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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.

Heat stroke deaths preventable 

According to the Annual Survey of Football Injury Research (2), during the most recent five year period from 2011 to 2015, there were an average of 2.2 deaths per year from exertional heat stroke, compared to 4.4 per year during the previous five year period (2006-201).  [In addition, there were two deaths in 2015 which were the result of athletes over-hydrating (e.g. hyponatremia]

The authors viewed the decline as "encouraging" and supported "continued efforts to educate coaches, school administrators, medical providers, players, and parents concerning the proper procedures and precautions when practicing or playing in the heat."  Prevention messaging, they said, "must go beyond hydrating [t] emphasize how to properly hydrate," noting that heat stroke and heat exhaustion can be prevented by careful control of various factors in the conditioning program of the athlete.

"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.

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.

As of April 2017, the seven key recommendations of the statement have been adopted by state high school athletic associations in seventeen states (Connecticut, New Jersey, Texas, North Carolina, Georgia, Iowa, Arizona, Florida, Arkansas, Utah, Missouri, Mississippi, Alabama, Nebraska, Illinois, Rhode Island, and Hawaii) and are under active consideration in many others. In those states that have adopted the guidelines, there have been ZERO heat stroke deaths in high school athletics.


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 1931-2016 . National Center for Catastrophic Sports Injury (March 13, 2017) 

Updated March 17, 2016, Revised and updated April 23, 2017