The year of 2023 was the hottest on record, which brings with it increased risks of heat
exposure for people around the world (NOAA; Périard et al., “Exercise under heat stress” 2).
Climate change is raising the temperature of the Earth, but awareness of the dangers of heat
exposure is not rising with it (“How to prevent”; Krohn et al. 1). Furthermore, prolonged heat
exposure can often lead to the development of a heat illness, especially in concurrence with
vigorous exercise (Périard et al., “Exertional heat stroke” 1). There are many different factors
that play into an individual’s susceptibility to heat illnesses, but one that is not often discussed is
para-athlete status. Individuals with paralytic impairments may have decreased ability to
thermoregulate (Alkemade et al. 1), which thereby increases the risk of heat illness in this
demographic. However, among all types of athletes, heat illness is a topic that is often allowed to
go by the wayside. Exertional heat illness is a serious concern for athletes (especially
para-athletes), and they should be more educated on causes, risk factors, and prevention
strategies in order to actively prevent such an affliction.
2. Earliest Findings
30 years ago, heat illness was even more of an obscure issue. The heat-related death rate
peaked in 1999 at a staggering 587 deaths (“Climate Change Indicators”; “National
Environmental”), which prompted efforts to reduce athletes’ risk of developing exertional heat
stroke (EHS) throughout the 2000’s. The following decade is when many studies began to be
published on the causes and treatment of heat illnesses. For example, a study published by the
American Journal of Sports Medicine in 2007 suggests that “[exertional] heat illness is generally
the result of increased heat production and impaired dissipation of heat,” and that “[it] should be
treated aggressively to avoid life-threatening complications”. At that time, EHS was the third
leading cause of death in athletes behind cardiac disorders and head/neck trauma. These studies
also gathered information on the myriad of causes that exist for the development of heat illness.
Over a dozen types of medications were found to increase risk, as well as medical conditions
such as sickle cell anemia, dehydration, sleep deprivation, sunburn, and obesity (Howe &
Boden). These inherent qualities were beneficial to identifying high-risk individuals and
subsequently providing them with better protection against EHS.
However, paralysis is a medical condition that has largely flown under the radar of
exertional heat illness (EHI) studies, only recently gaining attention ahead of the 2020 Olympic
games in Tokyo. Studies emerged as early as the 1990’s on thermoregulation in paralyzed
individuals, independent of the studies on EHI. They found that “individuals with quadriplegia
[(paralysis of all four limbs)] had the poorest tolerance to heat” (Yamasaki et al. 1). Nonetheless,
paralysis was never directly linked to greater risk of EHI until 2019, when “the [wet bulb globe
temperature (WBGT)] 2 weeks prior to the [2020 Olympic] games at the hottest moment of the
day (13:00 h) [was] 26.4±2.9°C and 28.6±2.8°C during the games.” This would have been the
hottest Olympics on record, and the Paralympics would be doomed to the same fate. The same
study states that at merely “18.4–22.2°C” there is an increased “risk of exertional heat stroke and
heat illness,” and recommends that “high risk individuals should be monitored or not compete.”
22°C is already a risky temperature for athletes to compete, let alone at temperatures higher than
28°C. Acknowledging the risk factor for paralyzed athletes, the researchers note that the heat
would “impose considerable heat strain” on the Paralympic athletes since they “often have a
reduced ability to thermoregulate.” (Gerrett et al. 1-3).
3. Environmental Causes
While medications and medical conditions are noted as “internal factors” in the onset of
heat illness, there also exist “external factors” pertaining to the environment. In fact, as
researchers have looked farther into the epidemiology of EHI in more recent years, one’s
environment is often the most significant determinant of risk of EHI. A research paper written by
Julien Périard, a professor at the University of Canberra Research Institute for Sport and
Exercise and expert on EHI, found that increased ambient temperature, high humidity, low
winds, and insulating clothing can all increase risk of people in such an environment developing
a heat illness (Périard et al., “Exercise under heat stress” 3-6). This translates into an even higher
risk for athletes to develop EHI, combining a sub-optimal environment with high physical
exertion. Para-athletes are at an even greater risk in conditions such as these, as they have a
lessened ability to maintain their body temperature even in mild climates (Alkemade et al 1).
