Heat Information

Printable version

Thirty minutes prior to the start of an activity, and again 60 minutes after the start of that activity, take temperature and humidity readings at the site of the activity. Using a digital sling psychrometer or Wet Bulb Globe Thermometer (WGBT) are recommended. Record the readings in writing and maintain the information in files of school administration. Each school is to designate who is responsible for these duties, generally the athletic director, head coach or certified athletic trainer.

If unable to use the digital sling psychrometer or WBGT, then calculate the Heat Index using temperature and humidity.  

• National Weather Service: https://www.wpc.ncep.noaa.gov/html/heatindex.shtml

If the Heat Index is below 95 degrees:

•      All Sports

o   Provide ample amounts of water. This means that water should always be available and athletes should be able to take in as much water as they desire.

o   Optional water breaks every 30 minutes for 10 minutes in duration.

o   Ice-down towels for cooling.

o   Watch/monitor athletes carefully for necessary action.

If the Heat Index is 95 degrees to 99 degrees:

•     All Sports

o   Provide ample amounts of water. This means that water should always be available and athletes should be able to take in as much water as they desire.

o   Optional water breaks every 30 minutes for 10 minutes in duration.

o   Ice-down towels for cooling.

o   Watch/monitor athletes carefully for necessary action.

•     Contact sports and activities with additional equipment:

o   Helmets and other possible equipment removed while not involved in contact.

o  Reduce time of outside activity. Consider postponing practice to later in the day.

           o   Recheck temperature and humidity every 30 minutes to monitor for increased Heat Index.

If the Heat Index is above 99 degrees to 104 degrees:

•     All Sports

o   Provide ample amounts of water. This means that water should always be available and athletes should be able to take in as much water as they desire.

o   Mandatory water breaks every 30 minutes for 10 minutes in duration.

o   Ice-down towels for cooling.

o   Watch/monitor athletes carefully for necessary action.

o   Alter uniform by removing items if possible.

o   Allow for changes to dry t-shirts and shorts.

o   Reduce time of outside activity as well as indoor activity if air conditioning is unavailable.

o   Postpone practice to later in the day.

•     Contact sports and activities with additional equipment

o   Helmets and other possible equipment removed if not involved in contact or necessary for safety. If necessary for safety, suspend activity.

           o   Recheck temperature and humidity every 30 minutes to monitor for increased Heat Index.

If the Heat Index is above 104 degrees:

•    All sports

o   Stop all outside activity in practice and/or play, and stop all inside activity if air conditioning is unavailable.

Note: When the temperature is below 80 degrees there is no combination of heat and humidity that will result in need to curtail activity.

 

• Exertional Heat Stroke (or EHS) is the leading cause of preventable death in high school athletics. 

• Exertional heat stroke can be prevented through acclimatization and taking  basic safety precautions. 

• Knowing the signs of exertional heat stroke and heat illness, and having an  emergency action plan in place can prevent serious illness and save lives.

1. Physical exertion and training activities should begin slowly and continue progressively. An athlete cannot be “conditioned” in a period of only two to three weeks. See WIAA Football Season Regulations

2. Begin with shorter, less intense practices and training activities, with longer recovery intervals between bouts of activity.

3. Minimize protective gear (such as helmets and pads) during first several practices, and introduce additional uniform and protective gear progressively over successive days.

4. Emphasize instruction over conditioning during the first several practices.

   • Rationale: The majority of heat-related deaths happen during the first few days of practice, usually prompted by doing too much, too soon, and in some cases with too much protective gear on too early in the season (wearing helmet, shoulder pads, pants and other protective gear). Players must be allowed the time to adapt safely to the environment, intensity, duration, and uniform/equipment.

5. Keep each athlete’s individual level of conditioning and medical status in mind and adjust activity accordingly. These factors directly affect exertional heat illness risk.

   • Rationale: Athletes begin each season’s practices and training activities at varying levels of physical fitness and varying levels of risk for exertional heat illness. For example, there is an increased risk if the athlete is obese, unfit, has been recently ill, has a previous history of exertional heat illness, or has Sickle Cell Trait.

6. Adjust intensity (lower) and rest breaks (increase frequency/duration), and consider reducing uniform and protective equipment, while being sure to monitor all players more closely as conditions are increasingly warm/humid, especially if there is a change in weather from the previous few days.

   • Rationale: Coaches must be prepared to immediately adjust for changing weather conditions, while recognizing that tolerance to physical activity decreases and exertional heat illness risk increases, as the heat and/or humidity rise. Accordingly, it is imperative to adjust practices and/or competitions to maintain safety and performance. Coaches can monitor the athletes’ weights pre and post practice to ensure adequate fluid replacement, and can follow guidelines for hot and humid weather including using Wet Bulb Globe Temperature (WBGT) readings.

