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From The National Athletic Trainers' Association

Pre-Season Heat-Acclimatization Guidelines

High School-Specific Guidelines For Reducing Heat Illness Risk

Player and tackling dummy

In 2009, the National Athletic Trainers' Association (NATA) issued  high school-specific pre-season heat-acclimatization guidelines (1) as part of its ongoing effort to reduce the number of heat-related athletic injuries in secondary schools.


The consensus statement lists seven key recommendations for a 14-day heat-acclimatization period prior to full-scale athletic participation by secondary school students:

  1. During the first five days of the heat-acclimatization process, no more than one practice per day.
  2. If a practice is interrupted by inclement weather or heat restrictions, the practice should recommence once conditions are deemed safe, but total practice time should not exceed three hours per day.
  3. A one-hour maximum walk-through is permitted during the first five days of the heat-acclimatization period, with a three-hour recovery period between the practice and walk-through (or vice versa).
  4. Helmets only during the first two days (no shoulder pads). Goalies, as in the case of field hockey and related sports, should not wear full protective gear or perform activities that would require protective equipment. During days three through five, only helmets and shoulder pads should be worn. Beginning on day six, all protective equipment may be worn and full contact drills may begin.
  5. Beginning no earlier than the sixth day and continuing through the 14th day, double-practice days must be followed by a single-practice day. On single-practice days, one walk-through is permitted, but it must be separated from the practice by at least three hours of continuous rest. When a double-practice day is followed by a rest day, another double-practice day is permitted after the rest day.
  6. On a double-practice day, neither practice's duration should exceed three hours total, and total practice time should be limited to a maximum of five total hours. Warm-up, stretching, cool-down, walkthrough, conditioning and weight-room activities are included as part of the practice time. The two practices should be separated by a break of at least three continuous hours in a cool environment.
  7. Because the risk of exertional heat illnesses during the pre-season heat-acclimatization period is high, the consensus statement strongly recommends that an athletic trainer be on site before, during, and after all practices.

New Position Statement To Modify Guidelines

In June 2014, the NATA announced plans to issue updated guidelines later last summer which modify the current guidelines in several respects, but they have not yet been published. Publication is now slated, according to Douglas Casa, the lead author of the new position statement, in August or September 2015.  
However, according to an Executive Summary released in June 2014,  the new heat acclimatization guidelines will be as follows:
  • Days 1-2: Single three hour practice OR single two hour practice and single one hour field session (a change from 2009 guidelines above); only helmets may be worn
  • Days 3-4: Single three hour practice OR single two hour practice and single one hour field session (a change from 2009 guidelines); only helmets and shoulder pads may be worn
  • Day 5: Single three hour practice OR single two hour practice and single one hour field session (a change from 2009 guidleines); full equipment may be worn
  • Days 1-5: Equipment guidelines for preseason participation only impact days 1-5 of the acclimatization period 

Heat stroke deaths preventable 

According to the Annual Survey of Football Injury Research (2), there were five deaths in 2011 of football players at the high school level from exertional heat stroke but none at the youth, professional or college level. In the last two years (2012-2013), there has been only one heat stroke fatality, "a positive trend that could continue due [to] the efforts at the state and national levels," said the survey.

The NATA's guidelines provide critical education for student athletes, parents, coaches, athletic trainers, medical professionals and school staff on ways to reduce the risk of heat illness.

Douglas J. Casa, PhD, ATC, FACSM, FNATA, co-chair of the task force, Professor, Department of Kinesiology, Director, Athletic Training Education, Chief Operating Officer, Korey Stringer Institute, and Research Associate, Human Performance Laboratory at the University of Connecticut, and the author of the NATA's forthcoming revised position statement on heat acclimitization and preventing and treating heat stroke, revealed that "when an athlete undergoes a proper heat-acclimatization program, the body's response to exercise and heat is improved, while athletes not following a proper program face measurable risks for heat illness. A proper plan in secondary school athletic programs is essential to minimize these risks."

