Heat Illness in Sport and Exercise

Heat Illness in Sport and Exercise

Prepared by : Christine May, Senior Research Consultant, Clearinghouse for Sport
Evaluation by : Dr Chris Abbiss, Associate Professor, School of Exercise and Health Sciences, Edith Cowan University (January 2018)
Last updated : 30 January 2020
Content disclaimer : See Clearinghouse for Sport disclaimer
Heat Illness in Sport and Exercise
Sport Australia

Introduction

Australia is synonymous with summer and sport. When these two extremes, hot environmental conditions and vigorous exercise, are combined it can produce a health and safety risk to athletes, officials, and spectators. 

This topic provides information for all sport-sector members so that participation in sport and exercise in hot conditions can be done in a safe manner. This information is intended to increase awareness of the risk to health and performance, and guide practice so that heat-related illnesses can be avoided.

Exercise-induced hyperthermia - defining the problem

runner on start block

Increases in the net-heat of the body, through metabolic and environmental influences, may compromise health and impair performance.

In response to a change in activity level and environmental conditions, our bodies initiate a series of processes that act to maintain internal (core) body temperature within a narrow range, around 37°C. This temperature regulation in humans (thermoregulation) is orchestrated by the hypothalamus in the brain, based on sensory information that detects heat gained by the body and heat lost to the environment. These involuntary processes allow the skin and limbs to vary in temperature while keeping the core body temperature as stable as possible. In the case of an elevation in body temperature (hyperthermia), heat loss mechanisms, such as increasing cardiac output, vasodilation (widening) of the skin’s blood vessels and sweating, are activated to maintain thermal homeostasis (stability or balance).   

When we exercise, our body converts metabolic energy into mechanical and thermal energy in order to produce movement. Approximately 75% of this energy is liberated as heat, making humans relatively inefficient and heavily reliant on heat loss through evaporative means [source: muscle efficiency, Wikipedia, (accessed 11 January 2018)]. As air temperature and body temperature rise, the potential for heat exchange between the skin and the environment is reduced. Furthermore, sweating increases as core body temperature rises until 39°C, when maximal sweat rates are achieved. The body’s inability to cope under enduring exertional heat-related stress can cause significant discomfort and impair exercise performance.

Thermoregulatory fatigue can occur at core temperatures around 40°C, irrespective of starting core temperature. The rate (i.e. how quickly) of heat storage is the main limiting factor in exercise performance. The body usually slows down (i.e. fatigue sets in) so that thermal failure can be avoided.

While the human body can tolerate small fluctuations (2-3˚C) in temperature, progression towards a critically high body temperature results in increasing symptom severityfrom cramps to exhaustion and finally heat strokewhich can be life threatening. When highly motivated athletes, who are accustomed to pushing themselves to the extent of their physical limits, fail to heed crucial warning signals, this already unfortunate event may become a tragedy.  

There are currently limited reliable data sources on the occurrence of heat-related illness, exertional heat stroke, or episodes with complications that result in death in Australia. There is some information available from research conducted in the United States which indicates that heat-related illness is one of the leading causes of death and injury among college and high school athletes..

Heat waves kill more people than any other natural hazard experienced in Australia. In 2009, a two-week heat wave in South Australia and Victoria caused at least 150 deaths and may have contributed to more than 370 deaths. Between the years 1803 and 1992, at least 4287 people died in Australia as a direct result of heat waves. Classical heat stoke is more characteristic of heatwaves, affecting the elderly, the very young, and those without adequate resources or means to escape the heat. However, those more physically capable who try to keep up their exercise regimen or play in a previously scheduled competition during phases of high heat load, are more likely to suffer from exertional heat stroke.

Although not specifically related to heat illness it is also important to note that during heat waves, particularly in Australia, bush fires may also become a significant risk and may exacerbate other heat related conditions. In December 2019, in response to unprecedented levels of smoke pollution from bush fires across the country the Australian Institute of Sport (AIS) developed a position statement on Smoke Pollution and Exercise to provide guidance and leadership specifically for the Australian high performance sport system. 

Where possible, direct links to full-text and online resources are provided. However, where links are not available, you may be able to access documents directly by searching our licenced full-text databases (note: user access restrictions apply). Alternatively, you can ask your institutional, university, or local library for assistance—or purchase documents directly from the publisher. You may also find the information you’re seeking by searching Google Scholar.

books iconBooks

  • Exertional Heat Illness: A Clinical and Evidence-Based Guide, William M. AdamsJohn F. Jardine (eds.), Springer, (2019). Provides clinicians, scientists and students with a comprehensive overview of exertional heat illness. Specifically, it addresses the prevention, recognition, treatment, and care of the various medical conditions that fall within the realm of exertional heat illness. 
  • Heat Stress in Sport and Exercise: Thermophysiology of Health and Performance, Julien D. Périard and Sébastien Racinais (eds.), Springer, (2019). The book is designed to provide a flowing description of the physiology of heat stress, the illnesses associated with heat exposure, recommendations on optimising health and performance, and an examination of Olympic sports played in potentially hot environmental conditions. Includes sport-specific chapters including: football/soccer, Australian football and rugby; American football; tennis; athletics; cycling; open-water swimming; and, triathlon and ultra-endurance events in tropical environments. 

Finder iconPosition Statements

  • Smoke Pollution and Exercise, Australian Institute of Sport, (December 2019). Bushfire smoke can pose a health risk to athletes. The health impact of bushfire smoke can vary based on an individual’s current health status and previous medical conditions. Current public health advice is aimed at high-risk groups, including people over 65, children 14 years and younger, pregnant women and those with existing heart or lung conditions. However, athletes involved in high performance sport can also be at higher risk while performing high intensity prolonged exercise outdoors and additional caution should be taken. 

ReadingReading

  • AIS advises athletes to be alert to smoke haze, media release, Australian Institute of Sport, (19 December 2019). Australian Institute of Sport (AIS) Chief Medical Officer Dr David Hughes has cautioned athletes to be vigilant regarding air pollution levels in bushfire-affected regions, and to adjust their training plans accordingly.
  • Extreme Heat: When Outdoor Sports Become Risky, Climate Central, (21 August 2019). Climate change’s impact is being felt throughout the world of sports as these extreme heat events become more common. On high heat index days, sports and heat become a dangerous mix. According to the Center for Disease Control, heat-related illnesses are the leading cause of death or disability among high school athletes. During hot, humid weather, sweat cannot evaporate as easily from the skin, so athletes are at greater risk of developing  illnesses such as heat exhaustion and heat stroke - the latter being potentially fatal. With an estimated 8 million high school athletes across the U.S., late summer is the time when many head back to football, soccer, field hockey, or track and field practice—and when parents, guardians and coaches need to be vigilant about the potential risk for exertional heat illnesses. 
  • Lives increasingly at risk from ‘angry climate’, media release, Climate and Health Alliance, (4 March 2013).
  • Management of exertional heat stroke: a practical update for primary care physicians, Edward Walter and Kiki Steel, British Journal of General Practice, Volume 68(668), pp.153-154, (2018). The number of cases of EHS appear to be on the rise; this may be due in part to increasing numbers of athletes participating in endurance events each year. Running USA estimates that 25 000 runners completed a marathon in the US during 1976; by 2016, this had grown to 507 600; similarly, the number of runners completing a half-marathon is estimated to have risen from 303 000 in 1990 to 1 900 000 in 2016. However, the incidence may also be rising; the US military has reported an eight-fold increase in the rate of hospitalisation from EHS, from 1.8 to 14.5 per 100 000 soldiers, over a 20-year period. 
  • ‘This Was Preventable’: Football Heat Deaths and the Rising Temperature, James Bruggers, Inside Climate News, (20 July 2018). Most states rank poorly on heat safety for their high school football players. Too many teens have paid the price, and temperatures are only getting worse. Includes information from the United States relating to which States take heat risk seriously for high school sports (i.e. by mandating heat safety measures). 

Report iconReports

  • Annual survey of football injury research 1931-2018, Kristen L. Kucera, David Klossner, Bob Colgate, Robert C. Cantu, National Centre for Catastrophic Sport Injury Research (US), (15 February 2019). Report includes a specific section on Heat Stroke which highlights that since 1995, 64 football players have died from heat stroke (47 high school, 13 college, 2 professional, and 2 organised youth). Ninety percent of recorded heat stroke deaths occurred during practice. During the most recent five year period from 2014-2018 there was an average of 2.2 heat stoke deaths per year compared to 3.2 per year during the previous five year period 2009-2013.
  • Catastrophic sports injury research: 34th Annual Report [Fall 1982 - Spring 2018], Kucera K, Cox L and Cantu R, National Centre for Catastrophic Sport Injury Research (US), (3 October 2019). This report summarises 36 years of data, covering over 2,686 incidence of catastrophic sports-related injuries in US high schools and colleges. From July 1, 2017 to June 30, 2018 there were a total of 99 catastrophic injuries/illnesses captured by NCCSIR among high school and college organized sport participants. Of these 15.2% were heat-related. 
  • The exceptional heatwave of January-February 2009 in south-eastern Australia, Australian Bureau of Statistics, Feature Article, Catalogue Number 1301.0, Year Book Australia, 2009-10 (2010).
  • Exertional heat illness in adolescents and adults: Epidemiology, thermoregulation, risk factors, and diagnosis, Francis G O'Connor and Douglas J Casa, UpToDate, Wolters Kluwer, (last updated 12 November 2018; literature review current through December 2019). Includes information on the epidemiology, risk factors, thermoregulation in the heat, determining risk, basic types and clinical presentation, differential diagnosis, and summary and recommendations relating to exertional heat illness. 
  • Recent trends in and preparedness for extreme weather events, Environment and Communications References Committee report to the Australian Senate, (August 2013). Australia has long been a land of weather extremes, 'a sunburnt country…of droughts and flooding rains'. However, recent extreme weather events have raised questions about whether the patterns and nature of these events are changing. Submission to the inquiry were recieved from the Climate and Health Alliance, among others. 

Research iconResearch

  • Epidemiology of exertional heat illness among U.S. high school athletes, Kerr Z, Casa D, Marshall M and Comstock R, American Journal of Preventative Medicine, Volume 44(1), pp.8-14, (2013). Although most exertional heat illnesses occurred in football, athletes in all sports and all geographic areas are at risk. Because exertional heat illness frequently occurs when medical professionals are not present, it is imperative that high school athletes, coaches, administrators, and parents are trained to identify and respond to it. Implementing effective preventive measures depends on increasing awareness of exertional heat illness and relevant preventive and therapeutic countermeasures.
  • The Epidemiology and Management of Exertional Heat Illnesses in High School Sports During the 2012/2013–2016/2017 Academic Years, Zachary Y. Kerr, Susan W. Yeargin, Yuri Hosokawa, Rebecca M. Hirschhorn, Lauren A. Pierpoint and Douglas J. Casa, Journal of Sport Rehabilitation, (February 2019). Recent data on exertional heat illness (EHI) in high school sports are limited yet warranted to identify specific settings with the highest risk of EHI. American football continues to have the highest overall EHI rate although the high competition EHI rate in girls’ cross-country merits additional examination. Regional differences in EHI incidence, coupled with sport-specific variations in management, may highlight the need for region- and sport-specific EHI prevention guidelines.
  • Epidemiology of Exertional Heat Illnesses in National Collegiate Athletic Association Athletes During the 2009–2010 Through 2014–2015 Academic Years, Susan W. Yeargin, Thomas P. Dompier, Douglas J. Casa, Rebecca M. Hirschhorn, and Zachary Y. Kerr, Journal of Athletic Training, Volume 54(1), pp.55-63, (2019). Athletic trainers reported Exertional heat illnesses (EHIs) to the NCAA Injury Surveillance Program. Only EHIs sustained during a sanctioned practice or competition were included. The EHI rate, specific diagnoses, and number of emergency transports were measured. Football players continue to experience the most EHIs; however, EHIs can potentially occur in all NCAA sports. Continued emphasis on preseason EHI policies and institution-specific environmental guidelines is needed to address EHI rates.
  • Exercise in the Heat for Children and Adolescents. Statement from the Commission for Pediatric Sports Medicine, German Society for Sports Medicine and Prevention (PDF  - 274KB), Lawrenz, W., German Journal of Sports Medicine, Volume 70, pp.265-268, (November 2019). › Exertional heat illness in children and adolescents is preventable by different measures. There should be sufficient time for recovery between repeated exercise bouts. Children and adolescents should drink sufficient quantities regularly and provide for sun protection of head and skin. During all athletic events in the heat with participation of children and adolescents, trained personnel and facilities capable of effectively treating all forms of heat illness, should be readily available on site.
  • Exertional Heat Stroke Management Strategies in United States High School Football, Kerr Z, Marshall S, Comstock R and Casa D, American Journal of Sports Medicine, Volume 42(1), pp.70-77, (2014). Preseason exertional heat stroke events, which are likely to be fatal if untreated, were reported by one fifth of all athletic trainers in high school football programs. The standard of care is (and should be) to treat proactively; therefore, treatment is not a perfect proxy for incidence. Nevertheless, there is an urgent need for improved education and awareness of exertional heat stroke in high school football. Areas of improvement include the greatly increased use of rectal thermometers and immersion in ice water.
  • Heat illness among high school athletes: United States, 2005-2009, Yard E, Gilchrist J, Haileyesus T, Murphy M, Collins C, McIlvain N and Comstock R, Journal of Safety Research, Volume 41(6), pp.471-474, (2010). During 2005–2009, the 100 schools sampled reported a total of 118 heat illnesses among high school athletes resulting in ≥ 1 day of time lost from athletic activity, a rate of 1.6 per 100,000 athlete-exposures, and an average of 29.5 time-loss heat illnesses per school year. The average corresponds to a weighted average annual estimate of 9,237 illnesses nationwide. The highest rate of time-loss heat illness was among football players, 4.5 per 100,000 athlete-exposures, a rate 10 times higher than the average rate (0.4) for the eight other sports. Time-loss heat illnesses occurred most frequently during August (66.3%) and while practicing or playing football (70.7%). No deaths were reported.
  • Heat stress incidence and matchplay characteristics in Women's Grand Slam Tennis, Matthew T.Smith, Machar Reid, Stephanie Kovalchik, Tim Wood, Rob Duffield, Journal of Science and Medicine in Sport, Volume 21(7), pp.666-670, (July 2018). An association between higher estimated WBGT and medical callouts (heat and non-heat related) was evident, with an increased call rate >32 °C WBGT, despite no heat-related retirements. As estimated WBGT increased, the number of winners and net approaches were reduced, while double faults increased, particularly >30 °C WBGT. Accordingly, the manner in which female players manage and play in the heat during women’s Grand Slam tennis appears to change at ≈30 °C WBGT.
  • Heat stress incident prevalence and tennis matchplay performance at the Australian Open, Matthew T.Smith, Machar Reid, Stephanie Kovalchik, Tim Wood, Rob Duffield, Journal of Science and Medicine in Sport, Volume 21(5), pp.467-472, (May 2018). Increased estimated WBGT increased total match doctor and trainer consults for heat related-incidents, post-match heat-related consults (>32 °C) and cooling device callouts (>28 °C). However, few matchplay characteristics were noticeably affected, with only reduced net approaches and increased aces evident in higher estimated WBGT environments.
  • High Thermoregulatory Strain During Competitive Paratriathlon Racing in the Heat, Ben T. Stephenson, et.al., International Journal of Sports Physiology and Performance, (2019). Paratriathletes face significant thermal strain during competition in the heat, as evidenced by high Tc, relative to previous research in able-bodied athletes and a high incidence of self-reported heat illness symptomatology. Differences in the Tc profile exist depending on athletes’ race category and wetsuit use.
  • The impact of different environmental conditions on cognitive function: A focused review, Taylor L, Watkins S. Marshall H, Dascombe B and Foster J, Frontiers in Physiology, Volume 6, (6 January 2016). Extreme environments; such as heat, hypoxia, and cold, can alter human cognitive function due to a variety of psychological and/or biological processes. This review provides updated knowledge regarding the effects of extreme environmental stressors on cognitive function and their biological underpinnings. This review discuss: (1) the current state of knowledge on the effects of heat, hypoxic and cold stress on cognitive function; (2) the potential mechanisms underpinning these alterations, and; (3) plausible interventions that may maintain cognitive function upon exposure to each of these environmental stressors. The available evidence suggests that the effects of heat, hypoxia, and cold stress on cognitive function are both task and severity dependent. Complex tasks are particularly vulnerable to extreme heat stress. Both simple and complex task performance appear to be vulnerable at even moderate altitudes; and cold stress also appears to negatively impact both simple and complex task performance.
  • Risk of heat illness in men and women: A systematic review and meta-analysis, Robert M.Gifford, et.al., Environmental Research, Volume 171, pp.24-35, (April 2019). The rate of HI was significantly increased in men compared with women. Risk for HI might be conferred by psychological and behavioral factors rather than physiological ones. Further research is required to delineate which groups are at greatest risk, leading to the development of mitigation strategies against HI. 
  • Sport-related exertional heat illness hospitalisations in Victoria, Australia: Incidence and trend over 11 years, S.McMahon & L.Fortington, Journal of Science & Medicine in Sport, Volume 22(Supplement 2), pp.S68, (October 2019). Sport-related EHI hospitalisation data with specific age, gender and sport characteristics can be used as a guide to develop EHI policies, and decision making on EHI risk mitigation and prevention. These data support specific age-related risks and therefore the specific participation characteristics for these age groups should be addressed in prevention measures. Fewer than expected cases were identified, particularly when considered the ratio of ED presentations relative to hospital admissions, leading to questions on the adequacy of data capture in this source. Alternative methods to measure annual changes should be considered.

