1
|
Wen J, Lin Z, Cheng J, Li C, Wang L, Zou Y, Wan X, Liu J, Wu J. Heat acclimation alleviates the heat stress-induced impairment of vascular endothelial cells. Tissue Cell 2024; 90:102520. [PMID: 39137536 DOI: 10.1016/j.tice.2024.102520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Revised: 07/29/2024] [Accepted: 08/08/2024] [Indexed: 08/15/2024]
Abstract
Heat acclimation (HA) is found to help decrease the incidence of heat-related illnesses such as heat syncope and exertional heat stroke. However, the response of vascular endothelial cells to HA remain to be elucidated. In this study, mouse brain microvascular endothelial cells (bEnd.3), human umbilical vein endothelial cells (HUVEC), and human aortic endothelial cells (HAEC) were selected. The cells were first subjected to HA at 40 ℃ for 2 h per day for 3 days, and then subjected to heat stress at 43 ℃ for 2 h or 4 h. After heat stress, HA-pretreated cells showed a significant increase in cell viability, cell integrity, a decrease in the proportion of S phase cells, cell apoptosis, and cytoskeletal shrinkage compared with the cells without HA pretreatment. Additionally, the expression of VEGF, ICAM-1, iNOS and EPO in HA-pretreated cells significantly increased. We also presented evidence that HA upregulated HSP70 and bcl-2, while downregulated p-p53 and bax. Notably, the suppression of HSP70 expression attenuated the protective role of heat acclimation. Furthermore, HA mitigated injuries in vital organs of mice exposed to heat stress. Conclusively, these findings indicated the HA can increase the vitality of vascular endothelial cells after heat stress, partially restore the function of vascular endothelial cells, and this protective effect may be related to the upregulation of HSP70 expression.
Collapse
Affiliation(s)
- Jirui Wen
- Department of Otolaryngology Head & Neck Surgery/Deep Underground Space Medical Center, West China Hospital, Sichuan University, No. 37 Guoxuexiang, Chengdu, China; State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Sichuan University, No.24, south Section 1, 1st ring road, Chengdu, China; Med-X Center for Manufaturing, Sichuan University, No.24, south Section 1, 1st ring road, Chengdu, China
| | - Zhengdong Lin
- Department of Otolaryngology Head & Neck Surgery/Deep Underground Space Medical Center, West China Hospital, Sichuan University, No. 37 Guoxuexiang, Chengdu, China
| | - Juan Cheng
- Department of Otolaryngology Head & Neck Surgery/Deep Underground Space Medical Center, West China Hospital, Sichuan University, No. 37 Guoxuexiang, Chengdu, China; State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Sichuan University, No.24, south Section 1, 1st ring road, Chengdu, China
| | - Can Li
- Department of Otolaryngology Head & Neck Surgery/Deep Underground Space Medical Center, West China Hospital, Sichuan University, No. 37 Guoxuexiang, Chengdu, China; State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Sichuan University, No.24, south Section 1, 1st ring road, Chengdu, China
| | - Ling Wang
- Department of Otolaryngology Head & Neck Surgery/Deep Underground Space Medical Center, West China Hospital, Sichuan University, No. 37 Guoxuexiang, Chengdu, China; State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Sichuan University, No.24, south Section 1, 1st ring road, Chengdu, China
| | - Yuhao Zou
- Department of Otolaryngology Head & Neck Surgery/Deep Underground Space Medical Center, West China Hospital, Sichuan University, No. 37 Guoxuexiang, Chengdu, China
| | - Xuehong Wan
- Department of Otolaryngology Head & Neck Surgery/Deep Underground Space Medical Center, West China Hospital, Sichuan University, No. 37 Guoxuexiang, Chengdu, China; State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Sichuan University, No.24, south Section 1, 1st ring road, Chengdu, China
| | - Jifeng Liu
- Department of Otolaryngology Head & Neck Surgery/Deep Underground Space Medical Center, West China Hospital, Sichuan University, No. 37 Guoxuexiang, Chengdu, China; State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Sichuan University, No.24, south Section 1, 1st ring road, Chengdu, China.
| | - Jiang Wu
- Department of Otolaryngology Head & Neck Surgery/Deep Underground Space Medical Center, West China Hospital, Sichuan University, No. 37 Guoxuexiang, Chengdu, China; State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Sichuan University, No.24, south Section 1, 1st ring road, Chengdu, China; Med-X Center for Manufaturing, Sichuan University, No.24, south Section 1, 1st ring road, Chengdu, China.
