024.103792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 01/09/2024] [Accepted: 01/10/2024] [Indexed: 02/27/2024]
Abstract
Small birds and mammals face similar energetic challenges, yet use of torpor to conserve energy while resting is considered less common among birds, especially within the most specious order Passeriformes. We conducted the first study to record the natural thermoregulatory physiology of any species from the family Hirundinidae, which we predicted would use torpor because of their specialised foraging by aerial pursuit of flying insects, that are less active during cold or windy weather. We used temperature telemetry on wild-living welcome swallows (Hirundo neoxena, 13 to 17 g) and found that skin temperature declined during nightly resting by an average by 5 °C, from daytime minima of 41.0 ± 0.8 °C to nightly minima of 36.3 ± 0.8 °C, and by a maximum of 8 °C to a minimum recorded skin temperature of 32.0 °C. The extent of reduction in skin temperature was greater on cold nights and following windy daytime (foraging) periods. Further, we found that transmitters glued directly to the skin between feather tracts (i.e., an apterium) provided a less variable and probably also more accurate reflection of body temperature than transmitters applied over closely trimmed feathers. A moderate decrease in skin temperature, equivalent to shallow torpor, would provide energy savings during rest. Yet, deeper torpor was not observed, despite a period of extreme rainfall that presumedly decreased foraging success. Further studies are needed to understand the resting thermoregulatory energetics of swallows under different environmental conditions. We advocate the importance of measuring thermal biology in wild-living birds to increase our knowledge of the physiology and ecological importance of torpor among passerine birds.
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Affiliation(s)
- Alice Barratt
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, Richmond, NSW, 2753, Australia.
| | - Christopher Turbill
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, Richmond, NSW, 2753, Australia; School of Science, Western Sydney University, Hawkesbury campus, Richmond, NSW, 2753, Australia.
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23
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McGarr GW, Meade RD, Notley SR, Akerman AP, Richards BJ, McCourt ER, King KE, McCormick JJ, Boulay P, Sigal RJ, Kenny GP. Physiological responses to 9 hours of heat exposure in young and older adults. Part III: Association with self-reported symptoms and mood state. J Appl Physiol (1985) 2024; 136:408-420. [PMID: 38153847 DOI: 10.1152/japplphysiol.00740.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 12/13/2023] [Accepted: 12/20/2023] [Indexed: 12/30/2023] Open
Abstract
Older adults are at greater risk of heat-related morbidity and mortality during heat waves, which is commonly linked to impaired thermoregulation. However, little is known about the influence of increasing age on the relation between thermal strain and perceptual responses during daylong heat exposure. We evaluated thermal and perceptual responses in 20 young (19-31 yr) and 39 older adults (20 with hypertension and/or type 2 diabetes; 61-78 yr) resting in the heat for 9 h (heat index: 37°C). Body core and mean skin temperature areas under the curve (AUC, hours 0-9) were assessed as indicators of cumulative thermal strain. Self-reported symptoms (68-item environmental symptoms questionnaire) and mood disturbance (40-item profile of mood states questionnaire) were assessed at end-heating (adjusted for prescores). Body core temperature AUC was 2.4°C·h [1.0, 3.7] higher in older relative to young adults (P < 0.001), whereas mean skin temperature AUC was not different (-0.5°C·h [-4.1, 3.2] P = 0.799). At end-heating, self-reported symptoms were not different between age groups (0.99-fold [0.80, 1.23], P = 0.923), with or without adjustment for body core or mean skin temperature AUC (both P ≥ 0.824). Mood disturbance was 0.93-fold [0.88, 0.99] lower in older, relative to young adults (P = 0.031). Older adults with and without chronic health conditions experienced similar thermal strain, yet those with these conditions reported lower symptom scores and mood disturbance compared with young adults and their age-matched counterparts (all P ≤ 0.026). Although older adults experienced heightened thermal strain during the 9-h heat exposure, they did not experience greater self-reported symptoms or mood disturbance relative to young adults.NEW & NOTEWORTHY Despite experiencing greater cumulative thermal strain during 9 h of passive heat exposure, older adults reported similar heat-related symptoms and lower mood disturbance than young adults. Furthermore, self-reported symptoms and mood disturbance were lower in older adults with common age-associated health conditions than young adults and healthy age-matched counterparts. Perceptual responses to heat in older adults can underestimate their level of thermal strain compared with young adults, which may contribute to their increased heat vulnerability.
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Affiliation(s)
- Gregory W McGarr
- Consumer and Clinical Radiation Protection Bureau, Health Canada, Ottawa, Ontario, Canada
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Robert D Meade
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Sean R Notley
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Ashley P Akerman
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Brodie J Richards
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Emma R McCourt
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Kelli E King
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - James J McCormick
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Pierre Boulay
- Faculty of Physical Activity Sciences, University of Sherbrooke, Sherbrooke, Quebec, Canada
| | - Ronald J Sigal
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
- Department of Medicine, Faculties of Medicine and Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Department of Cardiac Sciences, Faculties of Medicine and Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Department of Community Health Sciences, Faculties of Medicine and Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
- Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
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24
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Chang G, Moiteiro Manteigas H, Strutton PH, Mullington CJ. An evaluation of a healthy participant laboratory model of epidural hyperthermia: a physiological study. Int J Obstet Anesth 2024; 57:103961. [PMID: 38199895 DOI: 10.1016/j.ijoa.2023.103961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Revised: 11/01/2023] [Accepted: 11/27/2023] [Indexed: 01/12/2024]
Abstract
BACKGROUND Hyperthermia complicates 21% of cases of intrapartum epidural analgesia, but the mechanism is unclear. One hypothesis is that blockade of cholinergic sympathetic nerves prevents active vasodilation and sweating, thus limiting heat loss. Because labour increases heat production, this could create a situation in which heat production exceeds loss, causing body temperature to rise. This physiological study tested a novel laboratory model of epidural-related hyperthermia, using exercise to simulate the increased heat production of labour and surface insulation to simulate the effect of epidural analgesia. METHODS Twelve healthy non-pregnant participants (six female) cycled an ergometer for two hours at 20 Watts (W) on two occasions: once with surface insulation (intervention) and once without (control). Core temperature, skin temperature (eight sites), and heat loss (eight sites) were recorded. Mean body temperature and heat production were calculated. Values are mean (SD). RESULTS Exercise increased heat production on both visits (intervention 38 (18) W; control 37 (31) W; P = 0.94). Total heat loss was less on the intervention visit (intervention 115 (19) W; control 129 (23) W; P = 0.002). Core temperature increased on both visits (intervention 0.21 (0.37)°C; control 0.19 (0.27)°C; P < 0.001). The increase in mean body temperature was greater on the intervention visit (intervention 0.47 (0.41)°C; control 0.25 (0.19)°C; P = 0.007). CONCLUSIONS This laboratory model predicts that labour epidural analgesia limits heat loss by >14 W. Once the model is validated, it could be used to test the efficacy of potential interventions to prevent and treat epidural-related maternal hyperthermia.
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Affiliation(s)
- G Chang
- MSk Lab, Imperial College London, London, UK
| | - H Moiteiro Manteigas
- MSk Lab, Imperial College London, London, UK; Theatres and Anaesthetics, Imperial College Healthcare NHS Trust, London, UK
| | | | - C J Mullington
- MSk Lab, Imperial College London, London, UK; Theatres and Anaesthetics, Imperial College Healthcare NHS Trust, London, UK.
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25
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Meade RD, McCourt ER, McCormick JJ, Boulay P, Sigal RJ, Kenny GP. Body Core Temperature After Foot Immersion and Neck Cooling in Older Adults Exposed to Extreme Heat. JAMA 2024; 331:253-256. [PMID: 38127341 PMCID: PMC10739084 DOI: 10.1001/jama.2023.24417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 11/07/2023] [Indexed: 12/23/2023]
Abstract
This randomized study evaluates the hypothesis that foot immersion in cool water alone or with supplemental neck cooling mitigates increases in core temperature in older adults exposed to environmental conditions simulating deadly heat waves in North America.
