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Heat acclimation performance

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https://www.readbyqxmd.com/read/28542380/more-oxygen-during-development-enhanced-flight-performance-but-not-thermal-tolerance-of-drosophila-melanogaster
#1
Shayan Shiehzadegan, Jacqueline Le Vinh Thuy, Natalia Szabla, Michael J Angilletta, John M VandenBrooks
High temperatures can stress animals by raising the oxygen demand above the oxygen supply. Consequently, animals under hypoxia could be more sensitive to heating than those exposed to normoxia. Although support for this model has been limited to aquatic animals, oxygen supply might limit the heat tolerance of terrestrial animals during energetically demanding activities. We evaluated this model by studying the flight performance and heat tolerance of flies (Drosophila melanogaster) acclimated and tested at different concentrations of oxygen (12%, 21%, and 31%)...
2017: PloS One
https://www.readbyqxmd.com/read/28486332/short-term-heat-acclimation-and-precooling-independently-and-combined-improve-5-km-running-performance-in-the-heat
#2
C A James, A J Richardson, A G B Willmott, P W Watt, O R Gibson, N S Maxwell
Following heat acclimation (HA), endurance running performance remains impaired in hot vs temperate conditions. Combining HA with precooling demonstrates no additive benefit in intermittent sprint, or continuous cycling exercise protocols, during which heat strain may be less severe compared to endurance running. This study investigated the effect of short-term heat acclimation (STHA) combined with mixed-methods precooling, on endurance running performance and directly compared precooling and HA. Nine amateur trained runners completed 5 km treadmill time trials in the heat (32°C, 60% RH) under four conditions; no intervention (CON), precooling (PC), short-term heat acclimation (5 days - HA) and short-term heat acclimation with precooling (HA+PC)...
May 5, 2017: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/28482796/effects-of-cold-acclimation-on-gene-expression-in-fall-field-cricket-gryllus-pennsylvanicus-ionoregulatory-tissues
#3
Lauren E Des Marteaux, Alexander H McKinnon, Hiroko Udaka, Jantina Toxopeus, Brent J Sinclair
BACKGROUND: Cold tolerance is a key determinant of temperate insect distribution and performance. Chill-susceptible insects lose ion and water homeostasis during cold exposure, but prior cold acclimation improves both cold tolerance and defense of homeostasis. The mechanisms underlying these processes are mostly unknown; cold acclimation is thought to enhance ion transport in the cold and/or prevent leak of water and ions. To identify candidate mechanisms of cold tolerance plasticity we generated transcriptomes of ionoregulatory tissues (hindgut and Malpighian tubules) from Gryllus pennsylvanicus crickets and compared gene expression in warm- and cold-acclimated individuals...
May 8, 2017: BMC Genomics
https://www.readbyqxmd.com/read/28462685/effect-of-heat-exposure-on-cognition-in-persons-with-tetraplegia
#4
John P Handrakis, Zhen Ni Guan, John W Nulty, Oriana Tascione, Dwindally Rosado-Rivera, Daniel White, Charlene Bang, Ann Spungen, William A Bauman
Individuals with cervical spinal cord injury (SCI) have impaired thermoregulatory mechanisms due to interruption of motor, sensory, and autonomic neuropathways. To determine the effects of heat exposure on core body temperature (Tcore) and cognitive performance in persons with tetraplegia, eight individuals with chronic tetraplegia (C3-C7, AIS A-B) and 9 able-bodied controls were acclimated to 27°C at baseline (BL) before being exposed to 35°C for up to 120 minutes (Heat Challenge). Rectal temperature (Tcore), distal skin temperatures (Tsk<sub>avg</sub>), sweat rate (QS<sub>avg</sub>), microvascular skin perfusion (LDF<sub>avg</sub>), and plasma norepinephrine (NE) were measured...
May 2, 2017: Journal of Neurotrauma
https://www.readbyqxmd.com/read/28424950/estimated-work-ability-in-warm-outdoor-environments-depends-on-the-chosen-heat-stress-assessment-metric
#5
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
#6
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
#7
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
#8
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
#9
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
#10
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
#11
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
#12
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
#13
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
#14
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
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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