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Pediatric and Adult Nutrition in Chronic Diseases, Developmental Disabilities, and Hereditary Metabolic DisordersPrevention, Assessment, and Treatment$

Shirley W. Ekvall and Valli K. Ekvall

Print publication date: 2017

Print ISBN-13: 9780199398911

Published to Oxford Scholarship Online: April 2017

DOI: 10.1093/acprof:oso/9780199398911.001.0001

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Sports Nutrition

Sports Nutrition

Chapter:
(p.71) 7 Sports Nutrition
Source:
Pediatric and Adult Nutrition in Chronic Diseases, Developmental Disabilities, and Hereditary Metabolic Disorders
Author(s):

Karen Reznik Dolins

Martica Heaner

Publisher:
Oxford University Press
DOI:10.1093/acprof:oso/9780199398911.003.0007

Abstract and Keywords

This chapter discusses sports nutrition for children, including the health benefits of physical activity, the health risks of inactivity, hyperlipidemia, and hypercholesterolemia. Factors to be considered in nutritional evaluation are described, including , growth, weight, body composition, and dietary habits. Guidelines for physical activity are provided, including resistance training, cardiovascular exercise, flexibility, dietary management, and the fluid needs of active children.

Keywords:   sports nutrition, guidelines for physical activity, hydration, dangers of inactivity, benefits of exercise

Nutrition and physical activity play a dual role in good health. Because the two are inextricably linked, it is important to avoid focusing on one area while neglecting the other. Both regular exercise and good nutrition can provide a wide array of physiological, psychological, and functional health benefits to all children, especially those with chronic illnesses or developmental disorders. When implementing physical activity regimens, one should follow established exercise guidelines and make any necessary modifications as dictated by the child’s specific medical condition. Nutritional intake should meet the child’s basic nutrition needs to optimize health as well as to enhance the child’s physical performance.

Sports nutrition is a relatively new area of research. Little is known about the best protocols for physical activity and sports nutrition in many special populations, including ill children and those with disabilities. Exercise plans and nutrition regimens should be tailored to the specific needs of the child whenever possible.

Health Benefits of Physical Activity

Regular physical activity conditions the growing body in a variety of ways.1 It is essential for the development of strong, healthy bones and muscles; aids in weight control; and appears to have mental health benefits as well, resulting in a heightened sense of well-being. The fitness benefits of exercise lead to functional improvements in everyday life, including improved energy levels, stamina, posture, coordination, and stability. Physical activity also plays a role in disease management and prevention, helping children to optimize blood lipid and blood pressure levels, improve lung capacity and cardiovascular function, and maintain glucose tolerance.

Children with a chronic disease or developmental disorder will obtain the same benefits from regular physical activity as healthy children do. Exercise can help improve their quality of life. Sometimes a child with a chronic illness is discouraged from exercising. Unless there are disease or health condition–specific contraindications to certain types of exercise, physical activity should be encouraged to optimize the many physiological systems it affects, including the skeletal, muscular, and cardiovascular systems. Because all children can benefit from physical activity, it is important to allow them to be active, within individually determined limitations, and to teach them how do so safely.

Special Olympics is an international nonprofit organization that provides athletic training and competition to individuals with mental retardation. More than 4 million athletes in 170 countries and millions of volunteers participate in Special Olympics games every year. The programs include 30 summer and winter sports, such as swimming, cycling, golf, soccer, bowling, basketball, gymnastics, roller skating, running, and tennis. The association strives to help participants “develop improved physical fitness and motor skills, greater self-confidence, and a more positive self-image.”2

Not all physical activities are equivalent in the physiological changes they induce. Fitness training is highly specific. An exercise that is cardiovascular based, such as walking or running, may increase a child’s muscle mass to a lesser degree than what might be possible with a resistance activity such as weight training, calisthenics, or gymnastics. Conversely, many resistance activities may not provide significant cardiovascular improvements or the same rise in caloric expenditure as that provided by a traditional aerobic pursuit. Participating in a solitary fitness activity such as cycling will not produce the same neuromuscular and coordination benefits as performing a more skill-based activity. For that reason, it is important to cross-train—that is, to include a variety of different sports and activities in an overall program. Children who are encouraged to move not only will have fun but will be empowered by a sense of their own physical strength. The Centers for Disease Control calls for parents, schools, and communities to create opportunities for physical activities that are enjoyable and promote confidence in children’s and teens’ ability to be physically active.