resources iconResources 

Heat policy guidelines

Triathlon runners During vigorous and prolonged exposure to the heat there is an increased risk of heat-related illness and injury for athletes, officials, volunteers, and spectators. If warning signs are ignored or weather conditions extreme, heat-related episodes can quickly escalate to heat stroke with the potential for permanent injuries or even death. Although the incidence of exertional heat stroke is rare, sporting bodies and event organisers are encouraged to mitigate against the risk of heat illness and prevent situations that could exacerbate conditions.  

Sports Medicine Australia (SMA)

Sports Medicine Australia (SMA) has a leading role in Australia, in creating awareness of exertional heat illness and assisting members of the sport-sector to recognise and manage potentially dangerous situations that may result from exercising in hot weather

  • Hot weather guidelines (PDF  - 62 KB), Sports Medicine Australia, (2007). To help organisations, coaches, teachers and other individuals when conducting sport in hot weather, SMA has produced a set of guidelines. These guidelines are based on the latest research as well as the expertise of SMA’s medical and scientific members.
  • UV Exposure and heat illness guide (PDF  - 1.5 MB), SunSmart and SmartPlay, (2010). This guide outlines practical steps to create a safe and enjoyable environment for participation in sport and physical activity.
  • Beat the Heat: playing and exercising safely in hot weather, fact sheet (PDF  - 3.7 MB), Sports Medicine Australia, (2011). 


VicSport

Hot Weather Resources, VicSport, [accessed 19 December 2019]. Resources on this page can assist sport organisations to mitigate the risks of exertional heat illness during hot weather. The resources are relevant for state sport associations, regional sports assemblies, local governments, clubs, leagues and associations. Includes information and links to resources on exertional heat illness, hot weather guidelines, resources for state sport associations, resources for clubs, leagues and associations, and other resources. 


Other Australian state and national organisations have published policies to optimise the health of their members when playing sport in hot conditions:

General

  • Consensus recommendations on training and competing in the heat, Racinais S, et.al., British Journal of Sports Medicine, (11 June 2015). Exercising in the heat induces thermoregulatory and other physiological strain that can lead to impairments in endurance exercise capacity. The purpose of this consensus statement is to provide up-to-date recommendations to optimise performance during sporting activities undertaken in hot ambient conditions. The most important intervention one can adopt to reduce physiological strain and optimise performance is to heat acclimatise. Heat acclimatisation should comprise repeated exercise-heat exposures over 1–2 weeks. In addition, athletes should initiate competition and training in a euhydrated state and minimise dehydration during exercise. Following the development of commercial cooling systems (e.g., cooling-vest, etc.), athletes can implement cooling strategies to facilitate heat loss or increase heat storage capacity before training or competing in the heat. Moreover, event organisers should plan for suitable shaded areas, along with cooling and rehydration facilities, and schedule events in accordance with minimising the health risks of athletes, especially in mass participation events. Following the recent examples of the 2008 Olympics and the 2014 FIFA World Cup, sport governing bodies should consider allowing additional (or longer) recovery periods between and during events, for hydration and body cooling opportunities, when competitions are held in the heat.   
  • Policy Statement: climatic heat stress and exercising children and adolescents, Council on Sports Medicine and Fitness and Council on School Health, Pediatrics, Volume 128(3), pp.741-747, (2011). Results of new research indicate that, contrary to previous thinking, youth do not have less effective thermoregulatory ability, insufficient cardiovascular capacity, or lower physical exertion tolerance compared with adults during exercise in the heat when adequate hydration is maintained. Accordingly, besides poor hydration status, the primary determinants of reduced performance and exertional heat-illness risk in youth during sports and other physical activities in a hot environment include undue physical exertion, insufficient recovery between repeated exercise bouts or closely scheduled same-day training sessions or rounds of sports competition, and inappropriately wearing clothing, uniforms, and protective equipment that play a role in excessive heat retention. Because these known contributing risk factors are modifiable, exertional heat illness is usually preventable. 
  • Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015, Hew-Butler T, et.al., Clinical Journal of Sport Medicine, Volume 25(4), (July 2015). A panel of 17 international experts, representing 4 countries and 9 medical and scientific sub-specialties pertaining to athletic training, exercise physiology, sports medicine, water/sodium metabolism, and body fluid homeostasis, met to review guidelines. This document serves to replace the second International Exercise-Associated Hyponatremia (EAH) Consensus Development Conference Statement (2008) and launch an educational campaign designed to address the morbidity and mortality associated with a preventable and treatable fluid imbalance. Under-replaced sodium losses contribute to serum [Na+] independent of distance (Grade 1A). However, there is paucity of data supporting sodium loss as the primary mechanism of symptomatic EAH even in those who exercise for prolonged periods of time and in warm weather (Grade 2C). In these cases, relative over-drinking of hypotonic fluids with sustained non-osmotic AVP secretion is likely involved in the development of symptomatic EAH.  


International Olympic Committee (IOC)

  • International Olympic Committee consensus statement on thermoregulatory and altitude challenges for high-level athletes, Bergeron M, et.al., British Journal of Sports Medicine, Volume 46, p770-779 (2012). Challenging environmental conditions, including heat and humidity, cold, and altitude, pose particular risks to the health of Olympic and other high-level athletes. As a further commitment to athlete safety, the International Olympic Committee (IOC) Medical Commission convened a panel of experts to review the scientific evidence base, reach consensus, and underscore practical safety guidelines and new research priorities regarding the unique environmental challenges faced by international-level athletes. This consensus article is not intended to be a comprehensive review of environmental challenges and inclusive of all recommended safety procedures for training and competing in adverse climates. Rather, the intent is to highlight selected key environment-related risk factors that continue to challenge Olympic and other international-level athletes. The other priority is to re-emphasise and provide additional recommendations to address and minimise those risks associated with environmentally challenging conditions. 


United Kingdom

  • Exertional Heat StrokeFaculty of Sport and Exercise Medicine (FSEM) UK, (reviewed and updated May 2018). The Faculty of Sport and Exercise Medicine (FSEM) UK has produced a guide for the immediate recognition and treatment of exertional heatstroke (EHS). EHS is a potentially fatal hyperthermia that occurs in exercising individuals, characterised by central neurological dysfunction and a markedly elevated core temperature (above 40.5°C). There is a significant risk of short- and long-term complications, particularly if there are delays in recognition and treatment. Rapid recognition and urgent treatment is therefore a priority.


United States 

Archery iconArchery

Athletics iconAthletics

AFL iconAustralian Football

Bowls-smallBowls

canoeing-smallCanoe/Kayak

cricket-smallCricket 

Cricket Australia recommends the use of the Australian Cricket Community Cricket Playing in the Heat Guidelines as it provides Cricket organisers and participants a scientific approach in managing extreme heat conditions. The guidelines utilise a Heat Stress Risk Index (HSRI) tool that is also available through the MyCricket website and factors in the air temperature, humidity, sun radiation and wind.

Some examples of local policies include: 

Hockey-smallCroquet

cyclingCycling

  • Cycling Australia - Heat Policy (PDF  - 269 KB), January 2018. 

Equestrian-smallEquestrian

  • Equestrian Australia – Hot Weather Policy (PDF  – 624 KB), September 2017. Includes information for recognising and managing heat stress in both horses and human athletes.    

flying discFlying Disc

football-smallFootball

  • Football Federation Australia (FFA) – Heat Policy, [accessed 11 January 2018]
  • Football Federation South Australia - hot weather policy (PDF  - 39 KB), January 2014

golf-smallGolf 

  • Golf Australia - hot weather guidelines (PDF  - 116 KB). Adapted from Sports Medicine Australia policies for competitors, caddies, officials and volunteers. involved in the game of Golf in Australia (January 2010).

Gymnastics-smallGymnastics

Hockey-smallHockey 

  • Hockey Australia – Extreme Weather Guidelines (PDF  – 1 MB), September 2014. Includes UV Exposure and Heat Illness information and checklists, as well as hail, lightning, chill, and additional resources. 

Lacrosse-smallLacrosse

  • Australian Lacrosse Association – Heat Policy,(PDF  – 151 KB), May 2009

Netball-smallNetball

Equestrian-smallPolo

  • Australian Polo Federation – Heat Policy (PDF  – 551 KB ), March 2016 

Equestrian-smallPolocrosse

Equestrian-smallPony Club

rowing-smallRowing

Rugby-League-smallRugby League 

rugby-Union-smallRugby Union 

softball-smallSoftball

surf-life-saving-smallSurf Life Saving

 SwimmingSwimming

tennisTennis 

touch-Football-smallTouch Football

Triathlon-smallTriathlon

volleyball-smallVolleyball

Environmental heat load can be assessed using wet bulb globe temperature (WBGT). This integrated measurement takes into account the effects of air temperature, relative humidity, solar radiation, and wind speed. It is known that the risk of exertional heat illness in susceptible individuals increases as WBGT rises.

Where possible, direct links to full-text and online resources are provided. However, where links are not available, you may be able to access documents directly by searching our licenced full-text databases (note: user access restrictions apply). Alternatively, you can ask your institutional, university, or local library for assistance—or purchase documents directly from the publisher. You may also find the information you’re seeking by searching Google Scholar.

books iconBooks

  • Heat Stress in Sport and Exercise: Thermophysiology of Health and Performance, Julien D. Périard and Sébastien Racinais (eds.), Springer, (2019). The book is designed to provide a flowing description of the physiology of heat stress, the illnesses associated with heat exposure, recommendations on optimising health and performance, and an examination of Olympic sports played in potentially hot environmental conditions. Includes sport-specific chapters including: football/soccer, Australian football and rugby; American football; tennis; athletics; cycling; open-water swimming; and, triathlon and ultra-endurance events in tropical environments. 

ReadingReading

  • Mandatory pre-season guidelines reduce heat illness among high school football players, Science News/University of North Carolina, (10 April 2019). Researchers have found strong evidence that rates of heat-related illnesses, such as heat cramps and heat strokes, were reduced by half in states that had mandated guidelines to reduce exertional heat illness among high school football players. This is one of the first studies examining the effectiveness of state-mandated guidelines for reducing exertional heat illness among high school football players.
  • Mitigating Climate Impacts on Athletes: Sports Guidelines May Prevent Exertional Heat Illness, Wendee Nicole, Environmental Health Perspectives, (25 October 2019). The incidence of heat-related illnesses and deaths is expected to rise as heat waves become more frequent in some areas.Can policies that mandate risk-reducing behaviors lower the likelihood of heat illness and save lives? Few studies have addressed this issue, but recent research in Environmental Health Perspectives found that when states implemented guidelines to help ward off exertional heat illness (EHI) in student athletes, rates did, in fact, fall dramatically.
  • ‘This Was Preventable’: Football Heat Deaths and the Rising Temperature, James Bruggers, Inside Climate News, (20 July 2018). Most states rank poorly on heat safety for their high school football players. Too many teens have paid the price, and temperatures are only getting worse. Includes information from the United States relating to which States take heat risk seriously for high school sports (i.e. by mandating heat safety measures). 

Report iconReports

  • Caught behind: Climate change, extreme heat and the Boxing Day TestAustralian Conservation Foundation and Monash Climate Change Communication Research Hub, (December 2019). This report brings together climate, media and sports research to: Review the current management of extreme heat in Australian cricket; Investigate cricket's contributions to the risks posed by climate change; and, Question the viability of continuing to host the Boxing Day Test in December under a "business as usual" greenhouse gas scenario.
  • Reducing Heat Illness in College and High School Sports (PDF  -  5.8MB), United Educators Insurance, (2019). Heat-related illness is preventable, yet it's a leading cause of death and injury among college and high school athletes. All athletes are susceptible to the risks of exercising in a hot environment, but particularly those in high-exertion sports such as football, where studies show the majority of heatrelated illnesses occur. A review of United Educators (UE) claims arising from heat-related illnesses in athletes reveals that the primary cause of liability is poor planning for reduction of and response to this risk. Professional football provides a model for high school and college athletics. Since the NFL overhauled its practices around heat-related illnesses following the death of Korey Stringer in 2001, not a single player has died from heat exertion. By implementing heat-illness reduction programs, institutions can decrease or eliminate risk and enhance the overall safety of their athletic practices and competitions. Use this publication to help inform or assess your institution’s heat-illness reduction practices. 

