Prevention of Heat-Related Illness in Young Athletes

What is a heat injury?

Heat injury is a spectrum of conditions related to exposure to warm ambient conditions or the body's own intrinsic heat production during exercise. Muscles are metabolically inefficient — roughly 70–80% of the energy used in muscular contraction is released as heat — so during maximal effort the body must shed heat continuously. Without thermoregulation, an athlete would overheat fatally within minutes. The spectrum runs from mild to life-threatening:

• Heat edema
• Heat cramps
• Heat syncope
• Heat exhaustion
• Heat stroke — a medical emergency

Why it matters: heat stroke is survivable

Sudden death in young competitive athletes

In a review of 1,866 young competitive athletes (mean age 18 ± 5 years, 89% male) who died suddenly in the U.S. between 1980 and 2006, cardiovascular causes dominated, but heat accounted for a distinct and preventable share (54 deaths, ~3%).

Football-related heat deaths

Heat deaths during sport have risen over recent decades, and the pattern in football is strikingly consistent:

• Most common during August.
• More than 50% occur during morning practices, when humidity is highest.
• More than 70% of deaths occur in the first two weeks of practice — 22% within the first three days.
• Affected athletes are typically large: 79% had a BMI >30, and 86% played lineman positions.
• All deaths occurred under conditions rated high or extreme by the wet bulb globe temperature (WBGT), though several fell under lower threat levels when judged by the heat index alone — a key reason WBGT is preferred.

Source: Grundstein AJ, et al. International Journal of Biometeorology. 2012;56(1):11–20.

Optimize thermoregulation

Be prepared — before the season

Know your patients

• Confirm a good pre-participation physical.
• Flag risk factors: previous heat injury, "heavy sweaters," and sickle cell trait.
• Review the athlete's summer activities — acclimatization and baseline fitness.
• For those at risk, consider pre/post-practice weight measurement and first-void urine specific gravity.

Educate athletes and families

• Fever equals no play.
• Reinforce a practical hydration plan.

Medications and substances that raise risk

Be prepared — before practice

Measuring heat stress

Wet Bulb Globe Temperature (WBGT) is the most accurate field measure of heat stress because it weights the three factors that matter for an exercising body:

• 10% dry bulb (ambient air temperature)
• 20% black globe (radiant heat, e.g., sun and playing surface)
• 70% wet bulb (humidity)

The heat index, by contrast, assumes shade with a light breeze and partial cloud cover, so it can understate risk on a sunny field. WBGT is preferred for activity decisions.

Recognizing the spectrum

Mild heat injury — edema, cramps, syncope

• Usually self-limited (under 1 hour) and improves with minimal intervention.
• Stop exercise; move to a cool, shaded environment.
• Drink cool fluid; apply ice; position in Trendelenburg for syncope.

Moderate heat injury — heat exhaustion

Must be monitored closely because it can progress to heat stroke.

Severe heat injury — heat stroke

Differential diagnosis — "not so fast"

Altered mental status in a collapsed athlete is not automatically heat stroke. Consider: head injury, street drugs, a cardiac event, seizure disorder, hyponatremia, sickle cell crisis, febrile illness, and diabetic ketoacidosis.

Cool first, transport second

When heat stroke is suspected, begin cooling immediately — on site, before transport. Rapid cooling to a core temperature of about 39 °C is the priority.

External cooling maneuvers

• Cold-water / ice immersion — the fastest method; drops core temperature roughly 1 °F every 3 minutes.
• Ice bags to the groin, axilla, and head/neck.
• Cold towels.
• Water mist and fans.
• Establish IV access and give oxygen as soon as possible.

What NOT to do

• Do not give NSAIDs or antipyretics — they don't treat exertional hyperthermia.
• Do not cool to the point of shivering.
• Do not rely on an oral temperature.
• Do not assume that because the athlete is sweating they don't have heat stroke.
• Simply pouring water over the head is not adequate cooling.

Activity modification by WBGT

Adjust or cancel activity based on WBGT and the athlete's individual risk factors (RF). "High RF" athletes need more conservative thresholds than "Low RF" athletes.

Adapted from Casa D. In: Athletic Training and Sports Medicine. 2005.

Prevention in practice

Modify activity based on conditions

• Base decisions on WBGT, fitness / time of season, acclimatization status, and playing surface.
• Shorten or reschedule games and practices; move to the cooler part of the day (morning) or indoors.
• Decrease practice intensity and build in proper rest intervals.

Fluids

• Restricting fluid should never be used as punishment.
• Aim to drink at a rate equal to sweat rate — which means knowing the athlete's sweat rate.
• Use an electrolyte drink for exercise lasting more than 1 hour.
• Athletes drink more when fluids are cold and sweet.

Monitor and progress

• Track daily weights for early identification of fluid deficits.
• Use a progressive practice schedule to allow acclimatization.

Take-home message

• Heat injury is completely preventable.
• Heat stroke is a medical emergency.
• Exercise intensity, duration, and weather exposure are all modifiable.
• WBGT is the most accurate field measure of heat stress.
• Minimize risk factors and monitor for early signs.
• Proper hydration is important but is not a cure.
• Cool them down fast if heat stroke is identified.