7. Athletes must begin practices and training activities adequately hydrated.

   • Rationale: While proper hydration alone will not necessarily prevent exertional heat illness, it will decrease risk. Athletes can observe the color of their urine, which should be straw yellow or the color of lemonade, when adequately hydrated. A Urine Color Chart can be accessed at: http://www.urinecolors.com/themes/uctheme/assets/dehydration-chart.pdf

8. Recognize early signs of distress and developing exertional heat illness, and promptly adjust activity and treat appropriately. First aid should not be delayed!

   • Rationale: An athlete will often show early signs and/or symptoms of developing exertional heat illness. If these signs and symptoms are promptly recognized and the athlete is appropriately treated, serious injury can be averted and the athlete can often be treated, rested and returned to activity when the signs and symptoms have resolved.

9. Recognize more serious signs of exertional heat illness (clumsiness, stumbling, collapse, obvious behavioral changes and/or other central nervous system problems), immediately stop activity and promptly seek medical attention by activating the Emergency Medical System (call 911). On-site rapid cooling should begin immediately.

   • Rationale: Immediate medical treatment and prompt rapid cooling can prevent death or minimize further injury in the athlete with EHS. Ideally, equipment for Tarp-assisted Cooling Oscillation (TACO) method, or pools /  tubs of ice water to be used for rapid cooling of athletes should be available on-site and personnel should be trained and practiced in using these facilities for rapid cooling. Ice water baths are the preferred method for rapid cooling, however, if ice water pools or tubs are not available, then applying ice packs to the neck, axillae, and groin and rotating ice-water soaked towels to all other areas of the body can be effective in cooling an affected athlete. Remember, cool first, transport later.

10. An Emergency Action Plan (EAP) with clearly defined written and practiced protocols should be developed and in place ahead of time.  It can be helpful to engage the local EMS team to help understand when to transport athletes, ideally cooling the athlete prior to transportation, as the ambulance will not have a cooling mechanism.

    • Rationale: An EAP should be in place in case of any emergency, as a prompt and appropriate response in any emergency situation can save a life. The EAP should be designed and practiced to address all teams (freshman, junior varsity, and varsity) and all practice and game sites. For heat illness emergencies, emphasis must be placed on full body cooling prior to transport.

• Thermoregulation depends primarily on the evaporation of sweat to dissipate the heat produced by exercise.
• Predisposing factors that increase an athlete’s risk for heat illness include: dehydration, heat acclimatization, clothing/equipment, fitness level, recent or current illness, medication use, obesity, age and prior heat illness.
• Prevention of heat illness includes designing an environmental action plan, modifying activity time (including intensity and duration) and increasing frequency and length of rest periods, providing and monitoring adequate hydration, minimizing clothing and equipment, ensuring adequate heat acclimatization, early recognition of signs and symptoms and appropriate sports medicine care.

 NFHS Heat Related Illness (WBGT) PDF

 

SIGNIFICANCE

Heat illness is the leading cause of preventable death in high school athletes. These heat stroke deaths mainly occur in the summer months, at the beginning of conditioning for fall sports. Heat production during intense exercise is 15 to 20 times greater than at rest and can raise body core temperature one to two degrees Fahrenheit every five minutes unless heat is dissipated.

 

BACKGROUND

Thermoregulation

Athletes lose heat by evaporation, conduction, convection and radiation. Heat is lost from the skin by evaporation of sweat. Conductionis passive transfer of heat from warmer to cooler objects by direct contact. Heat transfer from the core to the peripheral muscles and skin and from skin to an ice bag is by conduction.

 

Convection is the warming of air next to the body and the displacement of that warm air by cool air. Wind accelerates convection. Radiationis the loss of heat from the warmer body to the cooler environment by electromagnetic waves. At rest, 20 percent of body heat loss is by evaporation and 50 percent by radiation. With exercise, up to 90 percent of heat loss is by evaporation. Thus, thermoregulation during exercise relies primarily on evaporation. Radiation becomes a more important source of heat loss during exercise as the air temperature falls significantly below body temperature.

The body normally maintains core temperature within the range of 95 to 104 degrees Fahrenheit. Brain temperature is always slightly higher than body temperature. The removal of body heat is controlled centrally by the hypothalamus 
and spinal cord and peripherally by centers in the skin and organs. The body compensates for the increased heat produced during exercise by increasing blood flow to the skin and increasing sweat production so as to increase heat loss 
by evaporation. Importantly, evaporation is less effective at high humidity and when sweat production decreases due to dehydration. When heat production exceeds the ability to dissipate the heat, then core temperature, along with brain temperature, rises excessively. The result is further decompensation of normal thermoregulation, decreased heat dissipation, decreased cerebral blood flow and decreased muscular strength. This sets the stage for heat illness.