Young Athletes’ Bill of Rights

The Young Athletes’ Bill of Rights3 includes the following:

  1. 1. The right to have the opportunity to participate in sports regardless of ability level.

  2. 2. The right to participate at a level commensurate with each child’s developmental level.

  3. 3. The right to have qualified adult leadership.

  4. 4. The right to participate in a safe and healthy environment

  5. 5. The right of each child to share leadership and decision making.

  6. 6. The right to play as a child and not as an adult.

  7. 7. The right to proper preparation for participation in sports.

  8. 8. The right to equal opportunity to strive for success.

  9. 9. The right to be treated with dignity by all involved.

  10. 10. The right to have fun through sports.

Benefits of regular exercise include cardiovascular fitness, muscular strength and stamina, flexibility and mobility, improved gross motor skills, improved agility and stability, hormonal regulation, and an improved sense of well-being and self-confidence.

Health Risks of Inactivity

Almost half of Americans aged 12 to 21 years are not vigorously active on a regular basis.4 Factors that play a role include increased time spent watching television and using computers, removal of physical activity from two-thirds of the schools, and fewer outdoor play opportunities for many children. Inactivity and poor nutrition go hand in hand. A child who is trapped in an increasingly inactive life may be inclined to eat more and to make poor food choices—especially if excess television watching subjects the child to the massive marketing campaigns that junk-food manufacturers aim at children. Survey data show that 41.3% of children spend 3 or more hours playing video or computer games and 32.5% watch television for 3 or more hours on school days.5 An underused, poorly fed body will suffer a decline in health status that may place the child at greater risk for a variety of health disorders and diseases.

Obesity

Obesity rates have been rising dramatically among America’s youth, although recent evidence suggests a leveling off at about 17%.6 Epidemiologic data reveal that a child who is obese at 12 years of age has approximately a 75% chance of being obese as an adult.7 Children with special health care needs may be especially prone to obesity in later years. As obesity increases, so does the risk for chronic diseases, including type 2 diabetes mellitus, dyslipidemia, (p.72) and hypertension in both children and adults. Tracking a child’s height, weight, and body composition throughout childhood can reliably indicate whether these parameters are within the recommended range.7 Because successful treatment of obesity in adults is rare, it has been suggested that aggressive treatment should start with the emergence of overweight in a children.8 Exercise, along with dietary and behavior modification, is an essential component of a treatment program for childhood obesity (see Chapter 18). The American Academy of Pediatrics (AAP) has urged pediatricians to take a proactive stance, advocating for physical education programs that promote fitness.9

Diabetes

The National Institutes of Health reported that the percentage of children diagnosed with type 2 diabetes rose from less than 5% before 1994 to between 30% and 50%.9 One of every 433 children younger than 20 years of age is affected.10 Type 2 diabetes is more prevalent in youth with a body mass index (BMI) greater than the 85th percentile in the United States and Europe.11 Impaired glucose tolerance was found in one study to affect 25% of obese children between 4 and 10 years of age and 21% of obese adolescents between 11 and 18 years of age.12 Clinicians must be on the lookout for undiagnosed symptoms of type 2 diabetes in overweight or inactive children. These symptoms include polyuria, polydipsia, polyphagia, blurred vision, fatigue, headache, poor wound healing, and weight loss (see Chapter 48).

Osteopenia

Bone density increases to approximately 90% of its peak level during the adolescent years. Weight-bearing physical activity (e.g., jumping), along with adequate calcium, magnesium, fluoride, and vitamin D intake, especially during growth periods, is essential to optimize peak bone density. Participation in weight-bearing physical activity throughout childhood and adolescence contributes to lifelong bone health.13

Certain types of activity are more weight-bearing than others and may result in greater bone mass increases due to greater force production or impact stimulus. Exercise stimulus is site specific. Jumping and high-impact movements with the lower body tend to affect the hip and lumbar spine. Forceful muscular action with the upper body, such as ball throwing, racket hitting, resistance training, and maneuvers with body weights (e.g., propulsive hand stands, swinging on rails), affect the wrist. Gymnasts, for example, have been found to have greater bone mineral density than age-matched controls. The magnitude of the force applied to the muscles and bones is more important in producing bone changes than the number of times that stress is applied. Gymnasts who perform high-impact movements sporadically exhibit better bone density than runners who experience moderate impact over an extended period.