Périard also asserts that overall athletic performance is hindered by these external factors, with
heat causing fatigue and increased perspiration rates, which only increases strain to maintain a
normal body temperature (Périard at. al., “Exercise under heat stress” 3). Furthermore, a separate
study led by Périard listed uniforms as an environmental cause of EHI, as they can “potentially
impede skin surface heat dissipation” (Périard et al., “Exertional heat stroke” 2). Heat dissipation
is paramount in maintaining a safe core temperature, and so any obstruction to this process can
be cause for concern regarding the vulnerability to EHI. All of these factors directly contribute to
high core temperature in athletes, as opposed to the predispository nature of internal factors.
Yet another determinant that can magnify the threat of heat illness is the environment that
one’s body is accustomed to. Environments can be adapted to by either acclimation (artificial
adaptation) or acclimatization (natural adaptation), both of which typically entail training and
spending time in an environment with a similar temperature and humidity level to the target
environment. Failure to acclimate to one’s environment can greatly increase fatigue and risk of
EHI/EHS in athletes. A study done by Périard in 2015 has shown that it takes approximately 5
days in an unfamiliar environment to fully acclimate to it, at which point 0% of subjects
experienced heat syncope during vigorous exercise. This is a significant improvement over the
44% of subjects that experienced such symptoms after the same intensity of exercise and only
one day of acclimatization (Périard et al., “Adaptations and mechanisms” 6). These results
confirm that athletes need to condition their body to work efficiently in the competition
environment, and not doing so can lead to harmful results such as heat syncope. In addition to
this, several other studies have concluded that lack of heat acclimation/acclimatization is
correlated with lower blood flow rates to crucial parts of the body, most notably, the skin. It is
also known to cause increased perspiration in response to thermal strain (Périard et al., “Exercise
under heat stress” 45; Périard et al., “Adaptations and mechanisms” 7; Gerrett et al. 1-10), which
only decreases hydration levels as well as overall heat dissipation from the body. Greater skin
temperature and decreased heat dissipation are textbook causes of EHI, so these circumstances
should be avoided at all costs. Dehydration is also known to weaken thermoregulation (Périard et
al., “Exertional heat stroke” 4; Périard et al., “Exercise under heat stress” 40-41), so athletes’
acclimation to their environment is crucial to maximize performance while minimizing fatigue
and susceptibility to EHI.
4. Mitigation Strategies
Much of the earlier research on this topic described the stages of heat illness as a
continuum, and most prescribed simply “aggressive cooling” as treatment (Howe & Boden;
Périard et al., “Exertional heat stroke”; Périard et al., “Exercise under heat stress” 1; Krohn et al.
1-9). However, as more research has been done on this topic, it appears that it is not enough to
simply treat exertional heat illness, and that prevention is far more effective at reducing the
overall number of EHI incidents, and most importantly, decreasing fatalities due to EHS.
As with causes, methods proven to have a significant impact on likelihood of a patient to
develop an EHI were largely consistent across studies. The most often mentioned methods were
ensuring hydration, rest, and prior acclimatization. This means athletes should train in the
competition environment for at least 5 days prior to the event, gradually increasing the amount of
equipment worn, as some uniforms (e.g., football) may be more insulating than others (Krohn et
al.; Howe & Boden 7). Additionally, athletes must consistently drink water throughout the event,
even if they do not perceive thirst, as “ad libitum [(as needed)] water intake can result in
incomplete fluid replacement or voluntary dehydration during exercise heat stress...” (Périard et
al., “Adaptations and mechanisms” 5). Athletes cannot purely rely on thirst levels to hydrate
themselves, and must do so proactively to maintain a strong thermoregulatory system during
exercise. This ensures adequate blood flow performance and thus builds stronger resistance to
EHI/EHS. In regards to rest, Périard suggests “mandated work-to-rest ratios,” but having had
adequate sleep the night before is arguably more important in reducing fatigue and thereby
thermal strain. One can have many breaks during exercise, but if they slept for an insufficient
amount of time the night before, they will be tired and fatigued no matter what. Rest must be
combined with hydration and acclimatization to actively prevent the onset of EHI.