 

Acclimatization

An effective protection against heat illness is acclimatization. Proper acclimatization requires progressively increasing the duration and intensity of exercise during the first 10 to 14 days of heat exposure. However, full heat acclimatization may require up to 12 weeks of exposure. With repeated exposure to heat, there is an increase in skin blood flow rate, more rapid onset of sweating, an increase in plasma volume and a decrease in metabolic rate. Equipment and clothing should be minimized during acclimatization. Heat acclimatization can be lost over two weeks without ongoing heat exposure, but the loss may be slower in better-conditioned athletes.

Measuring Environmental Risk of Heat Illness

As humidity increases, perspiration evaporates less readily. Heat loss by sweating can be dramatically impaired when the humidity is greater than 60 percent. The Heat Index is a calculation of the danger of heat illness based on ambient temperature and humidity. The Heat Index can be determined by going to the NWS chart:www.weather.gov/om/heat/images/heat_index.png. As the Heat Index rises, so does the risk of heat illness (Figure 10).

Wet bulb globe temperature (WBGT) is the most effective method for determining environmental heat risk, because it takes into account not only ambient temperature and humidity, but also solar radiation. WBGT employs a dry bulb thermometer that measures ambient temperature, a wet bulb thermometer that measures humidity and a black globe thermometer that measures radiant heat.

As WBGT increases, the risk for heat illness increases (Table 11). WBGT less than 65 is low risk. WBGT 65 to 73 is moderate risk, WBGT 73 to 82 is high risk, and WBGT greater than 82 is extreme risk of heat illness. Experts recommend that distance races should be cancelled if WBGT is 80 or above. Only acclimatized, fit, low-risk athletes should undertake limited exercise at WBGT 86 to 90. Exercise should absolutely be cancelled for everyone when WBGT is 90 or more. The WBGT Risk Indices were developed for athletes wearing only a T-shirt and light pants. Therefore, safe values should be adjusted downwards in the presence of equipment and clothing that inhibit evaporation.

MANAGEMENT AND PREVENTION

Practices and Contests 
he greater the risk of heat illness, the more steps should be taken to safeguard the athletes, and the greater consideration should be given to cancellation or postponement of a practice or contest. An Environmental Action Plan should be in effect, covering every athletic practice and competition, and it must delegate responsibility for decision-making (see Emergency Action Planning chapter).

1. Measure the WBGT when possible. If not, then determine the heat index. Re-measure several times throughout the event or practice. Infrared thermometers can be used to measure playing surface temperature. The greater the intensity and duration of an event, the greater the risk of heat illness. Long-distance endurance events place athletes at more risk than sports that have frequent breaks during play. Consideration should be given to reducing playing time, extending rest periods and creating regular stoppage of play for rest and hydration. Practices and contests should not be scheduled during the hottest part of the day (commonly 11 a.m. to 6 p.m.).

2. Minimize clothing and equipment (football or lacrosse practice without shoulder pads and helmets).

3. Provide unlimited opportunities for hydration (see Fluid Replacement and Dehydration chapter). Provide extra water for wetting clothes, hair and face. Hydration should never be withheld as a punishment!

4. In multi-session or multi-day events, monitor for cumulative dehydration by repeated measurement of body weight.

5. Allow a minimum of three, and preferably six, hours for recovery and rehydration between exercise sessions during “daily doubles.”

6. Assure acclimatization prior to high endurance/intensity exercise in heat.

7. Consider providing shade, air conditioning or fans on sidelines during contests and practices.

8. If at all possible, practices should be attended by an athletic trainer or team physician who is prepared to manage heat-related emergencies.

9. Identify athletes whose medical history places them at increased risk (see Risk Factors below).

RISK FACTORS FOR HEAT ILLNESS

1. Dehydration.Fluid loss during exercise occurs primarily by perspiration and respiration. Dehydration during exercise occurs more rapidly in hot environments, when perspiration exceeds oral fluid replacement. Moderate dehydration (three to five percent body weight) reduces exercise performance and makes the athlete more 
susceptible to fatigue and muscle cramps. With severe dehydration, sweat production and cutaneous blood flow decrease and the athlete is less able to dissipate the heat produced by exercise. Water deficits of six to 10 percent can occur with exercise in hot environments, reducing exercise tolerance and heat dissipation by decreasing cardiac output, sweat production, and skin and muscle perfusion.

In addition to losing fluid with sweating, electrolytes (salt or sodium and chloride) are also lost. The percentage of salt lost in sweat usually decreases with an improving level of heat acclimatization. Salt depletion can be a significant factor in muscle cramps. While cold water is a good fluid replacement during short duration exercise, a sports drink with six to eight percent carbohydrate is preferable during continuous activity lasting 45 minutes or more. Regular, scheduled fluid replacement is important because athletes typically do not become thirsty until they have already lost two percent of body weight in fluid. (See Fluid Replacement and Dehydration 
chapter). 