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Affiliation(s)
- Robert D. Meade
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Ontario, Canada
| | - Emma R. McCourt
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Ontario, Canada
| | - James J. McCormick
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Ontario, Canada
| | - Pierre Boulay
- Faculty of Physical Activity Sciences, University of Sherbrooke, Sherbrooke, Quebec, Canada
| | - Ronald J. Sigal
- Department of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Glen P. Kenny
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Ontario, Canada
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26
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Persson E, Ó Cuív C, Nord A. Thermoregulatory consequences of growing up during a heatwave or a cold snap in Japanese quail. J Exp Biol 2024; 227:jeb246876. [PMID: 38073475 PMCID: PMC10906667 DOI: 10.1242/jeb.246876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 12/06/2023] [Indexed: 01/26/2024]
Abstract
Changes in environmental temperature during development can affect growth, metabolism and temperature tolerance of the offspring. We know little about whether such changes remain to adulthood, which is important to understand the links between climate change, development and fitness. We investigated whether phenotypic consequences of the thermal environment in early life remained in adulthood in two studies on Japanese quail (Coturnix japonica). Birds were raised under simulated heatwave, cold snap or control conditions, from hatching until halfway through the growth period, and then in common garden conditions until reproductively mature. We measured biometric and thermoregulatory [metabolic heat production (MHP), evaporative water and heat loss (EWL, EHL) and body temperature] responses to variation in submaximal air temperature at the end of the thermal acclimation period and in adulthood. Warm birds had lower MHP than control birds at the end of the thermal acclimation period and, in the warmest temperature studied (40°C), also had higher evaporative cooling capacity compared with controls. No analogous responses were recorded in cold birds, although they had higher EWL than controls in all but the highest test temperature. None of the effects found at the end of the heatwave or cold snap period remained until adulthood. This implies that chicks exposed to higher temperatures could be more prepared to counter heat stress as juveniles but that they do not enjoy any advantages of such developmental conditions when facing high temperatures as adults. Conversely, cold temperature does not seem to confer any priming effects in adolescence.
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Affiliation(s)
- Elin Persson
- Lund University, Department of Biology, Section for Evolutionary Ecology, Sölvegatan 37, SE-223 63 Lund, Sweden
| | - Ciarán Ó Cuív
- Lund University, Department of Biology, Section for Evolutionary Ecology, Sölvegatan 37, SE-223 63 Lund, Sweden
| | - Andreas Nord
- Lund University, Department of Biology, Section for Evolutionary Ecology, Sölvegatan 37, SE-223 63 Lund, Sweden
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27
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Belval LN, Cramer MN, Moralez G, Huang DPT M, Watso JC, Fischer M, Crandall CG. Burn size and environmental conditions modify thermoregulatory responses to exercise in burn survivors. J Burn Care Res 2024; 45:227-233. [PMID: 37615621 PMCID: PMC10768759 DOI: 10.1093/jbcr/irad128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Indexed: 08/25/2023]
Abstract
This project tested the hypothesis that burn survivors can perform mild/moderate-intensity exercise in temperate and hot environments without excessive elevations in core body temperature. Burn survivors with low (23 ± 5%TBSA; N = 11), moderate (40 ± 5%TBSA; N = 9), and high (60 ± 8%TBSA; N = 9) burn injuries performed 60 minutes of cycle ergometry exercise (72 ± 15 watts) in a 25°C and 23% relative humidity environment (ie, temperate) and in a 40°C and 21% relative humidity environment (ie, hot). Absolute gastrointestinal temperatures (TGI) and changes in TGI (ΔTGI) were obtained. Participants with an absolute TGI of >38.5°C and/or a ΔTGI of >1.5°C were categorized as being at risk for hyperthermia. For the temperate environment, exercise increased ΔTGI in all groups (low: 0.72 ± 0.21°C, moderate: 0.42 ± 0.22°C, and high: 0.77 ± 0.25°C; all P < .01 from pre-exercise baselines), resulting in similar absolute end-exercise TGI values (P = .19). Importantly, no participant was categorized as being at risk for hyperthermia, based upon the aforementioned criteria. For the hot environment, ΔTGI at the end of the exercise bout was greater for the high group when compared to the low group (P = .049). Notably, 33% of the moderate cohort and 56% of the high cohort reached or exceeded a core temperature of 38.5°C, while none in the low cohort exceeded this threshold. These data suggest that individuals with a substantial %TBSA burned can perform mild/moderate intensity exercise for 60 minutes in temperate environmental conditions without risk of excessive elevations in TGI. Conversely, the risk of excessive elevations in TGI during mild/moderate intensity exercise in a hot environment increases with the %TBSA burned.
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Affiliation(s)
- Luke N Belval
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX 75231, USA
| | - Matthew N Cramer
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX 75231, USA
| | - Gilbert Moralez
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX 75231, USA
- Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Mu Huang DPT
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX 75231, USA
- Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Joseph C Watso
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX 75231, USA
| | - Mads Fischer
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, DK 1165, Denmark
| | - Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX 75231, USA
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28
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Rosales AM, Walters MJ, McGlynn ML, Collins CW, Slivka DR. Influence of topical menthol gel on thermoregulation and perception while walking in the heat. Eur J Appl Physiol 2024; 124:317-327. [PMID: 37505231 DOI: 10.1007/s00421-023-05279-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 07/18/2023] [Indexed: 07/29/2023]
Abstract
PURPOSE Menthol is known to elicit opposing thermoregulatory and perceptual alterations during intense exercise. The current purpose was to determine the thermoregulatory and perceptual effects of topical menthol application prior to walking in the heat. METHODS Twelve participants walked (1.6 m s-1, 5% grade) for 30 min in the heat (38 °C, 60% relative humidity) with either a 4% menthol or control gel on the upper (shoulder to wrist) and lower (mid-thigh to ankle) limbs. Skin blood flow (SkBF), sweat (rate, composition), skin conductivity, heart rate, temperature (skin, core), and thermal perception were measured prior to and during exercise. RESULTS Skin conductivity expressed as time to 10, 20, 30, and 40 µS was delayed due to menthol (559 ± 251, 770 ± 292, 1109 ± 301, 1299 ± 335 s, respectively) compared to the control (515 ± 260, 735 ± 256, 935 ± 300, 1148 ± 298 s, respectively, p = 0.048). Sweat rate relative to body surface area was lower due to menthol (0.55 ± 0.16 L h-1 m(2)-1) than the control (0.64 ± 0.16 L h-1 m(2)-1, p = 0.049). Core temperature did not differ at baseline between the menthol (37.4 ± 0.3 °C) and control (37.3 ± 0.4 °C, p = 0.298) but was higher at 10, 20, and 30 min due to menthol (37.5 ± 0.3, 37.7 ± 0.2, 38.1 ± 0.3 °C, respectively) compared to the control (37.3 ± 0.4, 37.4 ± 0.3, 37.7 ± 0.3 °C, respectively, p < 0.05). The largest rise in core temperature from baseline was at 30 min during menthol (0.7 ± 0.3 °C) compared to the control (0.4 ± 0.2 °C, p = 0.004). Overall, the menthol treatment was perceived cooler, reaching "slightly warm" whereas the control treatment reached "warm" (p < 0.001). CONCLUSION Menthol application to the limbs impairs whole-body thermoregulation while walking in the heat despite perceiving the environment as cooler.
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Affiliation(s)
- Alejandro M Rosales
- School of Health and Kinesiology, University of Nebraska at Omaha, 6001 Dodge Street, Omaha, NE, 68182, USA
- School of Integrative Physiology and Athletic Training, Montana Center for Work Physiology and Exercise Metabolism, University of Montana, 32 Campus Drive, Missoula, MT, 59812, USA
| | - Matthias J Walters
- School of Health and Kinesiology, University of Nebraska at Omaha, 6001 Dodge Street, Omaha, NE, 68182, USA
| | - Mark L McGlynn
- School of Health and Kinesiology, University of Nebraska at Omaha, 6001 Dodge Street, Omaha, NE, 68182, USA
| | - Christopher W Collins
- School of Health and Kinesiology, University of Nebraska at Omaha, 6001 Dodge Street, Omaha, NE, 68182, USA
| | - Dustin R Slivka
- School of Health and Kinesiology, University of Nebraska at Omaha, 6001 Dodge Street, Omaha, NE, 68182, USA.
