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Heat acclimation performance

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https://www.readbyqxmd.com/read/28424950/estimated-work-ability-in-warm-outdoor-environments-depends-on-the-chosen-heat-stress-assessment-metric
#1
Peter Bröde, Dusan Fiala, Bruno Lemke, Tord Kjellstrom
With a view to occupational effects of climate change, we performed a simulation study on the influence of different heat stress assessment metrics on estimated workability (WA) of labour in warm outdoor environments. Whole-day shifts with varying workloads were simulated using as input meteorological records for the hottest month from four cities with prevailing hot (Dallas, New Delhi) or warm-humid conditions (Managua, Osaka), respectively. In addition, we considered the effects of adaptive strategies like shielding against solar radiation and different work-rest schedules assuming an acclimated person wearing light work clothes (0...
April 19, 2017: International Journal of Biometeorology
https://www.readbyqxmd.com/read/28398156/a-simulated-heat-wave-has-diverse-effects-on-immune-function-and-oxidative-physiology-in-the-corn-snake-pantherophis-guttatus
#2
Z R Stahlschmidt, S S French, A Ahn, A Webb, M W Butler
Animals will continue to encounter increasingly warm environments, including more frequent and intense heat waves. Yet the physiological consequences of heat waves remain equivocal, potentially because of variation in adaptive plasticity (reversible acclimation) and/or aspects of experimental design. Thus, we measured a suite of physiological variables in the corn snake (Pantherophis guttatus) after exposure to field-parameterized, fluctuating temperature regimes (moderate temperature and heat wave treatments) to address two hypotheses: (1) a heat wave causes physiological stress, and (2) thermal performance of immune function exhibits adaptive plasticity in response to a heat wave...
July 2017: Physiological and Biochemical Zoology: PBZ
https://www.readbyqxmd.com/read/28389828/cross-adaptation-heat-and-cold-adaptation-to-improve-physiological-and-cellular-responses-to-hypoxia
#3
REVIEW
Oliver R Gibson, Lee Taylor, Peter W Watt, Neil S Maxwell
To prepare for extremes of heat, cold or low partial pressures of oxygen (O2), humans can undertake a period of acclimation or acclimatization to induce environment-specific adaptations, e.g. heat acclimation (HA), cold acclimation (CA), or altitude training. While these strategies are effective, they are not always feasible due to logistical impracticalities. Cross-adaptation is a term used to describe the phenomenon whereby alternative environmental interventions, e.g. HA or CA, may be a beneficial alternative to altitude interventions, providing physiological stress and inducing adaptations observable at altitude...
April 7, 2017: Sports Medicine
https://www.readbyqxmd.com/read/28343570/supplemental-intermittent-day-heat-training-and-the-lactate-threshold
#4
Stuart Gollan, Samuel Chalmers, Stephen Alderton, Kevin Norton
Heat acclimation over consecutive days has been shown to improve aerobic-based performance. Recently, it has been suggested that heat training can improve performance in a temperate environment. However, due to the multifactorial training demands of athletes, consecutive-day heat training may not be suitable. The current study aimed to investigate the effect of brief (8×30min) intermittent (every 3-4 days) supplemental heat training on the second lactate threshold point (LT2) in temperate and hot conditions...
April 2017: Journal of Thermal Biology
https://www.readbyqxmd.com/read/28177747/short-term-heat-acclimation-improves-the-determinants-of-endurance-performance-and-5-km-running-performance-in-the-heat
#5
Carl A James, Alan J Richardson, Peter W Watt, Ashley G B Willmott, Oliver R Gibson, Neil S Maxwell
This study investigated the effect of 5 days of controlled short-term heat acclimation (STHA) on the determinants of endurance performance and 5-km performance in runners, relative to the impairment afforded by moderate heat stress. A control group (CON), matched for total work and power output (2.7 W·kg(-1)), differentiated thermal and exercise contributions of STHA on exercise performance. Seventeen participants (10 STHA, 7 CON) completed graded exercise tests (GXTs) in cool (13 °C, 50% relative humidity (RH), pre-training) and hot conditions (32 °C, 60% RH, pre- and post-training), as well as 5-km time trials (TTs) in the heat, pre- and post-training...