An athlete may begin an activity in a dehydrated state due to inadequate rehydration following previous exercise, attempts to lose weight rapidly, diuretic medication, febrile illness, or gastrointestinal illness with vomiting or diarrhea. Measurement of body weight before and after activity is a good estimate of hydration 
status changes. Rehydration should be with a fluid volume that meets the weight lost with activity, ideally not exceeding 48 ounces per hour. Urine volume and color are another means by which to estimate hydration with lower volume and darker color representing greater dehydration.

2. Clothing and Equipment. Clothing and equipment inhibit heat loss from the body and increase the risk for heat illness. Dry clothing and equipment absorb sweat and prevent evaporative heat loss. Dark clothing or equipment produces radiant heat gain. Clothing and equipment decrease convective heat loss by interfering with air contact with the body. During periods of high WBGT or Heat Index, the risk of heat illnesses increases when clothing and equipment are worn. Thus, risk may be minimized through removing equipment and participating in drills wearing shirts and shorts only. Given that a great deal of heat is radiated from the head, helmets should be removed early on in hot and humid conditions.

3. Fitness.Physical training and improved cardiovascular fitness reduce the risk of heat illness.

4. Febrile Illness.A fever increases core temperature and decreases the ability of the body to compensate. It is dangerous to exercise with a fever, especially when WBGT is high. Athletes with a fever, respiratory illness, vomiting or diarrhea should not exercise, especially in a hot environment. 

5. Medications.Amphetamines (including ADHD medications), ephedrine, synephrine, ma huang and other stimulants increase heat production. Some medications have anti-cholinergic actions (amitriptyline, Atrovent) resulting in decreased sweat production. Diuretics can produce dehydration. Athletes taking medication for ADHD should be monitored closely for signs and symptoms of heat illness.

6. Obesity.Athletes with a high percentage of body fat are at increased risk for heat illness, as fat acts to insulate  the body and decreases the body’s ability to dissipate heat.

7. Sickle Cell Trait.Athletes with sickle cell trait (SCT) are at increased risk for a sickling crisis with exercise during hot weather. Special precautions should be taken in hot and humid conditions for athletes with SCT (see Sickle Cell Trait chapter).

8. A prior episode of heat illnessis a risk factor for a subsequent heat illness. After an episode of heat stroke, most athletes demonstrate normal thermoregulation within two months, but the rate of recovery is highly variable and may require up to a year or more. Decreased heat tolerance may affect 15 percent of athletes with a history of previous heat illness. 

STAGES OF HEAT ILLNESS

1. Exercise-associated Muscle Cramps (EAMC).Painful muscle spasms following prolonged exercise, often, but not always, in a hot environment. These are sometimes called “heat cramps.” Recognition:The cramps can occur without warning, can be excruciatingly painful, and may last several minutes or longer. They may be replaced by the onset of a cramp in another location. Severe episodes can last up to six to eight hours. Commonly, heat cramps affect the calf, but the thighs, hamstrings, abdomen and arms may be involved. Core temperature may be normal or increased and signs and symptoms of dehydration such as thirst, sweating and tachycardia may occur.

EAMC are usually associated with exercise-induced muscular fatigue, dehydration and a large loss of sodium through sweat. Sweat sodium losses that are incompletely replaced result in a total body sodium deficit. Low extracellular (outside of the cells in our body) sodium concentration is thought to alter nerve and muscle resting 
potential, resulting in EAMC. EAMC is more likely in athletes with high salt sweat content. Athletes with high salt sweat content or “salty sweaters” may be noticeable by salt staining on hats and clothing.

Management: EAMC usually responds to rest, prolonged stretching of involved muscle groups, and sodium replacement in fluid or food (e.g., one quarter teaspoon of table salt or one to two salt tablets in 500 ml of water or sports drink, tomato juice or salty snacks). In the case of severe full body cramps, the athlete should be 
transported by EMS to a hospital to receive intravenous fluids. Protracted cramping in the absence of signs of dehydration suggests dilutional hyponatremia (low sodium) and serum sodium levels should be measured prior to administering intravenous fluids.

2. Heat Exhaustion. Heat exhaustion is the inability to continue to exercise and can occur at any temperature, and is not necessarily associated with collapse. Heat exhaustion associated with dehydration is more common in a hot, humid environment. 

During high intensity exercise, blood flow to organs and skin decreases as blood flow to exercising muscle increases. When exercise, dehydration and humidity combine to make evaporative heat loss ineffective, the core body temperature increases. As core temperature rises, central controls of blood flow distribution begin to fail and the body attempts to increase blood flow to the skin in an effort to increase radiant and convective heat loss. The result is a loss of the original decrease in blood flow to the internal organs and to the skin. Through a series of complex physiological events, the pooled blood in the skin and extremities is unable to transport heat from the core to the skin. Muscular fatigue, decreased urine output, decreased cerebral flow, increased core temperature and fainting (syncope) can result.

