Kids and Heat: Making Exercise Safe

From Medscape Pediatrics An Expert Interview With Michael F. Bergeron, PhD Laurie Scudder, DNP, NP; Michael F. Bergeron, PhD Editor's Note: The American Academy of Pediatrics (AAP) Council on Sports Medicine and Fitness and the Council on School Health recently issued a policy statement titled "Climatic Heat Stress and Exercising Children and Adolescents". In a revision of a previous statement issued in 2000, this new policy statement relies on recent evidence to provide guidance to support clinicians in providing advice to children, teens, parents, coaches, and others that allows for safe participation in outdoor sports and exercise in a range of adverse climatic conditions including high heat and humidity. Laurie Scudder, DNP, NP, spoke with Michael F. Bergeron PhD, lead author of the policy statement; Director, National Institute for Athletic Health & Performance at Sanford Health ; and Professor, Department of Pediatrics at The University of South Dakota, about this policy and implications for clinicians. Medscape: Dr. Bergeron, the AAP policy statement is supported by a number of recent studies that compared body temperature regulation, exercise tolerance, and cardiovascular responses between similarly fit children and adults exposed to equally intensive exercise and environmental conditions and concluded that, assuming appropriate preventive measures are undertaken, children and adults tolerate these conditions equally well. Could you expand briefly on some of these key studies and findings? Dr. Bergeron: The earlier policy on this topic was based on physiologic and anatomic characteristics of children that had been thought to impair thermoregulatory ability, particularly during exercise in the heat. One of these factors was a reported low exercise economy; that is, there has been a concern that kids expend a much higher amount of energy during physical activity and consequently would produce more heat for a given level of exercise. However, at the same relative exercise intensity (commensurate with body size), there are no differences between children and adults. Second, children up to about 13 years of age have a much higher ratio of body surface area to their mass. That was thought to put them at a temperature regulation disadvantage, suggesting that they potentially could gain more heat from the sun and such. And children do have a lower sweating capacity up until the later teenage years. Some of the early evidence also suggested that their cardiovascular capacities including cardiac output were lower than adults. Collectively, all of that set the stage for a perspective that kids would be at a much higher risk for poorer physical performance and heat-related illness during physical activities in hot climates. However, more recent research, both my own and that of a number of others, does not support this notion. The more current research has done a better job in more directly comparing identical relative exercise intensities in the same environments with equal levels of hydration in adults and kids. Also, these studies do not support the contention that there is a maturational disadvantage during exercise in the heat. Therefore, the AAP Council on Sports Medicine and Fitness and the Council on School Health wanted to make the point in the new policy statement that the evidence does not suggest or support that children and adolescents are at any kind of thermoregulatory or cardiovascular disadvantage. Kids were also thought to not be able to adapt to the heat as well as adults. Again, more recent research does not support that. Of note, most of the research conducted in this area has been done with children 8 years of age and older. There is not a lot of research on temperature regulation with children younger than 8 years. Accordingly, there may be some differences in those earlier ages. However, when we're talking about sports and exertional heat illness, it is usually children and adolescents in the later elementary school into middle and high school years who are typically participating in these activities. Again, are there temperature regulatory differences in younger children? There may be, but that is not the population in the policy statement toward whom we're really directing the attention. The new policy focuses on the factors that do indeed put kids at risk. Although children are not at a maturational disadvantage for increased risk from exercise in the heat, there are a host of modifiable factors that do lead to higher risk when exercising in the heat. Medscape: As you noted, the new policy stresses that heat-related illnesses such as heat cramps, exhaustion, and stroke are caused by known, preventable risk factors. What are the biggest risk factors for incurring heat illnesses during sports? Dr. Bergeron: There are certainly a number of things that can increase risk. The environment itself, being hot, causes body temperature to go up even if you're not doing anything. When you exercise, your body produces a lot of heat. Normally there are a number of ways that the body gets rid