March 2017: Applied Physiology, Nutrition, and Metabolism, Physiologie Appliquée, Nutrition et Métabolisme
https://www.readbyqxmd.com/read/28177370/fermentation-products-as-feed-additives-mitigate-some-ill-effects-of-heat-stress-in-pigs
#6
S Kumar, B E Bass, M Bandrick, C L Loving, S L Brockmeier, T Looft, J Trachsel, D M Madson, M Thomas, T A Casey, J W Frank, T B Stanton, H K Allen
Heat stress (HS) may result in economic losses to pig producers across the USA and worldwide. Despite significant advancements in management practices, HS continues to be a challenge. In this study, an in-feed antibiotic (carbadox, CBX) and antibiotic alternatives ( [XPC], and [SGX] fermentation products) were evaluated in a standard pig starter diet as mitigations against the negative effects of HS in pigs. A total of 100 gilts were obtained at weaning (6.87 ± 0.82 kg BW, 19.36 ± 0.72 d of age) and randomly assigned to dietary treatments (2 rooms/treatment, 2 pens/room, 6 to 7 pigs/pen)...
January 2017: Journal of Animal Science
https://www.readbyqxmd.com/read/28052099/effects-of-thermal-regimes-starvation-and-age-on-heat-tolerance-of-the-parthenium-beetle-zygogramma-bicolorata-coleoptera-chrysomelidae-following-dynamic-and-static-protocols
#7
Frank Chidawanyika, Casper Nyamukondiwa, Lorraine Strathie, Klaus Fischer
Temperature and resource availability are key elements known to limit the occurrence and survival of arthropods in the wild. In the current era of climate change, critical thermal limits and the factors affecting these may be of particular importance. We therefore investigated the critical thermal maxima (CTmax) of adult Zygogramma bicolorata beetles, a biological control agent for the invasive plant Parthenium hysterophorus, in relation to thermal acclimation, hardening, age, and food availability using static (constant) and dynamic (ramping) protocols...
2017: PloS One
https://www.readbyqxmd.com/read/28035584/from-lab-to-real-world-heat-acclimation-considerations-for-elite-athletes
#8
Julia R Casadio, Andrew E Kilding, James D Cotter, Paul B Laursen
As major sporting events are often held in hot environments, increased interest in ways of optimally heat acclimating athletes to maximise performance has emerged. Heat acclimation involves repeated exercise sessions in hot conditions that induce physiological and thermoregulatory adaptations that attenuate heat-induced performance impairments. Current evidence-based guidelines for heat acclimation are clear, but the application of these recommendations is not always aligned with the time commitments and training priorities of elite athletes...
December 29, 2016: Sports Medicine
https://www.readbyqxmd.com/read/27935427/short-term-heat-acclimation-prior-to-a-multi-day-desert-ultra-marathon-improves-physiological-and-psychological-responses-without-compromising-immune-status
#9
Ashley G B Willmott, Mark Hayes, Kirsty A M Waldock, Rebecca L Relf, Emily R Watkins, Carl A James, Oliver R Gibson, Nicholas J Smeeton, Alan J Richardson, Peter W Watt, Neil S Maxwell
Multistage, ultra-endurance events in hot, humid conditions necessitate thermal adaptation, often achieved through short term heat acclimation (STHA), to improve performance by reducing thermoregulatory strain and perceptions of heat stress. This study investigated the physiological, perceptual and immunological responses to STHA prior to the Marathon des Sables. Eight athletes (age 42 ± 4 years and body mass 81.9 ± 15.0 kg) completed 4 days of controlled hyperthermia STHA (60 min·day(‒1), 45°C and 30% relative humidity)...
December 9, 2016: Journal of Sports Sciences
https://www.readbyqxmd.com/read/27932993/effect-of-permissive-dehydration-on-induction-and-decay-of-heat-acclimation-and-temperate-exercise-performance
#10
Rebecca A Neal, Heather C Massey, Michael J Tipton, John S Young, Jo Corbett
Purpose: It has been suggested that dehydration is an independent stimulus for heat acclimation (HA), possibly through influencing fluid-regulation mechanisms and increasing plasma volume (PV) expansion. There is also some evidence that HA may be ergogenic in temperate conditions and that this may be linked to PV expansion. We investigated: (i) the influence of dehydration on the time-course of acquisition and decay of HA; (ii) whether dehydration augmented any ergogenic benefits in temperate conditions, particularly those related to PV expansion...
