American Football:
Hyperthermia Deaths in USA
The environment has always interfered directly or indirectly with performance in sports activities.
Outdoor sports such as soccer, American football, rugby, among others, suffer from the adverse effects of weather conditions.
In this respect, two opposing climatic extremes arise, namely, the heat of summer or the cold of winter.
In this text, we will discuss the effects of heat and the human performance of athletes.
The thermal regulation of the athlete’s body is dependent on important physiological mechanisms.
There seems to be an internal body thermostat that should average 37 ° C, in order to maintain organic homeostasis (Cossio-Bolaños et al, 2013).
In athletic activity, the energy generated by the athlete’s body, the equivalent of 60–80% turns into heat directed to the environment. In contrast, 20–40% is redirected as a useful energy for performing motor tasks (Platonov, 2008 ; Cossio-Bolaños et al, 2013).
According to McArdle et al (2011), body thermoregulation during sports activity is maintained by four processes: radiation (transfer of heat that occurs by means of electromagnetic waves), conduction (transfer of heat from one medium to the other), convection (the loss of heat from the body surface to the surrounding air colder) and evaporation (loss of heat by transforming fluids into steam in dry air).
In addition, the same author reports that hormonal adjustments also participate in body thermoregulation, and that aldosterone and vasopressin contribute to this system.
Of the four operating physiological systems mentioned above evaporation is considered the main instrument of thermal regulation (McArdle et al, 2011).
When we refer to high temperature environmental conditions, the most important item to be monitored is the relative humidity of the air. An increase in relative air humidity would induce a decrease in sweat evaporation on the skin surface, making thermoregulation difficult (Vretaros, 2015).
A thermal pathological condition is called hyperthermia, a kind of heat-related trauma.
Hyperthermia would be the junction of fatigue with the exhaustion of the ability to perform work by the athlete. Some factors that interfere in hyperthermia include duration and intensity of exercise, environmental conditions, type of exercise, athlete’s VO2max value, physical fitness, hydration level, etc (Cossio-Bolaños et al, 2013).
Dehydration precedes the state of hyperthermia (Johnson et al, 2010).
In dehydration, there are large water losses and also a reduction in the strength levels of the athletes (Vretaros, 2015).
Platonov (2008) reports three important characteristics of a thermal trauma: muscular cramps, thermal body overload and thermal shock.
American football players wear specific clothing and equipment (including the shoulder pads and helmet) for safe practice.
In this sense, all this equipment and clothes create an internal microclimate in the athletes that hinders an effective loss of heat. This may adversely affect the players’ performance, as well as being affected by thermal injuries (Armstrong et al, 2010).
The body weight of American football players is another aspect that contributes negatively to the thermoregulation process during the summer.
The vast majority of athletes who occupies the position of offensive linemen and defensive linemen are overweight and obese. Players from other positions also have some similar characteristics.
Anzell et al (2013) verified the anthropometric evolution of American football players between the years 1942 and 2011. In the group of mixed linemen (offensive and defensive linemen, tight ends, and linebackers) in professional athletes there was an increase in body weight of 0,098–0,756 kg per year. In this same group the body fat percentile changed -0,053 to 0,170% per year.
In the study by Malina et al (2007), American footballers from 8,7 to 14,6 years of age were evaluated. Overall, 45,0% of overweight players were found and 42,6% were obese.
In other research with collegiate players, 50,6% of the total were overweight or obese (Mathews & Wagner, 2008).
Let’s think: an American football player with high percentile body fat added to the equipment and in the hot summer weather can suffer thermal injuries more than another athlete as less body weight. Right? Yes!
But why? We can speculate that the overweight or obese athlete has to withstand a much greater load of physiological stress than an athlete who has less weight during training or games.
Lower body surface area for body mass proportions and higher percentages of body fat increase the heat stock and inhibit the cooling of these players (Grundstein et al, 2012).
Alckmin et al (2018) studied fluid replacement in American football players, those who were overweight (4,35%) and obesity (26,09%) had increased cardiovascular risk. The tactical positions of offensive linemen and defensive linemen were the most at risk.
