The incidence of heat stroke is rising in the United States as the leading cause of death and disability among high school students, with younger adults particularly prone to sports-related heat injuries.

Such injuries among high school students and other young adults are mostly preventable, according to the Centers for Disease Control and Prevention. To that end, new guidelines for teenagers and young adults have been published by the National Athletic Trainer’s Association.

"The biggest change is the concept of cool first, transport second," said Douglas Casa, of the University of Connecticut's Korey Stringer Institute, named for the Minnesota Vikings player who died in 2001 of heat stroke, according to NPR.

Casa says nearly all deaths caused by heat stroke occur three to four days after trying something new, like training for a road race without first acclimating the body to a new environment. A combination of physical activity and high heat may cause overheating of the body along with severe dehydration. Heat injuries occur when the body reaches temperatures of 104 degrees Fahrenheit or higher, which may cause cellular damage after 30 minutes or so of elevated temperatures.

However, that 30-minute window is often consumed by response emergency response time as the victim awaits transport to the hospital. With that in mind, Casa and other experts now recommend immediate first-aid: a cold bath.

Lawrence Armstrong, a physiologist at the University of Connecticut, says heat stroke is a common risk for healthy young adults who engage in intense outdoor exercise. "Heat stroke occurs among young, healthy individuals who push themselves beyond the point of stopping because of peer pressure or organizational requirements," he told NPR. "But the deaths from exertional heat stroke are totally preventable."

Among advice for young athletes, Casa reminds young athletes to focus on general health when training in high heat, given that sleep deprivation and illnesses may also cause body temperatures to rise during intense exercise.

According to the Association, heat stroke from exercise is one of the three leading causes of sudden death in sports activities, with heat stroke deaths rising between 2005 and 2009 to higher rates than observed in any other five-year periods during the past 35 years. The statistics include 18 preventable deaths during those years, with an estimated 20 to 22 deaths from 2010 to this year.

Source: National Athletic Trainers' Association. Executive Summary of National Athletic Trainers’ Association Position Statement on Exertional Heat Illnesses: An update to the 2002 NATA Guidelines. 2014.