scholarly journals Exercise under heat stress: thermoregulation, hydration, performance implications and mitigation strategies

2021 ◽  
Author(s):  
Julien D. Periard ◽  
Thijs M.H. Eijsvogels ◽  
Hein A.M. Daanen
Keyword(s):  
Heat Stress ◽  
Exercise Performance ◽  
Thermal Strain ◽  
Mitigation Strategies ◽  
Body Core Temperature ◽  
Aerobic Performance ◽  
Future Research ◽  
Hydration Status ◽  
Fatigue Development ◽  
The Impact

A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance in the heat and how systemic and peripheral hemodynamic adjustments contribute to fatigue development is elucidated. This review also discusses strategies to mitigate the effects of hyperthermia and hypohydration on exercise performance in the heat, by examining the benefits of heat acclimation, cooling strategies and hyperhydration. Finally, contemporary controversies are summarized and future research directions provided.

scholarly journals Cellular and Molecular Adaptation of Bovine Granulosa Cells and Oocytes under Heat Stress

Animals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 110 ◽  
Author(s):  
Adnan Khan ◽  
Muhammad Zahoor Khan ◽  
Saqib Umer ◽  
Ibrar Muhammad Khan ◽  
Huitao Xu ◽  
...  
Keyword(s):  
Heat Stress ◽  
Dairy Cattle ◽  
Granulosa Cells ◽  
Elevated Temperatures ◽  
Mitigation Strategies ◽  
Future Research ◽  
Stressed Animal ◽  
Regulate Body Temperature ◽  
And Function ◽  
The Impact

Heat stress has long been recognized as a challenging issue that severely influences the reproductive functions of dairy cattle, disrupting oocyte development during fetal growth. These detrimental effects of heat stress are the result of either the hyperthermia associated with heat stress or the physiological adjustments made by the heat-stressed animal to regulate body temperature. In addition, elevated temperatures have been implicated in increasing the production of reactive oxygen species. Thus, understanding the impact of heat stress on reproductive functions, from a cellular to molecular level, might help in selecting heat-resilient dairy cattle and developing heat stress mitigation strategies. In the present paper, we have attempted to describe the changes in the reproductive system and function of dairy cattle in response to heat stress by reviewing the latest literature in this area. The review provides useful knowledge on the cellular and genetic basis of oocyte and granulosa cells in heat-stressed dairy cattle, which could be helpful for future research in this area.

Responses of Motor-Sport Athletes to V8 Supercar Racing in Hot Conditions

2007 ◽  
Vol 2 (2) ◽  
pp. 182-191 ◽  
Author(s):  
Matt B. Brearley ◽  
James P. Finn
Keyword(s):  
Perceived Exertion ◽  
Thermal Sensation ◽  
Sweat Rate ◽  
Thermal Strain ◽  
Body Core Temperature ◽  
Hydration Status ◽  
Borg Scale ◽  
Thermal Discomfort ◽  
Body Core ◽  
Cardiovascular Strain

Background:Despite the thermal challenge of demanding workloads performed in high cabin temperatures while wearing heavy heat-retardant clothing, information on physiological responses to racing V8 Supercars in hot conditions is not readily available.Purpose:To describe the thermal, cardiovascular, and perceptual strain on V8 Supercar drivers competing in hot conditions.Methods:Thermal strain was indicated by body-core temperature using an ingested thermosensitive pill. Cardiovascular strain was assessed from heart rate, hydration status, and sweat rate. Perceptual strain was estimated from self-rated thermal sensation, thermal discomfort (modified Gagge scales), perceived exertion (Borg scale), and perceptual strain index.Results:Prerace body-core temperatures were (mean ± SD) 37.7°C ± 0.4°C (range 37.0°C to 38.2°C), rising to 39.0°C ± 0.4°C (range 38.4°C to 39.7°C) postrace. Driver heart rates were >160 and >170 beats/min for 85.3% and 46.7% of racing, respectively. Sweat rates were 1.06 ± 0.12 L/h or 13.4 ± 1.2 mL · kg−1 · h−1, and postrace dehydration was 0.6% ± 0.6% of prerace body mass. Drivers rated thermal sensation as hot (10.3 ± 0.9), thermal discomfort as uncomfortable (3.1 ± 1.0), and perceived exertion as very hard to very, very hard (8.7 ± 1.7) after the races. Overall physiological and perceptual strain were 7.4 ± 1.0 and 7.1 ± 1.2, respectively.Conclusions:Despite the use of cooling, V8 Supercar drivers endure thermal, cardiovascular, and perceptual strain during brief driving bouts in hot conditions.