Recognition: Signs and symptoms of heat exhaustion include tachycardia, fatigue, weakness, piloerection (goose bumps), muscle cramps, nausea, vomiting, dizziness, syncope, headache, poor coordination and confusion. Rectal temperature is elevated, but below 104 degrees Fahrenheit (40 C). The skin may still be cool and 
sweating, or may be hot and dry. Decreased cerebral perfusion may produce confusion or syncope. Heat exhaustion can be confused with other causes of depressed mental status in the athlete, including concussion, cardiac causes, infection, drug use, hypoglycemia and hyponatremia. Heat exhaustion is characterized by an elevated core body temperature. Any athlete with altered mental state of unknown etiology must be removed from activity and further evaluated.

 

Management: While heat exhaustion may present similarly to other conditions, heat exhaustion should be assumed if any of the signs and symptoms are present. Elevate the legs to increase venous return and cardiac preload, rehydrate to correct volume depletion, and transfer to a cool, shaded location. Aggressive decrease in 
core temperature is indicated to prevent progression to heat stroke. If a team physician or athletic trainer is unavailable to assess the athlete, EMS should be activated so the athlete can be transported to an emergency facility. There should be no same-day return to activity for athletes with syncope, altered mental status, 
neurologic symptoms or core temperature greater than 104 degrees Fahrenheit. Adequate time for full recovery is necessary prior to returning to play.

 

3. Exertional Heat Stroke (EHS) is defined by the presence of a rectal temperature greater than 104 degrees Fahrenheit (40C) combined with altered mental status. As heat production continues to exceed the body’s capacity to dissipate the heat, then core temperature rises to a level that disrupts organ function. 

Recognition: There is usually sweat-soaked, pale skin. Hyperventilation, tachycardia, vomiting, diarrhea and shock frequently progress to arrhythmia, acute renal failure, rhabdomyolysis (the release of muscle potassium, acid and enzymes into the blood as muscle cells break open and die), pulmonary edema, disseminated intravascular coagulopathy (coagulation of blood throughout the vessels) and cardiac arrest. Often, central nervous system signs are the first to appear: altered mental status, confusion, seizures and coma.

Management: EHS is a medical emergency and EMS must be activated. Successful treatment requires early recognition. Rapid reduction in core temperature is the key to prevention of organ failure. This is best accomplished by immersion in ice water. Less effective substitutes include ice packs to the groin and armpits, cool mist fans and alcohol rubs. If optimal cooling can be provided in the field, if there are no other life-threatening complications and if there is the ability to monitor the athlete during cooling, then cooling may be completed prior to transport. Otherwise, while efforts at cooling may be initiated in the field, they should not delay “load and go” EMS transport to a facility capable of comprehensive care.

References

Almquist J. Duties of administrators regarding heat illness. High School Today. May 2009, 26-28.

American Academy of Pediatrics. Climactic heat stress and the exercising child and adolescent. Pediatrics 2000;106:158-59.

Armstrong LE, et al. Exertional heat illness during training and competition. American College of Sports Medicine position stand. Medicine and Science in Sports and Exercise 2007;39:556-572.

Armstrong LE, et al. Time course of recovery and heat acclimation ability of prior exertional heatstroke patients.

Medicine and Science in Sports and Exercise 1990;22:36-48. 
Bergeron MF. Heat cramps: Fluid and electrolyte challenges during tennis in the heat. Journal of Science and Medicine in Sport 2003;6:19-27.

Casa DJ, et al. Preseason heat-acclimatization guidelines for secondary school athletics. The inter-association task force for preseason secondary school athletics consensus statement. Journal of Athletic Training 2009;44:332-333.

Casa DJ, et al. National Athletic Trainers’ Association Position Statement: Fluid replacement for athletes. Journal of Athletic Training 2000;35:212-224.

National Collegiate Athletic Association. Guideline 2c: Prevention of heat illness. 2010-11 Sports Medicine Handbook (21st edition).

• Athletic performance declines with dehydration, beginning with a fluid loss equaling one to two percent of the athlete’s body weight.
• It is important for all athletes to begin each exercise session well-hydrated.
• Rehydration should consist of water, carbohydrates and electrolytes, as all are lost during exercise.
• Athletes should never be punished through the restriction of fluids.

 

SIGNIFICANCE

In order for an athlete to perform at an optimal level, close attention must be paid to the body’s water and electrolyte levels. With many athletes focusing on specific aspects of their sport, along with the outcome of the event, many neglect the need for fluid replacement during activity. Many athletic events pose a challenge (e.g., very little rest) for the athlete to maintain optimal fluid levels, so it is important for athletes to have water or a sports drink close at hand in order to avoid poor performance or other detrimental physiological effects due to dehydration.

