CHAPTER 6 - ENVIRONMENTAL CONDITIONS
Normal body heat gains or loses occur through:
Metabolic heat production
Conduction heat transfer by contact (standing on a hot ground)
Convection heat transfer
into or out of a moving fluid (air, liquid, etc)
Radiation heat transfer in the form of waves or pulses (sun rays)
heat transfer in the form of moisture, which is dissipated, into the air
Metabolic heat is the heat dissipated (given
off) from normal body functions
Hyperthermia is a condition where the body temperature is elevated.
Hyperthermia has caused a number of deaths among football players and distance runners in high school and college,
and recently in the NFL.
Regardless of the level of physical conditioning, prolonged exposure to extreme
heat can result in heat illness. Heat stress is preventable, but each year many
athletes suffer illness and death from some heat-related cause. Athletes who
exercise in hot, humid environments are particularly vulnerable to heat stress. The
physiological processes in the body will continue to function only as long as body temperature is maintained within a normal
range. Maintenance of normal temperature in a hot environment depends on the
ability of the body to dissipate heat.
Monitoring the Heat Index
DBT dry bulb temperature
WBT wet bulb temperature
GT Globe temperature measures the suns radiation
WBGT index: WBGT 0.1 x DBT + 0.7 x WBT + GT x 0.2
by the physiodyne or a sling psychrometer, both calculate the difference between DBT and WBT, which is relative humidity.
6-1 WBGT Index for outdoor activities (Wet Bulb Globe Temperature)
Range Signal Flag Activity
82-84.9 Green Alert
for possible increase of index
85-87.9 Yellow Active practice curtailed (unacclimated athletes)
88-89.9 Red Active
practice curtailed (all except most acclimated)
90+ All training stopped; team meetings or demonstrations
80-90 <70% observe risks
80-90 >70% 10 min rest every hour
90-100 <70% 10 min rest every hour
90-100 >70% suspend or adjust practice
>100 any % Suspend or adjust practice
Heat Rash, also called prickly heat, is a benign condition associated with a red, raised rash accompanied by sensations
of prickling and tingling during sweating. It usually occurs when the skin is continuously wet with unevaporated sweat. The rash is generally localized to areas of the body covered with clothing. Continually
toweling the body can prevent the rash from developing.
Heat syncope, or heat collapse, is associated
with rapid physical fatigue during over-exposure to heat. It is usually caused
by standing in heat for long periods or by not being accustomed to exercising in the heat.
It is caused by peripheral vasodilation of superficial vessels, hypotension, or a pooling of blood in the extremities,
which results in dizziness, fainting, and nausea. Heat syncope is quickly relieved
by laying the athlete down in a cool environment, and replacing fluids.
Heat cramps are painful muscle
spasms that occur most commonly in the calf and abdomen, although and muscle can be involved (Table 6-2). The occurrence of heat cramps is related to excessive loss of water and several electrolytes or ions, which
are essential elements in muscle contraction.
Profuse sweating involves losses of large amounts of water and small amounts
of sodium, potassium, magnesium, and calcium, thus disrupting the balance in concentration of these elements within the body.
This imbalance likely results in muscle contractions and cramps. Heat cramps
may be prevented by adequate replacement of electrolytes, and most important water.
Ingestion of salt tablets is not recommended. The immediate treatment
for heat cramps is ingestion of large amounts of water and mild stretching with ice massage of the muscle in spasm.
Heat exhaustion results from inadequate replacement of fluids lost through sweating (Table 6-2). Clinically,
the victim will collapse and manifest profuse sweating, pale skin, mildly elevated temperature (102 F), dizziness, hyperventilation,
and rapid pulse.
Immediate treatment of heat exhaustion requires ingestion and eventually intravenous replacement of large
quantities of water. A rectal temperature is recommended to differentiate from
heat exhaustion and heat stroke. In heat exhaustion, the rectal temperature will
be around 102 F. If possible, the athlete should be placed in a cool environment,
although it is more critical to replace fluids.
Heat stroke is a serious, life-threatening emergency (Table 6-2). The specific cause is unknown. It is clinically a collapse with loss of consciousness; flushed, hot skin
with less sweating than would be seen with heat exhaustion; shallow breathing; a rapid, strong pulse; and most important,
a core temperature of 106 F or higher. The heatstroke victim experiences a breakdown
of the thermoregulatory mechanism caused by excessively high body temperature; the body loses the ability to dissipate heat
Heatstroke can occur suddenly and without warning. The
athlete will not usually experience signs of heat cramps or heat exhaustion. The
possibility of death from heatstroke can be significantly reduced if body temperature is lowered to normal within forty-five
minutes. The long the body temperature is elevated to 106 F or higher, the higher
the mortality rate. Aggressive efforts must be taken to lower body temperature. Get the athlete to a cool environment. Strip
all clothing off necessary clothing, and sponge him or her down with cool water, and fan with a towel. Do not immerse the athlete in cold water. Transport to the
hospital as quickly as possible, do not wait on ambulance. Use common sense.
prevention of hyperthermia involves:
Gradual acclimatization (seven to ten days)
Identification of susceptible individuals
Routine weight record keeping (a loss of 3 to 5% bodyweight will reduce blood volume and could
lead to a health threat)
Unrestricted fluid replacement
Routine temperature and humidity readings
Constantly monitor athletes for signs of heat illness
FLUID AND ELECTROLYTE REPLACEMENT
Athletes find it hard
to vigorously exercise on a full stomach. The problem with fluid replacement is how rapidly the fluid can be eliminated from
the stomach into the intestine, from which it can enter the bloodstream. Cold
drinks (45 to 55 F) tend to empty more rapidly from the stomach than do warmer drinks; they are not more likely to induce
cramps, nor do they offer any particular threat to a normal heart.
