Understanding Environmental Heat Stress

This article has been republished from For Athletic Trainers with permission from the Korey Stringer Institute, a leader in heat stress awareness, education, and advocacy driven by a mission to maximize performance, optimize safety, and prevent sudden death due to the effects of exertional heat stress.

By: Yuri Hosokawa, PhD, ATC, LAT, Korey Stringer Institute, University of Connecticut

As the brutal summer heat takes a toll across the country, high school athletes and youth sport leagues are ramping up their summer camps and pre-season workouts in preparation for the fall season. While the importance of hydration is often emphasized during summer workouts, the use of environmental-based activity modification guidelines is often overlooked. The two major roles of environmental monitoring and activity modification guidelines are: (1) to minimize prolonged exposure to dangerous heat stress and (2) to optimize the use of practice time in the heat without overstraining the athletes.

Two of the well-accepted environmental-based activity modification guidelines for exercise in the heat are published by the National Athletic Trainers’ Association and the American College of Sports Medicine. Each guideline provides specific wet bulb globe temperature (WBGT) ranges and recommended modifications, with different types of athletic activities and populations in mind. Understanding the differences between the two guidelines will help clinicians decide which guideline better fits their needs.

National Athletic Trainers’ Association’s Guidelines (2015)¹

The most recent position statement from the National Athletic Trainers’ Association (NATA) provides example WBGT guidelines from the Georgia High School Athletics Association. The uniqueness of these guidelines is that it provides activity modification recommendations that best suits fall American football training. Epidemiological studies suggest that youth football athletes are one of the most vulnerable populations to exertional heat stroke given the time of the year they start the season and the unique physical demands in the heat that is amplified with wearing protective equipment. Therefore, having football specific modification guidelines required at the high school level across the country could direct not only the athletic trainers, but also the coaches and referees in what the appropriate modifications should be given the environmental temperatures.

It should be noted that the example provided by the NATA is adjusted for the regional environmental conditions normally observed in the state of Georgia during fall football training. Consequently, the temperature threshold may not be realistic for states in the northern part of the continental U.S. (i.e., the threshold temperatures are set too high to be practical). To address this potential regional discrepancy, Dr. Andrew Grundstein and his colleagues have proposed adjustment to the WBGT threshold by regions to account for the environmental differences observed (i.e. environmental conditions observed in Louisiana versus environmental conditions observed in Maine).

American College of Sports Medicine Guidelines(2007)²

Football is not the only form of physical activity that takes place during the summer months. While other team sports, such as soccer and lacrosse, may benefit from adapting the NATA guidelines, sports such as cross country may not find the guidelines as helpful due to the different nature of activity (i.e., intermittent vs. continuous activity). In such case, coaches and clinicians may be referred to the guidelines published by the American College of Sports Medicine (ACSM). Their activity modification recommendations are less specific to the type of sport, making it easier to implement as a global precaution for any type of physical activity in the heat. For that reason, the ACSM guidelines are also often implemented by various road race organizers in deciding if they should cancel, modify, or postpone mass participation events such as road running races.

It should also be noted that the same study by Dr. Grundstein and his colleagues have made the regional adjustments based on the ACSM guidelines to accommodate for the various climatology we observe in different part of the country.

Take Home Message

Environmental monitoring is a simple way for athletic trainers and coaches to reduce the risk of heat related injuries. It also ensures that the athletes are getting quality practice time during the summer days, where many athletes may be just getting ready to not only get used to the heat but also to exercise itself. For more information regarding the activity modification guidelines, please visit our website at ksi.uconn.edu or contact us here. #KnowYourConditions

Visit the Korey Stringer Institute for more information.

To learn more about the WBGT monitoring tool recomended by KSI and preferred by professional athletic trainers, watch this video on the Kestrel Heat Stress Line.

References:

1. Casa DJ, DeMartini JK, Bergeron MF, et al. National Athletic Trainers’ Association Position Statement: Exertional Heat Illnesses. J Athl Train. 2015;50(9):986-1000. doi:10.4085/1062-6050-50.9.07.
2. Armstrong LE, Casa DJ, Millard-Stafford M, Moran DS, Pyne SW, Roberts WO. American College of Sports Medicine position stand. Exertional heat illness during training and competition. Med Sci Sports Exerc. 2007;39(3):556-572. doi:10.1249/MSS.0b013e31802fa199.
3. Grundstein A, Williams C, Phan M, Cooper E. Regional heat safety thresholds for athletics in the contiguous United States. Appl Geogr. 2015;56:55-60. doi:10.1016/j.apgeog.2014.10.014.