Research iconResearch 

  • The Application of Heat Stress to Team Sports: Football/Soccer, Australian Football and Rugby, Katie Slattery and Aaron J. Coutts, in 'Heat Stress in Sport and Exercise: Thermophysiology of Health and Performance', Julien D. Périard and Sébastien Racinais (eds.), Springer, pp.181-202, (7 March 2019). This chapter addresses how an added heat stress affects football, Australian football and rugby players during both training and competition. Although these sports are typically played in the cooler winter months, players can still be exposed to hot conditions and this may affect health and performance. It is therefore important to understand how an increased thermal load influences the tactical, technical, physical and psychological constructs that contribute to team sport performance.
  • The Association between Mandated Preseason Heat Acclimatization Guidelines and Exertional Heat Illness during Preseason High School American Football Practices, Zachary Y. Kerr, et.al., Environmental Health Perspectives, (10 April 2019). The risk of heat-related illness and death may continue to increase in many locations as a consequence of climate change, but information on the effectiveness of policies to protect populations from the adverse effects of excessive heat is limited. In 2009, the National Athletic Trainers’ Association Inter-Association Task Force (NATA-IATF) released guidelines to reduce exertional heat illness (EHI) among U.S. high school athletes participating in preseason sports activities, including preseason practice sessions for American football. A subset of state high school athletic associations have implemented state-mandated guidelines consistent with the 2009 NATA-IATF recommendations, but their effectiveness for reducing preseason EHI is unknown. Our findings suggest that high school athletes would benefit from enactment of the 2009 NATA-IATF guidelines. Similar analyses of the effectiveness of other public health policies to reduce adverse health effects from ambient heat are warranted.
  • Exercise in the Heat for Children and Adolescents. Statement from the Commission for Pediatric Sports Medicine, German Society for Sports Medicine and Prevention (PDF  - 274KB), Lawrenz, W., German Journal of Sports Medicine, Volume 70, pp.265-268, (November 2019). › Exertional heat illness in children and adolescents is preventable by different measures. There should be sufficient time for recovery between repeated exercise bouts. Children and adolescents should drink sufficient quantities regularly and provide for sun protection of head and skin. During all athletic events in the heat with participation of children and adolescents, trained personnel and facilities capable of effectively treating all forms of heat illness, should be readily available on site.
  • Fatal Exertional Heat Stroke and American Football Players: The Need for Regional Heat-Safety Guidelines, Andrew J. Grundstein, Yuri Hosokawa, Douglas J. Casa, Journal of Athletic Training, Volume 53(1), pp.43-50, (2018). Weather-based activity modification in athletics is an important way to minimize heat illnesses. However, many commonly used heat-safety guidelines include a uniform set of heat-stress thresholds that do not account for geographic differences in acclimatization. The combination of lower exposure WBGTs and frequent extreme climatic values in milder climates during fatal EHSs indicates the need for regional activity-modification guidelines with lower, climatically appropriate weather-based thresholds. Established activity-modification guidelines, such as those from the American College of Sports Medicine, work well in the hotter climates, such as the southern United States, where hot and humid weather conditions are common. 
  • Implementing exertional heat illness prevention strategies in US High School Football, Kerr Z, Marshall S, Comstock R and Casa D, Medicine & Science in Sports & Exercise, Volume 46(1), pp.124-130, (2014). Approximately 6500 high school football athletes are treated annually for exertional heat illness (EHI). In 2009, the National Athletic Trainers Association (NATA)-led Inter-Association Task Force (NATA-IATF) released preseason heat acclimatization guidelines to help athletes become accustomed to environmental factors contributing to EHI. This study examines compliance with NATA-IATF guidelines and related EHI prevention strategies. A low proportion of surveyed high school football programs fully complied with all 17 NATA-IATF guidelines. However, many EHI prevention strategies were voluntarily implemented. State-level mandated EHI prevention guidelines may increase compliance with recognized best practices recommendations. Ongoing longitudinal monitoring of compliance is also recommended.
  • Managing heat and immune stress in athletes with evidence-based strategies, Pyne D, Guy J and Edwards A, International Journal of Sports Physiology and Performance, Volume 9, pp.744-750, (2014). Heat and immune stress can affect athletes in a wide range of sports and environmental conditions. The classical thermoregulatory model of heat stress has been well characterized, as has a wide range of practical strategies largely centered on cooling and heat-acclimation training. In the last decade evidence has emerged of an inflammatory pathway that can also contribute to heat stress. Studies are now addressing the complex and dynamic interplay between hyperthermia, the coagulation cascade, and a systemic inflammatory response occurring after transient damage to the gastrointestinal tract. Damage to the intestinal mucosal membrane increases permeability, resulting in leakage of endotoxins into the circulation. Practical strategies that target both thermoregulatory and inflammatory causes of heat stress include precooling; short-term heat-acclimation training; nutritional countermeasures including hydration, energy replacement, and probiotic supplementation; pacing strategies during events; and postevent cooling measures. Cooperation between international, national, and local sporting organizations is required to ensure that heat-management policies and strategies are implemented effectively to promote athletes' well-being and performance.
  • New guidelines are needed to manage heat stress in elite sports – The Fédération Internationale de Volleyball (FIVB) Heat Stress Monitoring Programme, Roald Bahr and Jonathan C Reeser, British Journal of Sports Medicine, Volume 46(11), pp.805-809, (2012). The goal of this research was to monitor heat stress and record cases of heat-related medical forfeits on the Swatch FIVB Beach Volleyball World Tour. The incidence of significant heat illness among athletes competing on the FIVB Beach Volleyball World Tour appears to be quite low, even though weather conditions frequently result in a WBGT index >32°C. Currently available guidelines appear to be inadequate to fully assess the risk of heat stress and too conservative to inform safety decisions in professional beach volleyball.
  • Practical recommendations for endurance cycling in hot/humid environments, Nichols D, Aspetar Sports Medical Journal, Volume 5, (2016). It is well documented that exercise in a warm environment poses a significant thermal challenge to the body and has the potential to reduce exercise performance. The combination of heat production from working muscles and reduction in the rate of heat loss due to high ambient temperatures and/or humidity results in an exacerbated rise in core temperature (hyperthermia) for any given exercise intensity. Hyperthermia per se impairs aerobic performance and consequently decreases power output compared with temperate environments. In addition, dehydration during exercise in the heat further exacerbates the thermal and cardiovascular strain and further impairs aerobic performance. This article provides practical recommendations for athletes and race organisers.
  • Practice beliefs of team physicians regarding the recognition and treatment of exertional heat stroke, Mazerolle S, Pagnotta K, Casa D, McDowell L and Armstrong L, Athletic Training & Sports Health Care: The Journal for the Practicing Clinician, Volume 5, Number 1, p20 (2013). The purpose of this basic inductive research study was to investigate team physicians’ practice beliefs regarding the recognition and immediate treatment of EHS and the ways to increase and promote the use of best practices within the athletic training profession. Many of the participants recognized that in their role as a team physician, they were responsible for promoting best practices, which they believed were Tre and CWI. However, they did not believe it was their professional responsibility to provide educational training for either skill to athletic trainers, but rather that the 2 parties must work together to develop appropriate patient care policies.
  • Preventing heat illness in the anticipated hot climate of the Tokyo 2020 Summer Olympic Game. Takeyasu Kakamu, Koji Wada, Derek R. Smith, Shota Endo and Tetsuhito Fukushima, Environmental Health and Preventive Medicine/BioMed Central, (published online 19 September 2017). Overall, our study suggests that the Tokyo 2020 Summer Olympics will be held amid extremely high WBGT conditions, including at levels deemed poorly suited for conducting sporting events. Combined efforts by all stakeholders during these events will therefore be necessary to deal with these challenging conditions so that athletes can perform their best and so heat illness can be minimized among individuals taking part in these activities. Sporting committees and the Olympic organizing committee should also consider WBGT in selecting venues and the timing of events to help minimize heat illness and enable maximum performance by athletes. Similarly, the organization of the 2020 Tokyo Olympics will need to manage heat as an occupational safety issue for staff and also provide multiple solutions to help heat illness among spectators and tourists.
  • Sports Medicine Staff Size Influences Exertional Heat Illness Policies in High School Football, Riana R. Pryor, Douglas J. Casa, Susan W. Yeargin and Zachary Y. Kerr, International Journal of Athletic Therapy and Training, Volume 23(4), pp.172-177, (2017). All high schools should implement exertional heat illness (EHI) safety strategies. We determined if there were differences in the implementation of EHI safety strategies between schools with and without additional paid athletic trainers (ATs) or a team physician present at preseason football practices. High schools with multiple ATs or a team physician implemented more EHI prevention and management strategies than schools with only a single AT, including training staff in EHI recognition and treatment and having an emergency action plan. However, schools with a paid team physician were more likely to have double practices in the first week of football practice. Schools with additional medical personnel at football preseason practices were more likely to implement EHI safety strategies.
  • The Use of Technology to Protect the Health of Athletes During Sporting Competitions in the Heat, Borja Muniz-Pardos, et.al., Frontiers in Sports and Active Living, (3 October 2019). Due to the metabolic demands of the sporting events and the high environmental temperatures, the risk of exertional heat stroke (EHS) is high. Careful planning by event organizers are needed to ensure that athletes are protected from irreversible long-term health damage, or even death during sporting competitions in the heat. 
  • Case studies

    During the first week of the Australian Open Tennis Tournament in January 2014 a heat-wave saw 970 tennis fans treated for heat exhaustion and officials invoked the extreme-heat policy for the first time. Play was suspended for four hours for all matches playing on outside courts as the temperature soared to 42˚C in Melbourne, with officials declaring conditions unsafe for players.

    The Australian Open uses a combination of air temperature, relative humidity, and wind-speed which together form the wet-bulb globe temperature (WBGT) as the basis for decisions that triggers a halt in play. The implementation of the Australian Open’s Extreme Heat Policy is at the discretion of the Tournament Referee. On the other hand, a WBGT reading of 26 prompts ice-vests to be sent to all courts with iced-towels and ice-baths available and 30.1 introduces a 10 min break in women’s singles matches, but only if the game progresses to the third set.

    The continuation of extreme weather conditions from 13-18 January, as round-two matches progressed, prompted considerable discussion from stakeholders and key experts: 

    The Bureau of Meteorology, Australian Government:

    The Tournament Officials:

    The players:

    On behalf of the spectators:

    • More than 1,000 tennis fans were treated for heat exhaustion’, Kate Hagan, Michael Chammas and Beau Donnelly, The Age (16 January 2014). Diana Egerton-Warburton, Chair of the Australasian College for Emergency Medicine’s public health committee, urged tournament organisers to consider issuing health warnings for spectators in extreme heat.

    Sport Science Experts:

    • Melting in Melbourne: Thoughts on the heat, Ross Tucker, The Science of Sport (16 January 2014). On his blog, Dr Tucker neatly tackles the big issue— the performance of top-level tennis players in temperatures ≥40 degree Celsius, and neatly discusses the issues surrounding the ‘hype’.
    • A very heated debate, Daisy Dumas, The Sydney Morning Herald (18 January 2014). Refer to comments provided by Dr Ollie Jay, University of Sydney. Dr Jay discussing the risks of exercise-induced heat stroke and highlights some of the ‘cultural misunderstandings’ around exercise and heat, citing the lack of evidence for the sex-based discrepancy to allow female players a rest-break in extreme conditions, but not men.
    • Too hot for tennis? The impact of heat on players, Phillippa Roxby, BBC News (16 January 2014). According to Doctor George Havenith, professor of environmental physiology and ergonomics from Loughborough University, players will be producing the heat equivalent of around 20 60W light bulbs. When the effects of direct sunshine and radiation from the court surface are taken into consideration, as well as heat from the spectators watching and the lack of air flow around the court, this could increase the heat count by up to another 50%.

    On 27 January 2014, following the event, the Tournament Director confirmed that the comprehensive annual event review would include a reappraisal of its controversial extreme heat policy.

    Although changes have been made, the issue of heat and player safety continues to be frequently debated during the Australian Tennis Open: 

    FINA (the Fédération Internationale de Natation) is the world governing body for the five aquatic disciplines of swimming, diving, water polo, synchronised swimming and open water swimming

    Water temperature played a part in the death of Francis Crippen, a 26 year-old Open Water Swimmer from the USA, at FINA’s 2010 10 km series in Fujairah, United Arab Emirates. The water was cited as being overly warm—above 30°C with several other swimmers being treated for heat exhaustion in hospital following completion of the race.

    FINA appointed a Task Force to conduct an independent and unbiased investigation to better understand the circumstances of the death of Crippen. In the final report submitted to FINA, the Task Force acknowledged "factors such as a combination of high physical exertion and fatigue in conjunction with high air and water temperatures, potential dehydration and heat exhaustion were all possible contributing causes which led to Francis Crippen’s progressive incapacitation. This led to a loss of consciousness in the water which ultimately resulted in drowning." The Task Force demanded FINA make athlete safety a top priority, and called to "update and amend the Rules and Regulations of Open Water Swimming to keep up with the sport as it moves forward as an Olympic Sport".

    Related media report:

    Specifically, the rules state:

    OWS 5.5—the water temperature should be a minimum of 16°C and a maximum of 31°C. It should be checked the day of the race, 2 hours before the start, in the middle of the course at a depth of 40 cm. This control should be done in the presence of a Commission made up of the following persons present: a Referee, a member of the Organising Committee and one coach from the teams present designated during the Technical Meeting.

    • OWS 5.5.1—The Safety Officer shall monitor temperature conditions periodically during the race.

    The Tokyo 2020 Olympic and Paralympic Games are set to be held in some of the hottest and most humid conditions of recent Summer Games history. Temperatures in Tokyo in July (during the Olympic Games) are generally expected to exceed 30°C with up to 80% humidity. Temperatures/conditions for the Paralympic Games (In August) are expected to be slightly better (estimated 1.5°C WBGT lower) but may still impose considerable heat strain. Some Paralympic athletes also have reduced thermoregulatory abilities which may cause additional difficulties.

    Strategies for organisers, teams and individual athletes to mitigate the conditions are therefore a key issue in the lead up to the events. 

    In June 2019 the Tokyo 2020 Organising Committee published an overview of plans and launched the Tokyo 2020 COOLING Project to minimise the impact of heat on everyone competing in, attending or working at the Games. These plans included misting sprays; access to additional water (fountains, water bottles for volunteers, allowing spectators to bring in their own water bottles); increasing the shaded areas available; ice baths and additional medical staff for athletes; hats, cooling towels and shortened shifts for volunteers. During the Games Tokyo 2020 will also provide weather forecasts, alerts and information on ways to mitigate heat and treat any resulting symptoms via its official website and mobile applications. Several of these measures have been trialled at test events in the lead up to the Games, however, few have been tried in conjunction with each other. 

    Other changes have included moving the start times for several events, such as the men's, women's and mixed triathlons and equestrian cross-country, to earlier time slots in the mornings. 

    The International Olympic Committee (IOC) also made the decision to move the Olympic marathon and race walking events 800km north to the city of Sapporo. The decision was opposed by the Tokyo Metropolitan Government who had been working on a variety of heat mitigation strategies for the event but has now been finalised. There has also been some pressure to consider moving other events, including the open water swimming and golf to cooler areas. Currently, the IOC has said that they will not be moving any other events. The Paralympic marathon events have not been moved as the temperatures are expected to be lower in Tokyo at that time. 