| |
Collapse
|
2
|
Watanabe K, Koch Esteves N, Gibson OR, Akiyama K, Watanabe S, González-Alonso J. Heat-related changes in the velocity and kinetic energy of flowing blood influence the human heart's output during hyperthermia. J Physiol 2024; 602:2227-2251. [PMID: 38690610 DOI: 10.1113/jp285760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Accepted: 04/03/2024] [Indexed: 05/02/2024] Open
Abstract
Passive whole-body hyperthermia increases limb blood flow and cardiac output (Q ̇ $\dot Q$ ), but the interplay between peripheral and central thermo-haemodynamic mechanisms remains unclear. Here we tested the hypothesis that local hyperthermia-induced alterations in peripheral blood flow and blood kinetic energy modulate flow to the heart andQ ̇ $\dot Q$ . Body temperatures, regional (leg, arm, head) and systemic haemodynamics, and left ventricular (LV) volumes and functions were assessed in eight healthy males during: (1) 3 h control (normothermic condition); (2) 3 h of single-leg heating; (3) 3 h of two-leg heating; and (4) 2.5 h of whole-body heating. Leg, forearm, and extracranial blood flow increased in close association with local rises in temperature while brain perfusion remained unchanged. Increases in blood velocity with small to no changes in the conduit artery diameter underpinned the augmented limb and extracranial perfusion. In all heating conditions,Q ̇ $\dot Q$ increased in association with proportional elevations in systemic vascular conductance, related to enhanced blood flow, blood velocity, vascular conductance and kinetic energy in the limbs and head (all R2 ≥ 0.803; P < 0.001), but not in the brain. LV systolic (end-systolic elastance and twist) and diastolic functional profiles (untwisting rate), pulmonary ventilation and systemic aerobic metabolism were only altered in whole-body heating. These findings substantiate the idea that local hyperthermia-induced selective alterations in peripheral blood flow modulate the magnitude of flow to the heart andQ ̇ $\dot Q$ through changes in blood velocity and kinetic energy. Localised heat-activated events in the peripheral circulation therefore affect the human heart's output. KEY POINTS: Local and whole-body hyperthermia increases limb and systemic perfusion, but the underlying peripheral and central heat-sensitive mechanisms are not fully established. Here we investigated the regional (leg, arm and head) and systemic haemodynamics (cardiac output:Q ̇ $\dot Q$ ) during passive single-leg, two-leg and whole-body hyperthermia to determine the contribution of peripheral and central thermosensitive factors in the control of human circulation. Single-leg, two-leg, and whole-body hyperthermia induced graded increases in leg blood flow andQ ̇ $\dot Q$ . Brain blood flow, however, remained unchanged in all conditions. Ventilation, extracranial blood flow and cardiac systolic and diastolic functions only increased during whole-body hyperthermia. The augmentedQ ̇ $\dot Q$ with hyperthermia was tightly related to increased limb and head blood velocity, flow and kinetic energy. The findings indicate that local thermosensitive mechanisms modulate regional blood velocity, flow and kinetic energy, thereby controlling the magnitude of flow to the heart and thus the coupling of peripheral and central circulation during hyperthermia.
Collapse
Affiliation(s)
- Kazuhito Watanabe
- Division of Sport, Health and Exercise Sciences, Department of Life Sciences, Brunel University London, Uxbridge, UK
- Faculty of Education and Human Studies, Akita University, Akita, Japan
| | - Nuno Koch Esteves
- Division of Sport, Health and Exercise Sciences, Department of Life Sciences, Brunel University London, Uxbridge, UK
- Research Centre, University College of Osteopathy, London, UK
| | - Oliver R Gibson
- Division of Sport, Health and Exercise Sciences, Department of Life Sciences, Brunel University London, Uxbridge, UK
- Centre for Physical Activity in Health and Disease, Brunel University London, Uxbridge, UK
| | - Koichi Akiyama
- Department of Anesthesiology, Kindai University Hospital, Osaka, Japan
| | - Sumie Watanabe
- Division of Sport, Health and Exercise Sciences, Department of Life Sciences, Brunel University London, Uxbridge, UK
- Faculty of Education and Human Studies, Akita University, Akita, Japan
| | - José González-Alonso
- Division of Sport, Health and Exercise Sciences, Department of Life Sciences, Brunel University London, Uxbridge, UK
| |
Collapse
|
3
|
Parikh K, Shepley BR, Tymko MM, Hijmans JG, Hoiland RL, Desouza CA, Sekhon MS, Ainslie PN, Bain AR. Cerebral uptake of microvesicles occurs in normocapnic but not hypocapnic passive hyperthermia in young healthy male adults. J Physiol 2023; 601:5601-5616. [PMID: 37975212 DOI: 10.1113/jp285265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 11/01/2023] [Indexed: 11/19/2023] Open
Abstract