Increased bone mineral density established during childhood has been found to be maintained in adults, even when they are no longer engaging in high levels of physical activity.14 Therefore, exercise in childhood may help reduce the risk of fractures in postmenopausal women. Young girls who undereat or are underweight may remain in a prepubertal state for many years, especially if they participate in sports in which weight control is emphasized. The delay in the onset of estrogen action can result in undermineralized bone.15 Young girls and women who are extremely active may also be susceptible to the cluster of conditions known as the female athletic triad: disordered eating, amenorrhea, and osteoporosis.

Hyperlipidemia and Hypercholesterolemia

Hyperlipidemia and hypercholesterolemia were recognized by the 1985 Panel for the National Institutes of Health Consensus Development Conference on the Health Implications of Obesity as two of the adverse effects of obesity. Dietary therapy, weight loss, and regular physical activity have been recommended as effective methods to lower elevated levels of total cholesterol, low-density lipoprotein (LDL) cholesterol and triglycerides and to raise low levels of high-density lipoprotein (HDL) cholesterol in overweight and obese persons with dyslipidemia.16 Aerobic fitness, as measured by peak oxygen uptake, is inversely related to blood cholesterol levels and fat mass.17 It has been demonstrated that aerobic training results in an increase in peak oxygen uptake when performed at intensities greater than 80% of maximal heart rate (see Chapter 32).

Factors To Be Considered in Nutritional Evaluation

Growth

A primary concern of the school-age child is the achievement of normal growth. Height and weight should be evaluated using National Center for Health Statistics growth charts, and BMI should be calculated (http://pediatrics.aappublications.org/content/pediatrics/125/2/361.full.pdf). Height and weight should be plotted routinely to allow for the identification of either overnutrition or undernutrition. When height and weight fall into markedly different percentiles, weight-for-height may be a more sensitive index of appropriate growth than weight-for-age because body weight is related more closely to size than to age. However, children may have atrophy of the extremities, making this calculation less useful. Growth charts have been developed for these disorders (see Appendix 2).

Weight

A healthy body weight is one that is in proportion to height. Although underweight or overweight (BMI >95th percentile) may have a detrimental effect on physical performance, altering the body weight will not necessarily improve performance. Any attempts to change the body weight of a child who is clearly underweight or overweight should be made with the aid of a physician or nutritionist to ensure adequate nutritional intake. Excessive weight loss may affect a child’s growth rate, nutrition status, hormone levels, and bone mineral content and may contribute to psychological stress preliminary to an eating disorder. It is also important to emphasize good nutrition through nutrition education so that the child, parent, or coach will avoid improper weight management, fluid restriction, and misuse of dietary supplements.8

Body Composition

Physiological changes in bone density and in the proportion of body water in adolescents going through puberty make it difficult to use body fat and weight measurements as rigid evaluation criteria.8 Because there are currently no standards of comparison for young athletes that are specific for sport and gender, the clinician must use sound clinical judgment and growth charts to assess optimal weight. Evaluation of body composition should take into account the fact that children have higher body water content and lower bone mineral content than adults, and therefore their body density is lower. Equations using conversion constants from adult samples may overestimate body fat by 3% to 6%. The chemical composition of fat-free mass (i.e., water, minerals, protein) changes with passage through puberty; therefore, use of skinfolds, body widths, and circumferences may not accurately assess changes in body fat. Estimates of body fat must use a multicomponent approach. Changes may be tracked using skinfold thickness without calculation of percent body fat. Use of body composition assessments to manipulate body fat for sports performance should be avoided because this practice may adversely affect growth and development.