 

BACKGROUND

Minimal fluid loss can impair performance during exercise. At moderate exercise intensity, the human body generally produces 0.5 to 1.5 liters of sweat in one hour, but this may be higher in some individuals. The sweat rate increases as the intensity of exercise increases. During intense exercise in hot conditions, some individuals can lose up to three liters of sweat in one hour. A one percent drop in body weight due to fluid loss can lead to an increased core body temperature during exercise. When an athlete loses one to two percent of body weight due to fluid loss, aerobic exercise performance can decrease. When an athlete loses three percent or more of body weight, there is an increased risk for heat illness. Prevention of dehydration occurs before exercise begins, and should include a hydration protocol agreed upon by coaches, athletic trainers and all others involved in the well-being and performance of a team or athlete. 

 

Pre-exercise Hydration 
It is important for all athletes to begin each exercise session well-hydrated. Ideally, athletes should monitor their weight before and after exercise sessions in order to replace any fluids lost. It is recommended that an athlete consume 16 ounces (two cups) of water two hours before exercise begins. Another eight to 16 ounces (one to two cups) should be consumed 15 minutes prior to exercise.

 

Maintaining Hydration During Exercise 
Fluid replacement during exercise should equal fluid lost through sweat and urine, at a rate no higher than 48 ounces per hour. As previously stated, fluid loss of one to two percent of body weight can decrease aerobic performance, so the goal of the athlete should be to minimize dehydration to less than two percent loss of body weight, with less than one percent loss of body weight being optimal.

Unfortunately, relying on the body’s thirst mechanism cannot prevent dehydration, so thirst should not be relied upon to determine fluid intake. By the time a person becomes thirsty, he or she is already dehydrated. An athlete should drink early and often, and be allowed unrestricted fluid replacement. Athletes should never be punished through the restriction of fluids. Unrestricted access to water or sports drinks should lead to the consumption of four to eight ounces (one-half to one cup) of fluid every 15 minutes. It is important to remember that some athletes may have a higher sweat rate than others and require more fluids to remain well hydrated. These athletes can safely tolerate up to 48 ounces per hour.

 

Some sports present rehydration challenges, such as soccer or certain running events. A cross country race can last up to 30 to 40 minutes for some runners and water stations should be set-up with consideration given to the course and climate. In all settings, allowing athletes to drink as much fluid as they feel necessary is important.

 

Post-exercise Rehydration 
Fluid replacement after exercise should aim at achieving the athlete’s pre-practice or pre-event weight. Ideally, this should occur before the next practice session or competition. However, this may not be possible if there is minimal time between competition. Consumption of 16-20 ounces (2-2½ cups) of fluid for every pound lost during exercise will help achieve normal fluid state. Rehydration should consist of water, carbohydrates and electrolytes, as all are lost during exercise.

At the beginning of the fall sports season, athletes often participate in twice daily practices, and rehydration becomes even more important during this time. Athletes may be weighed prior to and after each practice session. If the athlete has not returned back to previous weight before the start of the second session, the athlete should be held out of participation in order to avoid dehydration-related illness.

 

Hyponatremia

Hyponatremia is extremely rare in high school athletics, but deserves mention. This is a potentially deadly disorder that results from the over-consumption of fluids (water and sports drinks). It is most commonly seen during endurance 
events, such as marathons, when adult participants consume large amounts of water over several hours in the absence of significant sweating. The opposite of dehydration, hyponatremia is a condition where the sodium content of the 
blood is diluted to dangerous levels. Affected individuals may exhibit disorientation, altered mental status, headache, lethargy and seizures. The diagnosis can only be made by testing blood sodium levels. Suspected hyponatremia is a medical emergency and EMS (Emergency Medical Services) must be activated. It is treated by administering intravenous fluids containing sodium.

 

RECOGNITION

Dehydration is common in all sports and can occur very rapidly, especially in a warm or hot environment or if the athlete starts activity less than fully hydrated. All coaches and athletes must be aware of the signs and symptoms of dehydration (Table 17). The volume and color of urine is an excellent way of determining if an athlete is well hydrated. A normal amount of nearly clear or light-colored urine indicates that an athlete is well-hydrated; small amounts of dark urine point to the need to increase fluid intake. A Urine Color Chart can be accessed at: 
http://at.uwa.edu/admin/UM/urinecolorchart.doc.

 

Table 17.  Signs and symptoms of dehydration. 
 Thirst 
 Irritability 
 Headache 
 Weakness 
 Dizziness 
 Muscle cramps 
 Chills 
 Nausea and vomiting 
 Heat sensations in the head 
or neck 
 Decreased performance

PREVENTION AND MANAGEMENT

Sports drinks and energy drinks are commonly seen in advertisements and differ in their ingredients. A sports drink is designed to provide re-hydration during or after an athletic activity. Most sports drinks contain six to eight percent carbohydrate solution and are a good source of electrolytes. Carbohydrate and electrolyte concentrations are formulated to allow the body’s gastrointestinal tract to absorb the fluid as efficiently as possible. 

