Heat Illness in Sport and Exercise

Heat Illness in Sport and Exercise  
Prepared by  Prepared by: Dr Ralph Richards and Christine May, Senior Research Consultants, Clearinghouse for Sport, Australian Sports Commission
evaluated by  Evaluation by: Dr Chris Abbiss, Associate Professor, School of Exercise and Health Sciences, Edith Cowan University (January 2016)
Reviewed by  Reviewed by network: Australian Sport Information Network (AUSPIN)
Last updated  Last updated: 15 January 2018
Please refer to the Clearinghouse for Sport disclaimer page for
more information concerning this content.

Community Sport Coaching
Australian Sports Commission

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.


Key Messages 

1

Exertional or exercise induced heat stroke is a form of hyperthermia—a condition where the normal internal core temperature of the human body (generally 37°C) is elevated by as little as 2 to 3°C (39°C to 40°C) or higher.

2

Although the incidence of exertional heat stroke is rare, sporting bodies and event organisers are encouraged to understand the risk factors and have a clear policy regarding the risk of heat illness during competition and other sport participation.


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 no 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.  

  • Annual survey of football injury research 1931-2016, Kristen L. Kucera, David Klossner, Bob Colgate, Robert C. Cantu, National Centre for Catastrophic Sport Injury Research (US), (13 March 2017). Report includes a specific section on Heat Stroke which highlights that since 1995, 61 football players have died from heat stroke (46 high school, 11 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 2011-2015 there was an average of 2.2 heat stoke deaths per year compared to 4.4 per year during the previous five year period 2006-2010.
  • 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, Issue 1, p8-14 (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
  • 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, Issue 1, p70-7 (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, Number 6, p471-474 (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.
  • Catastrophic sports injury research: 34th Annual Report [Fall 1982 - Spring 2016, Kucera K, Cox L and Cantu R, National Centre for Catastrophic Sport Injury Research (US) (5 October 2017). This report summarises 34 years of data, covering over 2,400 incidence of catastrophic sports-related injuries in US high schools and colleges. From July 1, 2015 to June 30, 2016 there were a total of 112 catastrophic injuries/illnesses captured by NCCSIR among high school and college organized sport participants. Of these 6.9% were heat-related. 

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) 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 conditions

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

Archery iconArchery

AFL iconAustralian Football

Bowls-smallBowls

canoeing-smallCanoe/Kayak

cricket-smallCricket 

While neither Cricket Australia or the International Cricket Council (ICC) have specific heat policies Cricket Australia recommends that clubs,schools and associations apply commonsense guidelines to climatic conditions that exist within their respective regions and consult with the respective Sport Medicine Australia or health promotion organisation within their state or territory to assist in the development of local policies [source: Well Played: Safety and Legal Considerations (PDF  – 3.5 MB) includes information on heat, hydration, and sun protection].

Some examples of local policies include: 

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).

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 

  • Australian Rugby refers to the World Rugby – Heat Guideline (PDF  – 297 KB), [accessed 11 January 2018]

softball-smallSoftball

surf-life-saving-smallSurf Life Saving

 SwimmingSwimming

tennisTennis 

touch-Football-smallTouch Football

Indoor Sports  

  • Indoor sports Victoria - extreme heat guidelines (PDF  - 864 KB), [accessed 11 January 2018]. Includes indoor sports including Cricket, Netball, Soccer and Volleyball.

 

General

  • Consensus recommendations on training and competing in the heat, Racinais S, et.al., British Journal of Sports Medicine, published online (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, Number 3, p741-747 (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. 

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. 

Triathlon

United States 

Volleyball

tennisTennis - 2014 Australian Open, Melbourne

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: 

SwimmingSwimming - 2010 FINA Open Water Series, Fujairah

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.

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

Further resources have been added to expand relevant and specific topics for your interest.

Hyperthermia

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

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.

Exertional heat stroke (EHS). 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.

  • 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 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, Number 3, p296-299 (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, Number 7, p1197-1203 (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 in competitive athletes, Casa D, Armstrong L, Ganio M and Yeargin S, Current Sports Medicine Reports, Volume 4, Number 6, p309-317 (2005). This article focuses on critical misconceptions that pertain to the prevention, recognition, and treatment of EHS, including 1) the randomness of EHS cases, 2) the role of nutritional supplements in EHS, 3) temperature assessment, 4) onset of EHS and the possible lucid interval, 5) rapid cooling, and 6) return to play. Exploration of these topics will enhance the medical care regarding EHS.
  • 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, Number 3, p115-123 (2012).
  • 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, Number 4, p1883-1928 (2011). This article emphasizes significant recent advances regarding heat stress and its impact on exercise performance, adaptations, fluid electrolyte imbalances, and pathophysiology.
  • 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. 
  • 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, p742–748 (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.
  • 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, published online (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.
  • 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 

It is important to know the signs and symptoms of heat illness and how you should respond. 