The effects of acute dopamine reuptake inhibition on cognitive function during passive hyperthermia

2020 ◽  
Author(s):  
Phillip J. Wallace ◽  
Ricardo S Martins ◽  
Jake S Scott ◽  
Scott W Steele ◽  
Matthew Greenway ◽  
...  
Keyword(s):  
Heat Stress ◽  
Executive Function ◽  
Cognitive Function ◽  
Thermal Strain ◽  
Maze Learning ◽  
Test Battery ◽  
Cognitive Test ◽  
Set Shifting ◽  
Heart Rates ◽  
The Impact

Dopamine activity can modulate physical performance in the heat, but less is known about its effects on cognition during thermal stress. Twelves males completed a randomized, double-blinded protocol consisting of oral ingestion of 20 mg of methylphenidate (MPH) or placebo (lactose pill) during passive heating using a water-perfused suit (water temperature ~49°C). To identify the impact of peripheral versus central thermal strain, a cognitive test battery was completed at four different thermal states: baseline (BASE; 37.2±0.6˚C core, 32.9±0.7˚C skin), neutral core-hot skin (NC-HS; 37.2±0.3˚C, 37.4±0.3˚C), hyperthermic core-hot skin (HC-HS; 38.7±0.4˚C, 38.7±0.2˚C), and hyperthermic core-cooled skin (HC-CS; 38.5±0.4˚C, 35.1±0.8˚C). The cognitive test battery consisted of the 2-back task (i.e. working memory), set-shifting (i.e. executive function), Groton Maze Learning Task (i.e. executive function) and detection task (i.e. psychomotor processing). MPH led to significantly higher heart rates (~5-15 b·min-1) at BASE, NC-HS, and HC-HS (all p<0.05). There were no significant differences in the number of errors made on each task (all p<0.05). Participants were significantly faster (p<0.05) on the set-shifting task in the HC-HS timepoint, irrespective of drug condition (p>0.05). In summary, we demonstrated that 20 mg of MPH did not significantly alter cognitive function during either normothermia or moderate hyperthermia. Novelty: ● 20 mg of MPH did not significantly alter cognitive function during passive heat stress ● MPH led to significant higher heart rates (~5-15 bmin-1) in thermoneutral and during passive heat stress ● Future studies are needed to determine the mechanisms of why MPH improves physical but not cognitive performance during heat stress

Voluntary fluid intake, hydration status, and aerobic performance of adolescent athletes in the heat

2010 ◽  
Vol 35 (6) ◽  
pp. 834-841 ◽  
Author(s):  
Boguslaw Wilk ◽  
Brian W. Timmons ◽  
Oded Bar-Or
Keyword(s):  
Body Weight ◽  
Oxygen Uptake ◽  
Exercise Performance ◽  
Fluid Intake ◽  
Tap Water ◽  
Peak Oxygen Uptake ◽  
Adolescent Male ◽  
Aerobic Performance ◽  
Hydration Status ◽  
Time To Exhaustion