Johnson et al. (2010) report that between 1995 and 2001 there were 21 player deaths due to heat stress.
The authors report an equation of heat balance:
S=M-W+\-K+\-R+\-C+\-E
S= heat storage
M= metabolic heat production
W= external work
K= conduction
R= radiation
C= convection
E= evaporation
This same group of researchers compared three situations of use of clothes and equipment with American footbal players: 1) Control Group (which consisted of compression shorts, athletic shorts, ankle length socks, and sneakers), 2) Partial Uniform Group (which consisted of over-the-calf socks, sneakers, gloves, T-shirt, jersey, compression shorts, pants, and pads on knees and thighs) and 3) Full Uniform Group.
In a protocol of exercise until fatigue, the group with full uniform felt the highest thermal perception (7,4+\-0,4) in relation to the other groups.
In the research by Grundstein et al, (2012) there were 58 deaths of American football players from 1980 to 2009, in situations where the relative air unit was elevated.
According to the authors, the vast majority of deaths occurred in the pre-season month (august) and in the morning.
Acclimatization is a strategy to adapt the athlete’s body to adverse temperatures (McArdle et al, 2011 ; Platonov, 2008).
Cossio-Bolaños et al (2013) present the physiological advantages of applying acclimatization in athletes, namely: a)- improvement in body temperature at rest, b)- lower skin temperature, c)- reduction of internal temperature, d)- reduction in metabolism, e)- reduction in heart rate during exercise, f)- increased sweating and g)- increased evaporation.
A period ranging from seven to nine days would be required for optimal acclimatization. It seems that in this period of time, the first few days are the most difficult due to a significant drop in work capacity (Platonov, 2008).
So I found a scientific article that longitudinally analyzes the death of American football players for hyperthermia problems during the years of 1980 until 2010.
✅ The infographic was adapted from Grundstein et al, (2012). A retrospective analysis of American football hyperthermia deaths in the United States. International Journal of Biometeorology, 56 (01); 11–20.
- ** This text was originally written in my BLOG.***
- My BLOG: https://adrianovretaros.blogspot.com/
REFERENCES
Alckmin et al (2018). Estado de hidratação e composição corporal de jogadores de futebol americano flag. Revista Brasileira de Nutrição Esportiva, 12 (69); 04–12.
Anzell et al (2013). Changes in height, body weight, and body composition in American football players from 1942 to 2011. The Journal of Strength and Conditioning Research, 27 (02); 277–284.
Armstrong et al (2010). The American football uniform: uncompensable heat stress and hyperthermic exhaustion. Journal of Athletic Training, 45 (02), 117–127.
Cossio-Bolaños et al (2013). Treinamento em condições de calor e frio. IN: Arruda et al (Org). Futebol — Ciências aplicadas ao jogo e ao treinamento. São Paulo; Phorte.
Grundstein et al. (2012). A retrospective analysis of American football hyperthermia deaths in the United States. International Journal of Biometeorology, 56 (01); 11–20.
Hoffman, J. R. (2008). The applied physiology of American football. International Journal of Sports Physiology and Performance, 03 (03); 387–392.
Johnson et al, (2010). Perceptual responses while wearing an American football uniform in the heat. Journal of Athletic Training, 45 (02); 107–116.
Malina et al (2007). Overweight and obesity among youth participants in American football. The Journal of Pediatrics, 151 (04); 378–382.
Mathews, E. M., & Wagner, D. R. (2008). Prevalence of overweight and obesity in collegiate American football players, by position. Journal of American College Health, 57 (01); 33–38.
McArdle et al (2011). Fisiologia do Exercício. 7a.edição. Guanabara Koogan; Rio de Janeiro.
Platonov, VN (2008). Tratado geral de treinamento desportivo. São Paulo; Phorte.
Vretaros, A. (2015). Futebol: Bases científicas da preparação de força. E-Book; São Paulo.
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