Dietary Habits

Nutritional adequacy can be assessed with the use of a food frequency questionnaire and a 24-hour dietary recall. For the best assessment, both the parents and the child should be interviewed, and the child should be questioned away from the parents to avoid answers that are based on parental expectations.8 To facilitate recall of meal patterns, it is useful to ask not just what was consumed but details on dietary behaviors: Is breakfast normally eaten? Is lunch consumed at home or at school? What are the favorite snacks, and how often does snacking occur? Are dinners spent eating in front of the television or with the family? When are fluids consumed? Questions about the type, duration, and intensity of regular physical activities should be included to better assess energy expenditure.

(p.73) Guidelines for Physical Activity

Children, as well as adults, are advised to engage in moderate-intensity physical activity for 30 minutes on most days of the week.4 It is crucial to start young in order to instill familiarity and a positive association with fitness activities. A physical fitness program should include strength, flexibility, and aerobic components (see Appendix 7, Children’s Pyramid Physical Activity).

Resistance Training

Strength or resistance training using free weights or weight machines has been found to increase strength in children and adolescents. The AAP has confirmed that strength training programs for preadolescents and adolescents can prevent injuries and impact long-term health. Strength training can be safe and effective if proper resistance training techniques and safety precautions are followed. In 2008, the AAP issued the following recommendations for strength training18:

  • Before the individual begins a formal strength training program, a medical evaluation should be performed by a pediatrician. If indicated, a referral may be made to a sports medicine physician who is familiar with the various strength training methods as well as their risks and benefits for preadolescents and adolescents.

  • Preadolescents and adolescents should avoid competitive weight lifting, power lifting, body building, and maximal lifts until they reach physical and skeletal maturity.

  • Aerobic conditioning should be coupled with resistance training if general health benefits are the goal.

  • Strength training programs should include warm-up and cool-down components.

  • A general strengthening program should address all major muscle groups and exercise through the complete range of motion.

  • Specific strength training exercises should be learned initially with no load (resistance). Once the exercise skill has been mastered, incremental loads may be added.

  • Progressive resistance exercise requires successful completion of 8 to 15 repetitions in good form before the weight or resistance is increased. It is generally recommended that resistance training be performed 2 to 3 days a week.18,19

  • Any sign of injury or illness from strength training should be evaluated before the exercise in question is continued.

Other forms of resistance training use body weight and/or impact forces. Physical activity that places a load on the bone will stimulate bone growth and optimize bone mineral density. Jumping exercises such as jumping rope or jumping jacks are particularly effective. When modifying resistance exercise for a child’s special limitations, it is important to search for tools that may enhance performance. A variety of differently shaped weights and resistance-band products can make holding a weight easier. Many exercises can be performed by a person in a wheelchair.

Cardiovascular Exercise

The American College of Sports Medicine defines cardiorespiratory fitness as the ability to perform large-muscle, dynamic, moderate- to high-intensity exercise for prolonged periods. The following guidelines are recommended19:

  • An exercise session should include a warm-up period of approximately 10 minutes, an endurance phase of 20 to 60 minutes, and a cool-down period of 5 to 10 minutes.

  • The duration of the activity depends on its intensity. Easier movements can be performed for longer periods. Vigorous exercise should be performed in intervals, interspersing periods of work and rest, or for a shorter overall duration.

  • If recreational games are included along with bona fide fitness training, the experience of successful participation, as opposed to winning or losing, should be emphasized. Because the skill level and perception of effort are not always the same as the intensity level, monitoring of the heart rate and perceived exertion is recommended. Whenever possible, requirements should be modified to cope with the limitations of an ill or handicapped child.

  • Both the intensity and the duration of exercise determine the total caloric expenditure. Clinical and low-fit populations can improve the fitness with lower-intensity, longer-duration sessions. Intensity can be estimated by monitoring the heart rate, breathing rate, and/or perceived exertion. Looking for physical signs of fatigue, such as reduced ability or slack posture, can also be helpful.

  • Medications that may influence heart rate or fatigue should be considered when determining the amount and intensity of activity.

  • The recommended rate of progression in an exercise conditioning program depends on the functional capacity, medical and health status, age, individual activity preferences and goals, and the individual’s tolerance of the current level of training. Deconditioned individuals should be allowed more time to adapt to each stage of conditioning before progressing further.