Passive hyperthermia causes cerebral hypoperfusion primarily from heat-induced respiratory alkalosis. However, despite the cerebral hypoperfusion, it is possible that the mild alkalosis might help to attenuate cerebral inflammation. In this study, the cerebral exchange of extracellular vesicles (microvesicles), which are known to elicit pro-inflammatory responses when released in conditions of stress, were examined in hyperthermia with and without respiratory alkalosis. Ten healthy male adults were heated passively, using a warm water-perfused suit, up to core temperature + 2°C. Blood samples were taken from the radial artery and internal jugular bulb. Microvesicle concentrations were determined in platelet-poor plasma via cells expressing CD62E (activated endothelial cells), CD31+ /CD42b- (apoptotic endothelial cells), CD14 (monocytes) and CD45 (pan-leucocytes). Cerebral blood flow was measured via duplex ultrasound of the internal carotid and vertebral arteries to determine cerebral exchange kinetics. From baseline to poikilocapnic (alkalotic) hyperthermia, there was no change in microvesicle concentration from any cell origin measured (P-values all >0.05). However, when blood CO2 tension was normalized to baseline levels in hyperthermia, there was a marked increase in cerebral uptake of microvesicles expressing CD62E (P = 0.028), CD31+ /CD42b- (P = 0.003) and CD14 (P = 0.031) compared with baseline, corresponding to large increases in arterial but not jugular venous concentrations. In a subset of seven participants who underwent hypercapnia and hypocapnia in the absence of heating, there was no change in microvesicle concentrations or cerebral exchange, suggesting that hyperthermia potentiated the CO2 /pH-mediated cerebral uptake of microvesicles. These data provide insight into a potential beneficial role of respiratory alkalosis in heat stress. KEY POINTS: The hyperthermia-induced hyperventilatory response is observed in most humans, despite causing potentially harmful reductions in cerebral blood flow. We tested the hypothesis that the respiratory-induced alkalosis is associated with lower circulating microvesicle concentrations, specifically in the brain, despite the reductions in blood flow. At core temperature + 2°C with respiratory alkalosis, microvesicles derived from endothelial cells, monocytes and leucocytes were at concentrations similar to baseline in the arterial and cerebral venous circulation, with no changes in cross-brain microvesicle kinetics. However, when core temperature was increased by 2°C with CO2 /pH normalized to resting levels, there was a marked cerebral uptake of microvesicles derived from endothelial cells and monocytes. The CO2 /pH-mediated alteration in cerebral microvesicle uptake occurred only in hyperthermia. These new findings suggest that the heat-induced hyperventilatory response might serve a beneficial role by preventing potentially inflammatory microvesicle uptake in the brain.
Collapse
Affiliation(s)
- Khushali Parikh
- Faculty of Human Kinetics, Department of Kinesiology, University of Windsor, Windsor, ON, Canada
| | - Brooke R Shepley
- Faculty of Human Kinetics, Department of Kinesiology, University of Windsor, Windsor, ON, Canada
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
- Department of Human Health and Nutritional Sciences, College of Biological Science, University of Guelph, Guelph, ON, Canada
| | - Jamie G Hijmans
- Department of Integrative Biology, University of Colorado Boulder, Boulder, CO, USA
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
- Division of Neurosurgery, Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada
- Collaborative Entity for Researching Brain Ischemia, University of British Columbia, Vancouver, BC, Canada
| | | | - Mypinder S Sekhon
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
- Division of Neurosurgery, Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada
- Collaborative Entity for Researching Brain Ischemia, University of British Columbia, Vancouver, BC, Canada
- Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Anthony R Bain
- Faculty of Human Kinetics, Department of Kinesiology, University of Windsor, Windsor, ON, Canada
| |
Collapse
|
4
|
Fisher JT, Ciuha U, Ioannou LG, Simpson LL, Possnig C, Lawley J, Mekjavic IB. Cardiovascular responses to orthostasis during a simulated 3-day heatwave. Sci Rep 2022; 12:19998. [PMID: 36411293 PMCID: PMC9678862 DOI: 10.1038/s41598-022-24216-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 11/11/2022] [Indexed: 11/22/2022] Open
Abstract
Global warming has caused an increase in the frequency, duration, and intensity of summer heatwaves (HWs). Prolonged exposure to hot environments and orthostasis may cause conflicting demands of thermoregulation and blood pressure regulation on the vasomotor system, potentially contributing to cardiovascular complications and occupational heat strain. This study assessed cardiovascular and skin blood flow (SkBF) responses to orthostasis before, during and after a 3-day simulated HW. Seven male participants maintained a standard work/rest schedule for nine consecutive days split into three 3-day parts; thermoneutral pre-HW (25.4 °C), simulated HW (35.4 °C), thermoneutral post-HW. Gastrointestinal (Tgi) and skin (Tsk) temperatures, cardiovascular responses, and SkBF were monitored during 10-min supine and 10-min 60° head-up tilt (HUT). SkBF, indexed using proximal-distal skin temperature gradient (∆TskP-D), was validated using Laser-Doppler Flowmetry (LDF). The HW significantly increased heart rate, cardiac output and SkBF of the leg in supine; HUT increased SkBF of the arm and leg, and significantly affected all cardiovascular variables besides cardiac output. Significant regional differences in SkBF presented between the arm and leg in all conditions; the arm displaying vasodilation throughout, while the leg vasoconstricted in non-HW before shifting to vasodilation in the HW. Additionally, ∆TskP-D strongly correlated with LDF (r = -.78, p < 0.001). Prolonged HW exposure and orthostasis, individually, elicited significant changes in cardiovascular and SkBF variables. Additionally, varying regional blood flow responses were observed, suggesting the upper and lower vasculature receives differing vasomotor control. Combined cardiovascular alterations and shifts towards vasodilation indicate an increased challenge to industrial workers during HWs.