- School of Integrative Physiology and Athletic Training, Montana Center for Work Physiology and Exercise Metabolism, University of Montana, 32 Campus Drive, Missoula, MT, 59812, USA.
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29
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Notley SR, Mitchell D, Taylor NAS. A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 4: evolution, thermal adaptation and unsupported theories of thermoregulation. Eur J Appl Physiol 2024; 124:147-218. [PMID: 37796290 DOI: 10.1007/s00421-023-05262-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 06/13/2023] [Indexed: 10/06/2023]
Abstract
This review is the final contribution to a four-part, historical series on human exercise physiology in thermally stressful conditions. The series opened with reminders of the principles governing heat exchange and an overview of our contemporary understanding of thermoregulation (Part 1). We then reviewed the development of physiological measurements (Part 2) used to reveal the autonomic processes at work during heat and cold stresses. Next, we re-examined thermal-stress tolerance and intolerance, and critiqued the indices of thermal stress and strain (Part 3). Herein, we describe the evolutionary steps that endowed humans with a unique potential to tolerate endurance activity in the heat, and we examine how those attributes can be enhanced during thermal adaptation. The first of our ancestors to qualify as an athlete was Homo erectus, who were hairless, sweating specialists with eccrine sweat glands covering almost their entire body surface. Homo sapiens were skilful behavioural thermoregulators, which preserved their resource-wasteful, autonomic thermoeffectors (shivering and sweating) for more stressful encounters. Following emigration, they regularly experienced heat and cold stress, to which they acclimatised and developed less powerful (habituated) effector responses when those stresses were re-encountered. We critique hypotheses that linked thermoregulatory differences to ancestry. By exploring short-term heat and cold acclimation, we reveal sweat hypersecretion and powerful shivering to be protective, transitional stages en route to more complete thermal adaptation (habituation). To conclude this historical series, we examine some of the concepts and hypotheses of thermoregulation during exercise that did not withstand the tests of time.
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Affiliation(s)
- Sean R Notley
- Defence Science and Technology Group, Department of Defence, Melbourne, Australia
- School of Human Kinetics, University of Ottawa, Ottawa, Canada
| | - Duncan Mitchell
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
- School of Human Sciences, University of Western Australia, Crawley, Australia
| | - Nigel A S Taylor
- Research Institute of Human Ecology, College of Human Ecology, Seoul National University, Seoul, Republic of Korea.
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30
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Notley SR, Akerman AP, D'Souza AW, Meade RD, McCourt ER, McCormick JJ, Kenny GP. Dose-dependent nonthermal modulation of whole body heat exchange during dynamic exercise in humans. Am J Physiol Regul Integr Comp Physiol 2024; 326:R53-R65. [PMID: 37955132 DOI: 10.1152/ajpregu.00203.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 10/30/2023] [Accepted: 10/30/2023] [Indexed: 11/14/2023]
Abstract
To maintain heat balance during exercise, humans rely on skin blood flow and sweating to facilitate whole body dry and evaporative heat exchange. These responses are modulated by the rise in body temperature (thermal factors), as well as several nonthermal factors implicated in the cardiovascular response to exercise (i.e., central command, mechanoreceptors, and metaboreceptors). However, the way these nonthermal factors interact with thermal factors to maintain heat balance remains poorly understood. We therefore used direct calorimetry to quantify the effects of dose-dependent increases in the activation of these nonthermal stimuli on whole body dry and evaporative heat exchange during dynamic exercise. In a randomized crossover design, eight participants performed 45-min cycling at a fixed metabolic heat production (200 W/m2) in warm, dry conditions (30°C, 20% relative humidity) on four separate occasions, differing only in the level of lower-limb compression applied via bilateral thigh cuffs pressurized to 0, 30, 60, or 90 mmHg. This model provoked increments in nonthermal activation while ensuring the heat loss required to balance heat production was matched across trials. At end-exercise, dry heat loss was 2 W/m2 [1, 3] lower per 30-mmHg pressure increment (P = 0.006), whereas evaporative heat loss was elevated 5 W/m2 [3, 7] with each pressure increment (P < 0.001). Body heat storage and esophageal temperature did not differ across conditions (both P ≥ 0.600). Our findings indicate that the nonthermal factors engaged during exercise exert dose-dependent, opposing effects on whole body dry and evaporative heat exchange, which do not significantly alter heat balance.NEW & NOTEWORTHY To maintain heat balance during exercise, humans rely on skin blood flow and sweating to facilitate dry and evaporative heat exchange. These responses are modulated by body temperatures (thermal factors) and several nonthermal factors (e.g., central command, metaboreceptors), although the way thermal and nonthermal factors interact to regulate body temperature is poorly understood. We demonstrate that nonthermal factors exert dose-dependent, opposing effects on dry and evaporative heat loss, without altering heat storage during dynamic exercise.
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Affiliation(s)
- Sean R Notley
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Ashley P Akerman
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Andrew W D'Souza
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Robert D Meade
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Emma R McCourt
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - James J McCormick
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
- Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
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31
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Lei TH, Lin C, Amano T, Ooue A, Mündel T, Cotter JD, Fujii N, Nishiyasu T, Kondo N. Comparing thermoregulatory responses between short and long moderate intensity intermittent exercise protocols with the same duty cycle. J Therm Biol 2024; 119:103750. [PMID: 38071897 DOI: 10.1016/j.jtherbio.2023.103750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Revised: 10/31/2023] [Accepted: 11/01/2023] [Indexed: 02/25/2024]
Abstract
To date, the thermoregulatory response between continuous and intermittent exercises has been investigated whilst limited studies are available to examine the thermoregulatory responses between different modes of intermittent exercises. We sought to determine the effect of two patterns of short duration intermittent exercises (180:180 (3-min) and 30:30 s (30-s) work: rest) on thermoregulatory responses in a temperate environment (25 °C, 50% RH, vapor pressure: 1.6 kPa) with low airflow (0.2 m/s). Twelve male participants (Age:24.0(5.0) year; VO2max: 53(8) mL.kg-1.min-1; BSA:1.7(0.1) m2) cycled at 50% VO2max for 60 min in 3-min and 30-s intervals to result in the same 30-min net exercise duration. Core and skin temperatures, the percent increase of skin blood flow (forearm and chest) from baseline and local sweat rate (forearm and chest) were not different between 3-min and 30-s (all P > 0.35) from the onset of exercise to the end of the exercise. Similarly, the mean body temperature onsets of skin blood flow (forearm and chest) and local sweat rates (forearm and chest) were not different between different mode of intermittent exercises (all P > 0.1). Furthermore, thermal sensitivities of skin blood flow (forearm and chest) and local sweat rate (forearm and chest) with increasing mean body temperature were not different between different mode of intermittent exercises (all P > 0.1). We conclude that intermittent exercises with different work periods at moderate exercise intensity did not alter core temperature and thermoeffector responses in a temperate environment. (241/250).
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Affiliation(s)
- Tze-Huan Lei
- Occupational Safety and Health Group (OSHG), College of Safety Science and Engineering, Xi'an University of Science and Technology, Xi'an, China; Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, Kobe, Japan
| | - Chien Lin
- Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, Kobe, Japan
| | - Tatsuro Amano
- Faculty of Education, Niigata University, Niigata, Japan
| | - Anna Ooue
- Faculty of Food and Nutritional Sciences, Toyo University, Japan
| | - Toby Mündel
- Department of Kinesiology, Brock University, St. Catharines, Canada
| | - James David Cotter
- School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Naoto Fujii
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan
| | - Takeshi Nishiyasu
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan
| | - Narihiko Kondo
- Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, Kobe, Japan.
