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)
Evaporation heat transfer in the form of moisture, which is dissipated, into the air
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. Hest 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
Either by the physiodyne or a sling psychrometer, both calculate the difference between DBT and WBT, which is relative humidity.
TABLE 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 through sweating.
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.
The 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.
Frost nip involves the ears, nose, cheeks, chin, fingers, and toes. It commonly occurs when there is a high wind, sever 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.
Superficial frostbite 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
Sickle cell trait reaction
Flash-to-bang method is the time in seconds from lightning strike until sound of thunder is heard divided by five.
Lightning detectors determine how far storm is away
Stop activity and wait 30 minutes from time of last lightning or last thunder before continuing.