Collapse
Affiliation(s)
- Jason T. Fisher
- grid.445211.7Jozef Stefan International Postgraduate School, Ljubljana, Slovenia ,grid.11375.310000 0001 0706 0012Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova Cesta 39, SI-1000 Ljubljana, Slovenia
| | - Urša Ciuha
- grid.11375.310000 0001 0706 0012Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova Cesta 39, SI-1000 Ljubljana, Slovenia
| | - Leonidas G. Ioannou
- grid.11375.310000 0001 0706 0012Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova Cesta 39, SI-1000 Ljubljana, Slovenia
| | - Lydia L. Simpson
- grid.5771.40000 0001 2151 8122Division of Performance Physiology and Prevention, Department of Sports Science, University of Innsbruck, Innsbruck, Austria
| | - Carmen Possnig
- grid.5771.40000 0001 2151 8122Division of Performance Physiology and Prevention, Department of Sports Science, University of Innsbruck, Innsbruck, Austria
| | - Justin Lawley
- grid.5771.40000 0001 2151 8122Division of Performance Physiology and Prevention, Department of Sports Science, University of Innsbruck, Innsbruck, Austria ,grid.488915.9Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Igor B. Mekjavic
- grid.11375.310000 0001 0706 0012Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova Cesta 39, SI-1000 Ljubljana, Slovenia
| |
Collapse
|
5
|
Effectiveness of short-term isothermic-heat acclimation (4 days) on physical performance in moderately trained males. PLoS One 2022; 17:e0270093. [DOI: 10.1371/journal.pone.0270093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 06/04/2022] [Indexed: 11/18/2022] Open
Abstract
Introduction
A typical heat acclimation (HA) protocol takes 5–7 d of 60–90 minutes of heat exposure. Identifying the minimum dose of HA required to elicit a heat adapted phenotype could reduce financial constraints on participants and aid in the tapering phase for competition in hot countries. Therefore, the aim of this study was to investigate a 4 d HA regimen on physical performance
Methods
Twelve moderately trained males were heat acclimated using controlled hyperthermia (Tre>38.5°C), with no fluid intake for 90 min on 4 consecutive days, with a heat stress test (HST) being completed one week prior to (HST2), and within one-week post (HST3) HA. Eleven completed the control study of HST1 versus HST2, one week apart with no intervention. Heat stress tests comprised of cycling for 90 min @ 40% Peak Power Output (PPO); 35°C; 60%RH followed by 10 minutes of passive recovery before an incremental test to exhaustion. Physical performance outcomes time to exhaustion (TTE), PPO, end rectal temperature (Tre END), and heart rate (HREND) was measured during the incremental test to exhaustion.
Results
Physiological markers indicated no significant changes in the heat; however descriptive statistics indicated mean resting Tre lowered 0.24°C (-0.54 to 0.07°C; d = 2.35: very large) and end-exercise lowered by 0.32°C (-0.81 to 0.16; d = 2.39: very large). There were significant improvements across multiple timepoints following HA in perceptual measures; Rate of perceived exertion (RPE), Thermal Sensation (TS), and Thermal Comfort (TC) (P<0.05). Mean TTE in the HST increased by 142 s (323±333 to 465±235s; P = 0.04) and mean PPO by 76W (137±128 to 213±77 W; P = 0.03).
Conclusion
Short-term isothermic HA (4 d) was effective in enhancing performance capacity in hot and humid conditions. Regardless of the level of physiological adaptations, behavioural adaptations were sufficient to elicit improved performance and thermotolerance in hot conditions. Additional exposures may be requisite to ensure physiological adaptation.
Collapse
|
6
|
Henderson M, Halsey L. The metabolic upper critical temperature of the human thermoneutral zone. J Therm Biol 2022; 110:103380. [DOI: 10.1016/j.jtherbio.2022.103380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 05/11/2022] [Accepted: 10/21/2022] [Indexed: 11/11/2022]
|
7
|
Lovering AT, Kelly TS, DiMarco KG, Bradbury KE, Charkoudian N. Implications of a patent foramen ovale on environmental physiology and pathophysiology: Do we know the hole story? J Physiol 2022; 600:1541-1553. [PMID: 35043424 DOI: 10.1113/jp281108] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 01/14/2022] [Indexed: 11/08/2022] Open
Abstract
The foramen ovale is an essential component of the foetal circulation contributing to oxygenation and carbon dioxide elimination that remains patent under certain circumstances, in ∼ 30% of the healthy adult population, without major negative sequelae in most. Adults with a patent foramen ovale (PFO) have a greater tendency to develop symptoms of acute mountain sickness and high-altitude pulmonary oedema upon ascent to high altitude, and PFO presence is associated with worse cardiopulmonary function in chronic mountain sickness. This increase in altitude illness prevalence may be related to dysregulated cerebral blood flow associated with altered respiratory chemoreflex sensitivity; however, the mechanisms remain to be elucidated. Interestingly, men with a PFO appear to have a shift in thermoregulatory control to higher internal temperatures, both at rest and during exercise, and they have blunted thermal tachypnea. The teleological "reason" for this thermoregulatory shift is unclear, but the shift of ∼0.5°C in core body temperature does not appear to be sufficient to have any significant negative consequences in terms of risk of heat illness. Further work in this area is needed, particularly in women, to evaluate mechanisms of heat storage and dissipation in these individuals as compared to people without a PFO. Consequences of a PFO in SCUBA divers include a greater incidence of unprovoked decompression sickness, but whether PFO is beneficial or detrimental to breath hold diving remains unexplored. Whether PFO presence will explain interindividual variability in responses to, and consequences from, other environmental stressors such as spaceflight remain entirely unknown. Abstract figure legend Associations between PFO and altitude illnesses, core body temperature and diving. This article is protected by copyright. All rights reserved.