of that heat, the primary mechanism being sweating. Additionally, a breeze can very effectively contribute to a convective heat loss. The hotter it is, the more heat that your body will be producing, especially during intense exercise. The more humid it is, the more that you're going to sweat and the less effective that sweat is in releasing the energy or heat from the body because, in order for sweat to be effective in regulating temperature, it needs to evaporate. The more water in the air, the less evaporation, and you see that as sweat beads up on your skin or just rolls off to the ground. Hot and humid conditions that include intense solar radiation and a lack of a breeze are the worst conditions. Hazy, hot, humid, and still days are common, even in the late summer and early fall in some regions. When you look at what primarily causes kids to have problems, it usually comes down to doing too much for too long in too hot of an environment. Sometimes this occurs before a child or adolescent is acclimated to the heat. However, if you work young athletes hard enough and long enough in an extreme environment, even those who are used to these summer conditions are going to have problems. Also, kids typically do not tend to be well hydrated before, during, and after activities in the heat, especially with multiple same-day practice sessions or competitions and tournament scenarios. Insufficient recovery time and recovery nutrition are often important contributing problems, too. There are a host of other factors. Preseason practice starts in the late summer. Kids may have spent a lot of time indoors and are not used to the outdoor weather. They may also not be well rested, and are often not fit enough and prepared for the intensity, duration, and type of activities that they jump right into. This sets up a "perfect storm" for all the kids who are not acclimated and well prepared physically, nutritionally, restwise, or fitnesswise. Then you place this very motivated group of kids on a team with a motivated coach. This enthusiasm and sense of urgency to get these kids ready in a short amount of time, when they are not as prepared to tolerate the practices as coaches and parents think they are, readily prompts a number of risks and problems. Of course, you also have kids who don't want to quit or show "weakness". There are certainly a lot of factors. However, it usually boils down to doing too much, too long, too hard, in too hot of an environment. Medscape: The statement indicates that although most children can indeed exercise safely in the heat if the right precautions are taken and modifications are made, certain ones should be, at least temporarily, restricted from exercise in excessive heat including those with recent illnesses, diabetes insipidus, type 2 diabetes, obesity, cystic fibrosis, hyperthyroid conditions, or any acute or chronic condition that affects water-electrolyte balance or thermoregulation. All of these make intuitive sense. The document also noted that kids with sickle cell trait merit specific concern because exertional sickling may contribute to heat intolerance and related clinical problems. Can you discuss this a bit more? What specific recommendations would you make for this group of children? Dr. Bergeron: Sickle cell trait, of course, is different from sickle cell disease because most of the hemoglobin for those with sickle cell trait is normal, with anywhere from 30% to 40% having the sickle characteristic. By and large, routine physical activity, whether it's sports or playing, is not associated with any notable signs or symptoms. Accordingly, there are no restrictions for these children and adolescents, and these kids may not ever be aware that they potentially might have a problem. However, more and more, epidemiologic studies, case studies, and other research has found that exercise that is high enough in intensity and conducted in sufficient thermal stress can cause an effect similar to what might happen at altitude. A certain amount of measurable red blood cell sickling can cause potential occlusion at the small microvessels. This would also prompt a widespread immune system response that begins an entire cascade of events in the blood and vessels, via cell adhesion molecule activity and other changes that create the potential for localized vascular dysfunction prompting full blockage or restricted blood flow and consequent problems. It is not totally clear whether the exertional rhabdomyolysis often associated with sickle cell trait and intense, repeated exercise is the result of the activity level being too high or whether sickle cell trait was the primary independent contributing factor. The National Collegiate Athletic Association is now considering a proposal to require screening of all of their athletes, although this is still a contentious issue. The current thinking is that those with sickle cell trait should more deliberately build up their training; self-pace; and avoid high-intensity, repeated activities, especially at the end of a practice. If those athletes with sickle cell trait exhibit a