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| Heat and Athletic Activity |
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Released: 7/6/2001 |
Heat and Athletic
Activity
Heat injuries endanger the health of many athletes each
year. Those involved in athletics must know how to
recognize and provide emergency aid to the athlete
suffering from heat disorders. Most importantly, we must
know how to prevent heat injuries with proper attention
to conditioning, clothing, fluid intake, and be familiar
with the precautions for limiting play during times of
high temperatures and humidity.
Heat Regulation
A small gland in the brain called the hypothalamus
carefully regulates body temperature; as body
temperature rises, certain mechanisms are activated to
promote heat loss. These mechanisms include conduction
(transfer of heat from the warm body to a cooler
object); convection (transfer of heat from the warm body
to the cooler environmental air); evaporation
(transformation of water on the body surface into a
vapor); respiration (entrance of cooler air into the
body via the lungs); and radiation (transfer of heart
from the warm body to the cooler environment).
Physiologically, the body responds by dilating the blood
vessels in the skin, enhancing blood flow to the skin,
producing more sweat, and increasing the pulse and
respiratory rates.
Heat Injuries
If these heat loss mechanisms fail to restore normal
body temperature, the spectrum of heat injury syndromes
can occur – including heat cramps, heat exhaustion, or
heatstroke.
Heat cramps are the mildest form of hyperthermia or heat
injury. The athlete with heat cramps complains of muscle
twitching, cramps, and spasm. Treatment of the athlete
with heat cramps typically consists of encouraging
drinking to restore adequate hydration. The athlete
should stop activity and should rest in a cool
environment while replenishing fluids. Heat cramps
frequently occur at the beginning of the hot weather
season, before the athlete has had time to adequately
condition for participation at high temperature or
humidity. The body’s ability to improve its response to
heat exposure is called acclimatization.
The athlete with heat exhaustion, the next most severe
of the heat injury syndromes, complains not only of
muscle spasms and cramps, but also may complain of
headache, fatigue, weakness, lack of coordination, and
excessive thirst. He or she may be nauseated or have
diarrhea. On physical examination, he may have slow
mentations, weight loss, dry tongue and mouth, and
elevated body temperature. His skin is typically ashen,
cold, and clammy, and he may be sweating profusely.
Treatment consist of removing the athlete to a cool
place, sponging him with cool water, fanning him, and
encouraging him to drink cool fluids if the athlete is
able to do so. Placing ice packs in the axilla
(underarm) and hip/groin area can be helpful. If the
athlete is mentally confused and refuses to drink,
intravenous fluids are needed.
The athlete with heatstroke, the most severe form of
heat injury, may complain of all the symptoms of heat
exhaustion (headache, dizziness, fatigue, vomiting,
diarrhea), but his skin is hot and dry (i.e. no
sweating), not cold and clammy, since the normal
homeostatic sweating mechanism has been overwhelmed. In
addition, he may be confused or disoriented and
combative. He feels like he is burning up, and indeed,
his body temperature may rise to 104 or 105 degrees
Fahrenheit or greater.
Heatstroke is a medical emergency! If the athlete is not
rapidly cooled, he can die. The high body temperature
literally “burns up” tissues, and hence, alters function
of the heart, lungs, brain, kidneys, and other organ
systems. Treatment consists of rapid transport to an
emergency room facility for administration of
intravenous fluids and rapid cooling with either ice
water lavages or ice water immersion as indicated. While
waiting for transport, the athlete should be placed in a
cool environment, his clothing removed, and ice packs
placed about his body with fanning to speed cooling. If
the athlete is alert, encourage him to drink fluids.
Prevention of Heat Injuries
Prevention should be everyone’s first priority.
Preseason conditioning improves athletes’ ability
workout when the environmental heat and humidity are
high, processes know as acclimatization. The amount of
time an athlete takes to acclimatize can vary, and
coaches and athletic trainers should be more cautious in
the first few weeks of practice to make sure athletes
are adjusting to surrounding conditions. Athletes should
wear lightweight, light-colored, porous clothing, and
should be allowed to change into dry clothes as often as
necessary.
Water should be readily available, with athletes
encouraged to drink small amounts at frequent intervals
(before, during and after practice), even if they are
not thirsty. Athletes should be taught to “camel-up”
with fluids. Athletes lose 2% of body weight before
becoming thirsty, and satisfying thirst only replaces
50% of the fluid that is needed, so it is impossible to
“catch-up” with hydration once the athlete falls behind.
Electrolyte solutions (i.e. sports drinks)can also be
helpful to replace lost electrolytes, and some athletes
may prefer sports drinks to help them take in adequate
amounts of fluids. It may be helpful to weigh athletes
before and after practice to ensure adequate hydration
and to identify those particularly prone to fluid loss.
Whenever possible, practices should be held at cooler
times of the day (early morning or late afternoon), with
regular rest and water breaks. Those in charge of the
practice should assess environmental conditions, taking
into account not only the absolute temperature, but also
the relative humidity, since the latter strongly
influences the athlete’s ability to sweat. (Remember,
sweating is the body’s most effective means of heat
dissipation.) If heat and humidity add up to over 160
(i.e. temperature is 80 ° and 80% humidity) one should
be cautious and think prevention.
While all athletes must be carefully monitored for signs
of heat injury, certain athletes may be more prone to
heat stress and deserve special consideration. Among
these are out of shape athletes, obese athletes,
athletes with chronic diseases such as diabetes and
kidney disorders, athletes taking diuretics,
antihistamines, antidepressants, and other medications;
and athletes who are so eager to please the coach that
they may ignore impending symptoms of heat illness.
Athletes prone to profuse sweating are also at an
increased risk. Remember, too, that children are much
more susceptible to hyperthermia than adults because of
their reduced ability to regulate body temperature.
Children generate more metabolic heat per unit mass;
therefore, their sweating capacity is lower. They also
have less ability to transfer heat to the skin than
adults do.
Remember, heat related injuries are preventable but
require a commitment to the many issues outlined above.
These measures will not only optimize athletic
performance, but also improve overall sport safety.
This is provided for general information. It does not
purport to encompass all risks associated with
exercising in hot and humid weather, nor is it a
substitute for your own good judgment and consultation
with competent professional regarding specific fact
situations.
Expert consultant: Nicholas A. DiNubile, MD
Revised 2001.
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