Collapse
Affiliation(s)
| | - Tyler S Kelly
- University of Oregon, Department of Human Physiology, Eugene, OR
| | | | - Karleigh E Bradbury
- University of Oregon, Department of Human Physiology, Eugene, OR.,United States Army Research Institute of Environmental Medicine, Thermal & Mountain Medicine Division, Natick, MA
| | - Nisha Charkoudian
- United States Army Research Institute of Environmental Medicine, Thermal & Mountain Medicine Division, Natick, MA
| |
Collapse
|
8
|
Henderson ME, Brayson D, Halsey LG. The cardio-respiratory effects of passive heating and the human thermoneutral zone. Physiol Rep 2021; 9:e14973. [PMID: 34409765 PMCID: PMC8374383 DOI: 10.14814/phy2.14973] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 06/25/2021] [Accepted: 06/26/2021] [Indexed: 12/31/2022] Open
Abstract
The thermoneutral zone (TNZ) defines the range of ambient temperatures at which resting metabolic rate (MR) is at a minimum. While the TNZ lower limit has been characterized, it is still unclear whether there is an upper limit, that is, beyond which MR during rest increases, and if so, what physiological upregulations explain this. We take the first step to fill this knowledge gap by measuring MR and multiple physiological variables in participants exposed to ambient heat stress while resting. Thirteen participants were exposed for an hour to 28℃-50% relative humidity (RH) air, and both 40 and 50℃ each in 25% RH and humid (50% RH) conditions. Core and skin temperatures, blood pressure, sweat-, heart-, and breathing-rate, minute ventilation, and movement levels were recorded throughout each condition. MR increased 35% (p = .015) during exposure to 40℃-25% RH compared to baseline and a further 13% (p = .000) at in 50℃-50%RH. This was not explained by increased fidgeting (p = .26), suggesting physiological upregulation. However, while greater heat stress invoked increases in heart rate (64%, p = .000), minute ventilation (78%, p = .000), and sweat rate (74%. p = .000) when comparing 50℃-50% RH with baseline, the exact size of their relative energy cost is unclear and, therefore, so is their contribution to this increase in MR. Our study shows clear evidence that resting MR increases in humans at high temperature-there is a metabolic upper critical temperature, at least as low as 40℃. Further studies should pinpoint this value and fully explain this increased MR.
Collapse
Affiliation(s)
- Mary E.T. Henderson
- Centre for Research in Ecology, Evolution and BehaviourLife Sciences DepartmentWhitelands CollegeUniversity of RoehamptonLondonUnited Kingdom
| | - Daniel Brayson
- Dubowitz Neuromuscular CentreUCL, Great Ormond Street Institute of Child HealthHolborn, LondonUnited Kingdom
| | - Lewis G Halsey
- Centre for Research in Ecology, Evolution and BehaviourLife Sciences DepartmentWhitelands CollegeUniversity of RoehamptonLondonUnited Kingdom
| |
Collapse
|
9
|
Caldwell HG, Coombs GB, Howe CA, Hoiland RL, Patrician A, Lucas SJ, Ainslie PN. Evidence for temperature‐mediated regional increases in cerebral blood flow during exercise. J Physiol 2020; 598:1459-1473. [DOI: 10.1113/jp278827] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Accepted: 12/20/2019] [Indexed: 12/18/2022] Open
Affiliation(s)
- Hannah G. Caldwell
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia Okanagan Kelowna BC Canada
| | - Geoff B. Coombs
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia Okanagan Kelowna BC Canada
| | - Connor A. Howe
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia Okanagan Kelowna BC Canada
| | - Ryan L. Hoiland
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia Okanagan Kelowna BC Canada
| | - Alexander Patrician
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia Okanagan Kelowna BC Canada
| | - Samuel J.E. Lucas
- School of Sport Exercise and Rehabilitation Sciences & Centre for Human Brain Health University of Birmingham Birmingham UK
| | - Philip N. Ainslie
- Centre for Heart Lung and Vascular Health School of Health and Exercise Sciences University of British Columbia Okanagan Kelowna BC Canada
| |
Collapse
|
10
|
Kissling LS, Akerman AP, Cotter JD. Heat-induced hypervolemia: Does the mode of acclimation matter and what are the implications for performance at Tokyo 2020? Temperature (Austin) 2019; 7:129-148. [PMID: 33015241 DOI: 10.1080/23328940.2019.1653736] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Tokyo 2020 will likely be the most heat stressful Olympics to date, so preparation to mitigate the effects of humid heat will be essential for performance in several of the 33 sports. One key consideration is heat acclimation (HA); the repeated exposure to heat to elicit physiological and psychophysical adaptations that improve tolerance and exercise performance in the heat. Heat can be imposed in various ways, including exercise in the heat, hot water immersion, or passive exposure to hot air (e.g., sauna). The physical requirements of each sport will determine the impact that the heat has on performance, and the adaptations required from HA to mitigate these effects. This review focuses on one key adaptation, plasma volume expansion (PVE), and how the mode of HA may affect the kinetics of adaptation. PVE constitutes a primary HA-mediated adaptation and contributes to functional adaptations (e.g., lower heart rate and increased heat loss capacity), which may be particularly important in athletes of "sub-elite" cardiorespiratory fitness (e.g., team sports), alongside athletes of prolonged endurance events. This review: i) highlights the ability of exercise in the heat, hot-water immersion, and passive hot air to expand PV, providing the first quantitative assessment of the efficacy of different heating modes; ii) discusses how this may apply to athletes at Tokyo 2020; and iii) provides recommendations regarding the protocol of HA and the prospect for achieving PVE (and the related outcomes).