 

Sports drinks can provide water, energy and appropriate electrolytes during competition. A carbohydrate concentration of six to eight percent can provide energy, while the higher concentration of carbohydrates found in juices and energy drinks will produce slow emptying of the stomach and may leave the athlete feeling bloated. The lower concentration of sodium found in sports drinks may also help avoid abdominal cramping. While sports drinks provide some benefits during exercise (Table 18), the main focus of an athlete’s hydration protocol should be on water. With an adequate diet and water intake, athletes will be properly prepared for practice and competition.

 

Table 18.  Indications for the use of sports drinks. 
Traditional sports drinks with appropriate carbohydrates and sodium 
may provide additional benefit in the following general situations: 
 Prolonged continuous activity of greater than 45 minutes 
 Extremely intense activity with risk of heat illness 
 Hot and humid conditions 
 Individuals who are poorly hydrated prior to participation 
 Individuals with an increased sweat rate 
 Individuals with poor caloric intake prior to participation 
 Individuals with poor acclimatization to heat and humidity  

Energy drinks were originally marketed towards athletes as a means of rehydration and electrolyte replacement during activity. Companies that manufactured the energy drinks claimed they improved performance on the field – both in practice and games. In recent years, energy drink companies have targeted the general  population and the market has been saturated with different energy drinks containing many different ingredients.

 

In 2006, nearly 500 new energy drink brands were introduced, often touting false claims of performance enhancement and improved recovery. Energy drinks may contain carbohydrates, caffeine, taurine and other substances that manufacturers claim enhance performance. Energy drinks ARE NOTrecommended for pre-hydration or rehydration during or after activity. Some ingredients, such as caffeine, may act as a diuretic, and can lead to even greater fluid loss. Please see the NFHS Position Statement on The Use of Energy Drinks by Young Athletes.

 

References 
Casa DJ, et al. National Athletic Trainers’ Association Position Statement: Fluid replacement for athletes. Journal of Athletic Training 2000; 35:212-224.

 

McKeag DB, Moeller JL. ACSM’s Primary Care Sports Medicine. 2nd Ed, Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins, 2007.

 

Position Statement and Recommendations for Hydration to Minimize the Risk for Dehydration and Heat Illness, National Federation of State High School Associations; Sport Medicine Advisory Committee. April 2008.

 

Position Statement and Recommendations on the Use of Energy Drinks by Young Athletes. National Federation of State High School Associations; Sport Medicine Advisory Committee.October 2008.

POSITION STATEMENT AND RECOMMENDATIONS  FOR HYDRATION TO MINIMIZE THE RISK FOR  DEHYDRATION AND HEAT ILLNESS 
 
National Federation of State High School Associations (NFHS) 
Sports Medicine Advisory Committee (SMAC) 
 
 
DEHYDRATION, ITS EFFECTS ON PERFORMANCE, AND ITS RELATIONSHIP TO HEAT ILLNESS: 
 
 

Appropriate hydration before, during, and after exercise is an important ingredient to healthy and successful sports participation. 

Rapid weight loss represents a loss of body water.  A loss of just 1-2% of body weight (1.5 to 3 pounds for a 150 pound athlete) can negatively impact performance.  A loss of 3% or more of body weight can increase the risk for exertional heat related illness.  

Athletes should be weighed before and after warm weather practice sessions and contests to assess fluid losses.  

Athletes with high body fat percentages can become dehydrated faster than athletes with lower body fat percentages while working out under the same environmental conditions.

All athletes have different sweating rates and some lose much more salt through their sweat than others. 

Poor acclimatization/fitness levels can greatly contribute to an athlete’s dehydration problems.

Medications and fevers can each greatly contribute to an athlete’s dehydration problems and risk for heat illness.

Environmental temperatures and humidity both contribute to dehydration and heat illness.

Clothing, such as dark, bulky, or rubber protective equipment can drastically increase the chance of dehydration and heat illness.

Wet bulb temperature measurements should be taken 10-15 minutes before practices or contests. The results should be used with a heat index to determine if practices or contests should be started, modified, or stopped.

Even dry climates can have high humidity if sprinkler systems are scheduled to run before early morning practices start. This collection of water does not evaporate until environmental temperatures increase and dew points lower. 

A heat index chart should be followed to determine if practices/contests should be held. The NOAA National Weather Service’s heat index chart can be found at:http://www.weather.gov/om/heat/index.shtml#heatindex

 

The heat index for your location can be determined by entering your postal zip code into a weather web site.  However, best practice is to take the temperature and humidity one half hour before activity at the site with additional measurements throughout activity.

A relative humidity of 35 percent and a temperature of 95 degrees Fahrenheit are likely to cause heat illness, with heat stroke likely.

