A woman appears exhausted after running and places a hand over her head.
Runners are among the high-intensity athletes who should be especially cognizant of their exposure to heat on summer days. (For Spectrum Health Beat)

Early last summer, incoming Kent State University freshman Tyler Heintz, 19, fell severely ill during an early-morning football practice.

His breathing grew labored and he began to slip in and out of consciousness. An ambulance rushed him to a hospital, but he later died.

The cause: exertional heat stroke.

This dangerous condition can strike an athlete of any stature, even those who have reached the pinnacle of their sport. In August 2001, 6-foot-4, 335-pound offensive tackle Korey Stringer, of the Minnesota Vikings, died shortly after collapsing during drills on a hot, humid day.

The Centers for Disease Control and Prevention identifies groups most at risk of heat stroke, including the very young, the very old, the chronically ill, people who work outdoors and people in low-income households.

Athletes, however, are particularly at risk for exertional heat stroke.

It is not uncommon for an athlete to sweat 1 to 2 liters per hour on a hot day. A large football player can lose up to 15 pounds of water in a single practice session.

The problem is most athletes drink far less than they sweat, simply because they underestimate the extent of their sweat loss.


With summer underway, athletes young and old are more often found outdoors. It’s an essential time to impress the importance of proper hydration and rest.

Summer training camps for runners, soccer players and football players are proving grounds for excellence, but they can be ground zero for heat stroke trouble.

When athletes—especially runners and football players—participate in vigorous exercise in the warm months, dehydration can turn fatal.

Almost all heat-related deaths occur from May to September, according to the CDC, which also identifies exertional heatstroke as a leading cause of preventable, non-traumatic exertional sudden death for young athletes in the U.S.

Two-a-days, those notoriously difficult practices common to football, can often lead to trouble. Last year, the NCAA Division I Council banned two-a-days in preseason practices.

A 2016 study in the Journal of Athletic Training found that exertional heat exhaustion occurs at an increased rate in the first 14 days of practice, and especially in the first seven days.

About a decade ago, the National Athletic Trainers’ Association issued guidelines for preseason heat acclimatization. The guidelines establish a 14-day plan that helps athletes acclimatize to the heat. It zeroes in on the first three to five days of summer practice as the most important for progressive acclimatization.

On Day 1, for example, athletes shouldn’t participate in more than one practice and they should wear limited gear, as well as limiting the level of exertion and physical contact. For full-contact sports, “100 percent live contact drills should begin no earlier than Day 6.”

Coaches and training staff must carefully consider their approaches to summer practices, scrutinizing duration, intensity, time and place.

On especially hot days, for instance, the practice may need to be limited in length or simply rescheduled to a cooler part of the day.

Keeping watch

Athletes and parents need to be aware of the signs and symptoms of dehydration and heat stroke.

Keep in mind that thirst is not always the best indicator of dehydration. By the time a person senses thirst, the body may have already lost more than 1 percent of its total water. Athletes, coaches and parents should emphasize the importance of proper hydration before, during and after sporting activities—and then keep watch for any signs of trouble.

Some signs of mild to moderate dehydration include:

  • Thirst
  • Dry or sticky mouth
  • Not urinating much
  • Darker yellow urine
  • Dry, cool skin
  • Headache
  • Muscle cramps

Signs of severe dehydration include:

  • Not urinating, or very dark yellow or amber-colored urine
  • Dry, shriveled skin
  • Irritability or confusion
  • Dizziness or lightheadedness
  • Rapid heartbeat
  • Rapid breathing
  • Sunken eyes
  • Listlessness
  • Shock (not enough blood flow through the body)
  • Unconsciousness or delirium

When dehydration goes untreated, the body can no longer maintain homeostasis, which leads to heat stroke. This can cause impaired cardiovascular function and neurological failure.

An athlete experiencing heat stroke may become agitated, confused or unable to maintain balance.

The signs of heat stroke:

  • High body temperature
  • Hot, red, dry, or damp skin
  • Fast, strong pulse
  • Headache
  • Dizziness
  • Nausea
  • Confusion
  • Losing consciousness