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Published on April 15th, 2012 | by Papa Doc

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No Sweat – Good or Bad?

“No sweat” means “ it’s good,” right? Not always the case–when exercising in hot, humid weather, it means danger. Sweating can be a social problem, but it is a life-saving process for you on the track.

The core temperature of your body is maintained in a narrow range (about 97℉ – 100℉) in a wide variety of environments. This is necessary because at too low a temperature, bodily functions slow down and cease. At too high temperatures, the body essentially cooks.

The body gains heat from several sources. The major contribution is from metabolism and muscle activity: under most conditions, about 70 – 90% of total heat production. Radiation from hotter objects in the environment – such as the sun and hot pavement – is variable as is high air temperature, depending on the humidity and air movement.

Losing heat from the body involves two sets of activities: behavioral and physiological.
The behavioral responses are altering the amount of muscle activity, reducing clothing, quenching thirst, and seeking shade. The physiological processes are: 1) conduction to colder objects (usually a small loss); 2) convection which is dependent on air movement and an air temperature lower than the skin temperature (90-92℉); 3) radiation heat loss dependent on clothing and on the heat of surrounding objects; and 4) evaporation, usually the major means of heat loss when the air temperature is the same or higher than the skin temperature.

Sweating accounts for the main evaporative loss of heat; respiration also contributes a small amount of evaporative loss. The ability to lose heat by sweating depends on the ability to sweat efficiently both in volume and in the water content of the sweat, the delivery of blood flow to the skin (i.e., circulation must be adequate), and the sweat actually evaporating: limited by humidity > 60%, reduced air movement, and reduced by clothing and equipment (the extent of body covered and the type – e.g., non-breathing fabric).

Your ability to lose heat is further reduced by poor physical conditioning, high body fat, certain medications, inadequate hydration, alcohol and caffeine (by increasing urine water loss), sunburn (reduces the ability of the skin to sweat), fever, clothing and equipment, and lack of acclimatization.

TYPES OF HEAT INJURY

When heat loss is impaired, the body suffers heat stress and eventually actual injury in one of several forms: heat cramps, heat exhaustion or heat syncope and heat stroke. Heat cramps are the mildest form of injury. More severe is heat exhaustion or heat syncope. Heat stroke, when the body’s heat loss functions fail, is the most dangerous; it can be fatal. Although the milder forms may warn of impending heat stroke, heat stroke may occur without going through the less severe stages. Therefore, you must be alert to all warning signs and symptoms.

Heat cramps are just that: cramps in the limbs and/or abdomen. If there are cramps all over the body, this is a symptom of a more serious condition.

Heat exhaustion and syncope occur when the body is still coping with the excess heat, but is under major stress. The symptoms are weakness, exhaustion, dizziness, confusion, fainting, excessive thirst, cool sweaty skin, cramps, headache, and chills. The pulse will be rapid. The blood pressure will be normal to low. The body temperature is up to 104℉. The confusion can interfere with the behavioral activities to reduce heat. Therefore, it is imperative for teammates to watch out for each other.

Heat stroke is a true medical emergency. The body’s protective functions have failed. The symptoms of weakness, dizziness, confusion, headache and/or fainting are present, but the skin is now dry and hot. Nausea and vomiting occurs. Collapse with coma and seizures may occur. The pulse is very rapid and weak. The blood pressure is low. The body temperature is 104℉ or higher. Death is a distinct possibility when the body temperature is over 107℉.

TREATMENT OF HEAT INJURY

Heat cramps are treated by moving the skater to a cool, shaded environment with cooling measures such as fans or cold wet towels. Removing clothing, stretching the cramped muscles, and providing cool electrolyte-containing fluids should relieve the cramps. Your medical team must evaluate the skater.

When you are dealing with heat exhaustion or syncope, cooling measures (fans, cold towels, and ice packs) are essential as are electrolyte-containing fluids (if the skater is alert enough to swallow). Medical evaluation is required, and emergency room treatment often is also required.

Heat stroke is an absolute medical emergency. Call 911 while moving the skater to a cool, shaded environment. Immediately begin cooling with fans and ice packs (if available, provide an ice bath) until the emergency medical help arrives. The skater will not likely be able to take oral fluids and will need intravenous (IV) fluids.

PREVENTION OF HEAT INJURY

Acclimatization is conditioning the body to cope efficiently with heat, achieved by slowly increasing the amount of activity in a given climate over 1 – 2 weeks. This improves sweating capacity to allow more efficient evaporative cooling with less mineral loss. Acclimatization will reduce the body’s core temperature, improve the thirst response, and increase blood flow to the skin as well as improving the capacity of the heart to respond to the increased demands. You can lose acclimatization “progress” if you are inactive for more than a few days.

Environmental factors can be controlled by reducing or changing clothing, getting to a cooler or shadier area, reducing or stopping the physical activity, and by reducing the ambient temperature and humidity with fans and air conditioning.

Maintaining adequate hydration is critical, not only for coping with heat, but for physical performance in general. Also, water breaks allow the chance to move to a cooler environment.

The other interfering factors in body heat loss can be controlled. Improving general physical conditioning will reduce your level of body fat as well. Check with your doctor about any and all medicines you take (both OTC and prescription) and their effects on heat tolerance. Avoid alcohol and caffeine before exercise. Don’t exercise if you have a fever. Avoid sunburn – this also protects against skin cancer. If you are ill, reduce or avoid exercise until you are well. Wear the minimum clothing needed and use moisture-wicking and breathable fabrics.

Sweating can save your life, so “bathe” in it. Wearing a deodorant and washing your pads is still OK.

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