problem, then they should indeed promptly stop and get assessed. Sickle cell trait warrants concern, particularly when these kids are exercising hard and repeatedly in a hot environment. Otherwise, most activities are going to be just fine. Medscape: Can you speak to other risk factors that may put kids at risk for excessive heat retention or poor thermoregulation, such as uniforms? Dr. Bergeron: Uniforms and protective equipment are barriers to heat dissipation, whether it's a helmet, shoulder or leg pads, sleeves, or pants. All prevent heat from being dissipated and create a heavier metabolic and thermal load. It is harder work just to carry all that extra padding and the uniform, so metabolically, there is a greater demand. There are many other factors that are worth talking about. As the new policy statement from the AAP makes clear, you really need to look at everything including education, awareness, and preparation. It is the responsibility of coaches, parents, and the athletes themselves to be sure that they're ready and that they understand the risks and the signs and symptoms of a heat-related problem. It really comes down to monitoring and paying attention. We must recognize when children are having difficulty and get them off the field and promptly and properly attended to. It should also be appreciated that people with developing heat-related illness are often the worst ones to judge if they are having serious problems. Affected kids need to stop when they often don't want to because they don't want to be seen as weaker. However, these kids are also often not even capable of assessing themselves. It is incumbent on all involved, including the other players, to recognize and respond to developing problems. Of course, the adults involved need to ensure that sufficient preparatory steps are taken and emergency procedures are in place and practiced in order to reduce the risk for catastrophic outcomes. There is a lot of attention on hydration, as there should be. Hydration is integral to safety and performance in any athletic activity, especially in the heat. However, you can be pretty well hydrated and still get into trouble. So hydration is not the only answer. There is also concern about the high-caffeine energy drinks that kids have been using with more frequency recently. These may cause an increase in fluid loss or even mask fatigue and allow kids to push themselves too hard. I am often asked, "When is it unsafe to exercise, that is, at what temperature should kids not go out there?" It is really a sliding scale, with risk increasing as the number of risk factors increases. Then the urgency for some kind of offsetting action becomes greater. However, it is not the same for everybody and not the same for all conditions. It is important to assess both the athletes and the conditions with which you are dealing and appropriately and sufficiently accommodate for that. The main point of the AAP statement is to recognize that you can do a lot out in the heat and in a lot of environmental circumstances, as long as you make the appropriate adjustments. Medscape: That is a good segue to my next question. The AAP statement emphasizes the importance of preconditioning, suggesting that this process of acclimatization include graduated exposure over 10-14 days to increasing environmental temperatures as well as increased intensity and duration of physical activity. In your experience, is this time frame generally provided? Are there more specific guidelines available to describe this process? Dr. Bergeron: As I indicated earlier, preseason sports activities often focus on accomplishing a lot in a short amount of time with a high level of enthusiasm and motivation. Coaches and players often have a sense of urgency that they only have 2 weeks or so to prepare for the season and therefore must push. In the case of football, exertional heatstroke deaths most often occur in the first few days. Again, it goes back to doing too much, too long, too hard, and too soon. What coaches, parents, and the kids themselves need to realize is that they are not professional athletes and are typically not conditioning year-round. The kids are probably not as conditioned as they think they are, and coaches want them to be. Even those who live in a warm environment may be spending a lot of time indoors. They begin the season likely not used to exercising in hot conditions with high intensity and long duration, especially in a uniform. It really makes a lot of sense to give kids a chance to adapt, not only to the environment, but to the intensity, duration, and uniforms. If you give kids a chance to progressively adapt, they not only will be safer, but these young athletes will perform better too! In someone fully unacclimatized to the heat, it can take 10 days to 2 weeks for the body to adapt by increasing blood volume, so that exercise causes less cardiac stress and increasing sweating ability. With exercise-heat acclimatization, the body also conserves electrolytes, primarily sodium and chloride, to improve fluid retention. These are adaptations that happen