Home » Proper Acclimatization Key to Preventing EHS in Young Athletes, Especially Football Players

Proper Acclimatization Key to Preventing EHS in Young Athletes, Especially Football Players

A few years ago, I spent three brutally hot and humid July days presenting workshops on injury prevention to a large group of high school football players, parents and coaches at a well-known football "combine" in Williamsburg, Virginia. According to the iHydrate smartphone app developed by MomsTEAM, the heat index (temperature plus relative humidity) outside was a dangerous 123oF. Fortunately, I was able to give these talks in the comfort of an air-conditioned auditorium.

Brooke de Lench at football combine

It was no wonder that the events were standing room only; the parents wanted to be inside. I began each talk with information on heat injury prevention and ended with psychological and sexual injury prevention. The majority of questions I received throughout the sessions were about concussions. Given the weather, I recall being troubled that none were about heat-related illness, and suggested to the assembled parents that they might want to bring their children in from the dangerously hot and humid conditions where they were practicing.

The combine drew athletes from across the nation and you could tell that most of them were struggling to compete in the heat.  Interestingly, I spoke to a group of parents from Oklahoma, whose children were seemingly unaffected by the heat and performing well. In talking with their parents it became clear why that was - they were already acclimatized to the heat. A summer of being outside fixing fences, working with livestock, haying and landscaping had unwittingly prepared them for this type of high-intensity activity in high temperatures.

Mending fences in the summer heat

"Studies strongly suggest that heat acclimatization appears to be one of the best strategies for reducing the risk of heat-related illness," (1)  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.

After the combine, I called area hospitals to find out if my fears about heat-related illness had been justified. They confirmed that more than 20 athletes from the combine had been seen due to heat-related illness alone, and that several had experienced exertional heat stroke (EHS), the most severe form of heat-related illness, which can cause irreversible damage to vital organs including the brain, or even death. (2)  Not surprisingly, most cases had occurred on the first day of the combine, before the players acclimatized to the heat.

Heat Acclimatization Guidelines


EHS is the third leading cause of sudden death in high school athletes. (3,4) It is therefore critically important that football and other sports programs take steps to reduce the risk that participants will suffer heat-related illnesses, especially during hot weather in the summer and fall. One of the best ways to do so is by following heat acclimatization guidelines, such as those included in the consensus statementissued by the National Athletic Trainers' Association (NATA) and a number of other sports medicine organizations in 2009. (1)

MomsTEAM hydration expert Dr. Susan Yeargin, Assistant Professor in the Physical Education and Athletic Training Department at the University of South Carolina and a co-author of the consensus statement, has noted that the guidelines recommend a 14-day heat-acclimatization period prior to full-scale athletic participation by secondary school students.

Statistics suggest that these guidelines may already have prevented deaths. According to the Annual Survey of Football Injury Research, there were an average of 2.2 deaths per year from exertional heat stroke from 2011 to 2015, compared to 4.4 per year during the previous five years (2006-2010), not counting two deaths in 2015 which were the result of athletes over-hydrating. The survey 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." (5)Young football hydrating in heat
Plenty of education is still needed. As of April 2017, the seven key recommendations of the NATA statement, which was updated in 2015, have been formally adopted by state high school athletic associations in only seventeen states (Connecticut, New Jersey, Texas, North Carolina, Georgia, Iowa, Arizona, Florida, Arkansas, Utah, Missouri, Mississippi, Alabama, Nebraska, Illinois, Rhode Island, and Hawaii), although they are under active consideration in many others. (6)

To me, adoption of these guidelines seems like a no-brainer: In those states that have adopted the guidelines, there have been ZERO heat stroke deaths in high school athletics as of 2016. (7)  If your state hasn't adopted the guidelines, you owe it to your child to ask the state athletic association to do so immediately.

Note: Photos were taken of some of the Oklahoma football team members during the shooting of The Smartest Team: Making High School Football Safer (PBS)

Brooke de Lench is the Founding Executive Director of MomsTeam Institute, publisher of MomsTeam.com and director of Smart Teams Play Safe, Producer of The Smartest Team: Making High School Football Safer (PBS) and author of Home Team Advantage: The Critical Role of Mothers in Youth Sports (Harper Collins), and is well known as the "Mother of Youth Sports Safety" for her tireless advocacy and solutions-based work in safeguarding young athletes.


  1. Casa, Douglas J., Csillan, David. Preseason Heat-Acclimatization Guidelines for Secondary School Athletics. J Athl Train. 2009;44(3). doi:0.4085/1062-6050-44.3.332
  2. Walter EJ, Carraretto M. The neurological and cognitive consequences of hyperthermia. Critical Care. 2016;20(199). doi:10.1186/s13054-016-1376-4. 
  3. King MA, Leon LR, Mustico DL, Haines JM, Clanton TL. Biomarkers of multiorgan injury in a preclinical model of exertional heat stroke. J Appl Physiol. 2015;118:1207-1220. doi:10.1152/japplphysiol.01051.2014.
  4. Jardine DS. Heat illness and heat stroke. Pediatr Rev Am Acad Pediatric. 2007;28(7). doi:10.1542/pir.28-7-249.
  5. Kucera K, Klossner D, Colgate B, Cantu R. Annual Survey of Football Injury Research. National Center for Catastrophic Sport Injury Research; 2016. https://nccsir.unc.edu/files/2013/10/Annual-Football-2015-Fatalities-FIN.... Accessed June 23, 2017.
  6. Yeargin S. Pre-Season Heat-Acclimatization Guidelines. MomsTeam. http://www.momsteam.com/health-safety/pre-season-heat-acclimatization-gu.... Updated March 17, 2016. Accessed June 23, 2017
  7. Rauf D. Guidelines Stop Heat Stroke Deaths in High School Athletes. June 23, 2016. HealthDay. http://health.usnews.com/health-care/articles/2016-06-23/guidelines-stop.... Accessed June 23, 2017.
Published first on Huffington Post on August 7, 2017  Updated July 1, 2019