"Exertional heat stroke is the leading cause of preventable non-traumatic exertional sudden death for young athletes in the U.S., and studies strongly suggest that heat acclimatization appears to be one of the best strategies for reducing the risk of heat illness," says Francis G. O'Connor, MD, MPH, past president of the American Medical Society for Sports Medicine, associate professor at the Uniformed Services University and medical director for the Consortium on Health and Military Performance.

14-day heat acclimatization period

The heat-acclimatization period is defined as the initial 14 consecutive days of preseason practice for all student athletes. The goal of the acclimatization period is to radually increase exercise heat tolerance and enhance the ability to exercise safely and effectively in warm and hot conditions. This period should begin on the first day of practice or conditioning, prior to the start of the regular season. Any practices or conditioning conducted before this time should not be considered a part of the heat-acclimatization period.

Regardless of the conditioning program and conditioning status leading up to the first formal practice, all student athletes (including those who arrive at preseason practice after the first day of practice) should follow the 14-day heat-acclimatization plan.

David Csillan, MS, LAT, ATC, co-chair of the NATA task force and an athletic trainer at Ewing High School in Ewing, N.J., knows first-hand the dangers of heat illness in secondary students. According to Csillan, "these recommendations are only minimum standards, based on the best heat-acclimatization evidence available. Following these guidelines provides all secondary school athletes an opportunity to train safely and effectively during the preseason practice period." He also underscored the importance of a pre-participation physical examination administered by a physician for all student athletes.

George "Iceman" Gervin, a retired San Antonio Spurs player, NBA Hall of Fame recipient and champion of youth education and activities, supported the recommendations and important sports safety education. Gervin has founded a charter school and youth center, among other programs in the San Antonio community. "As someone who is committed to helping shape the future of our youth today - on and off the field and court - I applaud NATA and the other participating organizations on this important information. Here in San Antonio, we are making great strides to address youth wellness."

Other speakers on heat acclimatizaton at the NATA's 2009 annual meeting included Paul Saenz, DO, San Antonio Spurs team physician, who addressed the importance of these recommendations for all ages and levels of sport, from amateur to elite. "An integral part of these recommendations is to ensure all athletes are also well hydrated and that appropriate ventilation for indoor workout facilities and gyms are made available," he said.

Lynn Hickey, director of athletics at the University of Texas San Antonio, applauded the guidelines. She reinforced the importance of sports safety in secondary school sports and how vital this information is in college as well. "It is never too early to begin putting these guidelines into effect to ensure good health and safe sports participation."

In addition to NATA, the task force that developed the consensus statement comprises seven other groups, including American College of Sports Medicine, Gatorade Sports Science Institute, National Strength and Conditioning Association, United States Army Research Institute of Environmental Medicine, American Orthopaedic Society for Sports Medicine, American Medical Society for Sports Medicine and American Academy of Pediatrics.

Released at the NATA's 60th annual meeting in San Antonio in 2009, the statement also appears in the June 2009 issue of the NATA's Journal of Athletic Training.

As of March 17, 2016, the seven key recommendations of the statement have been adopted by state high school athletic associations in fifteen states (Connecticut, New Jersey, Texas, North Carolina, Georgia, Iowa, Arizona, Florida, Arkansas, Utah, Missouri, Mississippi, Rhode Island, Alabama, and Nebraska) and are under active consideration in 13 others.


National Athletic Trainers' Association

Korey Stringer Institute

1. Casa DJ, Csillan D. Preseason heat-acclimatization guidelines for secondary school athletics. J Athl Train. 2009;44(3):332-333.

2. Kucera KL, Klossner D, Colgate D, Cantu RC. Annual Survey of Football Injury Research 1931-2013 . National Center for Catastrophic Sports Injury (March 2014) 

Updated March 17, 2016, Revised and updated February 1, 2017