    A large number or articles and research have been published relating to the expected conditions and potential mitigation strategies for competitors, officials and spectators. In particular, for athletes, early and comprehensive acclimatisation, staying hydrated and pre-cooling strategies have been been highly recommended, including by the International Olympic Committee Beat the Heat resource.  

    Where possible, direct links to full-text and online resources are provided. However, where links are not available, you may be able to access documents directly by searching our licenced full-text databases (note: user access restrictions apply). Alternatively, you can ask your institutional, university, or local library for assistance—or purchase documents directly from the publisher. You may also find the information you’re seeking by searching Google Scholar.

    ReadingReading

    • Anti-heat costs for Tokyo Games rise 2.5 times to 10 billion yen, The Asahi Shimbun, (15 November 2019). Spending on anti-heat measures for the Tokyo Olympics and Paralympics will more than double to about 10 billion yen ($92 million) to protect athletes, spectators and staff from the expected sweltering weather next summer, officials said.
    • Hot to trot: Equine heat issues researched for Tokyo 2020 Olympics, Horsetalk.co.nz, (2 November 2019). Horses competing at the Tokyo Olympic Games next year have an array of science available to help them cope with what is expected to be a hot and humid environment.
    • JMA’s Tokyo 2020 Weather Portal Website for Olympic and Paralympic Games, World Meteorological Organization, (9 August 2019). The Japan Meteorological Agency (JMA) has launched a portal website for access to weather information for the Tokyo 2020 Olympic and Paralympic Games to be held from 24 July to 9 August 2020 and from 25 August to 6 September 2020, respectively. “Tokyo 2020 Weather Portal”
    • Tokyo 2020: The Heat Factor, Christoph Szubski, Sportify Cities, (2016). The 2020 Olympic Games in Tokyo will be held during the city’s summer period, which is the hottest and most humid time of the year. 
    • Tokyo Braces for the Hottest Olympics Ever, John Branch and Motoko Rich, New York Times, (11 October 2019). In 1964, the Tokyo Olympics were held in October. There was a reason for that. It was hot then. It’s hotter now.
    • Training for the heat, Scuttlebutt Sailing News, (21 November 2019). Sam Meech dreads the moment the door to the heat chamber is closed – he knows it’s going to be hot and it’s probably going to hurt – but also realizes it could be the difference when next year’s Olympics roll around.

    Research iconResearch

    • Ambient Conditions Prior to Tokyo 2020 Olympic and Paralympic Games: Considerations for Acclimation or Acclimatization Strategies, Nicola Gerrett, Boris R. M. Kingma, Robert Sluijter, and Hein A. M. Daanen, Frontiers in Physiology, (24 April 2019). The Tokyo Olympics and Paralympic games in 2020 will be held in hot and humid conditions. Heat acclimation (in a climatic chamber) or heat acclimatization (natural environment) is essential to prepare the (endurance) athletes and reduce the performance loss associated with work in the heat. Based on the 1990–2018 hourly meteorological data of Tokyo and the derived wet bulb globe temperature (WBGT) (Liljegren method), Heat Index and Humidex, it is shown that the circumstances prior to the games are likely not sufficiently hot to fully adapt to the heat.
    • Development of a Distributed Modeling Framework to Estimate Thermal Comfort along 2020 Tokyo Olympic Marathon Course, Satoshi Hirabayashi, et.al., Atmosphere, (30 May 2018). Heat stress is an issue for marathon races in the summer, such as the one planned for the 2020 Tokyo Summer Olympic games. The Tokyo Metropolitan Government is planning to grow existing street trees’ canopies to enlarge their shade to reduce air temperature and solar radiation. To formulate a baseline to assess the effect of street trees and buildings on human thermal comfort, Distributed-COMfort FormulA (D-COMFA), a prototype of a distributed computer model using a geographic information system (GIS) was developed. D-COMFA calculates the energy budget of a human body on a 1 m cell basis, using readily available datasets such as weather measurements and polygon data for street structures. D-COMFA was applied to a street segment along the marathon course in Tokyo on an hourly-basis on 9 August 2016, the hottest day in Tokyo in 2016. Our case study showed that the energy budget was positively related to the sky view factor, air temperature, and solar radiation. The energy budget was reduced on average by 26–62% in the shade throughout the day.
    • Exertional-heat stress-associated gastrointestinal perturbations during Olympic sports: Management strategies for athletes preparing and competing in the 2020 Tokyo Olympic Games, Ricardo J.S. Costa, et.al., Temperature, (7 May 2019). There is a growing body of evidence indicating heat exposure during exercise (i.e. exertional-heat stress) can substantially exacerbate these gastrointestinal perturbations, proportionally to the magnitude of exertional-heat stress, which is of major concern for athletes preparing for and competing in the upcoming 2020 Tokyo Olympic Games. To date, various hydration and nutritional strategies have been explored to prevent or ameliorate exertional-heat stress associated gastrointestinal perturbations. The aims of the current review are to comprehensively explore the impact of exertional-heat stress on markers of EIGS, examine the evidence for the prevention and (or) management of EIGS in relation to exertional-heat stress, and establish best-practice nutritional recommendations for counteracting EIGS and associated GIS in athletes preparing for and competing in Tokyo 2020.
    • Health risks and precautions for visitors to the Tokyo 2020 Olympic and Paralympic Games, Sachiko Nakamura, Koji Wada, Naoki Yanagisawa, Derek R. Smith, Travel Medicine and Infectious Disease, Volume 22, pp.3-7, (March-April 2018). In 2020, Japan will host the Tokyo Olympic and Paralympic Games in 2020 (Tokyo 2020) which will involve a large population influx from various countries to Tokyo, the most populated city in Japan. We summarize the potential health risks for visitors to Tokyo 2020, related to communicable disease risks and other health threats, based on recent national and local surveillance reports.
    • Heat-induced hypervolemia: Does the mode of acclimation matter and what are the implications for performance at Tokyo 2020? Lorenz S. Kissling, Ashley P. Akerman  & James D. Cotter, Temperature, (3 September 2019). 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-related issues and practical applications for Paralympic athletes at Tokyo 2020, Katy E. Griggs, Ben T. Stephenson, Michael J. Price & Victoria L. Goosey-Tolfrey, Temperature, (27 June 2019). This review aims to provide an overview of heat-related issues for Paralympic athletes alongside current recommendations to reduce thermal strain and technological advancements in the lead up to the Tokyo 2020 Paralympic Games. When competing in challenging environmental conditions, a number of factors may contribute to an athlete’s predisposition to heightened thermal strain. These include the characteristics of the sport itself (type, intensity, duration, modality, and environmental conditions), the complexity and severity of the impairment and classification of the athlete. For heat vulnerable Paralympic athletes, strategies such as the implementation of cooling methods and heat acclimation can be used to combat the increase in heat strain. At an organizational level, regulations and specific heat policies should be considered for several Paralympic sports. Both the utilization of individual strategies and specific heat health policies should be employed to ensure that Paralympics athletes’ health and sporting performance are not negatively affected during the competition in the heat at the Tokyo 2020 Paralympic Games.
    • Microclimate Variation and Estimated Heat Stress of Runners in the 2020 Tokyo Olympic Marathon, Eichi Kosaka, et.al., Atmosphere, Volume 9(5), (2018). The Tokyo 2020 Olympic Games will be held in July and August. As these are the hottest months in Tokyo, the risk of heat stress to athletes and spectators in outdoor sporting events is a serious concern. This study focuses on the marathon races, which are held outside for a prolonged time, and evaluates the potential heat stress of marathon runners using the COMFA (COMfort FormulA) Human Heat Balance (HBB) Model.
    • Planning for spectator thermal comfort and health in the face of extreme heat: The Tokyo 2020 Olympic marathons, Jennifer K.Vanos, et.al., Science of the Total Environment, Volume 657, pp.904-917, (20 March 2019). The 2020 Olympic Games marathon will be run through the streets of Tokyo on the mornings of August 2nd and 9th, a time of year that is typically hot, sunny, and humid. Few studies have assessed the potential impact of extreme heat along the marathon course to understand the multiple factors (e.g., radiation, wind flow) affecting human thermal comfort (TC) as influenced by urban design and vegetation. The current research establishes a baseline of microclimate conditions and scenarios to estimate the projected TC along the marathon route for spectators.
    • Preventing heat illness in the anticipated hot climate of the Tokyo 2020 Summer Olympic Games, Takeyasu Kakamu, Koji Wada, Derek R. Smith, Shota Endo & Tetsuhito Fukushima , Environmental Health and Preventive Medicine, Volume 22, (2017). To prepare for the upcoming 2020 Summer Olympics and Paralympics in Tokyo, all participants, including the athletes, staff, and spectators, will need to familiarize themselves with Tokyo’s hot and humid summer conditions. This paper uses the wet-bulb globe temperature (WBGT) index, which estimates the risk of heat illness, to compare climate conditions of sports events in Tokyo with the conditions of the past three Summer Olympics (held in Rio de Janeiro, London, and Beijing) and to subsequently detail the need for establishing appropriate countermeasures. 
    • Quantifying Thermal Stress for Sport Events—The Case of the Olympic Games 2020 in Tokyo, Andreas Matzarakis, et.al., Atmosphere, (5 December 2018). The effect of weather on sport events is largely discussed in the sports medicine and exercise physiology context. It is important, both for event organizers and for medical staff, to know whether the competition is happening at a time and place with extreme weather or in general not appropriate weather and climatic conditions. In order to find out, whether a place or time is appropriate, two factors should be included when establishing the effect of atmospheric conditions on visitors and athletes. These are the main climatic conditions, based on long term data, and the quantification of extreme events, like heat waves. The present analysis aims at determining what kind of data are required for an appropriate quantification of weather and climate thermal stress.
    • Thermal comfort along the marathon course of the 2020 Tokyo Olympics, Tsuyoshi Honjo, Yuhwan Seo, Yudai Yamasaki, Nobumitsu Tsunematsu, Hitoshi Yokoyama, Hiroaki Yamato & Takehiko Mikami, International Journal of Biometeorology, Volume 62, pp.1407–1419, (2018). The Olympic Games will be held in Tokyo in 2020 and the period will be the hottest period of the year in Japan.

    resources iconResources

    • Beat The Heat: Olympic Games Tokyo 2020Athlete 365, International Olympic Committee, (2019). This document addresses some “Frequently Asked Questions” about performing in hot and humid ambient conditions and provides recommendations to optimise performance and reduce the risk of heat illness.
    • Climate and Weather Guide for Tokyo 2020 Olympic and Paralympic Games, The Tokyo Organising Committee of the Olympic and Paralympic Games, (August 2019).  
    • Preparation for and Management during Equestrian Events held in thermally challenging environments (PDF  - 952 KB), Dr David Marlin, Dr Martha Misheff & Dr Peter Whitehead, Fédération Equestre Internationale, (March 2018). Whilst ideally all equestrian events would be run in optimal climatic conditions, this is often logistically not possible. Even events planned for ideal conditions can sometimes also experience unusually extreme weather. A significant amount of research has been undertaken and applied at major events since the early 1990s that has led to improved welfare for horses through good advice, event management and improved treatment.
    • Tokyo 2020 Weather Portal Website for Olympic and Paralympic Games, Japan Meteorological Agency, (accessed 8 January 2020). The site provides access to three-hourly and one-week forecasts and UV Index for individual event sites, high-resolution precipitation maps and links to other JMA products including weather warnings/advisories, seasonal forecasts, tropical cyclone analysis/forecasts as well as earthquake and tsunami information. 

    Hyperthermia and optimising health

    Male athlete lying on track
    There are many good open-source fact-sheets and resources available that define the problems associated with hyperthermia and its effects on human health. Collectively, they provide the following information to ensure that you:

    • know what heat illness is
    • understand what makes you more susceptible to heat illness or reduce your exercise tolerance
    • know the symptoms of heat illness
    • can perform strategies to treat a person suffering from a heat-related illness
    Hyperthermia is an abnormally elevated body core temperature that results when the rate of heat gained by the body is greater than the rate of heat loss. A body temperature of 40°C or higher is considered potentially life threatening.

    Heat illness refers to a spectrum of disorders that can be caused by excessive or prolonged exposure to heat, particularly when exercising. Even in temperate conditions, heat illness may occur in those exercising vigorously for more than 45 minutes. As air temperature and relative humidity rises, the risk of heat illness is further increased. However, it is not just environmental temperature that is important, over-exertion, prolonged sun exposure or working out in a poorly ventilated space can also contribute to the body’s inability to dissipate excess heat. If left untreated (i.e., cooling mechanisms remain ineffective, exercise continues) body temperature will continue to rise beyond the body’s ‘healthy’ limits which will lead to progressive functional decline, both physical and cognitive.

    Heat exhaustion is a condition of fatigue caused by prolonged exposure to high temperatures, particularly when combined with high humidity and strenuous activity. A person suffering from heat exhaustion will generally have a core body temperature of less than 40°C, with no neurological symptoms. People who suffer from heat exhaustion usually recover rapidly with assistance.

    Severe cases of heat-stress can lead to heat stroke, which is a life-threatening medical emergency. EHS can occur in previously healthy people, usually when exercising in hot and humid climates. It should be noted that heat exhaustion does not necessarily precipitate EHS. Although relatively rare, EHS is a more serious condition brought about, again, by the body’s inability to dissipate heat to the surrounding environment.

    Event officials should be specifically trained to recognise EHS and begin aggressive treatment in order to prevent further decline. Early diagnosis and appropriate management may improve the outcome for the participant and reduce any risk of injury or permanent organ damage. Although there is no universal definition for this illness, the accepted diagnostic criteria for EHS are central nervous system (CNS) dysfunction (e.g. delirium, coma) and internal (core) body temperature greater than 40°C.

    As the difference between heat exhaustion and heat stroke is not always obvious, athletes who have collapsed following exercise should be actively cooled according to the guidelines. Most importantly, if in doubt, treat for heat stroke. If the person remains seriously ill, confused, vomiting, or shows signs of altered consciousness call an ambulance and seek medical help.

    Is a common medical condition on a hot day and involves a loss of consciousness that is associated with overheating caused by hot environmental conditions or exercising in clothing which restricts heat loss. Participants who collapse after exercise are likely suffering from a post-exercise drop in blood pressure (postural hypotension); the body’s overriding response to defence in maintaining the blood flow to the brain. A collapse as a result of heat-illness during exercise is a sign of heat-stroke.

    Organ damage to liver, kidney, muscle and heart—the progression of heat stroke to multi-organ failure is the consequence of a delicate balance between acute physiologic alterations, direct cytotoxicity of heat and the balance between pro- and anti-inflammatory responses.  