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


Collapse

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.

  • Collapse in the endurance athlete, Sallis R, Sports Science Exchange, Number 95, (2004). Exercise-associated collapse is a relatively common occurrence in endurance events, especially those occurring in high heat and humidity. The cause is most often benign in athletes who collapse after finishing exercise with no loss of consciousness, normal vital signs, and normal mental status. On the other hand, more serious causes of collapse, e.g., heatstroke, can lead to serious organ damage and even death if not treated quickly and appropriately. It is essential that those providing medical care at endurance events or caring for these athletes be familiar with the appropriate management of the collapsed athlete to prevent a possible tragic outcome.
  • 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, Number 6, p413-424 (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.
  • 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, Number 14, p1157-1162 (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.
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. 
  • 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

      The following is a list of personal risk factors that may contribute to a decreased exercise tolerance or an increase in exertional heat-illness risk:

      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

      Pregnancy

          The following is a list of contributing modifiable risk factors that are the primary determinant of reduced performance and exertional heat-illness risk:

          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
          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

          Assess internal (core) temperature

          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 overcooling (termed ‘after-drop’ or rebound hyperthermia).    

          • Exertional heat stroke, Adams T, Stacey E, Stacey S, Martin D, British Journal of Hospital Medicine, Volume 73, Number 2, p72-78 (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.    

          • 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, Number 1, p84-93 (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.  
          • Cooling and hemodynamic management in heatstroke: practical recommendations (PDF  – 210 KB), Bouchama A, Dehbi M and Chaves-Carballo E, Critical Care, Volume 11, Number 3 (2007). This review failed to identify reliable clinical data in te optimal treatment of heatstroke which highlights the need for more conclusive research aimed at identifying the optimal cooling methods and hemodynamic management of heatstroke.
          • Cooling methods used in the treatment of exertional heat illness (PDF  - 180 KB), Smith J and Wallis L, British Journal of Sports Medicine, Volume 39, Number 8, p503-507 (2005). This article confirms the main predictor of outcome in exertional heat stroke is the duration and degree of hyperthermia. The authors suggest cooling patients using iced water immersion where possible, or the combination of other techniques as a practical alternative.  
          • Exertional heat stroke emergency kit (PDF  – 1.6 MB), preventing sudden death in sport, Korey Stringer Institute, Neag School of Education, University of Connecticut. A list of equipment (including information on price in $USD, lifespan, practicality and purchansing information) to ensure you are fully equipped to deal with a case of heat-illness.
          • How to respond to an exertional heat stroke emergency (PDF  – 1.1 MB), preventing sudden death in sport, Korey Stringer Institute, Neag School of Education, University of Connecticut. A step-by step first-aid guide. 

          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

          • 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, Number 5, p314-321 (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.
          • 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.

          Heat tolerance testing

          The ACSM roundtable conference assembled experts from the civilian sports medicine community and the Department of Defence to discuss relevant exertional heat illness issues, such as potential long-term consequences, the concept of thermotolerance, and the role of thermal tolerance testing in return-to-play decisions. A heat tolerance test has been devised, yet the validity of this test for a return to play clearance remains unclear. However, the concept of a heat tolerance test is highly regarded and further research in this area will improve our understanding of the mechanisms involved in heat intolerance. 

          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.

          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.   

          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.   

          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.

          • 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. 
          • A heat acclimation protocol for team sports, Sunderland c, Morris J and Nevill M, British Journal of Sports Medicine, volume 42, Issue 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.
          • Heat Acclimatization: Preparing athletes to compete in hot environments (abstract), Sparling P, International Sport Medicine Journal, Volume 1, Issue 2 (2000). Heat acclimatisation is an adaptive process that occurs when a person moves from a cool to a hot environment; most of the physiological adjustments take place within the first 10 to 14 days. Hydration status should be monitored daily – also body weight, fluid intake, urine output, and urine colour. For most sports activities, drinking about 1 litre of fluid per hour of a 6% carbohydrate-electrolyte sports beverage provides adequate fluid and energy substrate to sustain exercise performance. This guideline should be individualised based on body size, sweat rate, and type and intensity of exercise.
          • 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. Generally about 1-2-weks 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.
          • Preparing for and playing in the heat, Nadelen M, American College of Sports Medicine (2012). Athletes should progressively increase the intensity and duration of their training sessions over a 10 to 14 day period to become fully acclimated to their environment. Initially, training sessions should be short, about 40 minutes or less for the first couple of days; then progressing to a 2-4 hour training session by day 14. An individual properly acclimated should be able to train in a warm environment for one to two hours at an intensity equal to competition.
          • 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, Issue 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.