over a period of time. Although 2 weeks is ideal, progressing through those first few days more sensibly can really make a big difference. Medscape: The statement does not specifically address parents. What recommendations should a healthcare professional provide to parents and teens about readiness for hot weather sports? Dr. Bergeron: Preconditioning is important and something that needs to be done over a long period of time. When you look at the preseason period, whether it's football or soccer, the notion is that there are 2-3 weeks to get athletes in shape. The body does not adapt that quickly. Conditioning and fitness cannot be changed in a very short amount of time. However, an athlete can get fatigued and be seriously hurt in a very short amount of time. True changes, ie, measurable changes in fitness and conditioning, take a long period of time. Parents, kids, and coaches need to recognize that you are not going to make substantial gains in fitness and athletic capacity in 2-3 weeks. If you try to, you're just going to put these kids at risk for some kind of injury or maybe worse. Being rested, well fed, and well hydrated places athletes in a better state to tolerate the heat. Some research also has shown that being sleep deprived increases vulnerability to the heat. Kids can't be staying up late and ignoring meals. The discussion really needs to be that: If you're going to play sports, you need to have some kind of plan so that you're not just sitting idly and waiting for the season and then you go. It needs to be a balanced, multifaceted, long-term physical activity conditioning and recovery plan that helps prepare for that. However, it is also important to realize that these kids are playing sports primarily for fun, the socialization, and, hopefully, health. They are not professional athletes. If you work them like professional athletes, there will be consequences. They are primarily students and sports are a part-time activity. Unfortunately, a lot of parents, coaches, and sports academies have taken on more of a professional development model, which overlooks sufficient progressive adaptation, rest, and recovery -- and the fact that these kids are student athletes! Athletes, coaches, administrators, and parents must understand the real and more realistic objective. Medscape: The policy includes specific hydration recommendations, suggesting that 9- to 12-year-old children consume 100-250 mL every 20 minutes and that teens drink up to 1.0-1.5 L/hr during physical activity in the heat. Although water is usually sufficient, exercise of longer duration -- more than an hour or so or repeated same-day sessions -- may warrant use of electrolyte solutions. Is this true for children of all ages? What about younger kids? Are beverages containing carbohydrates warranted in some situations? Dr. Bergeron: It's difficult to give a hard-and-fast answer to that. If you're not going to be exercising very long and you're just going to be exercising once a day and you're having normal meals, then drinking water as you feel you need it during those activities and more if it's hotter is going to be just fine for even older kids. However, for the longer you go, the harder you go, and the hotter it is, the proportional value of something else besides water is going to increase. In other words, you're going to be expending more energy, whether it's because of high intensity, long duration, repeated bouts, or because the heat itself is causing you to use carbohydrates at a greater rate. Maybe then you're not going to get enough energy and electrolytes from meals alone. This happens with a lot of kids in tournament scenarios who are playing multiple times each day during a weekend event. They don't have time for sufficient meals between competitions. In these kinds of situations, there is likely an advantage of having some kind of carbohydrate-electrolyte drink. What does a child or adolescent need during physical activity from a nutrition perspective? They certainly need water. As they go longer and harder, they need some kind of carbohydrate, whether they're taking that in as a food snack or in a sport drink. As you get older, the volume of sweat is greater and the amount of electrolytes, primarily sodium and chloride, lost from sweat become greater too. I would say that replacing electrolytes from sweating is not generally of primary importance in somebody up to about 12-13 years of age. However, by 14-15 years of age, when the sweat rate is higher and the concentration of electrolytes is greater, salt loss is a larger issue. Parents will often note that their kids never had a problem with electrolyte deficits and muscle cramping at a younger age but do experience more problems at 14 or 15 years of age. Accordingly, they need to pay a little bit more attention to water and sodium loss through sweating, especially the more times they play and the more times they're exercising for longer durations. Again, it depends on the situation: the recovery time and meal opportunities; the duration of the activity; and how many times you're doing it on the