Heat Acclimatization for Linemen in High School Football

Exertional Heat illness (EHI) is the leading cause of preventable death and disability in high school athletics. EHI is a collection of illnesses including heat cramps, heat syncope (fainting), heat exhaustion and exertional heat stroke (EHS). These affect approximately 9,000 high school athletes annually, at a rate of about 1.20 per 100,000 athlete exposures.1

American football carries the highest risk of heat illness at a rate of 4.42 per 100,000 athlete exposures, about 11 times higher than all other sports combined. EHS was the cause of 159 fatalities in youth, high school and collegiate football players from 1955 to 2021, averaging two deaths per season.3 Unfortunately, the rate has continued to rise despite mitigation efforts with nine deaths in 2021.

Anderson et. al in “Preventing Exertional Heat stroke in Football: Time for a Paradigm Shift”2 discuss this negative trend, pointing out the one-size-fits-all approach fails to protect those most at risk. Football linemen make up 97 percent of all football EHS fatalities. There are many reasons for this, primarily due to the self-selection of larger athletes with both more lean mass and fat mass. Lean mass generates more heat, and fat mass retains it, making these athletes more susceptible to more heat generation and slower cooling. The most effective way to mitigate risk of EHS for our athletes is to focus on policies targeting this highest risk group. Consider the specific interventions suggested by Anderson et al to prevent EHS fatalities.

The largest focus on changes should be focused on training and conditioning, as 100 percent of EHS deaths have occurred during conditioning and none during game play. The first two to four days of practice in a new season have the highest risk. Previous efforts have focused on acclimatization, hydration and uniform modifications. Interestingly, while there has been a push to slowly transition from shorts and t-shirt to helmet and pads, 70 percent of EHS deaths from 1998 to 2018 happened in t-shirts, not pads. Instead, changes should be made in how these athletes are trained, specifically linemen.

One major way to reduce risk for linemen is to train these athletes for their position-specific game demands. A study in 2014 by Wellman et al was performed to evaluate the difference in movement and demands of different positions in collegiate football players by giving 33 athletes GPS devices with accelerometers and tracking their movements during 12 games.3 The study indicated that defensive backs, linebackers and wide receivers had significantly more distance and higher intensities than offensive linemen, defensive linemen and defensive ends.

For example, wide receivers ran approximately 6,048 yards vs. offensive linemen who ran 3,994 yards, with about 79 percent of the distance being low intensity. In fact, wide receivers ran at max intensity 345 yards on average, whereas offensive linemen ran 10 yards at max intensity. The study also tracked the overall number of movement efforts and found that offensive linemen had statistically more moderate acceleration efforts than quarterbacks and running backs, but less maximal acceleration efforts (approximately 1.5 times per game).

Therefore, given the differences in distance and intensity required for game performances, their training should reflect this. It is the recommendation of the Collegiate Strength and Conditioning Coaches Association (CSCCa) to adopt a 50/30/20/10 rule for conditioning by reducing workloads each week by the corresponding percentage amount to ramp up over the first four weeks, and to also keep in mind the FIT rule (frequency, intensity volume and time of rest interval).

However, even with reducing repetitions and speeds, timed mile runs or sustained sprinting for distance (conditioning tests), particularly in the first two weeks, are still going to put linemen at risk, and these workouts are not consistent with their game play demands. Therefore, it is recommended to focus on position-specific conditioning and eliminate serial sprints for linemen.

Risk factors can both be categorized as individual and organizational. The individual risk factor is the body habitus and individual athlete’s underlying medical diseases, such as sickle cell disease. Organizational risks include the training program, as well as organizational culture, which may unintentionally encourage athletes to disregard their personal safety to prove a “no quitting” attitude. Additionally, it is an unequivocal recommendation by multiple bodies that physical exertion should never be used as punishment; this is a high risk move.

Additionally, modify/reduce physical activity when higher heat loads exist. The average temperature during recent football EHS deaths was 90.8 (32.7C) and wet bulb globe temperature was 76.7 F (24.8C). While hot and humid weather can be a risk factor, athletes, particularly linemen who generate more heat and retain it, can be at risk in cooler and “normal” environments.3

The focus on preventing EHS and EHI overall should be primarily targeting those most at risk – linemen who are at higher risk due to higher heat production and retention. Solely relying on uniform modification is not enough. Additionally, hydration, while important, is an ineffective cooling strategy on its own, and overhydration has led to three high school football players’ deaths in the last 20 years due to hyponatremia (low/diluted sodium).

It is important to also look at athletes on an individual basis. Overall, to reduce EHS in athletes, changes must be made by targeting specifically linemen who have had the highest fatalities and modify their training programs to target position-specific demands of game play.

References

1. Kerr ZY, Casa DJ, Marshall SW, Comstock RD. Epidemiology of exertional heat illness among U.S. high school athletes. Am J Prev Med. 2013 Jan;44(1):8-14. doi: 10.1016/j.amepre.2012.09.058. PMID: 23253644.

2. Anderson SA, Eichner ER, Bennett S, Boden BP, Colgate B, Courson R, Davis JK, Elkins GA, Judge LW, Krueger M, Kucera KL, Niehoff K, Rooks Y, Tucker JB, Roberts WO. Preventing Exertional Heat Stroke in Football: Time for a Paradigm Shift. Sports Health. 2024 Jun 14:19417381241260045. doi: 10.1177/19417381241260045. Epub ahead of print. PMID: 38874455; PMCID: PMC11569638.

3. Wellman, Aaron D.1; Coad, Sam C.1; Goulet, Grant C.2; McLellan, Christopher P.1. Quantification of Competitive Game Demands of NCAA Division I College Football Players Using Global Positioning Systems. Journal of Strength and Conditioning Research 30(1):p 11-19, January 2016. | DOI: 10.1519/JSC.0000000000001206.

Dr. Scott Goodsell and Dr. Jackson Bagby are sports medicine fellows at the University of Nebraska Medical Center. Dr. Kody Moffatt is a physician at Children’s Nebraska and the University of Nebraska Medical Center, and he is a member of the NFHS Sports Medicine Advisory Committee.