  • Cardiorespiratory exercise should be performed on most days of the week. An ill or deconditioned individual can benefit from breaking up longer sessions. For example, three 10-minute sessions can be used instead of one 30-minute session.

  • If a child has limited mobility or is confined to a wheelchair, an aerobic effect can be elicited by rhythmic, continuous movements of the arms.

Flexibility

According to the American College of Sports Medicine, flexibility is the ability to move a joint through its complete range of motion. The following recommendations should be considered when performing range-of-motion exercises19:

  • Avoid stretching “cold.” An active warm-up period that includes mobility and temperature-raising movements should precede vigorous stretching. Alternatively, stretching can be performed after physical activity, rather than before it. However, an active warm-up should be included before vigorous activity.

  • Several types of stretching can improve range of motion, including static, ballistic, and proprioceptive neuromuscular facilitation. Static stretching, in which a position is held for 10 to 30 seconds to the point of mild discomfort but never pain, is the most commonly recommended method.

  • Yoga, Pilates, and other flexibility-based disciplines can improve flexibility. One should be careful to avoid extreme positioning, uncomfortable joint angles, and progressing faster than is comfortable.

  • Three to four repetitions of a stretch that is held for 10 to 30 seconds are performed on at least 2 to 3 days per week. Daily stretching is most effective.

  • Children with limited mobility can be assisted with their stretching exercises.

Dietary Management

The nutritional requirements for active children are similar to those for sedentary children, allowing for the additional energy needs of activity. Calories consumed must be adequate to provide for physical activity as well as normal growth. It can be difficult to assess energy expenditure in children because of variations in age, gender, stage of development, and body composition. A compendium has been developed to assign energy costs to various activities in children, but practitioners should use caution because this remains a work in progress.20,21 It also should be recognized that children whose movements are less efficient require more kilocalories per unit of body weight.

A variety of foods should be included from each of the food groups in the Choose MyPlate guidelines (http://www.choosemyplate.gov/). To achieve the health benefits of physical activity, active youth should be encouraged to minimize their intake of saturated fats and cholesterol, consume sweets in amounts that will allow for the maintenance of energy balance, and consume adequate dietary calcium and vitamin K, along with physical activity, to allow for optimal bone mineralization. These nutrients are ideally obtained through whole foods rather than supplements. A child can be educated as to appropriate types of snacks and times of snacking to enhance energy levels. The child should be taught how to make nutritious choices, such as selecting a healthier item from a vending machine or a fast-food restaurant. Breakfast helps replenish glycogen stores that are depleted overnight. (p.74) If a child feels too excited or nervous to eat before an event, rather than pressuring the child to eat, one should encourage the consumption of liquids such as sports drinks or juices.

Excessive consumption of protein, calories, or other nutrients will not improve athletic performance. The use of protein supplementation is not recommended and has not been shown to improve athletic performance, muscle development, or strength. Research on the safety and efficacy of other nutritional supplements in enhancing exercise performance is unavailable in children. Of concern, young athletes using such supplements may develop a false sense of security and may be less likely to attribute progress to their training and diet. Some coaches may encourage a child to overeat or supplement or may deny regular fluids as part of the training discipline. Efforts should be made to educate coaches and parents on the special needs of a child with a medical condition (Table 7–1). Guidelines on snacks and their timing are as follows:

Table 7–1. Caloric Equivalents of a Child’s Activities (in Kilocalories per 10 Minutes of Activity)

Activity

Body Weight (kg)

20

25

30

35

40

45

50

55

60

65

Basketball

34

43

51

60

  68

  77

  85

  94

102

110

Calisthenics

13

17

20

23

  26

  30

  33

  36

  40

  43

Cycling

  10 km/hr

15

17

20

23

  26

  29

  33

  36

  39

  42

  15 km/hr

22

27

32

36

  41

  46

  50

  55

  60

  65

  Figure skating

40

50

60

70

  80

  90

100

110

120

130

  Ice hockey (on-ice time)

52

65

78

91

104

117

130

143

156

168

Running

  8 km/hr

37

45

52

60

  66

  72

  78

  84

  90

  95

  10 km/hr

48

55

64

73

  79

  85

  92

100

107

113

  Soccer (game)