    Signs and symptoms of heat illness
    Use the following list of typical signs and symptoms that a person with heat illness may experience


    Where possible, direct links to full-text and online resources are provided. However, where links are not available, you may be able to access documents directly by searching our licenced full-text databases (note: user access restrictions apply). Alternatively, you can ask your institutional, university, or local library for assistance—or purchase documents directly from the publisher. You may also find the information you’re seeking by searching Google Scholar.

    books iconBooks

    • Exertional Heat Illness: A Clinical and Evidence-Based Guide, William M. AdamsJohn F. Jardine (eds.), Springer, (2019). Provides clinicians, scientists and students with a comprehensive overview of exertional heat illness. Specifically, it addresses the prevention, recognition, treatment, and care of the various medical conditions that fall within the realm of exertional heat illness. 
    • Heat Stress in Sport and Exercise: Thermophysiology of Health and Performance, Julien D. Périard and Sébastien Racinais (eds.), Springer, (2019). The book is designed to provide a flowing description of the physiology of heat stress, the illnesses associated with heat exposure, recommendations on optimising health and performance, and an examination of Olympic sports played in potentially hot environmental conditions. Includes sport-specific chapters including: football/soccer, Australian football and rugby; American football; tennis; athletics; cycling; open-water swimming; and, triathlon and ultra-endurance events in tropical environments. 

    ReadingReading

    • Heat Illness and Endurance Athletes: The Science of Staying Safe When It Gets Hot, Corrine Malcolm, Trainright.com, (accessed 6 January 2020). Many experienced endurance athletes are well versed in hydration and cooling strategies, but as a community it is crucial for all athletes to understand the signs and symptoms of heat illness, how to prevent it, and how to help athletes suffering from it.
    • NATA Offers 10 Tips to Prevent Heat Illness and Dehydration, National Athletic Trainers' Association [USA], (5 July 2018). Many parts of the country are experiencing extreme heat this summer, but for the most part, outdoor activities continue as planned. Young athletes participating in summer and pre-season sports are particularly susceptible in July and August. To guard against heat illnesses and dehydration, the National Athletic Trainers’ Association offers these important recommendations. 

    Report iconReports

    • Exertional heat illness in adolescents and adults: Epidemiology, thermoregulation, risk factors, and diagnosis, Francis G O'Connor and Douglas J Casa, UpToDate, Wolters Kluwer, (last updated 12 November 2018; literature review current through December 2019). Includes information on the epidemiology, risk factors, thermoregulation in the heat, determining risk, basic types and clinical presentation, differential diagnosis, and summary and recommendations relating to exertional heat illness. 
    • Sport & Climate Impacts: How much heat can sport handle? (PDF  – 1.9 MB), Menzies L, The Climate Institute, (2015). Sport is embedded in the lives of Australians, its culture and economy. As with other aspects of Australian life, sport is starting to feel the impact of climate change. This report synthesises recent research on the physical impacts of extreme weather and analyses sport’s vulnerability and resilience. This report finds that most sports are struggling to cope, especially at the local level. Heat policies are often ambiguous and may vary at state, national and international level, with ambiguity about their application. Duty of care thresholds vary within and across sports from 32°C to 41°C. The CSIRO and the Bureau of Meteorology predict the number of days over 35°C across the nation will increase significantly by the end of the century. Hot days will increase 2.5 times in Adelaide, treble in Melbourne and Hobart, quadruple in Sydney, be six times higher in Canberra and 20 times higher in Brisbane. In Perth, for more than two months out of a given year, the mercury will soar over 35°C, as it will for 10 months in Darwin. 

    Research iconResearch 

    • The Application of Heat Stress to Team Sports: Football/Soccer, Australian Football and Rugby, Katie Slattery and Aaron J. Coutts, in 'Heat Stress in Sport and Exercise: Thermophysiology of Health and Performance', Julien D. Périard and Sébastien Racinais (eds.), Springer, pp.181-202, (7 March 2019). This chapter addresses how an added heat stress affects football, Australian football and rugby players during both training and competition. Although these sports are typically played in the cooler winter months, players can still be exposed to hot conditions and this may affect health and performance. It is therefore important to understand how an increased thermal load influences the tactical, technical, physical and psychological constructs that contribute to team sport performance.
    • Crawling to the finish line: why do endurance runners collapse? Implications for understanding of mechanisms underlying pacing and fatigue, St Clair Gibson A, De Koning J, Thompson K, Roberts W, Micklewright D, Raglin J and Foster C, Sports Medicine, Volume 43(6), pp.413-424, (2013). This review provides a comprehensive theoretical understanding of collapses that occur during exercise as a result of postural hypotension, caused by hyperthermia and other conditions. This paper identifies the sequence of dynamic changes in posture and gait, termed the ‘Foster collapse positions’, which might serve as a protective mechanism in the event that the athlete is highly motivated enough to continue their effort to reach the finish line, in the face of catastrophic failure.
    • Dehydration is how you define it: comparison of 318 blood and urine athlete spot checks, Hew-Butler TD, Eskin C, Bickham J, et al., BMJ Open Sport & Exercise Medicine, Volume 4(1), (2018). This article sort to compare blood versus urine indices of dehydration in 318 collegiate athletes undergoing routine screenings. Findings indicate that urine concentration thresholds classified 27%–55% of collegiate athletes as dehydrated, while no athlete was dehydrated according to blood [Na+] measurement. Practitioners should caution against using urine indices to diagnose or monitor dehydration, because urinary output is a response rather than a reflection of (tightly regulated) blood tonicity.
    • Exercise-associated collapse: an evidence based review and primer for clinicians, Asplund C, O’Connor F and Noakes T, British Journal of Sports Medicine, Volume 45(14), pp.1157-1162, (2011). This article looks at exercise-associated collapse (EAC), which commonly occurs after the completion of endurance running events in the absence of neurological, biochemical or thermal abnormalities. EAC is now believed to be principally the result of transient postural hypotension caused by lower extremity pooling of blood once the athlete stops running and the resultant impairment of cardiac baroreflexes. Treatment options are discussed.
    • Exercise in the Heat for Children and Adolescents. Statement from the Commission for Pediatric Sports Medicine, German Society for Sports Medicine and Prevention (PDF  - 274KB), Lawrenz, W., German Journal of Sports Medicine, Volume 70, pp.265-268, (November 2019). › Exertional heat illness in children and adolescents is preventable by different measures. There should be sufficient time for recovery between repeated exercise bouts. Children and adolescents should drink sufficient quantities regularly and provide for sun protection of head and skin. During all athletic events in the heat with participation of children and adolescents, trained personnel and facilities capable of effectively treating all forms of heat illness, should be readily available on site.
    • Exertional Heat Stroke, Navarro, Chelsea S., Casa, Douglas J., Belval, Luke N., & Nye, Nathaniel S., Current Sports Medicine Reports, Volume 16(5), pp.304-305, (2017). EHS is one of the top three causes of sudden death in athletes. Provides an overview of the pathophysiology, risk factors, recognition, and treatment of the condition. 
    • Exertional heat stroke, Adams T, Stacey E, Stacey S, Martin D, British Journal of Hospital Medicine, Volume 73(2), pp.72-78, (2012). A very comprehensive review outlining the potentially lethal condition of exertional heat stroke, providing guidance for recognition and treatment in field conditions.  States that exertional heat stroke is the third highest cause of death for athletes.
    • Exertional heat stroke: Strategies for prevention and treatment from the sports field to the emergency department, Pryor R, Casa D, Holschen, J, O'Connor F and Vandermark L, Clinical Pediatric Emergency Medicine, Volume 14(4), pp.267-278, (2013). Exertional heat illness is a category of conditions commonly seen during sports participation in the hot summer months. Exertional heat stroke, in particular, is a dangerous condition involving hyperthermia and central nervous system dysfunction, which, if not properly treated, is potentially deadly. All on-site medical personnel, emergency physicians, and coaches involved in sports participation need to be aware of the recognition and treatment of heat illnesses. Emergency physicians must be equally aware of recognition, treatment, and return-to-play decisions to ensure athletes are quickly and effectively treated and return to sport participation safely.
    • Exertional heatstroke: clinical characteristics, diagnostic and therapeutic considerations, Zeller L, Novack V, Barski L, Jotkowitz A and Almog Y, European Journal of Internal Medicine, Volume 22(3), pp.296-299, (2011). A retrospective study which suggests that a delayed diagnosis and management of exertional heat stroke may adversely affect outcome. Protracted systemic inflammatory response syndrome (SIRS) may complicate the course of exertional heat stroke.  
    • Exertional heat stroke during a cool weather marathon: a case study, Roberts W, Medicine and Science in Sports and Exercise, Volume 38(7), pp.1197-1203, (2006). This article documents a case study of a well-trained male runner aged in his late 30’s who collapsed before the finish line of a 42.1-km marathon event contested in cool conditions (6-9.5°C and 62-99% r.h.). Despite the cool conditions the runner presented with hyperthermia (40.7°C), respiratory failure leading to intubation, and neurological, renal and cardiology function impairment. He reported having a viral syndrome a week prior to the race and was paced by a ‘fresh’ runner in the last 16 km of the race. Discharge occurred 5 days following the incident and after months of recovery, returned to running problem-free.   
    • Exertional heat stroke: new concepts regarding cause and care (PDF  - 293 KB), Casa D, Armstrong L, Kenny G, O’Connor F and Huggins R, Current Sports Medicine Reports, Volume 11(3), pp.115-123, (2012). When athletes, warfighters, and laborers perform intense exercise in the heat, the risk of exertional heat stroke (EHS) is ever present. The recent data regarding the fatalities due to EHS within the confines of organized American sport are not promising: during the past 35 years, the highest number of deaths in a 5-year period occurred from 2005 to 2009. This reminds us that, regardless of the advancements of knowledge in the area of EHS prevention, recognition, and treatment, knowledge has not been translated into practice. This article addresses important issues related to EHS cause and care. We focus on the predisposing factors, errors in care, physiology of cold water immersion, and return-to-play or duty considerations.
    • Heat Stress and Thermal Strain Challenges in Running, Michael Bergeron, Journal of Orthopaedic & Sports Physical Therapy, Volume:44(10), pp.831–838, (2014). Running well and safely in the heat is challenging for all runners, from recreational to elite. As environmental heat stress (heat stress modulated or augmented by air temperature, humidity, wind speed, and solar radiation) and the intensity and duration of a training run or race increase, so are metabolic heat production, the parallel need for heat transfer from the body to maintain thermal equilibrium, the consequent increase in blood flow to the skin, and the concomitant sweating response progressively and proportionally amplified. An accumulating total body-water deficit from extensive sweating and escalating level of cardiovascular and thermal strain will, in due course, considerably challenge a runner's physiology, perception of effort, and on-course well-being and performance. However, with the appropriate preparation and modifications to planned running intensity and distance, runners can safely tolerate and effectively train and compete in a wide range of challenging environmental conditions. Clinicians play a key role in this regard as an effective resource for providing the most effective guidelines and making the best overall individual recommendations regarding training and competing in the heat.
    • Heat Stress, Hydration, and Heat Illness in Elite Tennis Players, Julien D. Périard and Olivier Girard, in 'Tennis Medicine', Giovanni Di Giacomo, Todd S. Ellenbecker, W. Ben Kibler (eds.), Springer, pp.573-587, (9 January 2019). Tennis is a popular sport predominately played in the summer months on outdoor courts. Compared to cool conditions, playing tennis under heat stress leads to exacerbated thermal (i.e., core and skin temperatures), physiological (e.g., heart rate) and perceptual (e.g., perceived exertion and thermal comfort/sensation) strain, which in turn may influence physical performance and match tactics. 
    • Integrated physiological mechanisms of exercise performance, adaptation, and maladaptation to heat stress, Sawka M, Leon L, Montain S and Sonna L, Comprehensive Physiology, Volume 1(4), pp.1883-1928 (2011). This article emphasizes significant recent advances regarding heat stress and its impact on exercise performance, adaptations, fluid electrolyte imbalances, and pathophysiology.
    • Implementing exertional heat illness prevention strategies in US High School Football, Kerr Z, Marshall S, Comstock R and Casa D, Medicine & Science in Sports & Exercise, Volume 46(1), pp.124 (2014). Approximately 6500 high school football athletes are treated annually for exertional heat illness (EHI). In 2009, the National Athletic Trainers Association (NATA)-led Inter-Association Task Force (NATA-IATF) released preseason heat acclimatization guidelines to help athletes become accustomed to environmental factors contributing to EHI. This study examines compliance with NATA-IATF guidelines and related EHI prevention strategies.A low proportion of surveyed high school football programs fully complied with all 17 NATA-IATF guidelines. However, many EHI prevention strategies were voluntarily implemented. State-level mandated EHI prevention guidelines may increase compliance with recognized best practices recommendations. Ongoing longitudinal monitoring of compliance is also recommended.
    • Managing heat and immune stress in athletes with evidence-based strategies, Pyne D, Guy J and Edwards A, International Journal of Sports Physiology and Performance, Volume 9(5), pp.744-750 (2014). Heat and immune stress can affect athletes in a wide range of sports and environmental conditions. The classical thermoregulatory model of heat stress has been well characterized, as has a wide range of practical strategies largely centered on cooling and heat-acclimation training. In the last decade evidence has emerged of an inflammatory pathway that can also contribute to heat stress. Studies are now addressing the complex and dynamic interplay between hyperthermia, the coagulation cascade, and a systemic inflammatory response occurring after transient damage to the gastrointestinal tract. Damage to the intestinal mucosal membrane increases permeability, resulting in leakage of endotoxins into the circulation. Practical strategies that target both thermoregulatory and inflammatory causes of heat stress include precooling; short-term heat-acclimation training; nutritional countermeasures including hydration, energy replacement, and probiotic supplementation; pacing strategies during events; and postevent cooling measures. Cooperation between international, national, and local sporting organizations is required to ensure that heat-management policies and strategies are implemented effectively to promote athletes' well-being and performance.
    • Misdiagnosis of exertional heat stroke and improper medical treatment, Druyan A, Janovich R and Heled Y, Military Medicine, Volume 176(11), pp.1278-1280, (2011). The following case report depicts a soldier who presented primarily with confusion and behavioural changes during physical exercise and later lost consciousness. He was misdiagnosed by the field physician as suffering from supraventricular tachycardia, was treated as such and only diagnosed as suffering from EHS later in the emergency room. Our main aims are: to highlight the possibility of misdiagnosis of EHS even among trained physicians, to describe the main symptoms of EHS, and to emphasize the importance of early diagnosis and proper treatment.
    • On-site treatment of exertional heat stroke, Sloan, B. K., Kraft, E. M., Clark, D., Schmeissing, S. W., Byrne, B. C., & Rusyniak, D. E., The American Journal of Sports Medicine, Volume 43(4), pp.823–829, (2015).  The purpose of this article was to describe an on-site exertional heat stroke treatment protocol and to compare the outcomes of patients treated on site to those transferred to hospitals. On-site treatment of athletes who develop exertional heat stroke appears to be both safe and effective. On-site treatment may decrease the local burden of critically ill patients to emergency departments during large athletic events. 
    • Overview of Exertional Heat Illness, William M. Adams and John F. Jardine, in  Adams W., Jardine J. (eds) 'Exertional Heat Illness', Springer, (2019). Exertional heat illness (EHI) is a cause for concern in athletic, military, occupational, and recreational settings where individuals are participating in physical activity, especially in hot environmental conditions.
    • The pathopysiology of heat stroke: an integrative view of the final common pathway, Epstein Y, Roberts W, The Scandinavian Journal of Medicine and Science in Sports, Volume 21, pp.742–748, (2011). This review integrates the current theoretical and accepted knowledge of physiological alterations into one model that depicts a common pathway from heat stress to heat stroke.
    • Practical recommendations for endurance cycling in hot/humid environments, Nichols D, Aspetar Sports Medical Journal, Volume 5, (2016). It is well documented that exercise in a warm environment poses a significant thermal challenge to the body and has the potential to reduce exercise performance. The combination of heat production from working muscles and reduction in the rate of heat loss due to high ambient temperatures and/or humidity results in an exacerbated rise in core temperature (hyperthermia) for any given exercise intensity. Hyperthermia per se impairs aerobic performance and consequently decreases power output compared with temperate environments. In addition, dehydration during exercise in the heat further exacerbates the thermal and cardiovascular strain and further impairs aerobic performance. This article provides practical recommendations for athletes and race organisers.
    • Practice beliefs of team physicians regarding the recognition and treatment of exertional heat stroke, Mazerolle S, Pagnotta K, Casa D, McDowell L and Armstrong L, Athletic Training & Sports Health Care: The Journal for the Practicing Clinician, Volume 10(10), (2012). The National Athletic Trainers’ Association and the American College of Sports Medicine each have a position statement for exertional heat illnesses that outlines proper assessment of core body temperature via rectal thermometry (Tre) and treatment via rapid cooling by cold water immersion (CWI). The purpose of this basic inductive research study was to investigate team physicians’ practice beliefs regarding the recognition and immediate treatment of EHS and the ways to increase and promote the use of best practices within the athletic training profession. Many of the participants recognized that in their role as a team physician, they were responsible for promoting best practices, which they believed were Tre and CWI. However, they did not believe it was their professional responsibility to provide educational training for either skill to athletic trainers, but rather that the 2 parties must work together to develop appropriate patient care policies.
    • Preventing heat illness in the anticipated hot climate of the Tokyo 2020 Summer Olympic Game. Takeyasu Kakamu, Koji Wada, Derek R. Smith, Shota Endo and Tetsuhito Fukushima, Environmental Health and Preventive Medicine/BioMed Central, (19 September 2017). Overall, our study suggests that the Tokyo 2020 Summer Olympics will be held amid extremely high WBGT conditions, including at levels deemed poorly suited for conducting sporting events. Combined efforts by all stakeholders during these events will therefore be necessary to deal with these challenging conditions so that athletes can perform their best and so heat illness can be minimized among individuals taking part in these activities. Sporting committees and the Olympic organizing committee should also consider WBGT in selecting venues and the timing of events to help minimize heat illness and enable maximum performance by athletes. Similarly, the organization of the 2020 Tokyo Olympics will need to manage heat as an occupational safety issue for staff and also provide multiple solutions to help heat illness among spectators and tourists.
    • Preventing Death from Exertional Heat Stroke - The Long Road from Evidence to Policy, Casa D, Hosokawa Y, Belval L, Adams W, Stearns R., Kinesiology Review, Volume 6(1), p.99-109, (February 2017). Exertional heat stroke (EHS) is among the leading causes of sudden death during sport and physical activity. However, previous research has shown that EHS is 100% survivable when rapidly recognized and appropriate treatment is provided. Establishing policies to address issues related to the prevention and treatment of EHS, including heat acclimatization, environment-based activity modification, body temperature assessment using rectal thermometry, and immediate, onsite treatment using cold-water immersion attenuates the risk of EHS mortality and morbidity. This article provides an overview of the current evidence regarding EHS prevention and management. The transfer of scientific knowledge to clinical practice has shown great success for saving EHS patients. Further efforts are needed to implement evidence-based policies to not only mitigate EHS fatality but also to reduce the overall incidence of EHS.
    • The second Summer Youth Olympic Games in Nanjing, People's Republic of China: preparing youth athletes to compete in the heat, Brito J, Racinais S and Nassis G, Open Access Journal of Sports Medicine, (1 September 2014). The second Summer Youth Olympic Games took place in Nanjing, People’s Republic of China during the peak of the summer (August). Nanjing has been reported as one of the hottest cities in China, with temperatures reaching as high as 40°C. The estimated average wet bulb globe temperature for Nanjing in August is 32°C, which has been classified as a very high risk/stop play condition for heat illness and injury. Current guidelines for exercise in the heat appear to be inadequate or too conservative, and mostly focus on adult elite athletes. Therefore, proper preventive measures are warranted to reduce the risks of heat illness and injury. With proper heat acclimatisation and monitoring, youth athletes can exercise reasonably well and safely in the heat. Special attention should be devoted to athletes exposed to long and extensive sunny and hot conditions. If proper preventive measures are taken, the risk of heat illness and injury can be greatly reduced.
    • The Use of Technology to Protect the Health of Athletes During Sporting Competitions in the Heat, Borja Muniz-Pardos, et.al., Frontiers in Sports and Active Living, (3 October 2019). Due to the metabolic demands of the sporting events and the high environmental temperatures, the risk of exertional heat stroke (EHS) is high. Careful planning by event organizers are needed to ensure that athletes are protected from irreversible long-term health damage, or even death during sporting competitions in the heat. 
    • What Is the Best Practice for the Treatment of Exertional Heat Illnesses (Heat Cramps, Heat Syncope, Heat Exhaustion, and Exertional Heat Stroke)? Nicholas D. Peterkin, MD; Joseph S. Atkin, MD; Eric E. Coris, MD, Athletic Training and Sports Health Care, Volume 8(3), pp. 97-99, (May 2016). During sports events, monitoring exercising athletes for signs of disease and having a good emergency plan in place for possible EHS is critical for protecting athletes. Heat illness may present as mild heat edema or heat cramps to more severe heat syncope, heat exhaustion, or heat stroke. Early recognition based on signs and symptoms should prompt immediate action to limit progression of injury.