2016: Frontiers in Physiology
https://www.readbyqxmd.com/read/27927623/metabolic-and-functional-characterization-of-effects-of-developmental-temperature-in-drosophila-melanogaster
#11
Mads F Schou, Torsten N Kristensen, Anders Pedersen, B Göran Karlsson, Volker Loeschcke, Anders Malmendal
The ability of ectotherms to respond to changes in their thermal environment through plastic mechanisms is central to their adaptive capability. However, we still lack knowledge on the physiological and functional responses by which ectotherms acclimate to temperatures during development, and in particular, how physiological stress at extreme temperatures may counteract beneficial acclimation responses at benign temperatures. We exposed Drosophila melanogaster to 10 developmental temperatures covering their entire permissible temperature range...
February 1, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/27903515/passive-heat-acclimation-improves-skeletal-muscle-contractility-in-humans
#12
Sebastien Racinais, Mathew G Wilson, Julien D Périard
The aim of this study was to investigate the effect of repeated passive heat exposure (i.e. acclimation) on muscle contractility in humans. Fourteen non-heat acclimated males completed two trials including electrically evoked twitches and voluntary contractions in thermoneutral conditions (COOL: 24ºC, 40% RH) and hot ambient conditions in the hyperthermic state (HOT: 44-50ºC, 50% RH) on consecutive days in a counterbalanced order. Rectal temperature was ~36.5ºC in COOL and was maintained at ~39ºC throughout HOT...
November 30, 2016: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/27894884/modulation-of-the-heat-shock-response-is-associated-with-acclimation-to-novel-temperatures-but-not-adaptation-to-climatic-variation-in-the-ants-aphaenogaster-picea-and-a-rudis
#13
Sara Helms Cahan, Andrew D Nguyen, John Stanton-Geddes, Clint A Penick, Yainna Hernáiz-Hernández, Bernice B DeMarco, Nicholas J Gotelli
Ecological diversification into thermally divergent habitats can push species toward their physiological limits, requiring them to accommodate temperature extremes through plastic or evolutionary changes that increase persistence under the local thermal regime. One way to withstand thermal stress is to increase production of heat shock proteins, either by maintaining higher baseline abundance within cells or by increasing the magnitude of induction in response to heat stress. We evaluated whether environmental variation was associated with expression of three heat shock protein genes in two closely-related species of woodland ant, Aphaenogaster picea and A...
February 2017: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
https://www.readbyqxmd.com/read/27882829/the-effects-of-heat-stress-on-a-number-of-hematological-parameters-and-levels-of-thyroid-hormones-in-foundry-workers
#14
Sahar Norloei, Mohammad Javad Jafari, Leila Omidi, Soheila Khodakarim, Davood Bashash, Mohammad Bagher Abdollahi, Mina Jafari
The objective of this research was to determine the effects of heat stress on some hematological parameters and thyroid hormones among foundry workers. This study was performed on 25 heat-acclimated subjects while 10 office workers were selected as the control group. Wet bulb globe temperature (WBGT) was determined to estimate the heat stress. Blood sampling was conducted before and after the daily work shift. The mean value of the WBGT index was 35 °C. The levels of plasma osmolality (p = 0.04) and white blood cells (p = 0...
November 24, 2016: International Journal of Occupational Safety and Ergonomics: JOSE
https://www.readbyqxmd.com/read/27881668/restoration-of-thermoregulation-after-exercise
#15
Glen P Kenny, Ryan McGinn
Performing exercise, especially in the hot conditions, can heat the body causing significant increases in internal body temperature. To offset this increase, powerful and highly developed autonomic thermoregulatory responses (i.e., skin blood flow and sweating) are activated to enhance whole-body heat loss; a response mediated by temperature sensitive receptors in both the skin and the internal core regions of the body. Independent of thermal control of heat loss, nonthermal factors can have profound consequences on the body's ability to dissipate heat during exercise...