We determined whether beverage flavoring and composition would stimulate voluntary drink intake, prevent dehydration, and maintain exercise performance in heat-acclimated adolescent males running in the heat. Eight adolescent (age, 13.7 ± 1.1 years) runners (peak oxygen uptake, 59.5 ± 4.0 mL·kg–1·min–1) underwent at least four 80-min exercise heat-acclimation sessions before completing 3 experimental sessions. All sessions were performed at 30 °C and 60%–65% relative humidity. Each experimental session consisted of five 15-min treadmill runs at a speed eliciting 65% peak oxygen uptake, with a 5 min rest prior to each run. Ten minutes after the final run, a time to exhaustion test was performed at a speed eliciting 90% peak oxygen uptake. Counterbalanced experimental sessions were identical, except for fluid intake, which consisted of tap water (W), flavored water (FW), and FW with 6% carbohydrate and 18 mmol·L–1 NaCl (CNa) consumed ad libitum. Fluid intake and body weight were monitored to calculate dehydration. Voluntary fluid intake was similar to fluid losses in W (1032 ± 130 vs. 1340 ± 246 g), FW (1086 ± 86 vs. 1451 ± 253 g), and CNa (1259 ± 119 vs. 1358 ± 234 g). As a result, significant dehydration was avoided in all trials (–0.45% ± 0.68% body weight in W, –0.66% ± 0.50% body weight in FW, and –0.13% ± 0.71% body weight in CNa). Core temperature increased by ~1 °C during exercise, but was not different between trials. Time to exhaustion was not different between trials and averaged 8.8 ± 1.7 min. Under exercise conditions more closely reflecting real-life situations, heat-acclimatized adolescent male runners can appropriately gauge fluid intake regardless of the type of beverage made available, resulting in consistency in exercise performance.

scholarly journals Effects of Ramadan Fasting on Body Composition, Aerobic Performance and Lactate, Heart Rate and Perceptual Responses in Young Soccer Players

2011 ◽  
Vol 29 (1) ◽  
pp. 79-91 ◽  
Author(s):  
Alpay Güvenç
Keyword(s):  
Heart Rate ◽  
Body Composition ◽  
Aerobic Exercise ◽  
Blood Lactate ◽  
Exercise Performance ◽  
Perceived Exertion ◽  
Soccer Players ◽  
Aerobic Performance ◽  
Hydration Status ◽  
Ramadan Fasting

Effects of Ramadan Fasting on Body Composition, Aerobic Performance and Lactate, Heart Rate and Perceptual Responses in Young Soccer PlayersThe purpose of this study was to examine the effects of Ramadan fasting on body composition, aerobic exercise performance and blood lactate, heart rate and perceived exertion in regularly trained young soccer players. Sixteen male soccer players participated in this study. Mean age, stature, body mass and training age of the players were 17.4±1.2 years, 175.4±3.6 cm, 69.6±4.3 kg and 5.1±1.3 years, respectively. During the Ramadan period, all subjects voluntarily chose to follow the fasting guidelines and abstained from eating and drinking from sunrise to sunset. Body composition, hydration status, dietary intake and sleep duration were assessed on four occasions: before Ramadan, at the beginning of Ramadan, at the end of Ramadan and 2 weeks after the end of Ramadan. On each occasion, aerobic exercise performance and blood lactate, heart rate and rating of perceived exertion responses of players were also determined during an incremental running test. Repeated measures of ANOVA revealed that body mass, percentage of body fat, fat-free mass, hydration status, daily sleeping time and daily energy and macronutrient intake of players did not vary significantly throughout the study period (p>0.05). However, players experienced a small but significant decrease in skinfold thicknesses over the course of the study (p<0.05). Although ratings of perceived exertion at submaximal workloads increased during Ramadan (p<0.05), blood lactate and heart rate responses had decreased by the end of Ramadan (p<0.05). In line with these changes, peak running performance and running velocity at anaerobic threshold also improved by the end of Ramadan (p<0.05). Improvements in aerobic exercise performance with time were probably due to the effects of pre-season training program that was performed after the break of the fast (Iftar) during the month of Ramadan. The results of the present study suggest that if regular training regimen, body fluid balance, daily energy intake and sleep duration are maintained as before Ramadan, Ramadan fasting does not have detrimental effects on aerobic exercise performance or body composition in young soccer players.