    resources iconResources

    • Exertional heat stroke (EHS), Korey Stringer Institute, Neag School of Education, University of Connecticut, (accessed 6 January 2020).
  • What makes someone more susceptible?

    Significant situational risk factors can contribute to an athlete, official, or spectator being at risk of hyperthermia. It should be noted that individual responses to heat illness vary. 
    Situational risk factors



      • High environmental
        heat load

        (i.e., a wet bulb globe temperature ≥28°C, high solar radiation, low air movement, tail-wind or no wind, water temperature ≥31°C or wearing a wetsuit in water-based sports)

      • Poor race
        scheduling

        (i.e., competition involving moderate to high intensity exercise, previously scheduled,
        in what turns out to be the
        hottest part of the day)

      • Disregarding sport regulations

      • Ignoring symptoms
        of heat illness

      • Improper treatment
        or diagnosis

    Personal risk factors



      • Physical fitness status
        (e.g., low level of fitness or inadequate preparation)

      • History of exertional heat illness

      • Recent or
        current illness

        that may have negative
        residual effects on:
      • .....................................................

        Hydration status
        (e.g., gastrointestinal distress including vomiting, diarrhoea)
        .....................................................
      • .....................................................

        Regulation of body temperature
        (e.g., fever, infection)
        .....................................................

      • Current medication
        (e.g., dopamine re-uptake inhibitors, diuretics)

      • Certain health conditions
        (e.g., diabetes, obesity, cystic fibrosis, genetic mutations, eczema, burns)

      • Extreme motivation
        (e.g., fit individuals have a higher capacity for exercise, so heat production is higher; when coupled with high motivation to resist fatigue, the athlete may place him/herself at risk)

      • Pregnancy

    Data on the effects of exercise on core temperature during pregnancy are limited. Current recommendations suggest that pregnant women should avoid physical activity in excessively hot or humid environments and ensure that they drink sufficient water before, during, and after physical activity. 

    During pregnancy basal metabolic rate, and therefore heat production, is increased above non-pregnant levels, but thermoregulation steadily improves. There is some evidence that during fetal neural tube development (35-42 days from the last menstrual period) raising core body temperature above 39°C can increase the risk of neural tube abnormalities. The International Olympic Committee expert group recommendations indicate that the risk is highest 20–30 days after conception and that hyperthermia should be avoided, especially during the first trimester. The recommendations also suggest that exercising at 60–70% of VO2max in a controlled environment for up to 60 min should be safe as it does not appear to raise core temperature above 38°C.

    Modifiable risk factors



      • Unmatched physical exertion to physical fitness

      • Excessive metabolic heat gains
        (e.g., prolonged warm-up or activity other than racing)

      • Excessive environmental heat gain
        (e.g., pre-race exposure, inappropriate clothing)

      • Competition scheduling
        (e.g., research expected climate for location, phase of season and time of day)

      • Motivation
        (e.g., to achieve personal best or the challenge of beating another competitor or winning)

      • Improper acclimatisation

      • Dehydration

      • Insufficient sleep/rest

      • Low physical fitness

      • Inappropriate or excessive clothing

      • Race format/execution
        (e.g., aggressive tactics requiring an ‘all-out’ effort)

    What to do?

    What to do
    if you think someone is suffering from heat-illness?


      • Stop exercise immediately

      • Remove them from field/area of play

      • Assess internal (core) temperature

      • Remove excessive clothing

      • Lie down in shade or cool place

      • Raise legs and pelvis to improve blood pressure

      • Cool by wetting skin liberally and vigorous fanning to enhance evaporative cooling

      • Apply ice to groin, armpits and neck

      • Give cool water if conscious

      • Call ambulance by dialing Triple Zero (000) in Australia

      • Monitor symptoms

    Adams et al. suggests the TABC acronym for the modification to the usual first aid resuscitation algorithm, where ‘T’ represents the immediate consideration being given to the core body temperature. Rectal temperature should be periodically performed in any competitor who has collapsed or lost consciousness at the end of a sporting event. Cooling can be ceased once rectal temperature reaches 38.5°C to avoid over-cooling (termed ‘after-drop’ or rebound hyperthermia).

    Rectal temperature (Tre) is the “gold-standard” method for assessing internal (core) body temperature and is also the preferred and recommended method to accurately assess body temperature in the case of diagnosing heat stroke. However, cooling should not be delayed in an individual suspected of exertional heat stroke where rectal temperature monitoring is not possible. 

    Currently, Sports Medicine Australia only recognises rectal temperature as a valid measure of internal (core) body temperature.  

    • Exertional heat stroke, Adams T, Stacey E, Stacey S, Martin D, British Journal of Hospital Medicine, Volume 73(2), pp.72-78, (2012).  

    The severity of complications of heat-stroke increases with the duration of the high body temperature. Two important therapeutic objectives in patients with exertional heat stroke are cooling and supporting system function. The outcome (severity) of any heat-related injury heavily relies on:

    1

    10min
    Rapid treatment

    (i.e., immediate; within 10 min of heat stroke)

    2

    tick
    Appropriate treatment

    (i.e., consider what access you have to facilities
    or cooling methods)

    The relevant research indicates that not only survival, but full recovery occurs in the vast majority of cases if the athlete is treated promptly using aggressive cooling strategies. Athletes with rectal temperatures greater than 42°C and profound neurological dysfunction who are identified and treated appropriately often leave first-aid care without hospitilisation or resulting injuries.     

    Iced-water immersion with circulated water is superior for rapidly and effectively reducing body temperature, and considered the ‘gold standard’ treatment for exercised induced hyperthermia. Although, this may be impractical due to the condition of the patient [e.g., presence of vomiting or diarrhoea or the need to perform cardiopulmonary resuscitation (CPR)], or logistical difficulties [i.e., the location of patient to an appropriate facility] at an event. As one of the most important objectives in treating heat stroke is to decrease body temperature as quickly as possible, an alternative method including whole-body cold water accompanied by ice massage of major muscle groups is also recommended, although cooling rates are not as high. Other strategies including the application of ice or iced-water soaked towels, cold water immersion of the extremities, or continuously running cold water over the skin, may be used to facilitate cooling.

    “Cool first - transport second”. One of the most controversial aspects of exertional heat stroke care is the concept that reducing the level of hyperthermia via cooling takes precedence over transferring the patient to obtain further medical care. It is recommended that 20 minutes of effective cooling be used on-site before the patient is taken to hospital, such that rectal temperature is reduced to less than 39°C.    

    In the acute recovery phase following exertional heat stroke (i.e., hour/s), patients should have achieved the following to be discharged from medical care:


      • stable normal resting body temperature established

      • tolerate oral fluids

      • pass urine

      • return to normal cognition

    Naturally, athletes will then want to know when they can safely return to training and competition. In the absence of appropriate evidence-based recommendations due to ethical limitations that prevent withholding appropriate care, the current recommendations are based on common sense to ensure a closely supervised and carefully planned incremental return to physical activity. Current research indicates that most individuals recover completely for exertional heat stroke within a few weeks, but this may vary up to 15 months.

    Return to play
    Baseline minimum recommendations from experts to guide the return to play


      • 1


        Refrain from exercise for 7 days following the exertional heat episode
      • 2


        Visit a physician to assure no residual signs and symptoms and for clearance to begin light exercise
      • 3


        Perform light exercise indoors in air-conditioned facility until well tolerated
      • 4


        Perform intense exercise indoors in air-conditioned facility until well tolerated
      • 5


        Within 4 weeks of episode, undergo an exercise heat-tolerance test (HTT) to gain approval for progressing to exercising in the heat
      • 6


        Perform light exercise in the heat until well tolerated
      • 7


        Perform light exercise in the heat in full equipment until well tolerated
      • 8


        Perform intense exercise in the heat in full equipment until well tolerated
      • 9


        After 2-4 weeks of achieving heat tolerance with vigorous activity, the athlete may return to normal practice or game conditions

    Many people today spend the majority of their time in climate controlled environments (i.e. air-conditioned homes, cars, schools, workplaces, etc.). This can lead to difficulties when starting an exercise program/training/competing in the heat and requires a process of acclimatisation. 

    Exercise in the heat induces physiological adaptations that improve thermoregulation, attenuate physiological strain, and can reduce the risk of serious heat illness. Heat acclimatisation can improve aerobic performance in warm/hot environments and potentially in temperate environments. Given adequate water and protection from the sun, a healthy individual can adapt (within individual limits) to extended exposure to natural weather-related heat stress.

    The adaptations include increased sweat rate, decreased sweat sodium and chloride concentrations, improved skin blood flow, lowered body temperatures, reduced cardiovascular strain, improved fluid balance, altered metabolism, and enhanced cellular protection. The magnitudes of these adaptations are determined by the intensity, duration, frequency, and number of heat exposures. Environmental conditions (i.e. dry or humid heat) influence adaptation, as well as individual variability of one’s genotype.

    The effect of heat acclimation on submaximal exercise performance can be quite dramatic and occur within a matter of days, such that acclimated individuals can easily complete tasks in the heat that would otherwise be difficult. Full adaptation to high intensity exercise, as experienced in competition in the heat, may take weeks. The greatest adaptations occur within the first week and the thermoregulatory benefits of heat acclimation are generally thought to be complete after 10 days to 2 weeks exposure; however, additional small improvements in physiological tolerance may take longer.