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Del Ferraro S, Falcone T, Morabito M, Bonafede M, Marinaccio A, Gao C, Molinaro V. Mitigating heat effects in the workplace with a ventilation jacket: Simulations of the whole-body and local human thermophysiological response with a sweating thermal manikin in a warm-dry environment. J Therm Biol 2024; 119:103772. [PMID: 38145612 DOI: 10.1016/j.jtherbio.2023.103772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 11/20/2023] [Accepted: 12/01/2023] [Indexed: 12/27/2023]
Abstract
Climate change is increasingly affecting human well-being and will inevitably impact on occupational sectors in terms of costs, productivity, workers' health and injuries. Among the cooling garment developed to reduce heat strain, the ventilation jacket could be considered for possible use in workplaces, as it is wearable without limiting the user's mobility and autonomy. In this study, simulations with a sweating manikin are carried out to investigate the effects of a short-sleeved ventilation jacket on human thermophysiological responses in a warm-dry scenario. Simulations were performed in a climatic chamber (air temperature = 30.1 °C; air velocity = 0.29 m/s; relative humidity = 30.0 %), considering two constant levels of metabolic rate M (M1 = 2.4 MET; M2 = 3.2 MET), a sequence of these two (Work), and three levels of fan velocities (lf = 0; lf=2; lf=4). The results revealed a more evident impact on the mean skin temperature (Tsk) compared to the rectal temperature (Tre), with significant decreases (compared to fan-off) at all M levels, for Tsk from the beginning and for Tre from the 61st minute. Skin temperatures of the torso zones decreased significantly (compared to fan-off) at all M levels, and a greater drop was registered for the Back. The fans at the highest level (lf=4) were significantly effective in improving whole-body and local thermal sensations when compared to fan-off, at all M levels. At the intermediate level (lf=2), the statistical significance varied with thermal zone, M and time interval considered. The results of the simulations also showed that the Lower Torso needs to be monitored at M2 level, as the drop in skin temperature could lead to local overcooling and thermal discomfort. Simulations showed the potential effectiveness of the ventilation jacket, but human trials are needed to verify its cooling power in real working conditions.
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Affiliation(s)
- Simona Del Ferraro
- Laboratory of Ergonomics and Physiology, Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL, Via Fontana Candida 1, 00078, Monte Porzio Catone, Rome, Italy.
| | - Tiziana Falcone
- Laboratory of Ergonomics and Physiology, Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL, Via Fontana Candida 1, 00078, Monte Porzio Catone, Rome, Italy.
| | - Marco Morabito
- Institute of BioEconomy (IBE), National Research Council, Via Madonna Del Piano 10, 50019, Sesto Fiorentino, FI, Italy; Centre of Bioclimatology, University of Florence, Piazzale Delle Cascine 18, 50144, Florence, Italy.
| | - Michela Bonafede
- Laboratory of Occupational and Environmental Epidemiology, Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL, Via Stefano Gradi 55, 00143, Rome, Italy.
| | - Alessandro Marinaccio
- Laboratory of Occupational and Environmental Epidemiology, Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL, Via Stefano Gradi 55, 00143, Rome, Italy.
| | - Chuansi Gao
- Aerosol and Climate Laboratory, Division of Ergonomics and Aerosol Technology, Department of Design Sciences, Faculty of Engineering, Lund University, Sölvegatan 26, Lund, Sweden.
| | - Vincenzo Molinaro
- Laboratory of Ergonomics and Physiology, Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL, Via Fontana Candida 1, 00078, Monte Porzio Catone, Rome, Italy.
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Ioannou LG, Tsoutsoubi L, Gkiata P, Brown HA, Periard JD, Mekjavic IB, Kenny GP, Nybo L, Flouris AD. Effect of sportswear on performance and physiological heat strain during prolonged running in moderately hot conditions. Scand J Med Sci Sports 2024; 34:e14520. [PMID: 37839051 DOI: 10.1111/sms.14520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 09/01/2023] [Accepted: 10/01/2023] [Indexed: 10/17/2023]
Abstract
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.
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Affiliation(s)
- Leonidas G Ioannou
- FAME Laboratory, Department of Physical Education and Sport Science, University of Thessaly, Trikala, Greece
| | - Lydia Tsoutsoubi
- FAME Laboratory, Department of Physical Education and Sport Science, University of Thessaly, Trikala, Greece
| | - Paraskevi Gkiata
- FAME Laboratory, Department of Physical Education and Sport Science, University of Thessaly, Trikala, Greece
| | - Harry A Brown
- Research Institute for Sport and Exercise (UCRISE), University of Canberra, Bruce, Australian Capital Territory, Australia
| | - Julien D Periard
- Research Institute for Sport and Exercise (UCRISE), University of Canberra, Bruce, Australian Capital Territory, Australia
| | - Igor B Mekjavic
- Department of Automatics, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, Faculty of Health Sciences, University of Ottawa, Ottawa, Ontario, Canada
| | - Lars Nybo
- Department of Nutrition, Exercise and Sports, August Krogh Building, University of Copenhagen, Copenhagen, Denmark
| | - Andreas D Flouris
- FAME Laboratory, Department of Physical Education and Sport Science, University of Thessaly, Trikala, Greece
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Andrade MT, Wanner SP, Santos WME, Mendes TT, Nunes-Leite MMS, de Oliveira GGA, Carmo AAL, Carvalho MV, Silami Garcia E, Soares DD. Ad libitum ice slurry ingestion and half-marathon performance in a hot environment: A study comparing the effects of the amount and moment of ingestion between ice slurry and water at 37 °C. J Therm Biol 2024; 119:103781. [PMID: 38232473 DOI: 10.1016/j.jtherbio.2023.103781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 12/07/2023] [Accepted: 12/21/2023] [Indexed: 01/19/2024]
Abstract
Ice slurry ingestion during prolonged exercises may improve performance in hot environments; however, the ideal amount and timing of ingestion are still uncertain. We determined whether ad libitum ice slurry ingestion influences physiological and perceptual variables and half-marathon performance while comparing the effects of the amount and moment of ingestion between ice slurry and water at 37 °C. Ten trained participants (28 ± 2 years; mean and SD) were required to run two half marathons while consuming either ice slurry (-1 °C; Ad-1) or water (37 °C; 37 CE) ad libitum. They then performed two other half marathons where, during one, they were required to ingest an amount of water equivalent to the amount consumed during the Ad-1 trial (Pro37), and in the other, to ingest ice slurry in the amount consumed during the 37 CE trial (Pro-1). During the half marathons, dry-bulb temperature and relative humidity were controlled at 33.1 ± 0.3 °C and 60 ± 3%, respectively. Ad-1 ingestion (349.6 ± 58.5 g) was 45% less than 37 CE ingestion (635.5 ± 135.8 g). Physical performance, heart rate, perceived exertion, body temperatures, and thermal perception were not influenced by the temperature or amount of beverage ingestion. However, a secondary analysis suggested that lower beverage ingestion was associated with improved performance (Ad-1 + Pro37 vs. 37 CE + Pro-1: -4.0 min, Cohen's d = 0.39), with a significant relationship between lower beverage ingestion and faster running time (b = 0.02, t = 4.01, p < 0.001). In conclusion, ice slurry ingestion does not affect performance or physiological or perceptual variables during a half marathon in a hot environment. Preliminary evidence suggests that lower beverage ingestion (ice slurry or warm water) is associated with improved performance compared to higher ingestion.