scholarly journals Effects of hydration status on cognitive performance and mood

2014 ◽  
Vol 111 (10) ◽  
pp. 1841-1852 ◽  
Author(s):  
Natalie A. Masento ◽  
Mark Golightly ◽  
David T. Field ◽  
Laurie T. Butler ◽  
Carien M. van Reekum
Keyword(s):  
Water Consumption ◽  
Cognitive Abilities ◽  
The Elderly ◽  
Future Research ◽  
Hydration Status ◽  
Fluid Regulation ◽  
Optimal Maintenance ◽  
And Function ◽  
The Impact

Although it is well known that water is essential for human homeostasis and survival, only recently have we begun to understand its role in the maintenance of brain function. Herein, we integrate emerging evidence regarding the effects of both dehydration and additional acute water consumption on cognition and mood. Current findings in the field suggest that particular cognitive abilities and mood states are positively influenced by water consumption. The impact of dehydration on cognition and mood is particularly relevant for those with poor fluid regulation, such as the elderly and children. We critically review the most recent advances in both behavioural and neuroimaging studies of dehydration and link the findings to the known effects of water on hormonal, neurochemical and vascular functions in an attempt to suggest plausible mechanisms of action. We identify some methodological weaknesses, including inconsistent measurements in cognitive assessment and the lack of objective hydration state measurements as well as gaps in knowledge concerning mediating factors that may influence water intervention effects. Finally, we discuss how future research can best elucidate the role of water in the optimal maintenance of brain health and function.

scholarly journals The Impact of Anthropogenic Climate Change on Egyptian Livestock Production

Animals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3127
Author(s):  
Amira A. Goma ◽  
Clive J. C. Phillips
Keyword(s):  
Climate Change ◽  
Heat Stress ◽  
Milk Production ◽  
Human Population ◽  
Production Systems ◽  
Livestock Production ◽  
Mitigation Strategies ◽  
Animal Products ◽  
Alternative Scenarios ◽  
The Impact

Egypt is one of the hottest countries in the world, and extreme climate events are becoming more frequent, which is consistent with the warming of the planet. The impact of this warming on ecosystems is severe, including on livestock production systems. Under Egyptian conditions, livestock already suffer heat stress periods in summer. The predicted increases in temperature as result of climate change will affect livestock production by reducing growth and milk production because of appetite suppression and conception rate reductions and will increase animal welfare concerns. In severe cases, these effects can result in death. We review the heat stress effects on livestock behaviour, reproduction, and production in the context of predicted climate change for Egypt over the course of this century and offer alternative scenarios to achieve food security for a growing human population. As an example, we combine predictions for reduced milk production during heat stress and human population trajectories to predict that milk availability per person will decline from 61 kg/year in 2011 to 26 kg/year in 2064. Mitigation strategies are discussed and include the substitution of animal-based foods for plant-based foods and laboratory-grown animal products.

scholarly journals Climate Change–Related Heat Stress and Subjective Well-Being in Australia

2019 ◽  
Vol 11 (3) ◽  
pp. 505-520 ◽  
Author(s):  
Kerstin K. Zander ◽  
Simon Moss ◽  
Stephen T. Garnett
Keyword(s):  
Climate Change ◽  
Life Satisfaction ◽  
Heat Stress ◽  
Heat Waves ◽  
Productivity Loss ◽  
Climate Change Impacts ◽  
Well Being ◽  
Future Research ◽  
Subjective Well Being ◽  
The Impact

Abstract There is mounting evidence that climate change impacts compromise people’s well-being. Many regions of Australia have experienced record hot temperatures and more frequent and longer heat waves with substantial consequences for people, economies, and ecosystems. Using data from an Australia-wide online survey with 1101 respondents, we investigated the relationship between self-reported measures of heat stress and different dimensions of subjective well-being. After controlling for socioeconomic factors known to affect well-being, we found that heat stress was linked to people’s certainty about and planning for their future but not to their life satisfaction, happiness, social state, capabilities, or purpose in life. This result indicates that, while heat is not associated with present well-being, many people worry about the effect that increased heat will have on their future well-being. People who were uncertain about their future were also more likely than those who did not feel uncertain to think that heat compromised their productivity. People who agreed that they were competent and capable in their activities rated their heat stress–related productivity loss lower than those who disagreed. The findings are relevant for future studies using life-satisfaction approaches to assess consequences of climate change impacts and to studies in “happiness economics.” We recommend that future research on the impact of climate change on well-being go beyond simply life satisfaction and happiness and test multiple dimensions of well-being.