Collapse
Affiliation(s)
- Lorenz S Kissling
- The School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Ashley P Akerman
- The School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand.,Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - James D Cotter
- The School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| |
Collapse
|
11
|
Ota A, Takeda R, Imai D, Naghavi N, Kawai E, Saho K, Morita E, Suzuki Y, Yokoyama H, Miyagawa T, Okazaki K. The effects of aging on the distribution of cerebral blood flow with postural changes and mild hyperthermia. Eur J Appl Physiol 2019; 119:1261-1272. [DOI: 10.1007/s00421-019-04118-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 03/01/2019] [Indexed: 11/24/2022]
|
12
|
Tsuji B, Hoshi Y, Honda Y, Fujii N, Sasaki Y, Cheung SS, Kondo N, Nishiyasu T. Respiratory mechanics and cerebral blood flow during heat-induced hyperventilation and its voluntary suppression in passively heated humans. Physiol Rep 2019; 7:e13967. [PMID: 30637992 PMCID: PMC6330649 DOI: 10.14814/phy2.13967] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 11/15/2018] [Indexed: 02/01/2023] Open
Abstract
We investigated whether heat-induced hyperventilation can be voluntarily prevented, and, if so, how this modulates respiratory mechanics and cerebral blood flow in resting heated humans. In two separate trials, 10 healthy men were passively heated using lower body hot-water immersion and a water-perfused garment covering their upper body (both 41°C) until esophageal temperature (Tes ) reached 39°C or volitional termination. In each trial, participants breathed normally (normal-breathing) or voluntarily controlled minute ventilation (VE ) at a level equivalent to that observed after 5 min of heating (controlled-breathing). Respiratory gases, middle cerebral artery blood velocity (MCAV), work of breathing, and end-expiratory and inspiratory lung volumes were measured. During normal-breathing, VE increased as Tes rose above 38.0 ± 0.3°C, whereas controlled-breathing diminished the increase in VE (VE at Tes = 38.6°C: 25.6 ± 5.9 and 11.9 ± 1.3 L min-1 during normal- and controlled-breathing, respectively, P < 0.001). During normal-breathing, end-tidal CO2 pressure and MCAV decreased with rising Tes , but controlled-breathing diminished these reductions (at Tes = 38.6°C, 24.7 ± 5.0 vs. 39.5 ± 2.8 mmHg; 44.9 ± 5.9 vs. 60.2 ± 6.3 cm sec-1 , both P < 0.001). The work of breathing correlated positively with changes in VE (P < 0.001) and was lower during controlled- than normal-breathing (16.1 ± 12.6 and 59.4 ± 49.5 J min-1 , respectively, at heating termination, P = 0.013). End-expiratory and inspiratory lung volumes did not differ between trials (P = 0.25 and 0.71, respectively). These results suggest that during passive heating at rest, heat-induced hyperventilation increases the work of breathing without affecting end-expiratory lung volume, and that voluntary control of breathing can nearly abolish this hyperventilation, thereby diminishing hypocapnia, cerebral hypoperfusion, and increased work of breathing.