          Research iconResearch

          • 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, Issue 12, e83148 (2013).    
          • 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
          • Central and peripheral fatigue during passive and exercise-induced hyperthermia,  Périard J, Caillaud C and Thompson M, Medicine and Science in Sports and Exercise, Volume 43, Number 9, p1657-1665 (2011).  
          • Cardiovascular strain impairs prolonged self-paced exercise in the heat,  Périard J, Cramer M, Chapman P, Caillaud C and Thompson M, Experimental Physiology, Volume 96, Number 2, p134-144 (2010).
          • 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, published online (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.
          • Emergency preparedness in high school-based athletics: a review of the literature and recommendations for sport health professionals, Olympia R and Brady J, The Physician and Sportsmedicine, Volume 41, Number 2, p15-25 (2013).
          • Exercise modality modulates body temperature regulation during exercise in uncompensable heat stress, Schlader Z, Raman A, Morton R, Stannard S and Mundel T, European Journal of Applied Physiology, Volume 111, Number 5, p757-766 (2011).
          • Exertional heat stroke, Adams T, Stacey E, Stacey S, Martin D, British Journal of Hospital Medicine, Volume 73, Number 2, p72-78 (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, Issue 4, p267-278 (2013).
          • Heat Stress and Thermal Strain Challenges in Running, Michael Bergeron, Journal of Orthopaedic & Sports Physical Therapy, Volume:44(10), pp.831–838, (2014). 
          • 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, published online (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.
          • 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, Number 1, p124 (2014).
          • 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, p744-750 (2014)
          • Misdiagnosis of exertional heat stroke and improper medical treatment, Druyan A, Janovich R and Heled Y, Military Medicine, Volume 176, Number 11, p1278-1280 (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, Number 11, p3013-3023 (2014).
          • 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, Number 8, p1561-1569 (2011).
          • 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).
          • 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.
          • Reducing sports heat illness risk, Bergeron M, Pediatrics, Volume 34(6), (June 2013). 
          • 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.
          • 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, Issue 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.  

          Resources

          • A work health and safety guide for fit businesses (PDF  – 4.2 MB), Fitness Australia. An easy to understand introduction to Work Health & Safety, this guide can be used by existing fitness businesses and those starting a new business or changing location. It contains practical considerations example checklists to help you evaluate your existing program or assist in starting a new program to enhance the effectiveness and success of your business. This guide contains specific information pertaining to the health risks (e.g., heat illness, dehydration) associated with hot weather conditions and the use of saunas. 
          • Beat the heat: playing and exercising in hot weather (PDF  – 3.7 MB), Sports Medicine Australia.
          • Heat stress and exercise, Better Health Channel, Department of Health, Victorian Government, (November 2015). 
          • Preventing physical activity induced heat illness in school settings (PDF  – 1.5 MB), Shannon H, Stewart I and Stewart K, In: Proceedings of the 26th ACHPER International Conference: Creating Active Futures, Queensland University of Technology, Brisbane, Queensland (8-10 July 2009).
          • UV exposure and heat illness guide (PDF  – 1.5 MB), Sports Medicine Australia. This guide outlines practical steps to create a safe and enjoyable environment for participation in sport and physical activity. It provides facts from SunSmart and SmartPlay and tips for creating UV and heat illness guidelines, and a UV exposure and heat illness checklist.
          • Heat Acclimatization, Korey Stringer Institute, University of Connecticut (website). 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.
          • Exertional heat stroke (EHS), Korey Stringer Institute, Neag School of Education, University of Connecticut.
          • Fit Facts: Beat the heat before it beats you (PFD  – 184 KB), American Council on Exercise (ACE). 
          • “Hot Races” reiterate precautions for marathon runners, news archive, American College of Sports Medicine.
          • Prolonged exercise in the heat (PDF  - 376 KB), Periard J, ASPETAR Sports Medicine Journal, Volume 2, Number 1, p8-15 (2013). An article outlining the impact of prolonged exercise performance in hot conditions which details strategies to optimise performance and improve heat tolerance.
          • Stay cool: getting too hot can be dangerous, National Institute of Health, Department of Health and Human Services, United States of America.

          Reading

           

           Video iconClearinghouse Videos

          Please note a number of the resources below (as indicated) are restricted to ‘GOLD' AIS Advantage small AIS Advantage members only.
          Please see the Clearinghouse membership categories for further information.

          Other videos
          • Heat management and Hydration, Cricket Australia. 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)



           



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