scholarly journals Impact of muscle injury and accompanying inflammatory response on thermoregulation during exercise in the heat

2000 ◽  
Vol 89 (3) ◽  
pp. 1123-1130 ◽  
Author(s):  
Scott J. Montain ◽  
William A. Latzka ◽  
Michael N. Sawka
Keyword(s):  
Creatine Kinase ◽  
Heat Stress ◽  
Core Temperature ◽  
Interleukin 6 ◽  
Muscle Injury ◽  
Treadmill Exercise ◽  
Inflammatory Responses ◽  
Thermal Strain ◽  
Upper Body ◽  
Body Core Temperature

This study examined whether muscle injury and the accompanying inflammatory responses alter thermoregulation during subsequent exercise-heat stress. Sixteen subjects performed 50 min of treadmill exercise (45–50% maximal O2 consumption) in a hot room (40°C, 20% relative humidity) before and at select times after eccentric upper body (UBE) and/or eccentric lower body (LBE) exercise. In experiment 1, eight subjects performed treadmill exercise before and 6, 25, and 30 h after UBE and then 6, 25, and 30 h after LBE. In experiment 2, eight subjects performed treadmill exercise before and 2, 7, and 26 h after LBE only. UBE and LBE produced marked soreness and significantly elevated creatine kinase levels ( P < 0.05), but only LBE increased ( P < 0.05) interleukin-6 levels. In experiment 1, core temperatures before and during exercise-heat stress were similar for control and after UBE, but some evidence for higher core temperatures was found after LBE. In experiment 2, core temperatures during exercise-heat stress were 0.2–0.3°C ( P < 0.05) above control values at 2 and 7 h after LBE. The added thermal strain after LBE ( P < 0.05) was associated with higher metabolic rate ( r = 0.70 and 0.68 at 2 and 6–7 h, respectively) but was not related ( P > 0.05) to muscle soreness ( r = 0.47 at 6–7 h), plasma interleukin-6 ( r = 0.35 at 6–7 h), or peak creatine kinase levels ( r = 0.22). Local sweating responses (threshold core temperature and slope) were not altered by UBE or LBE. The results suggest that profuse muscle injury can increase body core temperature during exercise-heat stress and that the added heat storage cannot be attributed solely to increased heat production.

scholarly journals 46 The impact of heat stress on feedlot operations; nutritional and breeding options to reduce its impact

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 37-38
Author(s):  
Jenny Jennings
Keyword(s):  
Heat Stress ◽  
Management Strategies ◽  
Past Research ◽  
Mitigation Strategies ◽  
Economic Losses ◽  
Feeding Strategies ◽  
Wind Speeds ◽  
Diet Formulation ◽  
Low Wind Speeds ◽  
The Impact

Abstract Heat stress can and always will be an issue in the feedlot industry. Heat stress can decrease performance in feedlot animals leading to substantial economic losses. High environmental temperatures, relative humidity, solar radiation, and low wind speeds can be life-threatening to beef cattle when these conditions occur simultaneously. Management strategies to decrease or alleviate heat stress-related production losses have been a focus of research for a long period of time. There is a plethora of research completed on the additions of shades, sprinklers, air circulation of covered pens, as well as the physiological changes cattle experience. The physiological discoveries have revealed a lot about how the animal copes with certain stressors and has aided in potential mitigation strategies. The use of sprinklers and shades are the most popular additions to feedlots; however, certain nutritional management strategies and breed selection can be viable options as well. My objectives to address those management strategies were to compile and review past research that specifically addresses bunk management, diet formulation, feeding strategies, and breed characteristics as well as incorporate current information available on the cattle we feed today.

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