36

45

54

63

  72

  81

  90

  99

108

117

Swimming

  Breast stroke 30 m/min

19

24

29

34

  38

  43

  48

  53

  58

  62

  Front crawl

25

31

37

43

  49

  56

  62

  68

  74

  80

  Back stroke

17

21

25

30

  34

  38

  42

  47

  51

  55

Tennis

22

28

33

39

  44

  50

  55

  61

  66

  72

Walking

  4 km/hr

17

19

21

23

  26

  28

  30

  32

  34

  36

  6 km/hr

24

26

28

30

  32

  34

  37

  40

  43

  48

Adapted with permission from Bar-Or O. Pediatric Sports Medicine for the Practitioner. New York: Springer; 1983.

  • One to 2 hours before exercise: fruit or vegetable juice, sports drink, fresh fruit

  • Two to 3 hours before exercise: fruit or vegetable juice, sports drink, fresh fruit, breads, bagels, crackers

  • Three or more hours before exercise: fruit or vegetable juice, sports drink, fresh fruit, breads, bagels, crackers, low-fat yogurt, pasta with tomato sauce, cereal with low-fat milk

  • Within 2 hours after exercise: fresh fruit, sports drink, bread, bagels, crackers

Fluid Needs of Active Children

Dehydration can dramatically affect a child’s ability to perform well. As little as a 2% decrease in body weight from fluid loss (e.g., a 1.2-lb loss for a 60-lb child) can lead to a significant decrease in muscular strength and stamina.22 Adequate hydration is essential to regulate body temperature. Additional factors contributing to reduced performance and heat illness include extreme exertion in the heat and the wearing of uniforms and equipment that act to retain heat. Research shows that children are able to safely exercise in the heat as long as they maintain adequate hydration, avoid clothing that may result in heat retention, and rest sufficiently.22

Challenges to maintaining adequate hydration include children’s diminished sense of thirst; a child may be quite dehydrated before he or she feels thirsty. Fluid should be readily available, and fluid breaks should be scheduled regularly. Children should be advised to drink on a schedule rather than relying on thirst.

One must be alert for signs of dehydration or underfeeding, including early fatigue, irritability, or a sudden drop in performance. Those supervising exercise for children with special needs should be aware that certain conditions will increase the likelihood of heat illness. For example, children with mental retardation may not recognize the need to replace fluid losses. Those with diabetes mellitus, diabetes insipidus, or gastrointestinal infection may experience greater than normal fluid losses. Certain congenital heart defects may result in excessive sweating, whereas cystic fibrosis may result in diminished thirst. Certain medications have diuretic effects. Finally, anorexia or obesity also affects thermoregulation.

Based on these consideration, the AAP has issued the following recommendations for exercising in cold or hot weather or for prolonged periods22:

  • The intensity of activities that last 15 minutes or longer should be reduced whenever relative humidity, solar radiation, and air temperature are above critical levels. One way of increasing rest periods on a hot day is to substitute players on a team frequently.

  • At the beginning of a strenuous exercise program or after traveling to a warmer climate, the intensity and duration of exercise should be limited initially and then gradually increased over a period of 10 to 14 days to ensure acclimatization to the heat. If such a period is not available, practice and competition periods should be curtailed.

  • Before prolonged physical activity, the child should be well hydrated. During the activity, periodic drinking should be enforced. For example, every 20 minutes, a child weighing 40 kg should drink 150 mL of cold tap water or a flavored carbohydrate-electrolyte beverage (250 mL for an adolescent weighing 60 kg), even if the child does not feel thirsty. Weighing before and after a training session can verify hydration status if the child is weighed wearing little or no clothing.

  • Clothing should be light-colored, lightweight, and limited to one layer of absorbent material to facilitate evaporation of sweat. Sweat-saturated garments should be replaced by dry garments. Rubberized sweatsuits should never be used to produce loss of weight.

Children and adolescents with medical conditions have special issues with respect to participation in athletic activities. The pediatrician can play an important role in determining whether a child with a health condition should participate in certain sports by assessing the child’s health status, suggesting appropriate equipment or modifications to decrease the risk of injury, and educating the athlete and parents on the risks of injury in relation to the child’s condition.23

(p.75) References

Bibliography references:

1. Centers for Disease Control and Prevention. Health benefits of physical exercise. http://www.cdc.gov/physicalactivity/basics/pa-health/. Accessed June 6, 2016.