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Affiliation(s)
- Marcelo T Andrade
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, (MG), Brazil; Psychology Program, Belo Horizonte, (MG), Brazil.
| | - Samuel P Wanner
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, (MG), Brazil
| | - Weslley M E Santos
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, (MG), Brazil
| | - Thiago T Mendes
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, (MG), Brazil; Department of Physical Education, Universidade Federal da Bahia, Salvador, (BA), Brazil
| | - Matheus M S Nunes-Leite
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, (MG), Brazil
| | - Gustavo G A de Oliveira
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, (MG), Brazil
| | - Adriano A L Carmo
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, (MG), Brazil
| | - Moisés V Carvalho
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, (MG), Brazil; Department of Human Movement Sciences, Universidade Do Estado de Minas Gerais, Ibirité, (MG), Brazil
| | - Emerson Silami Garcia
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, (MG), Brazil
| | - Danusa D Soares
- Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, (MG), Brazil
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Duan G, Song C, Liu Y, Fu Z, Zhang C, Han X, Li Y, Zhou Y. Study on the dynamic effects of plateau hypoxic and cold environment on the thermal adaptation of short-term sojourners in Xizang. J Therm Biol 2024; 119:103774. [PMID: 38128423 DOI: 10.1016/j.jtherbio.2023.103774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 11/13/2023] [Accepted: 11/30/2023] [Indexed: 12/23/2023]
Abstract
The plateau hypoxic environment can affect the thermoregulation process of the human body, and due to the different acclimatization ability to the hypoxic environment, the thermal requirements among the people who enter Xizang at different times may be different. Accordingly, this study aims to clarify how plateau hypoxic environments influence the physiological and subjective responses of people entering Xizang at different times. And field experiments were conducted in Xi'an and Lhasa, respectively, to compare the thermal responses and oxygen responses of the subjects under different temperature conditions on the plain, the first day of entering Xizang and the 15th day of entering Xizang. The results showed that under the hypoxic environment, the thermal sensation of the subjects decreased. With the extension of the time entering Xizang, the influence of the hypoxic environment on thermal comfort was gradually weakened, but under the low temperature environment, the effect of hypoxia on thermal response was not significantly reduced. The results of this study can help to reveal how plateau hypoxic environments affect human thermal comfort and provide a theoretical basis for the design of indoor thermal environment parameters suitable for sojourners entering Xizang at different times.
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Affiliation(s)
- Guannan Duan
- School of Building Services Science and Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, 710055, China
| | - Cong Song
- State Key Laboratory of Green Building, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, 710055, China; School of Building Services Science and Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, 710055, China.
| | - Yanfeng Liu
- State Key Laboratory of Green Building, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, 710055, China; School of Building Services Science and Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, 710055, China
| | - Zhiguo Fu
- Xizang Autonomous Region Construction Survey and Design Institute, Lhasa, Xizang, 850000, China
| | - Cong Zhang
- Xizang Autonomous Region Construction Survey and Design Institute, Lhasa, Xizang, 850000, China
| | - Xu Han
- Institute of Military Environmental Teaching & Research, Army Engineering University of PLA, Nanjing, Jiangsu, 210007, China
| | - Yong Li
- Institute of Military Environmental Teaching & Research, Army Engineering University of PLA, Nanjing, Jiangsu, 210007, China
| | - Yong Zhou
- School of Management, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, 710055, China
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Carter HH, Pienaar O, Coleman A, Cheng JL, MacDonald MJ, Naylor LH, Green DJ. The effects of water temperature on cerebral blood flow during aquatic exercise. Eur J Appl Physiol 2024; 124:219-225. [PMID: 37419991 PMCID: PMC10786737 DOI: 10.1007/s00421-023-05264-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 06/20/2023] [Indexed: 07/09/2023]
Abstract
PURPOSE Recent studies suggest that episodic increases in cerebral blood flow (CBF) may contribute to the improvement in brain health associated with exercise training. Optimising CBF during exercise may enhance this benefit. Water immersion in ~ 30-32 °C augments CBF at rest and during exercise; however, the impact of water temperature on the CBF response has not been investigated. We hypothesised that cycle ergometry in water would increase CBF compared to land-based exercise, and that warm water would attenuate the CBF benefits. METHODS Eleven young heathy participants (nine males; 23.8 ± 3.1 yrs) completed 30 min of resistance-matched cycle exercise in three separate conditions; non-immersion (Land), 32 °C and 38 °C water immersion up to the level of the waist. Middle cerebral artery velocity (MCAv), blood pressure, and respiratory measures were assessed throughout the exercise bouts. RESULTS Core temperature was significantly higher in the 38 °C immersion than 32 °C (+ 0.84 ± 0.24 vs + 0.04 ± 0.16, P < 0.001), whilst mean arterial pressure was lower during 38 °C exercise compared to Land (84 ± 8 vs 100 ± 14 mmHg, P < 0.001) and 32 °C (92 ± 9, P = 0.03). MCAv was higher in 32 °C immersion compared to the Land and 38 °C conditions throughout the exercise bout (68 ± 10 vs 64 ± 11 vs 62 ± 12 cm/s, P = 0.03 and P = 0.02, respectively). CONCLUSION Our findings suggest that cycle exercise in warm water attenuates the beneficial impact of water immersion on CBF velocity due to redistribution of blood flow to subserve thermoregulatory demand. Our findings suggest that, whilst water-based exercise can have beneficial effects on cerebrovascular function, water temperature is a key determinant of this benefit.
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Affiliation(s)
- Howard H Carter
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, WA, 6009, Canada
| | - Oliver Pienaar
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, WA, 6009, Canada
| | - Alexander Coleman
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, WA, 6009, Canada
| | - Jem L Cheng
- Department of Kinesiology, McMaster University, Hamilton, ON, Canada
| | | | - Louise H Naylor
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, WA, 6009, Canada
| | - Daniel J Green
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, WA, 6009, Canada.
- School of Humans Sciences (M408), 35 Stirling Highway, Crawley, Perth, WA, 6009, Canada.
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Hubáček J, Gvoždík L. Terrestrial amphibians respond to rapidly changing temperatures with individual plasticity of exploratory behaviour. J Therm Biol 2024; 119:103757. [PMID: 38043243 DOI: 10.1016/j.jtherbio.2023.103757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 11/09/2023] [Accepted: 11/10/2023] [Indexed: 12/05/2023]
Abstract
Terrestrial ectotherms react to acute changes in environmental temperatures by adjusting their behaviour. Evaluating the adaptive potential of these behavioural adjustments requires information on their repeatability and plasticity. We examined behavioural response (exploration) to acute temperature change in two amphibian taxa, alpine (Ichthyosaura alpestris) and smooth (Lissotriton vulgaris) newts. These responses were investigated at both population and individual levels under multiple thermal contexts (dimensions), represented by the direction and range of changing temperature and rearing thermal regimes. Population-level analyses showed species-specific, non-additive effects of direction and range of temperature change on acute thermal reaction norms for exploration, but explained only a low amount (7-23%) of total variation in exploration. In contrast, within- and among-individual variation in acute thermal reaction norm parameters explained 42-50% of total variation in the examined trait. Although immediate thermal responses varied among individuals (repeatability = 0.07 to 0.53), they were largely shaped by environmental contexts during repeated trials. We conclude that these amphibians respond to acute temperature change through individual plasticity of behavioural traits. A repeated-measures approach under multiple thermal contexts will be needed to identify the selective and plastic potential of behavioural responses used by juvenile newts and perhaps other ectotherm taxa to cope with rapidly changing environmental temperatures.
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Affiliation(s)
- Jiří Hubáček
- Czech Academy of Sciences, Institute of Vertebrate Biology, Brno, Czech Republic; Department of Botany and Zoology, Faculty of Sciences, Masaryk University, Brno, Czech Republic
| | - Lumír Gvoždík
- Czech Academy of Sciences, Institute of Vertebrate Biology, Brno, Czech Republic.
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Nybo L, Rønnestad B, Lundby C. High or hot-Perspectives on altitude camps and heat-acclimation training as preparation for prolonged stage races. Scand J Med Sci Sports 2024; 34:e14268. [PMID: 36350277 DOI: 10.1111/sms.14268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 10/19/2022] [Accepted: 10/19/2022] [Indexed: 11/11/2022]
Abstract
Adaptation to heat stress and hypoxia are relevant for athletes participating in Tour de France or similar cycling races taking place during the summertime in landscapes with varying altitude. Both to minimize detrimental performance effects associated with arterial desaturation occurring at moderate altitudes in elite athletes, respectively, reduce the risk of hyperthermia on hot days, but also as a pre-competition acclimatization strategy to boost blood volume in already highly adapted athletes. The hematological adaptations require weeks of exposure to manifest, but are attractive as an augmented hemoglobin mass may improve arterial oxygen delivery and hence benefit prolonged performances. Altitude training camps have in this context a long history in exercise physiology and are still common practice in elite cycling. However, heat-acclimation training provides an attractive alternative for some athletes either as a stand-alone approach or in combination with altitude. The present paper provides an update and practical perspectives on the potential to utilize hypoxia and heat exposure to optimize hematological adaptations. Furthermore, we will consider temporal aspects both in terms of onset and decay of the adaptations relevant for improved thermoregulatory capacity and respiratory adaptations to abate arterial desaturation during altitude exposure. From focus on involved physiological mechanisms, time course, and responsiveness in elite athletes, we will provide guidance based on our experience from practical implementation in cyclists preparing for prolonged stage races such as the Tour de France.
