Last summer brought several devastating training- and practice-related deaths at just about every level of football. Each incident had its own set of special circumstances, but the heat and/or humidity was at least partly culpable every time.

As coaches, we were frustrated and haunted by questions and second-guessing. Even with all the scientific information available, unfortunately, no clear-cut answers are available. We must, however, continue to search for and apply every piece of wisdom we can unearth for the safety of the athletes on our watch. Knowing the basic physiological stresses induced by a hot environment and how the body responds and adapts to them is a first step.

Research has taught us that summer conditioning procedures are necessary for heat-acclimatization purposes. We know that the training must be gradual, progressive and prudently executed, with detailed attention paid to the environmental conditions.

Simply stated, the body's cardiovascular system adjusts to external heat during exercise by shunting blood to the skin, which improves the body's ability to cool itself by dissipating internal heat, but diminishes the blood supply to the working muscles. This "catch-22" stresses the cardiovascular system to meet the competing demands of the thermoregulatory system and the requirements of muscle metabolism.

If the air temperature is mildly warm, the body can release a portion of the internal heat overload through sweat evaporation. When high humidity is coupled with warm air temperature, the body's thermal stress is doubled and the body's ability to evaporate the sweat and cool itself may be stifled.

Acclimatization can reduce the risks. The process encompasses about 10 to 14 short, less intense training sessions in the warmer environment. The initial duration of the workouts should be between 20 to 30 minutes at a low to moderate intensity level with liberal fluid breaks.

Also, there should be a gradual build-up in the frequency of the sessions. Our football training, for example, involves two days per week from mid-May through mid-June, before progressing to three to four days per week from mid-June through July.

In parts of the country that have extremely hot and humid climates, it would be wise to hold the initial workout sessions during a part of the day (early morning/early evening) when the conditions are milder. This will enable a gradual acclimatization to the variable conditions throughout the course of the day.

The gradual, systematic and progressive steps of acclimatization will eventually produce well-conditioned athletes who have a much higher heat tolerance than their sedentary counterparts or those who rush blindly into summer conditioning drills.

Measuring warning signs

Our sports medicine staff uses a "sling psychrometer" -- a hand-held instrument that measures the heat-stress index -- before every scheduled workout or practice. The heat-stress index is calculated as the Wet Bulb Globe Temperature (WBGT), which takes into account the air temperature, relative humidity and solar radiation.

It's important to know the relative humidity, which is a measure of how much moisture the air contains, because it affects how much heat can be lost through the evaporation of sweat. A hot and humid day compounded with limited air movement severely hampers the body's ability to cool itself through convection.

The WBGT index is a practical measurement for assessing potentially harmful environmental conditions. The readings are gauged into low, moderate, high and hazardous risk categories. Those readings provide both the sports medicine and coaching staffs with solid information that assists them in making prudent decisions on the duration and intensity of the workout/practice.

If the reading gauges a "high" or "hazardous" risk, the activity should be rescheduled for another time when the conditions are safer.

Two heat-related stresses that are of paramount concern are heat exhaustion and heat stroke. Coaches must be aware of the symptoms and immediate care procedures for each problem.

Heat exhaustion, while rarely a life-threatening condition, can precede more serious problems if left unattended. The symptoms of heat exhaustion include headache, nausea, dizziness, light-headedness, rapid pulse and muscle cramps.

An athlete with any of those symptoms should be required to cease the activity, then be taken to a cool, shady area to either sit or lie down in a supine (with slightly elevated feet) position. Cool liquids (for example, water or a sports drink) can be administered gradually. Activity should not be resumed until all of the symptoms have passed and qualified medical clearance has been granted.

Heat exhaustion, when left unheeded, can lead to heat stroke -- a significantly more dangerous condition. The symptoms of heat stroke can vary but may include disorientation; an extremely high body temperature (above 103 degrees Fahrenheit orally); red, hot, dry skin; rapid, strong pulse; nausea and/or vomiting; throbbing headache; and/or unconsciousness.

If any of those warning signs is detected, the following emergency procedures should be enacted immediately.

Call 911, or the closest, most readily available medical staff in your situation. (An emergency plan for such incidents should be firmly in place and regularly reviewed by all staff members).

Get the victim to an air conditioned or cool, shady area.

Cool the victim with any available means: water hose, shower, wet towels, fanning, etc.

If severe nausea and vomiting are apparent, do not administer fluids. Make sure that the airway is clear if the individual is unconscious.

If possible, monitor body temperature until it drops below 101 degrees Fahrenheit.

Hydration

It is vitally important to incorporate and maintain a sound hydration strategy for workouts, practices and games. Unfortunately, an athlete's thirst mechanism is a poor indicator of actual fluid needs.

During exercise, athletes should start drinking cool (50-59 degrees) fluids at a rate of at least eight ounces every 15 to 20 minutes. Water is fine, but for intense activities lasting longer than one hour, the sports carbohydrate/electrolyte drinks may be a better choice because they provide needed energy and mineral replacement, as well as fluid replacement.

Fruit juices and soft drinks that have a 12 percent or higher carbohydrate concentration are not good choices during exercise, as they may cause gastrointestinal distress by slowing gastric emptying. Fruit juices are fine for post-exercise recovery purposes, though it might be a good idea to stay clear of carbonated, caffeinated soft drinks altogether.

Pre-hydration is a critical component in this strategy. Athletes should drink the appropriate beverages liberally throughout the day and evening. They should be encouraged to take a plastic water bottle to meetings and classes and to drink from them regularly.

About two hours before an intense workout or competition, at least 17 or 18 ounces of fluid should be gradually ingested.

Post-exercise/competition hydration calls for at least 20 to 24 ounces of fluid for every pound of body weight lost (which is primarily fluid loss).