Ingestion of hypertonic solutions containing simple
sugars and electrolytes tends to slow gastric emptying, thus depriving the working cell of much-needed fluid. A solution that contains only 5 percent glucose will significantly retard the replacement of lost fluids. If the event lasts for more than 45 minutes, it may be necessary to replace glucose
by consuming electrolyte solutions.
Low temperatures accentuated by wind and dampness can pose major
problems for athletes.
Sixty-five percent of the heat produced by the body is lost through radiation. This loss occurs most often from the warm, vascular areas of the head and neck, which may account for as
much as 50 percent of total heat loss. 22% of heat loss is through evaporation,
of which two thirds is through the skin and one third is through the respiratory trait.
Shivering ceases below a body temperature
of 85 to 90 F. Death is imminent if the core temperature rises to 107 F or drops
to between 77 and 85 F.
COMMON COLD INJURIES
Local cooling of the body can result in tissue damage ranging from superficial
to deep. Exposure to damp, freezing cold can cause frost nip. In contrast, exposure
to dry temperatures well below freezing more commonly produces s deep, freezing type of frostbite.
nip involves the ears, nose, cheeks, chin, fingers, and toes. It commonly occurs
when there is a high wind, severe cold or both. The skin initially appears very
firm, with cold, painless areas that may peel or blister in twenty-four to seventy-two hours.
Affected areas can be treated early by firm, sustained pressure of the hand (without rubbing), by blowing hot breath
on the spot, or if the injury is to the fingertips, by placing them in the armpits.
Chilblains result form prolonged and constant exposure to cold for many hours. In time, there is skin redness, swelling, tingling, and pain in the toes and fingers.
involves only the skin and subcutaneous tissue. The skin appears pale, hard,
cold, and waxy. Palpating the injured area will reveal a sense of hardness but
with yielding of the underlying deeper tissue structures. When rewarming, the
superficial frostbite will at first feel numb, then will sting and burn. Later
the area may produce blisters and be painful for a number of weeks.
Deep frostbite is a serious injury indicating tissues
that are frozen. This medical emergency requires immediate hospitalization. As with frost nip and superficial frostbite, the tissue is initially cold, hard, pale
or white, and numb. Rapid rewarming is required, including hot drinks, heating
pads, or hot water bottles that are 100 to 110 F. During rewarming, the tissue
will become blotchy red, swollen, and extremely painful. Later the injury may
become gangrenous, causing a loss of tissue.
Acute mountain sickness Individuals who go from a low to moderate altitude of
7,000 to 8,000 feet will experience mild to moderate symptoms of acute mountain sickness.
Symptoms include headache, nausea, vomiting, sleep disturbance, and dyspnea, which my last up to three days. These symptoms have been attributed to a tissue disruption in the brain that affect the sodium and potassium
balance. This imbalance can cause excess fluid retention within the cells and
the subsequent occurrence of abnormal pressure.
Pulmonary edema At an altitude of 9,000 to 10,000 feet. Lungs may accumulate a small amount of fluid within the alveolar walls.
In most individuals this fluid is absorbed in a few days, but in some it continues to collect and forms pulmonary edema. Symptoms of high-latitude pulmonary edema are dyspnea, cough, headache, weakness,
and in some cases, unconsciousness. The treatment of choice is to move the athlete
to a lower altitude as soon as possible and give oxygen. The condition rapidly
resolves once the athlete is at a lower altitude.
Sickle cell trait reaction Approximately
8 to 10 percent of African Americans have sickle cell trait. In most, the trait
is benign. In high altitudes when the abnormal hemoglobin molecules become deoxygenated
as a result of exercise, the cell clump together. The process causes an abnormal
sickle shape to the red blood cell, which can be easily destroyed. This condition
can cause an enlarged spleen, which in some cases has been known to rupture at high altitudes.
Not mentioned in the book are symptoms which may include nausea, dyspnea, involuntary muscle spasms (especially the
lower back and legs).
There is an accepted method for estimating the distance
of an approaching thunderstorm. The "Flash-To-Bang" theory measures the time from when you see lightning to the time
you hear the associated thunder. A measure of 5 seconds from Flash-To-Bang means lightning is one mile away. Ten
seconds equals 2 miles; 15 seconds equals 3 miles, etc. When the Flash-to-Bang count is 30 seconds, it’s
time to seek safe shelter. However, you should be aware of its pitfall. It is sometimes hard to associate the proper
clap of thunder to the corresponding flash.