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Affiliation(s)
- Lars Nybo
- Department of Nutrition, Exercise and Sport, University of Copenhagen, Copenhagen, Denmark
| | - Bent Rønnestad
- Inland Norway University of Applied Sciences, Lillehammer, Norway
| | - Carsten Lundby
- Inland Norway University of Applied Sciences, Lillehammer, Norway
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Notley SR, Mitchell D, Taylor NAS. A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise. Eur J Appl Physiol 2024; 124:1-145. [PMID: 37796292 DOI: 10.1007/s00421-023-05276-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 07/04/2023] [Indexed: 10/06/2023]
Abstract
In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.
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Affiliation(s)
- Sean R Notley
- Defence Science and Technology Group, Department of Defence, Melbourne, Australia
- School of Human Kinetics, University of Ottawa, Ottawa, Canada
| | - Duncan Mitchell
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
- School of Human Sciences, University of Western Australia, Crawley, Australia
| | - Nigel A S Taylor
- Research Institute of Human Ecology, College of Human Ecology, Seoul National University, Seoul, Republic of Korea.
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Notley SR, Mitchell D, Taylor NAS. Learning in human thermoregulation during exercise. Eur J Appl Physiol 2024; 124:377. [PMID: 37966509 DOI: 10.1007/s00421-023-05362-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 10/26/2023] [Indexed: 11/16/2023]
Affiliation(s)
- Sean R Notley
- Defence Science and Technology Group, Department of Defence, Melbourne, Australia
| | - Duncan Mitchell
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
- School of Human Sciences, University of Western Australia, Crawley, Australia
| | - Nigel A S Taylor
- College of Human Ecology, Research Institute of Human Ecology, Seoul National University, Seoul, Republic of Korea.
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Bartlett AA, Chaseling GK, Brodesco N, Debray A, Iglesies-Grau J, Pageaux B, Burrell CN, Cramer MN, Gagnon D. Thermoregulatory and perceptual implications of varying torso soft armour coverage during treadmill walking in dry heat. Applied Ergonomics 2024; 114:104146. [PMID: 37820411 DOI: 10.1016/j.apergo.2023.104146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 09/21/2023] [Accepted: 09/28/2023] [Indexed: 10/13/2023]
Abstract
Modular armour allows soldiers to adjust the level of coverage according to the threat level. We hypothesized that armour configurations with lower levels of torso soft armour coverage attenuate physiological and perceptual responses during exercise in the heat. Fifteen adults (5 females/10 males, 26 ± 5 years) walked (5 km/h, 1% incline, 1h) in dry heat (38 °C, 20% humidity) while wearing body armour that provided; i) high coverage (HC: 0.57 ± 0.09 m2, 18.5 ± 0.3 kg), ii) moderate coverage (MC: 0.44 ± 0.07 m2, 18.1 ± 0.3 kg), iii) low coverage (LC1: 0.21 ± 0.03 m2, 17.4 ± 0.1 kg), or iv) low coverage with weight equalization (LC2: 0.21 ± 0.03 m2, 18.6 ± 0.2 kg). Core temperature (Tcore), heart rate (HR), metabolic heat production (M-W), whole-body sweat rate (WBSR), and perceptual responses were measured. M-W during exercise (629 ± 126 W) did not differ between configurations (p = 0.30). The change in Tcore (HC: 0.88 ± 0.37 °C, MC: 0.85 ± 0.32 °C, LC1: 0.91 ± 0.38 °C, LC2: 0.89 ± 0.42 °C, p = 0.93), HR (HC: 97 ± 14 bpm, MC: 103 ± 16 bpm, LC1: 96 ± 15 bpm, LC2: 97 ± 20 bpm, p = 0.08), and WBSR (HC: 10.2 ± 3.4 g/min, MC: 10.3 ± 4.3 g/min, LC1: 9.9 ± 4.7 g/min, LC2: 10.4 ± 4.5 g/min, p = 0.84) did not differ between configurations. Perceptual responses did not differ between configurations (all p ≥ 0.15). Reducing torso soft armour coverage, with minimal reductions in armour load, does not reduce physiological or perceptual strain during walking in dry heat.
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Affiliation(s)
- Audrey-Ann Bartlett
- Montreal Heart Institute, Montreal, QC, Canada; École de Kinésiologie et des Sciences de l'Activité Physique, Faculté de Médecine, Université de Montréal, Montreal, QC, Canada
| | | | - Nicoleta Brodesco
- Montreal Heart Institute, Montreal, QC, Canada; École de Kinésiologie et des Sciences de l'Activité Physique, Faculté de Médecine, Université de Montréal, Montreal, QC, Canada
| | | | | | - Benjamin Pageaux
- École de Kinésiologie et des Sciences de l'Activité Physique, Faculté de Médecine, Université de Montréal, Montreal, QC, Canada; Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montréal, QC, Canada; Centre Interdisciplinaire de Recherche sur le Cerveau et l'Apprentissage, Montréal, QC, Canada
| | - Craig N Burrell
- Defence Research and Development Canada - Toronto Research Centre, Toronto, ON, Canada
| | - Matthew N Cramer
- Defence Research and Development Canada - Toronto Research Centre, Toronto, ON, Canada
| | - Daniel Gagnon
- Montreal Heart Institute, Montreal, QC, Canada; École de Kinésiologie et des Sciences de l'Activité Physique, Faculté de Médecine, Université de Montréal, Montreal, QC, Canada.
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Wang X, Lai B, Yan R, Li Y, Ning B, Wang Q. Enhancing physiological recovery and subsequent exercise performance in the heat using a phase-change material cooling blanket. J Therm Biol 2024; 119:103810. [PMID: 38350267 DOI: 10.1016/j.jtherbio.2024.103810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 12/24/2023] [Accepted: 01/26/2024] [Indexed: 02/15/2024]
Abstract
This study aimed to assess the effect of a phase-change material (PCM) cooling blanket for cooling between exercise bouts on recovery of physiological parameters and subsequent exercise performance in the heat. Eighteen male volunteers were recruited to participate in human trials involving two exhaustive treadmill running bouts (Bout1 for 3 km and Bout2 for 1.5 km) in a climate chamber (temperature = 33 °C; relative humidity = 40%). Participants were randomly subjected to one of two cooling conditions for a 10-min period between exercise bouts: CON: natural cooling; 10-min PCM: with a PCM cooling blanket for 10 min. Several physiological parameters including mean skin temperature (Tskin), oral temperature (Toral), core temperature (Tcore), heart rate (HR), mean arterial pressure (MAP), respiratory rate (RR), peripheral capillary oxygen saturation (SpO2), average running speed and rating of perceived exertion (RPE) scale score were analyzed. The results showed that compared to the CON group, participants in the 10-min PCM group had a significant lower Tskin, Tcore, HR and RR at post-cooling, as well as greater reductions in mean skin temperature (ΔTskin) and core temperature (ΔTcore) from post-Bout1 to post-cooling. Additionally, the 10-min PCM group exhibited significantly lower peak Tcore, peak HR and RPE scale score during Bout2, while the average running speed during Bout2 was significantly higher. The present study suggests that cooling with a PCM cooling blanket can enhance physiological recovery and subsequent exercise performance in the heat.
