Football has always been a dangerous sport — broken bones and torn muscles are routine for players who face deadly spinal injuries and head trauma every time they take the field. The death of Minnesota Vikings star Korey Stringer Wednesday adds heat exhaustion to the list of deadly gridiron dangers. 

Stringer, 27, a 335-pound Pro-Bowl tackle, had already vomited three times and had a body temperature of 108 degrees when he collapsed during a practice workout Tuesday. His death came one week after 18-year-old University of Florida freshman fullback Eraste Autin, whose body temperature was also 108 degrees, died of heat stroke as well. 

While Stringer appears to be the first NFL heat-stroke fatality, the problem has been a growing concern for high-school and college football teams. According to the University of North Carolina, 17 school players have died from heat-related causes since 1995. Four died in 2000 alone, says a study published by the National Center for Catastrophic Sport Injury Research. 

Dr. Fred Mueller, chairman of UNC's Department of Exercise and Sports Science, who also heads the NCCSIR, said the rate of heat-related deaths among high school and college players has risen in the past five years. 

"There are so many precautions you can take — everything from hydrating properly to giving rest breaks to working out in cooler parts of the day," Mueller told the Miami Herald. "I hear stories of high school players practicing in full gear in the middle of a summer day. As parents and educators, we have to watch our kids closely and make sure their football practices are safe," he said. 

Heat stroke is a critical medical emergency that requires immediate attention. Symptoms include cramping in the stomach and extremities, nausea, fatigue, fainting, weight loss, dizziness, elevated skin temperature, profuse sweating or a sudden reduction in sweating. The heavy padding football players wear makes them more susceptible to it than other outdoor athletes. 

Limiting practices to the cooler times of day, suspending them when humidity is high, and making sure athletes are drinking large quantities of water continuously can completely eliminate the risk of heat stroke, experts say. 

But football coaches know this. 

"There are no more educated individuals in the world about heat problems and signs of heat stroke than college coaches," Mike Kruczek, coach of the University of Central Florida football team, told the South Florida Sun-Sentinel. 

In fact, college players aren't required to practice during the summer. But these precautions can get swept away as young athletes try to measure up against their team mates, prove themselves to coaches and satisfy their own ambitions. Practice sessions that may not be officially required become culturally mandatory. 

Vikings trainer Chuck Barta said that on the day Stringer collapsed, five other Vikings had heat-related problems. 

"You recognize you have the heat, you recognize you have to force fluids down them, you also use ice towels to keep them cool on the outside so they don't sweat as much," said Barta, who said he sometimes recommends toning down the practice intensity because of heat. 

But Barta said determining how hot is too hot is difficult, and he didn't remember if he'd scaled back workouts Tuesday. 

Mueller would disagree. His research provides temperature and humidity guidelines indicating "danger" and "critical" zones. 

Following Autin's death, Hurricanes coach Steve Spurrier said the University of Florida would be changing its approach to conditioning. 

"I think the one thing we've learned as coaches…is that when we do drills in the future and a guy is really tired and so forth, you can't push him," Spurrier told the Sun-Sentinel. 

But eliminating all summer practices are out of the question. Taking the field in the fall unprepared and out of shape can be just as dangerous, he said.