November 23, 2016: Journal of Applied Physiology
https://www.readbyqxmd.com/read/27571045/a-comparison-of-2-practical-cooling-methods-on-cycling-capacity-in-the-heat
#16
COMPARATIVE STUDY
Saul A Cuttell, Victor Kiri, Christopher Tyler
CONTEXT: Cooling the torso and neck can improve exercise performance and capacity in a hot environment; however, the proposed mechanisms for the improvements often differ. OBJECTIVE: To directly compare the effects of cooling the neck and torso region using commercially available devices on exercise capacity in a hot environment (temperature = 35°C ± 0.1°C, relative humidity = 50.1% ± 0.7%). DESIGN: Crossover study. SETTING: Laboratory...
July 2016: Journal of Athletic Training
https://www.readbyqxmd.com/read/27524970/acclimation-training-improves-endurance-cycling-performance-in-the-heat-without-inducing-endotoxemia
#17
Joshua H Guy, David B Pyne, Glen B Deakin, Catherine M Miller, Andrew M Edwards
PURPOSE: While the intention of endurance athletes undertaking short term heat training protocols is to rapidly gain meaningful physical adaption prior to competition in the heat, it is currently unclear whether or not this process also presents an overt, acute challenge to the immune system. The aim of this study was therefore to examine the effects of heat training on both endurance performance and biomarkers associated with inflammatory and immune system responses. METHODS: Moderately-actively males (n = 24) were allocated randomly to either HOT (n = 8, 35°C, and 70% RH; NEUTRAL (n = 8, 20°C, and 45% RH); or a non-exercising control group, (CON, n = 8)...
2016: Frontiers in Physiology
https://www.readbyqxmd.com/read/27511024/hsp72-and-hsp90%C3%AE-mrna-transcription-is-characterised-by-large-sustained-changes-in-core-temperature-during-heat-acclimation
#18
Oliver R Gibson, James A Tuttle, Peter W Watt, Neil S Maxwell, Lee Taylor
Increased intracellular heat shock protein-72 (Hsp72) and heat shock protein-90α (Hsp90α) have been implicated as important components of acquired thermotolerance, providing cytoprotection during stress. This experiment determined the physiological responses characterising increases in Hsp72 and Hsp90α mRNA on the first and tenth day of 90-min heat acclimation (in 40.2 °C, 41.0 % relative humidity (RH)) or equivalent normothermic training (in 20 °C, 29 % RH). Pearson's product-moment correlation and stepwise multiple regression were performed to determine relationships between physiological [e...
November 2016: Cell Stress & Chaperones
https://www.readbyqxmd.com/read/27467216/local-versus-whole-body-sweating-adaptations-following-14-days-of-traditional-heat-acclimation
#19
Martin P Poirier, Daniel Gagnon, Glen P Kenny
The purpose of this study was to examine if local changes in sweat rate following 14 days of heat acclimation reflect those that occur at the whole-body level. Both prior to and following a 14-day traditional heat acclimation protocol, 10 males exercised in the heat (35 °C, ∼20% relative humidity) at increasing rates of heat production equal to 300 (Ex1), 350 (Ex2), and 400 (Ex3) W·m(-2). A 10-min recovery period followed Ex1, while a 20-min recovery period separated Ex2 and Ex3. The exercise protocol was performed in a direct calorimeter to measure whole-body sweat rate and, on a separate day, in a thermal chamber to measure local sweat rate (LSR), sweat gland activation (SGA), and sweat gland output (SGO) on the upper back, chest, and mid-anterior forearm...
August 2016: Applied Physiology, Nutrition, and Metabolism, Physiologie Appliquée, Nutrition et Métabolisme
https://www.readbyqxmd.com/read/27446126/proteomic-and-physiological-analysis-of-the-response-of-oat-avena-sativa-seeds-to-heat-stress-under-different-moisture-conditions
#20
Lingling Chen, Quanzhu Chen, Lingqi Kong, Fangshan Xia, Huifang Yan, Yanqiao Zhu, Peisheng Mao
Seeds lose their viability when they are exposed to high temperature and moisture content (MC) during storage. The expression and metabolism of proteins plays a critical role in seed resistance to heat stress. However, the proteome response to heat stress in oat (Avena sativa) seeds during storage has not been revealed. To understand mechanisms of heat stress acclimation and tolerance in oat seeds, an integrated physiological and comparative proteomic analysis was performed on oat seeds with different MC during heat stress...
2016: Frontiers in Plant Science
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