    It is important to be aware that variations in an individual's typical daily routine, such as sleep loss, poor nutrition, glycogen depletion, bacterial and viral infections, and certain medications can delay heat acclimatisation. When additional stressors such as these are present, it is prudent to reduce the duration of exercise and heat exposures accordingly, and temporarily reduce performance expectations.

    Heat acclimation is transient and gradually disappears if the athlete does not maintain continued and repeated heat exposure. There is no consistent agreement concerning the rate of decay for heat acclimation. It appears that adaptations that occur quickly, such as heart rate improvement, also decay more rapidly than thermoregulatory adaptations that take longer to respond. Many studies report the beneficial effects of 2 weeks heat acclimatisation can be maintained for approximately one month.

    Evidence is also emerging that inducing heat acclimation outdoors in a natural field setting may provide more specific adaptations based on direct exposure to the exact environmental and exercise conditions to be encountered during competition; rather than acclimation protocols conducted in a laboratory setting.

    Where possible, direct links to full-text and online resources are provided. However, where links are not available, you may be able to access documents directly by searching our licenced full-text databases (note: user access restrictions apply). Alternatively, you can ask your institutional, university, or local library for assistance—or purchase documents directly from the publisher. You may also find the information you’re seeking by searching Google Scholar.

    books iconBooks

    • Exertional Heat Illness: A Clinical and Evidence-Based Guide, William M. AdamsJohn F. Jardine (eds.), Springer, (2019). Provides clinicians, scientists and students with a comprehensive overview of exertional heat illness. Specifically, it addresses the prevention, recognition, treatment, and care of the various medical conditions that fall within the realm of exertional heat illness. 
    • Heat Stress in Sport and Exercise: Thermophysiology of Health and Performance, Julien D. Périard and Sébastien Racinais (eds.), Springer, (2019). The book is designed to provide a flowing description of the physiology of heat stress, the illnesses associated with heat exposure, recommendations on optimising health and performance, and an examination of Olympic sports played in potentially hot environmental conditions. Includes sport-specific chapters including: football/soccer, Australian football and rugby; American football; tennis; athletics; cycling; open-water swimming; and, triathlon and ultra-endurance events in tropical environments. 

    ReadingReading

    • Extreme heat in sport: why using a fixed temperature cut-off isn’t as simple as it seems, Ollie Jay, Associate Professor, Exercise and Sport Science; Director, Thermal Ergonomics Laboratory, University of Sydney & Samuel Chalmers, Postdoctoral Fellow in Sport Physiology and Performance, Western Sydney University, The Conversation, (12 January 2018). There are several factors that must be collectively considered when predicting heat stress risk of an athlete.
    • It’s time for Australia to change its attitude to extreme heat, Liz Hanna, Australian National University, The Conversation, (21 January 2014). Complacency can kill. You would have to be living under a rock to be unaware that heat exposure can be deadly. Yet every year Australia – supposedly the “clever country” – endangers the lives of everyone from elite athletes to construction workers by making them work in the summer heat.
    • Management of exertional heat stroke: a practical update for primary care physicians, Edward Walter and Kiki Steel, British Journal of General Practice, Volume 68(668), pp.153-154, (2018). A GP may have contact with athletes in one of three ways: a patient seeking advice before participation in a race; the GP providing medical cover on race day; or afterwards if a patient has suffered from EHS. This article aims to highlight current advice and research areas in the treatment of a patient.
    • New Law Requiring Training in Heat Illness for all California Coaches Takes Effect January 1, 2019California Interscholastic Federation, (accessed 6 January 2020). on June 1, 2018 AB 2800, California High School Coaching Education and Training Program: heat illness, was signed into law by Governor Brown that now will require coaches when renewing their CPR/FIRST AID, Concussion and Sudden Cardiac Arrest (SCA) certification that they also complete training in the signs and symptoms of heat illness. The law takes effect on January 1, 2019.
    • Prolonged exercise in the heat (PDF  - 376 KB), Periard J, ASPETAR Sports Medicine Journal, Volume 2(1), pp.8-15, (2013). An article outlining the impact of prolonged exercise performance in hot conditions which details strategies to optimise performance and improve heat tolerance. 