same day. You need to get your nutrition in there one way or the other. If you can't do it with meals, you need to be thinking about something else. Medscape: The statement also emphasizes the importance of trained personnel and facilities capable of treating heat illness being readily available. This may not always be the case in lower-resource communities. Can you expand on this? What specific types of facilities should be available? An emergency action plan with clearly written protocols is also recommended. Are there resources to assist schools and communities with development of these plans? Dr. Bergeron: Part of the effectiveness of cooling is early recognition. So the first step is to recognize that there's a problem and promptly respond. If an athlete is believed to be overheated, then he or she should be immediately stopped and taken out of the sun and heat. If there is an opportunity for getting indoors into air-conditioning or in the shade, that should be done. Rehydrate if possible. If it appears that athlete children or adolescents have crossed the threshold to exertional heatstroke because their body temperature is elevated, this is an emergency. Although checking body temperature is not always feasible, if the affected youth is showing central nervous system changes or collapses, then having something like a wading pool or tub filled with water and ice available can save a life. Promptly submerging most of the body in cold water or rotating cold wet towels and fanning are not expensive solutions. This just requires forethought and having and promptly implementing a plan. That is what is spelled out in the policy statement: You need to have an emergency action plan in place. It doesn't have to be extensive. It would be nice if you had an athletic trainer on-site. Unfortunately, a lot of schools don't have that luxury. However, you at least need to have people learn the signs and symptoms of heat illness and have a sense of urgency when they see evolving heat illness; it's a lot easier to catch it early. You can always put athletes back in a game, but once they collapse with exertional heatstroke, there's no do over. Now you're dealing with a medical emergency. Again, having the education and awareness to recognize an emergency and the forethought to have on-site some kind of simple, rapid cooling system available, such as a wading pool and some water and ice, can save a life. Medscape: Are there resources available for schools and communities that don't have a trainer available and wish to develop emergency action plans? Dr. Bergeron: There are a number of resources. The American College of Sports Medicine (ACSM) has a 2007 position statement on Exertional Heat Illness During Training and Competition. It includes a lot of information about the physiology and recognition of problems with heat. They outline suggested equipment and supplies for treating heat-related illnesses, what should be on hand, and how to treat athletes should they have problems. The National Athletic Trainers' Association has a number of guidelines, too. A 2010 paper outlined the prevention, recognition, and treatment of a number of problems and describes simply the equipment that should be on hand.[1] Medscape: You also served as lead author for the ACSM's 2005 consensus statement on heat stress and injury risk in youth football players. Are there any notable differences between these 2 recommendations? Dr. Bergeron: There are not many differences. The ACSM youth statement was specific to youth and high school football. Therefore, the recommendations are very specific to the football preseason period. That is one of the only, if not the only, sports-specific guidelines for reducing risk in the heat of which I'm aware. However, as we said in the AAP policy statement, you can apply those guidelines as a template for other sports. The whole idea is that the foundation of what we recommended with the ACSM in 2005 is the same foundation in the AAP statement. You need to be educated and prepared. Athletes need to acclimate and progress slowly. Adults need to monitor and respond. The bottom line is very similar. Medscape: Are there any other key elements of this new statement that you would like to emphasize? Dr. Bergeron: Although these guidelines provide more latitude, they are not intended to downplay the challenge or the health threat of environmental heat stress and exercise in the heat. The main point is worth reiterating: Risk can be substantially reduced if modifiable factors are appreciated and appropriately addressed. If the workload is adjusted and these recommendations followed, most, if not all, exertional heat-related problems would be averted. The statement should provide some degree of comfort that sports and exercise can be fun and safe even in the summertime. Again, it's not that you don't recognize that there can be challenges and problems, but we don't always have to shut everything down. Kids never play themselves to death. It's really the scenarios and circumstances that adults create and inflict on them that cause problems. References