Collapse
Affiliation(s)
- Bun Tsuji
- Department of Health SciencesPrefectural University of HiroshimaHiroshimaJapan
- Faculty of Health and Sport SciencesUniversity of TsukubaTsukuba CityIbarakiJapan
| | - Yuta Hoshi
- Faculty of Health and Sport SciencesUniversity of TsukubaTsukuba CityIbarakiJapan
| | - Yasushi Honda
- Faculty of Health and Sport SciencesUniversity of TsukubaTsukuba CityIbarakiJapan
| | - Naoto Fujii
- Faculty of Health and Sport SciencesUniversity of TsukubaTsukuba CityIbarakiJapan
| | - Yosuke Sasaki
- Faculty of Health and Sport SciencesUniversity of TsukubaTsukuba CityIbarakiJapan
| | | | - Narihiko Kondo
- Graduate School of Human Development and EnvironmentKobe UniversityKobeJapan
| | - Takeshi Nishiyasu
- Faculty of Health and Sport SciencesUniversity of TsukubaTsukuba CityIbarakiJapan
| |
Collapse
|
13
|
Willmott AGB, Hayes M, James CA, Dekerle J, Gibson OR, Maxwell NS. Once- and twice-daily heat acclimation confer similar heat adaptations, inflammatory responses and exercise tolerance improvements. Physiol Rep 2018; 6:e13936. [PMID: 30575321 PMCID: PMC6302546 DOI: 10.14814/phy2.13936] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Accepted: 11/08/2018] [Indexed: 11/29/2022] Open
Abstract
This experiment aimed to investigate the efficacy of twice-daily, nonconsecutive heat acclimation (TDHA) in comparison to once-daily heat acclimation (ODHA) and work matched once- or twice-daily temperate exercise (ODTEMP, TDTEMP) for inducing heat adaptations, improved exercise tolerance, and cytokine (immune) responses. Forty males, matched biophysically and for aerobic capacity, were assigned to ODHA, TDHA, ODTEMP, or TDTEMP. Participants completed a cycling-graded exercise test, heat acclimation state test, and a time to task failure (TTTF) at 80% peak power output in temperate (TTTFTEMP : 22°C/40% RH) and hot conditions (TTTFHOT : 38°C/20% RH), before and after 10-sessions (60 min of cycling at ~2 W·kg-1 ) in 45°C/20% RH (ODHA and TDHA) or 22°C/40% RH (ODTEMP or TDTEMP). Plasma IL-6, TNF-α, and cortisol were measured pre- and postsessions 1, 5, and 10. ODHA and TDHA induced equivalent heat adaptations (P < 0.05) (resting rectal temperature [-0.28 ± 0.22, -0.28 ± 0.19°C], heart rate [-10 ± 3, -10 ± 4 b·min-1 ], and plasma volume expansion [+10.1 ± 5.6, +8.5 ± 3.1%]) and improved heat acclimation state (sweat set point [-0.22 ± 0.18, -0.22 ± 0.14°C] and gain [+0.14 ± 0.10, +0.15 ± 0.07 g·sec-1 ·°C-1 ]). TTTFHOT increased (P < 0.001) following ODHA (+25 ± 4%) and TDHA (+24 ± 10%), but not ODTEMP (+5 ± 14%) or TDTEMP (+5 ± 17%). TTTFTEMP did not improve (P > 0.05) following ODHA (+14 ± 4%), TDHA (14 ± 8%), ODTEMP (9 ± 10%) or TDTEMP (8 ± 13%). Acute (P < 0.05) but no chronic (P > 0.05) increases were observed in IL-6, TNF-α, or cortisol during ODHA and TDHA, or ODTEMP and TDTEMP. Once- and twice-daily heat acclimation conferred similar magnitudes of heat adaptation and exercise tolerance improvements, without differentially altering immune function, thus nonconsecutive TDHA provides an effective, logistically flexible method of HA, benefitting individuals preparing for exercise-heat stress.
Collapse
Affiliation(s)
- Ashley G. B. Willmott
- Environmental Extremes LaboratoryUniversity of BrightonBrightonEastbourneUnited Kingdom
| | - Mark Hayes
- Environmental Extremes LaboratoryUniversity of BrightonBrightonEastbourneUnited Kingdom
| | - Carl A. James
- Environmental Extremes LaboratoryUniversity of BrightonBrightonEastbourneUnited Kingdom
- Institut Sukan Negara (National Sports Institute)National Sports ComplexKuala LumpurMalaysia
| | - Jeanne Dekerle
- Environmental Extremes LaboratoryUniversity of BrightonBrightonEastbourneUnited Kingdom
| | - Oliver R. Gibson
- Centre for Human Performance, Exercise and Rehabilitation (CHPER)Brunel University LondonUxbridgeUnited Kingdom
| | - Neil S. Maxwell
- Environmental Extremes LaboratoryUniversity of BrightonBrightonEastbourneUnited Kingdom
| |
Collapse
|
14
|
Davis JT, Hay MW, Hardin AM, White MD, Lovering AT. Effect of a patent foramen ovale in humans on thermal responses to passive cooling and heating. J Appl Physiol (1985) 2017; 123:1423-1432. [PMID: 28819008 DOI: 10.1152/japplphysiol.01032.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 08/11/2017] [Accepted: 08/11/2017] [Indexed: 11/22/2022] Open
Abstract
Humans with a patent foramen ovale (PFO) have a higher esophageal temperature (Tesoph) than humans without a PFO (PFO-). Thus the presence of a PFO might also be associated with differences in thermal responsiveness to passive cooling and heating such as shivering and hyperpnea, respectively. The purpose of this study was to determine whether thermal responses to passive cooling and heating are different between PFO- subjects and subjects with a PFO (PFO+). We hypothesized that compared with PFO- subjects PFO+ subjects would cool down more rapidly and heat up slower and that PFO+ subjects who experienced thermal hyperpnea would have a blunted increase in ventilation. Twenty-seven men (13 PFO+) completed two trials separated by >48 h: 1) 60 min of cold water immersion (19.5 ± 0.9°C) and 2) 30 min of hot water immersion (40.5 ± 0.2°C). PFO+ subjects had a higher Tesoph before and during cold water and hot water immersion (P < 0.05). However, the rate of temperature change was similar between groups for each condition. Within a subset of 18 subjects (8 PFO+) who experienced thermal hyperpnea, PFO+ subjects experienced thermal hyperpnea at a higher absolute Tesoph but with a blunted magnitude compared with PFO- subjects. These data suggest that PFO+ subjects have a higher Tesoph at rest and have blunted thermal hyperpnea during passive heating.NEW & NOTEWORTHY Patent foramen ovale (PFO) is found in ~25-40% of the population. The presence of a PFO appears to be associated with a greater core body temperature and blunted ventilatory responses during passive heating. The reason for this blunted ventilatory response to passive heating is unknown but may suggest differences in thermal sensitivity in PFO+ subjects compared with PFO- subjects.