 

A relative humidity of 70 percent and a temperature of 95 degrees Fahrenheit are very likely to cause heat illness, with heat stroke very likely.

 

 
WHAT TO DRINK DURING EXERCISES: 
 

For most exercising athletes, the ideal fluid for pre-hydration and re-hydration is water.  Water is quickly absorbed, well tolerated, an excellent thirst quencher, and cost effective.   
 
 
The use of a sports drink with appropriate carbohydrates (CHO) and sodium as described below may prove beneficial in some general situations and for some individuals.   
 
 
Traditional sports drinks with appropriate CHO and sodium may provide additional benefit in the following general situations: 
  Prolonged continuous activity of greater than 45 minutes 
  Extremely intense activity with risk of heat injury 
  Extremely hot and humid conditions 
 
 
Traditional sports drinks with appropriate CHO and sodium may provide additional benefit for the following individual conditions: 
  Poor hydration prior to participation 
  Increased sweat rate 
  Poor caloric intake prior to participation 
  Poor acclimatization to heat and humidity 
 
 
A 6-8% addition of CHO to water is the maximum that should be utilized.  Any greater concentration will produce slow emptying from the stomach and a bloated feeling to the athlete. 
 
 
The other ingredient that may be helpful is a low concentration ( 0.3 - 0.7 g/L) of sodium which may help with cramping.   
 
 
All fluids should be served cold to optimize gastric emptying. 
 
 
  
WHAT NOT TO DRINK DURING EXERCISE: 
 
 
Fruit juices with greater than 8 percent carbohydrate content and soda can both result in a bloated feeling and abdominal cramping. 
 
 
Beverages containing caffeine, alcohol, and carbonation are not to be used because of the high risk of dehydration associated with excess urine production, or decreased voluntary fluid intake. 
 
 

These stimulants may increase the risk of heart or heat illness problems  when exercising. 

 
Many of these drinks are being produced by traditional water, soft drink,  and sports drink   companies and may provide confusion to the sports community. As is true with other forms of    supplements these "power drinks or fluid supplements" are not regulated by the FDA.  Thus,    the purity and accuracy of contents on the label are not guaranteed.   
  
Many of these beverages, which claim to provide additional power, energy, etc., have   additional ingredients that are not necessary, some that are potentially harmful, and some  that actually include substances banned by such governing bodies as the NCAA and the  USOC.  

 
HYDRATION TIPS AND FLUID GUIDELINES: 
 
 
In general, athletes do not voluntarily drink sufficient water to prevent dehydration during physical activity. 
 
 
Drink early, by the time you’re thirsty, you’re already dehydrated. 
 
 
Drink before, during, and after practices and games. Specifically, the American College of Sports Medicine recommends the following:

Drink 16 ounces of fluid 2 hours before exercise.

Drink another 8 to 16 ounces 15 minutes before exercise. During exercise, drink 4 to 16 ounces of fluid every 15 to 20 minutes.

During exercise, drink 4 to 16 ounces of fluid every 15 to 20 minutes.

After exercise, drink 24 ounces of fluid for every pound lost during  exercise to achieve normal    fluid statue within 6 hours.

 

The volume and color of your urine is an excellent way of determining if you’re well hydrated. Largeamounts of clear urine mean your hydrated, small amounts of dark urine mean that you need to drink more! A Urine Color Chart can be accessed at: http://at.uwa.edu/admin/UM/urinecolorchart.doc 

 

The NFHS SMAC strongly recommends that coaches, certified athletic trainers, physicians, and other school personnel working with athletes not provide or encourage use of any beverages for hydration of these youngsters other than water and appropriate sports drinks that meet the above criteria.  They should also make information on the potential harm and lack of benefit associated with many of these other beverages available to parents and athletes.    
 
 
 
References: 
 
Casa DJ, Armstrong LE, Hillman SK, Montain SJ, Reiff RV, Rich BSE, Roberts WO, Stone JA.

National Athletic Trainers’ Association Position Statement:  Fluid Replacement for Athletes.  Journal of Athletic Training. 35(2):212-224, 2000.   
 
McKeag DB, Moeller JL. ACSM’s Primary Care Sports Medicine. 2nd Ed, Philadelphia: Wolters 
Kluwer/Lippincott Williams & Wilkins, 2007. 
 
 
Revised and Approved April 2008 

Heatstroke and heat exhaustion is preventable if the proper precautions are taken.  Have water available at all times and to allow the athlete to drink water whenever he/she needs it.  Never restrict the amount of water an athlete drinks, and be sure the athletes are drinking the water. 

In addition, allow time for young athletes to adapt to the weather and provide rest more often.  Progressive acclimatization is critical.  Provide for gradual increases in frequency, duration and intensity of physical activity. The key is recovery.  Also, remove equipment during rest periods and change to dry shirts.