5. Limitations
These strategies have been proven to be effective in mitigating EHI risk, but they can be
unfeasible in certain situations. For instance, it may not always be possible for athletes to
acclimate to the environment, as the conditions may not allow for it. As previously mentioned,
this occurred before the 2020 Olympics in Tokyo, which was the main contributor to the 78
athletes that developed EHI during the games, even with extra precautions in place (Soligard et
al.). Moreover, athletes that travel often are at risk because they simply do not spend enough time
in each location to become properly acclimated. For athlete rest time, the amount of rest that can
viably be offered during exercise may be limited by the sport in question, and it is difficult to
mandate a bed time to ensure adequate sleep as well. These things can impede the prevention of
EHI through the methods listed.
Simultaneously, limitations concerning treatment of EHI also exist. Typically, a cold bath
is prescribed to reduce core temperature (Howe & Boden 7; Hosokawa et al. 3-4), but this is not
always possible or trivial to provide. Thick pads such as those used in football can greatly
obstruct the administration of care, especially in an instance of EHS, where the athlete may not
be able to take it off themselves. Treating para-athletes gives rise to an entirely new set of
challenges, mainly due to the lack of resources and studies on EHI/EHS treatment specific to
their condition (Fukuhara et al. 1-2). The typical cold bath technique may not be convenient
when an athlete is in a wheelchair, and may require a team of people to coordinate. Additionally,
some athletes with mental impairments may not be cooperative in efforts to cool them down via
cold bath (Hosokawa et al. 2-4). Thus, prevention is the most consequential measure to take
against exertional heat illness in para-athletes.
6. Athlete Mentality and Awareness
Toxic mentalities among athletes also hamper EHI prevention, and can indirectly increase
risk by decreasing hydration. It was stated previously that ad libitum water intake is not
sufficient to maintain adequate hydration during exercise, and this is due to a multitude of
factors. It seems that athletes aren’t taking advantage of their opportunities to maintain their
hydration and temperature as much as they need to be. As sports medicine professor Austin
Krohn reports in a research paper, “even with increased efforts in promoting education and
hydration, the incidence of death from exertional heat stroke continues to rise” (Krohn et al. 1).
The answer as to why likely has to do with athlete mentality and stoicism. A study published by
Malvin Janal, a Health Research Specialist at NYU, observed the perception of pain among
athletes during exercise under different adverse conditions. He discovered that, when he
“evaluated the effects of exercise on innocuous as well as noxious intensities of heat and
ischaemia[,] [exercise] diminished the perception of painful but not non-painful levels of heat”
(Janal 2). As a result, athletes may not realize that they are experiencing hyperthermic
(excessively high body temperature) symptoms, and possibly developing EHI. If an athlete does
not realize that they are experiencing such symptoms, they are likely to continue play when they
should be taking a break and/or hydrating. Thus, athlete awareness of their condition is essential
to the prevention of EHI. However, even when athletes are aware of the heat stress they are
under, they may continue to play in spite of this, often because of internal pressures to perform
well. Périard agrees with Janal, asserting that the high levels of motivation and exertion seen in
professional sport can inhibit natural responses to hyperthermia (Périard et al., “Exertional heat
stroke” 2). This abnormal ignorance to heat stress can cause escalation of EHI in athletes, and
can potentially lead to life threatening consequences. Therefore, athletes must be fully aware of
their cooling and hydration needs, and be consistent with employment of prevention strategies to
mitigate risk of EHI during play.
7. Conclusion
In sum, exertional heat illness and exertional heat stroke are extremely serious and
prevalent ailments incurred by athletes, and there are many risk factors associated with
vulnerability to them. Para-athletes are at an increased risk under all circumstances due to their
impaired thermoregulatory system, and should take extra precautions to avoid EHI/EHS
development. Para-athletes also introduce complications to the treatment process, and so their
condition exponentially decreases their ability to both prevent and treat EHI/EHS. Athletes, and
especially para-athletes need to be fully aware of the dangers of these illnesses, and be educated
on the correct steps to take to curtail risk. This education combined with increased opportunities
for rest, hydration, and cooling for athletes at sporting events can keep heat-related illnesses and
deaths to a minimum.
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