Collapse
Affiliation(s)
- James T Davis
- Department of Kinesiology, Recreation, and Sport, Indiana State University, Terre Haute, Indiana
| | - Madeline W Hay
- Department of Human Physiology, University of Oregon, Eugene, Oregon; and
| | - Alyssa M Hardin
- Department of Human Physiology, University of Oregon, Eugene, Oregon; and
| | - Matthew D White
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Vancouver, British Columbia, Canada
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, Oregon; and
| |
Collapse
|
15
|
Tipton MJ, Harper A, Paton JFR, Costello JT. The human ventilatory response to stress: rate or depth? J Physiol 2017. [PMID: 28650070 DOI: 10.1113/jp274596] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Many stressors cause an increase in ventilation in humans. This is predominantly reported as an increase in minute ventilation (V̇E). But, the same V̇E can be achieved by a wide variety of changes in the depth (tidal volume, VT ) and number of breaths (respiratory frequency, ƒR ). This review investigates the impact of stressors including: cold, heat, hypoxia, pain and panic on the contributions of ƒR and VT to V̇E to see if they differ with different stressors. Where possible we also consider the potential mechanisms that underpin the responses identified, and propose mechanisms by which differences in ƒR and VT are mediated. Our aim being to consider if there is an overall differential control of ƒR and VT that applies in a wide range of conditions. We consider moderating factors, including exercise, sex, intensity and duration of stimuli. For the stressors reviewed, as the stress becomes extreme V̇E generally becomes increased more by ƒR than VT . We also present some tentative evidence that the pattern of ƒR and VT could provide some useful diagnostic information for a variety of clinical conditions. In The Physiological Society's year of 'Making Sense of Stress', this review has wide-ranging implications that are not limited to one discipline, but are integrative and relevant for physiology, psychophysiology, neuroscience and pathophysiology.
Collapse
Affiliation(s)
- Michael J Tipton
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, PO1 2ER, UK
| | - Abbi Harper
- Clinical Fellow in Intensive Care Medicine, Southmead Hospital, Bristol, BS10 5NB, UK
| | - Julian F R Paton
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences, University Walk, University of Bristol, Bristol, BS8 1TD, UK
| | - Joseph T Costello
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, PO1 2ER, UK
| |
Collapse
|
16
|
Tyler CJ, Reeve T, Hodges GJ, Cheung SS. The Effects of Heat Adaptation on Physiology, Perception and Exercise Performance in the Heat: A Meta-Analysis. Sports Med 2016; 46:1699-1724. [DOI: 10.1007/s40279-016-0538-5] [Citation(s) in RCA: 167] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
|
17
|
Tsuji B, Hayashi K, Kondo N, Nishiyasu T. Characteristics of hyperthermia-induced hyperventilation in humans. Temperature (Austin) 2016; 3:146-60. [PMID: 27227102 PMCID: PMC4879782 DOI: 10.1080/23328940.2016.1143760] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 01/14/2016] [Accepted: 01/14/2016] [Indexed: 11/11/2022] Open
Abstract
In humans, hyperthermia leads to activation of a set of thermoregulatory responses that includes cutaneous vasodilation and sweating. Hyperthermia also increases ventilation in humans, as is observed in panting dogs, but the physiological significance and characteristics of the hyperventilatory response in humans remain unclear. The relative contribution of respiratory heat loss to total heat loss in a hot environment in humans is small, and this hyperventilation causes a concomitant reduction in arterial CO2 pressure (hypocapnia), which can cause cerebral hypoperfusion. Consequently, hyperventilation in humans may not contribute to the maintenance of physiological homeostasis (i.e., thermoregulation). To gain some insight into the physiological significance of hyperthermia-induced hyperventilation in humans, in this review, we discuss 1) the mechanisms underlying hyperthermia-induced hyperventilation, 2) the factors modulating this response, and 3) the physiological consequences of the response.
Collapse
Affiliation(s)
- Bun Tsuji
- Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan; Department of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Keiji Hayashi
- Junior College, University of Shizuoka , Shizuoka, Japan
| | - Narihiko Kondo
- Faculty of Human Development, Kobe University , Kobe, Japan
| | - Takeshi Nishiyasu
- Institute of Health and Sport Sciences, University of Tsukuba , Tsukuba City, Japan
| |
Collapse
|