2. Special Olympics. Website. www.specialolympics.org. Accessed June 6, 2016.

3. Martens R, Seefeldt V, eds. Guidelines for Children’s Sports. Washington, DC: American Alliance for Health, Physical Education, Recreation and Dance; 1979.

4. US Department of Health and Human Services. 2008 Physical Activity Guidelines for Americans. ODPHP Publication No. U0036; October 2008. Washington, DC: US DHHS, Office of Disease Prevention and Health Promotion. http://www.health.gov/paguidelines/pdf/paguide.pdf. Accessed June 6, 2016.

5. Centers for Disease Control and Prevention, Youth Risk Behavior Survey. Trends in the Prevalence of Physical Activity and Sedentary Behaviors: National YRBS, 1991–2013. http://www.cdc.gov/healthyyouth/data/yrbs/results.htm. Accessed June 6, 2016.

6. Ogden CL, Carroll MD, Kit BK, Flegal KM. Prevalence of childhood and adult obesity in the United States, 2011–2012. JAMA. 2014; 311:806.

7. Klish WJ. Childhood obesity. Pediatr Rev. 1998; 19:312.

8. Hoelscher DM, Kirk S, Ritchie L, Cunningham-Sabo L; Academy Positions Committee. Position of the Academy of Nutrition and Dietetics: interventions for the prevention and treatment of pediatric overweight and obesity. J Acad Nutr Diet. 2013; 113:1375.

9. US Preventive Services Task Force. Screening for obesity in children and adolescents: US Preventive Services Task Force recommendation statement. Pediatrics. 2010; 125:361.

10. Pettitt DJ, Talton J, Dabelea D, et al. Prevalence of Diabetes in U.S. Youth in 2009: the SEARCH for Diabetes in Youth Study. Diab Care. 2014; 37:402.

11. Rosenbloom, AL, Silverstein JH, Amemiya S, Zeitler P, Klingensmith GJ. Type 2 diabetes in children and adolescents. Pediatr Diabetes. 2009; 10(suppl 12):17.

12. Sinha R, Fisch G, Teague B, et al. Prevalence of impaired glucose tolerance among children and adolescents with marked obesity. N Engl J Med. 2002; 346:802.

13. Gunter KB, Almstedt HC, Janz KF. Physical activity in childhood may be the key to optimizing lifespan skeletal health. Exerc Sport Sci Rev. 2012; 40:13.

14. Bass S, Pearce G, Bradney M, et al. Exercise before puberty may confer residual benefits in bone density in adulthood: studies in active prepubertal and retired female gymnasts. J Bone Miner Res. 1998; 13:500.

15. Roemmich JN, Richmond RJ, Rogol AD. Consequences of sport training during puberty. J Endocrinol Invest. 2001; 24:708.

16. Stefanick ML. Physical activity for preventing and treating obesity-related dyslipoproteinemias. Med Sci Sports Exerc. 1999; 31(11 suppl):S609.

17. Baquet G, VanPraagh E, Berthoin S. Endurance training and aerobic fitness in young people. Sports Med. 2003; 33:1127.

18. American Academy of Pediatrics Council on Sports Medicine and Fitness, McCambridge TM, Stricker PR. Strength training by children and adolescents. Pediatrics. 2008; 121:835.

19. American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription, 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2014.

20. Ridley K, Olds T. Assigning energy costs to activities in children: a review and synthesis. Med Sci Sports Exerc. 2008; 40:1439.

21. Lyden K, Keadle SK, Staudenmayer J, Freedson P, Alhassan S. Energy cost of common activities in children and adolescents. J Phys Act Health. 2013;10:62.

22. Council on Sports Medicine and Fitness and Council on School Health, Bergeron MF, Devore C, Rice SG; American Academy of Pediatrics. Climatic heat stress and exercising children and adolescents. Pediatrics. 2011; 128:e741.

23. Rice SG. Medical conditions affecting sports participation. Pediatrics. 2008; 121:841. (p.76)