Jul 26, 2016Feeling The Heat
When the temperature creeps higher and higher during summer workouts and practices, athletic trainers must turn their attention to the heat. Exertional heat illnesses are categorized in a continuum of severity, from exercise-associated muscle cramping (EAMC) to the potentially fatal exertional heat stroke (EHS). Complete prevention of these conditions is difficult, but adhering to the following evidence-based recommendations can put athletic trainers in the best position to succeed.
To start, one key to prevention is preparation. Athletic departments should have established emergency action plans (EAPs) for potential EHS. All stakeholders should receive yearly training on the EAP, and it should be practiced regularly. Additionally, practices and workouts completed in the heat require the presence of a cold-water immersion tub for immediate treatment of individuals presenting with the signs or symptoms of EHS. With proper recognition and treatment, heat-related illnesses can generally be rectified in less than an hour, regardless of severity.
When it comes to getting athletes ready to train in sweltering weather, recent research suggests that implementing intrinsic heat acclimatization guidelines decreases the incidence of heat-related illness. Many states have already implemented their own rules on this. By gradually increasing the duration and intensity of exercise in the heat, as well as the onset of protective equipment (i.e., shoulder pads in football), athletes are able to adapt to the rising temperatures. Furthermore, heat acclimatization offers profound benefits in maintaining a lower core temperature and heart rate, expanding plasma volume, increasing sweat capacity, and decreasing perceived exertion during exercise in the heat. To maximize the benefits of heat acclimatization, clinicians should facilitate a gradual increase of heat exposure and exercise intensity over 10 to 14 days.
It’s also important to consider other intrinsic factors when it comes to heat illness prevention, especially an athlete’s overall wellness and hydration status. An ill player should be afforded a day off, as the amount gained from one practice pales in comparison to the extra demand participating will put on their body, delaying recovery and putting them at risk for heat-related illness.
Hydration state affects thermoregulatory mechanisms as well, with dehydration causing a 0.27 to 0.36°F increase in core temperature for every one percent loss in body mass. Thus, to maintain temperature regulation, the goal of hydration during exercise in the heat should be to replace sweat losses to prevent more than two percent body mass loss. Providing regular rest breaks with access to fluids during practices or workouts will aid in the maintenance of hydration status and allow for recovery.
Finally, don’t forget about extrinsic factors, such as environmental conditions, exercise intensity, and uniforms/protective equipment. These can all influence thermoregulation by limiting the efficacy of sweat evaporation and blood flow to the skin.
For instance, increased wet bulb globe temperature (WBGT) decreases the body-to-environment temperature gradient, which limits the athlete’s ability to dissipate heat. Higher exercise intensities induce greater metabolic heat production, leading to rapid elevations in core temperature. And uniforms/ protective equipment can decrease sweat evaporation and compromise heat balance, also increasing core temperature. Therefore, work-to-rest ratios should be adjusted daily to meet the demands brought on by environmental conditions, exercise intensity, and uniforms/protective equipment.
Bringing everything together, exertional heat illnesses can be prevented if appropriate precautions are implemented during exercise sessions. Being prepared ahead of time is a key place to start. Then, proper acclimatization periods will improve safety and athletes’ ability to perform in hot and humid environmental conditions. Adequate access to fluids and shaded areas will help maintain hydration and recovery during rest breaks. Lastly, monitoring WBGT to increase the amount of rest time and alter uniforms is key to improving the safety of practices during times of high risk.
Brendon McDermott, PhD, ATC, is an Associate Professor in the Athletic Training Education Program at the University of Arkansas. He also serves on the Medical and Science Advisory Board of the Korey Stringer Institute. Dr. McDermott can be reached at: [email protected].
Cory Butts, MS, is a Doctoral Research Assistant in the Human Performance Laboratory at the University of Arkansas.
References
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.
Casa DJ, McDermott BP, Lee EC, Yeargin SW, Armstrong LE, Maresh CM. Cold water immersion: the gold-standard for exertional heatstroke treatment. Exerc Sports Sci Rev. 2007;35(3):141-149.
Racinais S, Alonso JM, Coutts AJ, et al. Consensus recommendations on training and competing in the heat. Sports Med. 2015;45(7):925-938.
Attanasio SM, Adams WM, Stearns RL, Huggins RA, Casa DJ. Occurrence of exertional heat stroke in high school football athletes before and after implementation of evidence-based heat-acclimatization guidelines. J Athl Train (Suppl). 2016;51(6):S-167.
Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand: Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-390.
Armstrong LE, Johnson EC, Casa DJ, et al. The American football uniform: uncompensable heat stress and hyperthermic exhaustion. J Athl Train. 2010;45(2):117-127.