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Affiliation(s)
- Xin Wang
- Department of Critical Care Medicine, The Fifth Medical Center of Chinese PLA General Hospital, No.8 of East Street, Beijing, 100071, China
| | - Bin Lai
- Department of Emergency Medicine, The Third Medical Center of Chinese PLA General Hospital, No.69 of Yongding Road, Beijing, 100039, China
| | - Rui Yan
- Department of Thoracic Surgery, The Third Medical Center of Chinese PLA General Hospital, No.69 of Yongding Road, Beijing, 100039, China
| | - Yan Li
- Department of Critical Care Medicine, The Fifth Medical Center of Chinese PLA General Hospital, No.8 of East Street, Beijing, 100071, China
| | - Bo Ning
- Department of Intensive Care Unit, Air Force Medical Center of China, No.30 of Fucheng Road, Beijing, 100142, China.
| | - Qian Wang
- Department of Emergency Medicine, The Third Medical Center of Chinese PLA General Hospital, No.69 of Yongding Road, Beijing, 100039, China.
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43
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Levesque DL, Breit AM, Brown E, Nowack J, Welman S. Non-Torpid Heterothermy in Mammals: Another Category along the Homeothermy-Hibernation Continuum. Integr Comp Biol 2023; 63:1039-1048. [PMID: 37407285 DOI: 10.1093/icb/icad094] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 06/14/2023] [Accepted: 06/29/2023] [Indexed: 07/07/2023] Open
Abstract
Variability in body temperature is now recognized to be widespread among whole-body endotherms with homeothermy being the exception rather than the norm. A wide range of body temperature patterns exists in extant endotherms, spanning from strict homeothermy, to occasional use of torpor, to deep seasonal hibernation with many points in between. What is often lost in discussions of heterothermy in endotherms are the benefits of variations in body temperature outside of torpor. Endotherms that do not use torpor can still obtain extensive energy and water savings from varying levels of flexibility in normothermic body temperature regulation. Flexibility at higher temperatures (heat storage or facultative hyperthermia) can provide significant water savings, while decreases at cooler temperatures, even outside of torpor, can lower the energetic costs of thermoregulation during rest. We discuss the varying uses of the terms heterothermy, thermolability, and torpor to describe differences in the amplitude of body temperature cycles and advocate for a broader use of the term "heterothermy" to include non-torpid variations in body temperature.
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Affiliation(s)
| | - Ana M Breit
- School of Biology and Ecology, University of Maine, 04469 Orono, ME, USA
| | - Eric Brown
- School of Biology and Ecology, University of Maine, 04469 Orono, ME, USA
| | - Julia Nowack
- School of Biological and Environmental Sciences, Liverpool John Moores University, L3 3AF Liverpool, UK
| | - Shaun Welman
- Department of Zoology, Nelson Mandela University, Gqeberha 6031, South Africa
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Keicher L, Shipley JR, Schaeffer PJ, Dechmann DKN. Contrasting Torpor Use by Reproductive Male Common Noctule Bats in the Laboratory and in the Field. Integr Comp Biol 2023; 63:1087-1098. [PMID: 37237444 PMCID: PMC10714913 DOI: 10.1093/icb/icad040] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 05/01/2023] [Accepted: 05/23/2023] [Indexed: 05/28/2023] Open
Abstract
Metabolic processes of animals are often studied in controlled laboratory settings. However, these laboratory settings often do not reflect the animals' natural environment. Thus, results of metabolic measurements from laboratory studies must be cautiously applied to free-ranging animals. Recent technological advances in animal tracking allow detailed eco-physiological studies that reveal when, where, and how physiological measurements from the field differ from those from the laboratory. We investigated the torpor behavior of male common noctule bats (Nyctalus noctula) across different life history stages using two approaches: in controlled laboratory experiments and in the field using calibrated heart rate telemetry. We predicted that non-reproductive males would extensively use torpor to conserve energy, whereas reproductive males would reduce torpor use to promote spermatogenesis. We did not expect differences in torpor use between captive and wild animals as we simulated natural temperature conditions in the laboratory. We found that during the non-reproductive phase, both captive and free-ranging bats used torpor extensively. During reproduction, bats in captivity unexpectedly also used torpor throughout the day, while only free-ranging bats showed the expected reduction in torpor use. Thus, depending on life history stage, torpor behavior in the laboratory was markedly different from the wild. By implementing both approaches and at different life history stages, we were able to better explore the limitations of eco-physiological laboratory studies and make recommendations for when they are an appropriate proxy for natural behavior.
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Affiliation(s)
- Lara Keicher
- Max Planck Institute of Animal Behavior, Am Obstberg 1, 78315 Radolfzell, Germany
- Department of Biology, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - J Ryan Shipley
- Swiss Federal Institute for Forest, Snow, and Landscape Research WSL, Zürcherstraße 111, Birmensdorf 8903 CH, Switzerland
| | - Paul J Schaeffer
- Department of Biology, Miami University, 700 E. High St., Oxford, OH 45056, USA
| | - Dina K N Dechmann
- Max Planck Institute of Animal Behavior, Am Obstberg 1, 78315 Radolfzell, Germany
- Department of Biology, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
- Centre for the Advanced Study of Collective Behaviour, Universitätsstraße 10, 78457 Konstanz, Germany
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45
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McKechnie AE, Freeman MT, Brigham RM. Avian Heterothermy: A Review of Patterns and Processes. Integr Comp Biol 2023; 63:1028-1038. [PMID: 37156524 DOI: 10.1093/icb/icad029] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 05/02/2023] [Accepted: 05/05/2023] [Indexed: 05/10/2023] Open
Abstract
Many birds reduce rest-phase energy demands through heterothermy, physiological responses involving facultative, reversible reductions in metabolic rate and body temperature (Tb). Here, we review the phylogenetic distribution and ecological contexts of avian heterothermy. Heterothermy has been reported in 140 species representing 15 orders and 39 families. Recent work supports the view that deep heterothermy is most pronounced in phylogenetically older taxa whereas heterothermy in passerines and other recently diverged taxa is shallower and confined to minimum Tb > 20°C. The reasons why deep heterothermy is absent in passerines remain unclear; we speculate an evolutionary trade-off may exist between the capacity to achieve low heterothermic Tb and the tolerance of hyperthermic Tb. Inter- and intraspecific variation in heterothermy is correlated with factors including foraging ecology (e.g., territoriality and defense of food resources among hummingbirds), food availability and foraging opportunities (e.g., lunar phase predicts torpor use in caprimulgids), and predation risk. Heterothermy also plays a major role before and during migration. Emerging questions include the magnitude of energy savings associated with heterothermy among free-ranging birds, the role phylogenetic variation in the capacity for heterothermy has played in evolutionary radiations into extreme habitats, and how the capacity for heterothermy affects avian vulnerability to rapid anthropogenic climate change.
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Affiliation(s)
- Andrew E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria 0001, South Africa
- DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield 0028, South Africa
| | - Marc T Freeman
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria 0001, South Africa
- DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield 0028, South Africa
| | - R Mark Brigham
- Department of Biology, University of Regina, Regina, SK S4S 0A2, Canada
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Abstract
Animal flight uses metabolic energy at a higher rate than any other mode of locomotion. A relatively small proportion of the metabolic energy is converted into mechanical power; the remainder is given off as heat. Effective heat dissipation is necessary to avoid hyperthermia. In this study, we measured surface temperatures in lovebirds (Agapornis personatus) using infrared thermography and used heat transfer modelling to calculate heat dissipation by convection, radiation and conduction, before, during and after flight. The total non-evaporative rate of heat dissipation in flying birds was 12× higher than before flight and 19× higher than after flight. During flight, heat was largely dissipated by forced convection, via the exposed ventral wing areas, resulting in lower surface temperatures compared with birds at rest. When perched, both before and after exercise, the head and trunk were the main areas involved in dissipating heat. The surface temperature of the legs increased with flight duration and remained high on landing, suggesting that there was an increase in the flow of warmer blood to this region during and after flight. The methodology developed in this study to investigate how birds thermoregulate during flight could be used in future studies to assess the impact of climate change on the behavioural ecology of birds, particularly those species undertaking migratory flights.