    Report iconReports

    Research iconResearch 

    • A heat acclimation protocol for team sports, Sunderland c, Morris J and Nevill M, British Journal of Sports Medicine, volume 42(5), (2008). This study assesses the impact of an acclimation protocol base upon intermittent high-intensity exercise, as found in many team sports. The impact of four short heat acclimation sessions (30-45 minutes duration, each session) of high-intensity intermittent running the heat (30 degrees C) and 27% relative humidity was examined on female athletes. Subjects were divided into three groups: (1) an intermittent high-intensity exercise group; (2) a moderate training group, and; (3) a control group that did not train, but was exposed to the same heat conditions. In a post-acclimation trial distance run, the capacity of the intermittent exercise group (i.e. acclimation group) was increased by 33%, but was unchanged in the moderate and control groups. The acclimation group had a lower rectal temperature and slower rate of rise in rectal temperature, and an increase in self-reported thermal comfort after acclimation.
    • Acute whole-body cooling for exercise-induced hyperthermia: a systematic review, McDermott B, Casa D, Ganio M, Lopez R, Yeargin S, Armstrong L and Maresh C, Journal of Athletic Training, Vollume 44(1), pp.84-93, (2009). This article discusses the literature supporting a range of cooling methodologies for the treatment of exercise-induced hyperthermia. This article suggests that iced-water immersion should be included if possible, but continual dousing of the patient combined with fanning and continually rotating cold wet towels represents a viable alternative until advanced cooling is possible. Cooling before transfer to hospital cannot be overemphasised. 
    • Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports, Periard J, Racinais S and Sawka M, Scandinavian Journal of Medicine & Science in Sports, Volume 25(Supplement 1), (2015). This review examines the physiological adaptations associated with heat acclimation induction regimens, and emphasises their application to competitive athletes and sports.
    • Age-related decrements in heat dissipation during physical activity occur as early as the age of 40, Larose J, Boulay P, Sigal R, Wright H and Kenny G, PLOS one, Volume 8(12), e83148 (2013). Older adults typically experience greater levels of thermal strain during physical efforts in the heat compared to young individuals. While this may be related to an age-dependent reduction in whole-body sweating, no study has clearly delineated at what age this occurs. In the present study, we report direct measurements of human heat dissipation during physical activity in the heat in males ranging in age from 20–70 years. Over the sum of two hours, the change in body heat content was greater in males 40–70 years compared to young males (all P<0.05). Our findings suggest that middle-aged and older adults have impairments in heat dissipation when doing physical activity in the heat, thus possibly increasing their risk of heat-related illness under such conditions.
    • American College of Sports Medicine Roundtable on Exertional Heat Stroke—return to duty/return to play: Conference Proceedings, O’Connor F, Casa D, Bergeron M, Carter R, Deuster P, Heled Y. Kark J, Leon L, McDermott B, O’Brien K, Roberts W and Sawka M, Current Sports Medicine Reports, Volume 9(5), pp.314-321, (2010). On 22-23 October 2008, an ACSM Roundtable was convened to discuss return-to-play or return-to-duty for people who have experienced exertional heat illness (EHI) and to develop consensus-based recommendations. Although the group was unable to move forward with new consensus recommendations, they clearly documented critical clinical concerns and scientific questions, including the following: 1) no uniform core definitions of EHI; 2) limited validated criteria to assess recovery from exertional heat stroke (EHcasaS); and 3) inadequate ability to predict who may be predisposed to a subsequent heat injury after EHS. Areas of potential future research are identified.
    • Analysis of heat illness policies and guidelines published by sports organisations in Victoria, Australia [powerpoint presentation] (PDF  – 1.8 MB), Prasanna Gamage, Australian Centre for Research into Injury in Sport and its Prevention (ACRISP), (2017). Provides an overview of the research which analysed 25 documents from Victorian sports organisations. The research highlighted the gaps and limitations of existing documents, with considerable variation in quality and contents, and a clear suggestion for them to be revised and updated with more current and comprehensive information. A conference abstract on this topic is also available
    • An Exertional Heat Stroke Survivor's Return to Running: An Integrated Approach on the Treatment, Recovery, and Return to Activity, Adams WM, Hosokawa Y, Huggins RA, Mazerolle SM, Casa DJ., Journal of Sport Rehabilitation, Volume 25(3), (August 2016). This case supports prior literature examining the factors that predispose individuals to EHS. Although evidence-based best practices regarding prompt recognition and treatment of EHS ensure survival, this case highlights the lack of medical follow-up and physician-guided return to activity after EHS.
    • Application of evidence-based recommendations for heat acclimation: Individual and team sport perspectives, J. Luke Pryor, et,al., Temperature, Volume 6(1), pp.37-49. (13 October 2018). Heat acclimation or acclimatization (HA) occurs with repeated exposure to heat inducing adaptations that enhance thermoregulatory mechanisms and heat tolerance leading to improved exercise performance in warm-to-hot conditions. HA is an essential heat safety and performance enhancement strategy in preparation for competitions in warm-to-hot conditions for both individual and team sports. Yet, some data indicate HA is an underutilized pre-competition intervention in athletes despite the well-known benefits; possibly due to a lack of practical information provided to athletes and coaches. Therefore, the aim of this review is to provide actionable evidence-based implementation strategies and protocols to induce and sustain HA.
    • The Association between Mandated Preseason Heat Acclimatization Guidelines and Exertional Heat Illness during Preseason High School American Football Practices, Zachary Y. Kerr, et.al., Environmental Health Perspectives, (10 April 2019). The risk of heat-related illness and death may continue to increase in many locations as a consequence of climate change, but information on the effectiveness of policies to protect populations from the adverse effects of excessive heat is limited. In 2009, the National Athletic Trainers’ Association Inter-Association Task Force (NATA-IATF) released guidelines to reduce exertional heat illness (EHI) among U.S. high school athletes participating in preseason sports activities, including preseason practice sessions for American football. A subset of state high school athletic associations have implemented state-mandated guidelines consistent with the 2009 NATA-IATF recommendations, but their effectiveness for reducing preseason EHI is unknown. Our findings suggest that high school athletes would benefit from enactment of the 2009 NATA-IATF guidelines. Similar analyses of the effectiveness of other public health policies to reduce adverse health effects from ambient heat are warranted.
    • Aural canal, esophageal, and rectal temperatures during exertional heat stress and the subsequent recovery period, Gagnon D, Lemire B, Jay O and Kenny G, Journal of Athletic Training, Volume 45(2), pp.157-163, (2010). The measurement of body temperature is crucial for the initial diagnosis of exertional heat injury and for monitoring purposes during a subsequent treatment strategy. However, little information is available about how different measurements of body temperature respond during and after exertional heat stress. We found that Tac, Tes, and Tre presented different temporal responses during and after both scenarios of exertional heat stress and a subsequent recovery period. Although these results may not have direct practical implications in the field monitoring and treatment of individuals with exertional heat injury, they do quantify the extent to which these body temperature measurements differ in such scenarios.
    • Core temperature measurement: methods and current insights, Moran D, Mendal L, Sports Medicine, Volume 32(14), pp.879-885 (2002). The purpose of this paper is to review the various existing methods of T(c) measurements in order to focus on the breakthrough needed for a simple, noninvasive, universally used device for T(c) measurement which is essential for preventing climatic injuries during sports events.
    • Effect of short-term heat acclimation on endurance time and skin blood flow in trained athletes, Chen T, Tsai P, Lin J, Lee N and Liang M, Journal of Sports Medicine, (18 June 2013). This study examined whether short-term (i.e. five days) vigorous cycling exercise and heat exposure could achieve heat acclimatisation in trained athletes and the effect of heat acclimatisation on cutaneous blood flow. This research concluded that heat acclimatisation can be achieved with five sessions of high-intensity cycling exercise in the heat in trained athletes. It found that redistribution of cutaneous blood flow in the skin and exercising muscle, and enhanced cardiovascular adaptations, provide the heat-acclimated athletes with the capability to increase their endurance time in a hot environment.
    • Effects of active warm up on thermoregulation and intermittent-sprint performance in hot conditions, Bishop D and Maxwell N, SmartPlay research details (2009). The aim of the research was to determine the effect of active warm-up on team-sport performance in a hot environment (35 degrees Celsius) by simulating the metabolic and thermoregulatory responses of trained team-sport athletes.
    • Exercise in the Heat for Children and Adolescents. Statement from the Commission for Pediatric Sports Medicine, German Society for Sports Medicine and Prevention (PDF  - 274KB), Lawrenz, W., German Journal of Sports Medicine, Volume 70, pp.265-268, (November 2019). › Exertional heat illness in children and adolescents is preventable by different measures. There should be sufficient time for recovery between repeated exercise bouts. Children and adolescents should drink sufficient quantities regularly and provide for sun protection of head and skin. During all athletic events in the heat with participation of children and adolescents, trained personnel and facilities capable of effectively treating all forms of heat illness, should be readily available on site.
    • Exertional heat illness: the role of heat tolerance testing, Kazman J, Heled Y, Lisman P, Druyan A, Deuster P and O’Connor F, Current Sports Medical Reports, Volume 12(2), pp.101-105, (2013). Exertional heat stroke (EHS) is a common clinical problem for both athletes and warriors; however, evidence-based guidance for return-to-play/duty (RTP/RTD) decisions is limited. Heat tolerance testing (HTT) has been proposed as a potential tool that, when combined with appropriate clinical information, may assist in RTP/RTD decisions. However, currently, no standard of care is available for performing HTT. The Israeli Defense Forces (IDF) HTT protocol, which was developed over decades of careful research, has proven useful for IDF warriors and is utilized by other militaries to assist in RTD decisions. The present case studies are used to discuss the efficacy of the IDF HTT in determining RTD for two warriors who experienced EHS. Strengths and limitations of the IDF HTT, along with current and potential roles in clinical decision-making and in future thermoregulation research, are discussed.
    • Exertional heat illness risk factors and physiological responses of youth football players, Susan W.Yeargin, et.al., Journal of Sport and Health Science, (7 March 2019). Research aimed to determine which intrinsic and extrinsic exertional heat illness (EHI) risk factors exist in youth American football players and observe perceptual and physiological responses of players during events (games and practices). Extrinsic (disproportionate work ratios, environmental conditions) and intrinsic (higher body mass index) EHI risk factors exist in youth football. Certain risk factors may be influenced by event and league type. National youth football organizations need to create thorough guidelines that address EHI risk factors for local leagues to adopt.
    • Exertional Heat Stroke, the Return to Play Decision, and the Role of Heat Tolerance Testing: A Clinician's Dilemma, O'Connor, Francis G. Current Sports Medicine Reports, Volume 17(7), pp.244-248, (July 2018). Although clear guidelines have been established for successful treatment of EHS, the process of safely returning individuals to play/duty is not well established (3–5). This gap in clinical knowledge is due largely to the practical and ethical challenges of systematically researching potential assessment and treatment approaches in a human population. This special communication reviews current guidance on RTP/D decisions after an EHS event, discusses the current literature and evidence base for addressing heat tolerance, and examines the risks of further EHS events. In particular, we address the potential role of heat tolerance testing in the decision process.
    • Heat Acclimatization and Exertional Heat Illness Prevention in Youth Football Programs, Poole, Jordan A, Stearns, Rebecca L., & Lopez, Rebecca M., Strength & Conditioning Journal, Volume 39(2), (April 2017). The purpose of this article is to review the existing literature regarding thermoregulation of younger athletes and to provide guidelines for coaches and clinicians on how to prevent ehi for safer participation in youth football.
    • Heat acclimatization to improve athletic performance in warm-hot environments, Sawka M, Periard J and Racinais S, Gatorade Sport Science Exchange # 153, (201?). Generally about 1-2-weeks of daily exposures of 90 minutes are required; but highly aerobic fit athletes can heat acclimatise in half that time. Heat acclimatisation is specific to the climatic heat stress (desert or tropic) and physical exercise intensities the athletes are exposed to, which should simulate the expected competitive environment.
    • Implementing exertional heat illness prevention strategies in US High School Football, Kerr Z, Marshall S, Comstock R and Casa D, Medicine & Science in Sports & Exercise, Volume 46(1), pp.124-130, (2014). Approximately 6500 high school football athletes are treated annually for exertional heat illness (EHI). In 2009, the National Athletic Trainers Association (NATA)-led Inter-Association Task Force (NATA-IATF) released preseason heat acclimatization guidelines to help athletes become accustomed to environmental factors contributing to EHI. This study examines compliance with NATA-IATF guidelines and related EHI prevention strategies. A low proportion of surveyed high school football programs fully complied with all 17 NATA-IATF guidelines. However, many EHI prevention strategies were voluntarily implemented. State-level mandated EHI prevention guidelines may increase compliance with recognized best practices recommendations. Ongoing longitudinal monitoring of compliance is also recommended.
    • Managing heat and immune stress in athletes with evidence-based strategies, Pyne D, Guy J and Edwards A, International Journal of Sports Physiology and Performance, Volume 9, pp.744-750, (2014). Heat and immune stress can affect athletes in a wide range of sports and environmental conditions. The classical thermoregulatory model of heat stress has been well characterized, as has a wide range of practical strategies largely centered on cooling and heat-acclimation training. In the last decade evidence has emerged of an inflammatory pathway that can also contribute to heat stress. Studies are now addressing the complex and dynamic interplay between hyperthermia, the coagulation cascade, and a systemic inflammatory response occurring after transient damage to the gastrointestinal tract. Damage to the intestinal mucosal membrane increases permeability, resulting in leakage of endotoxins into the circulation. Practical strategies that target both thermoregulatory and inflammatory causes of heat stress include precooling; short-term heat-acclimation training; nutritional countermeasures including hydration, energy replacement, and probiotic supplementation; pacing strategies during events; and postevent cooling measures. Cooperation between international, national, and local sporting organizations is required to ensure that heat-management policies and strategies are implemented effectively to promote athletes' well-being and performance.
    • Misdiagnosis of exertional heat stroke and improper medical treatment, Druyan A, Janovich R and Heled Y, Military Medicine, Volume 176(11), pp.1278-1280, (2011). The following case report depicts a soldier who presented primarily with confusion and behavioural changes during physical exercise and later lost consciousness. He was misdiagnosed by the field physician as suffering from supraventricular tachycardia, was treated as such and only diagnosed as suffering from EHS later in the emergency room. Our main aims are: to highlight the possibility of misdiagnosis of EHS even among trained physicians, to describe the main symptoms of EHS, and to emphasize the importance of early diagnosis and proper treatment.
    • National Collegiate Athletics Association strength and conditioning coaches’ knowledge and practices regarding prevention and recognition of exertional heat stroke, Valdes A,  Hoffman J, Clark M and Stout J, Journal of Strength and Conditioning Research, Volume 28(11), pp.3013-3023 (2014). The purpose of this study was to assess and determine content knowledge of National Collegiate Athletic Association Strength and Conditioning Coaches (SCCs) regarding prevention and recognition of exertional heat stroke (EHS) and to determine whether the type of professional certification is an indicator of enhanced content knowledge. In conclusion, SCCs seemed to lack essential knowledge to prevent or recognize EHS in each of the factors assessed. It is recommended that consideration be given to include EHS prevention and recognition competencies as part of the professional preparation and certification requirements for SCCs.
    • Neuromuscular function following prolonged intense self-paced exercise in hot climatic conditions,  Périard J, Cramer M, Chapman P, Caillaud C and Thompson M, European Journal of Applied Physiology, Volume 111(8), pp.1561-1569, (2011). Muscle weakness following constant load exercise under heat stress has been associated with hyperthermia-induced central fatigue. However, evidence of central fatigue influencing intense self-paced exercise in the heat is lacking. The purpose of this investigation was to evaluate force production capacity and central nervous system drive in skeletal muscle pre- and post-cycle ergometer exercise in hot and cool conditions. Voluntary activation during the post-exercise MVC declined to 93.7% (hot) and 93.9% (cool) (P < 0.05 vs. control). The post-exercise decline in voluntary activation represented ~20% of the decrease in mean force production in both conditions. Therefore, the additional increase in rectal temperature did not exacerbate the loss of force production following self-paced exercise in the heat. The impairment in force production indicates that the fatigue exhibited by the quadriceps is mainly of peripheral origin and a consequence of the prolonged contractile activity associated with exercise.
    • Practical recommendations for endurance cycling in hot/humid environments, Nichols D, Aspetar Sports Medical Journal, Volume 5, (2016). It is well documented that exercise in a warm environment poses a significant thermal challenge to the body and has the potential to reduce exercise performance. The combination of heat production from working muscles and reduction in the rate of heat loss due to high ambient temperatures and/or humidity results in an exacerbated rise in core temperature (hyperthermia) for any given exercise intensity. Hyperthermia per se impairs aerobic performance and consequently decreases power output compared with temperate environments. In addition, dehydration during exercise in the heat further exacerbates the thermal and cardiovascular strain and further impairs aerobic performance. This article provides practical recommendations for athletes and race organisers.
    • Predisposing Factors for Exertional Heat Illness, J. Luke Pryor, Julien D. Périard, Riana R. Pryor, in 'Exertional Heat Illness: A Clinical and Evidence-Based Guide', William M. Adams and John F. Jardine (eds.), Springer, pp.29-57, (21 November 2019). Exertional heat illnesses constitute an array of medical conditions comprising mild (heat syncope, heat rashes, exercise-associated muscle cramping, and heat exhaustion) to life-threatening disorders (exertional heat stroke). It is imperative that individuals, practitioners, and policymakers are well informed about the risk of and predisposing factors to exertional heat illnesses. Primary among these risk factors is heat stress which is the result of the combined effects of protective equipment or clothing, metabolic rate, and environmental conditions. Heat stress is a known hazard to both physical performance and health (e.g., exertional heat illness risk). Modifiable and non-modifiable risk factors are discussed as well as preventative strategies to mitigate the influence of heat stress and exertional heat illness risk.
    • Preventing heat illness in the anticipated hot climate of the Tokyo 2020 Summer Olympic Game. Takeyasu Kakamu, Koji Wada, Derek R. Smith, Shota Endo and Tetsuhito Fukushima, Environmental Health and Preventive Medicine/BioMed Central, (19 September 2017). Overall, our study suggests that the Tokyo 2020 Summer Olympics will be held amid extremely high WBGT conditions, including at levels deemed poorly suited for conducting sporting events. Combined efforts by all stakeholders during these events will therefore be necessary to deal with these challenging conditions so that athletes can perform their best and so heat illness can be minimized among individuals taking part in these activities. Sporting committees and the Olympic organizing committee should also consider WBGT in selecting venues and the timing of events to help minimize heat illness and enable maximum performance by athletes. Similarly, the organization of the 2020 Tokyo Olympics will need to manage heat as an occupational safety issue for staff and also provide multiple solutions to help heat illness among spectators and tourists.
    • Reducing sports heat illness risk, Bergeron M, Pediatrics, Volume 34(6), (June 2013). 
    • Short-term heat acclimation training improves physical performance: a systematic review, and exploration of physiological adaptations and application for team sports, Chalmers S, Esterman A, Eston R, Bowering K, and Norton K, Sports Medicine, Volume 44(7), (2014). Many studies have demonstrated that longer-term heat acclimation training (≥8 heat exposures) improves physical performance. The aim of this systematic review was to determine if seven or fewer heat exposures can improve physical performance in healthy adults. The review identified that aerobic-based performance benefit from short-term heat acclimation (STHA) training. This is possibly through a number of cardiovascular, thermoregulatory, and metabolic adaptations improving the perception of effort and fatigue through a reduction in anaerobic energy release and elevation of the anaerobic threshold. These results should be viewed with caution due to the level of available evidence, and the limited number of papers that met the inclusion criteria of the review. STHA training can be applied in a team-sport environment during a range of instances within the competitive season. A mixed high-intensity protocol may only require five sessions of60 minutes duration to potentially improve aerobic-based performance in trained athletes.
    • Specific exercise heat stress protocol for a triathlete's return from exertional heat stroke, Johnson E, Kolkhorst F, Richburg A, Schmitz A, Martinez J and Armstrong L, Current Sports Medical Reports, Volume 12(2), pp.106-109, (2013). A triathlete collapsed with exertional heatstroke (EHS) during 2 races over 3 months. The American College of Sports Medicine recommends a heat tolerance test (HTT) following EHS if there is a concern with return to play. The classical walking HTT may not be the best test to evaluate elite triathletes' heat tolerance due to race intensity, nor is it suited to evaluate acclimation ability, which may play a role in risk of heat illness. Is the athlete capable of returning to racing or should he retire from sport due to heat intolerance? Up to 90 min of cycling (70% of V˙O2max; 36°C, 50% relative humidity) was followed by 9 d of exercise heat acclimation and a final identical exercise heat stress test. After acclimation, exercise duration before reaching a gastrointestinal temperature (Tgi) of 39.5°C increased 25 min, sweat rate increased 0.5 L·h, initial Tgi decreased 0.85°C, and rate of Tgi rise decreased 0.6°C·h. Adaptations were deemed acceptable, and the athlete was allowed to return to competition. The athlete has since raced in hot environments without incident.
    • Validity and reliability of devices that assess body temperature during indoor exercise in the heat, Ganio M, Brown C, Casa D, Becker S, Yeargin S, McDermott B, Boots L, Boyd P, Armstrong L and Maresh C, Journal of Athletic Training, Volume 44(2), pp.124-135, (2009). To assess the validity and reliability of commonly used temperature devices compared with rectal temperature in individuals exercising in a controlled, high environmental temperature indoor setting and then resting in a cool environment. Even during laboratory exercise in a controlled environment, devices used to measure forehead, temporal, oral, aural, and axillary body sites did not provide valid estimates of rectal temperature. Only intestinal temperature measurement met the criterion. Therefore, we recommend that rectal or intestinal temperature be used to assess hyperthermia in individuals exercising indoors in the heat.
    • Validity of devices that assess body temperature during outdoor exercise in the heat, Casa D, Becker S, Ganio M, Brown C, Yeargin S, Roti M, Siegler J, Blowers J, Glaviano N, Huggins R, Armstrong L and Maresh C, Journal of Athletic Training, Volume 42(3), pp.333-342, (2007). Rectal temperature is recommended by the National Athletic Trainers' Association as the criterion standard for recognizing exertional heat stroke, but other body sites commonly are used to measure temperature. Few authors have assessed the validity of the thermometers that measure body temperature at these sites in athletic settings. Compared with rectal temperature (the criterion standard), gastrointestinal temperature was the only measurement that accurately assessed core body temperature. Oral, axillary, aural, temporal, and field forehead temperatures were significantly different from rectal temperature and, therefore, are considered invalid for assessing hyperthermia in individuals exercising outdoors in the heat.
    • The validity of the heat tolerance test in prediction of recurrent exertional heat illness events, Haggai Schermann, et.al., Journal of Science & Medicine in Sport, Volume 21(6), pp.549-552, (June 2018). Heat-tolerance-testing (HTT) protocol is used as a screening test for secondary prevention of exertional heat illness (EHI) in the military. Subjects whose test results are positive (heat-intolerant, HI) are presumed to be at higher risk of repeated EHI events than heat-tolerant subjects (HT) and are therefore prevented from return to combat duty, but may return to unsupervised recreational activity. Our aim was to determine, whether HTT results predict the risk of repeated episodes of exertional heat illness (EHI).

    resources iconResources

    • Best practice guideline: Smoke Pollution & Exercise, Australian Institute of Sport, (December 2019). Often co-occurring with heat bushfire smoke can pose a health risk to athletes. The health impact of bushfire smoke can vary based on an individual’s current health status and previous medical conditions. Increases in exercise intensity and duration result in increased airway exposure to polluted air, the AIS recommends modifying training, or training locations. 
    • Exertional heat stroke emergency kit (PDF  – 1.6 MB), Korey Stringer Institute, Neag School of Education, University of Connecticut, (accessed 19 December 2019). A list of equipment (including information on price in $USD, lifespan, practicality and purchasing information) to ensure you are fully equipped to deal with a case of heat-illness.
    • Heat Acclimatization, Korey Stringer Institute, University of Connecticut (website accessed 19 December 2019). Heat acclimation (i.e. acclimatization) plays a large part in the body’s physical responses and overall ability to cope with heat exposure. The Korey Stringer Institute provides useful information about the heat acclimation process.
    • Heat Illness Prevention [online course], National Federation of State High School Associations [USA], (accessed 6 January 2020). Exertional Heat Stroke is the leading cause of preventable death in high school athletics. To help you minimize the risk of heat illness at your school, this course has designed to provide the fundamentals of a strong heat acclimatization plan and guidelines for limiting activities to account for changing environmental conditions and other contributing risk factors. It highlights the importance of an appropriate hydration plan and establishing an Emergency Action Plan in case of a suspected exertional heat stroke.
    • How to respond to an exertional heat stroke emergency (PDF  – 1.1 MB), Korey Stringer Institute, Neag School of Education, University of Connecticut, (accessed 19 December 2019). A step-by step first-aid guide. 
    • Taking a rectal temperature, Drugs.com, (last updated 24 September 2019).

    Video iconClearinghouse videos

    Video iconOther videos
    • Heat management and Hydration, Cricket Australia, (accessed 6 January 2020). Heat management and hydration are important, as they directly impact on players’ performance and health. There are key ways to help players manage their body temperature. These videos provide tips on how to help players stay cool and hydrated while training or competing in cricket.
    • Training & Competition in the Heat Conference, ASPETAR Conference, Doha, Qatar, (23-24/03/2014)

     

    Related Topics

     



    Is this information complete? 

    The Clearinghouse for Sport is a sector-wide knowledge sharing initiative, and as such your contributions are encouraged and appreciated. If you would like to suggest a resource, submit a publication, or provide feedback on this topic, please contact us.
    Alternatively, if you would like to be kept up to date with research and information published about this topic, please request a research profile setup.