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Affiliation(s)
- Agnès Lewden
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
- Univ Brest, CNRS, IRD, Ifremer, LEMAR, IUEM, F-29280 Plouzané, France
| | | | - Graham N. Askew
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
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Lesku JA, Barker RG, Elmes H, Robert KA, Tworkowski L, Dutka TL. Wild white-capped noddies keep a cool head in a heated situation. J Therm Biol 2023; 118:103754. [PMID: 38000146 DOI: 10.1016/j.jtherbio.2023.103754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 11/02/2023] [Accepted: 11/03/2023] [Indexed: 11/26/2023]
Abstract
Sunning, or sunbathing, is a behavior observed in diverse birds from at least 50 taxonomic families. While sunning, birds exhibit signs of heat stress, notably panting, indicating a risk of overheating. Given that even modest increases in brain temperature can impair brain function, sunning birds may have mechanisms that selectively cool the brain. Sunning birds could cool the brain using active physiological mechanisms (e.g., an ophthalmic rete or sleeping) or passive adaptations, such as light-colored plumage over the cranium. White-capped noddies are tropical seabirds that sunbathe in direct sunlight on cloudless days. Using infrared thermography on wild birds, we found that the white cap is 20 °C cooler than that of the black back while sunning. A deceased bird showed the same thermal profile, indicating that this difference arises from dichromatic coloration and not underlying physiology. Thus, the white cap may extend the duration of time noddies can sunbathe and keep the brain cool, near core body temperature, while allowing the rest of the body to heat up, perhaps to displace or kill parasites.
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Affiliation(s)
- John A Lesku
- School of Agriculture, Biomedicine and Environment, La Trobe University, Melbourne, Australia; Research Centre for Future Landscapes, La Trobe University, Melbourne, Australia
| | - Robert G Barker
- School of Agriculture, Biomedicine and Environment, La Trobe University, Melbourne, Australia
| | - Hannah Elmes
- School of Agriculture, Biomedicine and Environment, La Trobe University, Melbourne, Australia
| | - Kylie A Robert
- School of Agriculture, Biomedicine and Environment, La Trobe University, Melbourne, Australia; Research Centre for Future Landscapes, La Trobe University, Melbourne, Australia
| | - Lauren Tworkowski
- School of Agriculture, Biomedicine and Environment, La Trobe University, Melbourne, Australia
| | - Travis L Dutka
- School of Agriculture, Biomedicine and Environment, La Trobe University, Melbourne, Australia; Research Centre for Future Landscapes, La Trobe University, Melbourne, Australia.
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Notley SR, Mitchell D, Taylor NAS. A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 2: physiological measurements. Eur J Appl Physiol 2023; 123:2587-2685. [PMID: 37796291 DOI: 10.1007/s00421-023-05284-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 07/14/2023] [Indexed: 10/06/2023]
Abstract
In this, the second of four historical reviews on human thermoregulation during exercise, we examine the research techniques developed by our forebears. We emphasise calorimetry and thermometry, and measurements of vasomotor and sudomotor function. Since its first human use (1899), direct calorimetry has provided the foundation for modern respirometric methods for quantifying metabolic rate, and remains the most precise index of whole-body heat exchange and storage. Its alternative, biophysical modelling, relies upon many, often dubious assumptions. Thermometry, used for >300 y to assess deep-body temperatures, provides only an instantaneous snapshot of the thermal status of tissues in contact with any thermometer. Seemingly unbeknownst to some, thermal time delays at some surrogate sites preclude valid measurements during non-steady state conditions. To assess cutaneous blood flow, immersion plethysmography was introduced (1875), followed by strain-gauge plethysmography (1949) and then laser-Doppler velocimetry (1964). Those techniques allow only local flow measurements, which may not reflect whole-body blood flows. Sudomotor function has been estimated from body-mass losses since the 1600s, but using mass losses to assess evaporation rates requires precise measures of non-evaporated sweat, which are rarely obtained. Hygrometric methods provide data for local sweat rates, but not local evaporation rates, and most local sweat rates cannot be extrapolated to reflect whole-body sweating. The objective of these methodological overviews and critiques is to provide a deeper understanding of how modern measurement techniques were developed, their underlying assumptions, and the strengths and weaknesses of the measurements used for humans exercising and working in thermally challenging conditions.
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Affiliation(s)
- Sean R Notley
- Defence Science and Technology Group, Department of Defence, Melbourne, Australia
- School of Human Kinetics, University of Ottawa, Ottawa, Canada
| | - Duncan Mitchell
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
- School of Human Sciences, University of Western Australia, Crawley, Australia
| | - Nigel A S Taylor
- College of Human Ecology, Research Institute of Human Ecology, Seoul National University, Seoul, Republic of Korea.
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McDermott BP, Atkins WC. Response on: Whole-body cooling effectiveness of cold intravenous saline following exercise hyperthermia. Am J Emerg Med 2023; 74:165-166. [PMID: 37793950 DOI: 10.1016/j.ajem.2023.09.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 09/20/2023] [Indexed: 10/06/2023] Open
Affiliation(s)
- Brendon P McDermott
- Exercise Science Research Center, University of Arkansas, Fayetteville, AR, United States of America.
| | - Whitley C Atkins
- Exercise Science Research Center, University of Arkansas, Fayetteville, AR, United States of America; Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, TX, United States of America.
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50
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Masoud AA, Alansare AB, Finch AE. Physiological effects of exercise in heat while wearing a polyester versus cotton T-shirt in physically active men with obesity: a pilot study. J Sports Med Phys Fitness 2023; 63:1358-1365. [PMID: 37721720 DOI: 10.23736/s0022-4707.23.15164-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2023]
Abstract
BACKGROUND Obesity may impair evaporation especially during exercising in heat. Polyester sportwear is proposed to improve the evaporation but its effectiveness remains overlooked. We investigated physiological effects of exercise in heat while wearing a polyester versus cotton T-shirt on thermoregulation, perspiration, and cardiovascular regulations. METHODS Physically active men with obesity (N.=7; 21.7±1.7 years old; VO2peak 36.8±8.7 mL/kg/min; body fat percentage 34.7±4.3%) performed two randomized, crossover walking sessions for 30 mins (27 °C; 12% relative humidity) while wearing a polyester or cotton T-shirt, separated by a 7-day wash out period. Thermoregulation was assessed by measuring tympanic, torso (back and chest), and peripheral (forehead and forearm) skin temperatures. Perspiration rate was estimated as the difference in body weight (pre minus post walking). Heart rate was measured by a Polar heart rate monitor. Systolic and diastolic blood pressure were measured by a sphygmomanometer. All measurements were performed pre, during, and post each session. Two-way ANOVA examined main effects of time, fabric type, and their interactions on the study's outcomes. RESULTS Back and chest temperatures increased (∆=1.6 °C and 0.9 °C, respectively) while forehead and forearm temperatures decreased (∆=-0.5 °C and -1.6 °C, respectively) over time (P<0.05 for all). Only forehead temperature had an interaction effect for time by fabric type where greater decrease was observed during the polyester T-shirt session compared to the cotton T-shirt session (∆=-0.1 vs. -0.8 °C; P=0.016). Heart rate (∆=27.8 beat/min) and systolic blood pressure (∆=7.5 mmHg) increased while diastolic blood pressure (∆=-5.0 mmHg) decreased over time (P<0.05 for all). No difference observed for perspiratory rate (P>0.05). CONCLUSIONS The current findings do not support the superiority of polyester or cotton sportwear for better thermoregulatory, perspiratory, and cardiovascular regulations in physically active men with obesity. Future research should examine the effectiveness of other alternative fabrics of sportwear for better physiological responses when exercising in the heat, particularly in adults with obesity.
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Affiliation(s)
- Abdulaziz A Masoud
- Department of Physical Education, College of Education, Jazan University, Jazan, Saudi Arabia
- University of New Mexico, Department of Health Exercise and Sport Sciences, Albuquerque, NM, USA
| | - Abdullah B Alansare
- Department of Exercise Physiology, College of Sport Sciences and Physical Activity, King Saud University, Riyadh, Saudi Arabia -
| | - Alfred E Finch
- Department of Kinesiology, Recreation, and Sport, College of Health and Human Services, Indiana State University, Terre Haute, IN, USA
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