Middle Childhood Physical Development PDF

Chapter 8:Middle Childhood Physical Development Learning Objectives: Middle Childhood Physical Development 1. Describe adrenarche and its behavioral significance. 2. Describe growth patterns in middle childhood. 3. Explain the benefits and risks of...

Chapter 8:Middle Childhood Physical Development Learning Objectives: Middle Childhood Physical Development 1. Describe adrenarche and its behavioral significance. 2. Describe growth patterns in middle childhood. 3. Explain the benefits and risks of organized sports for children. 4. Discuss approaches to overweight and obesity in children. 5. Discuss sleep in middle childhood. 6. Discuss common illnesses of middle childhood. 7. Describe brain development during middle childhood. 8. Discuss the causes of death in middle childhood. 9. Discuss childhood suicide and children’s understanding of death. Adrenarche Figure 8-1. DHEAS over the lifespan source Adrenarche or maturation of the adrenal gland is an important physiological event of middle childhood. The adrenal gland has two parts to it, the adrenal cortex and the adrenal medulla. The adrenal medulla is part of the sympathetic nervous system and secretes adrenalin. The adrenal cortex secretes several hormones including cortisol, a hormone that is critical to the body’s response to physical and psychological stress. The hypothalamic-pituitary-adrenal (HPA) axis refers to cortisol secretion, which is regulated by ACTH from the pituitary gland, which in turn is regulated by CRH from the hypothalamus. Psychological stress elicits greater HPA axis activity in some children making them more sensitive to stress (Kryski et al., 2013; Watamura et al., 2004). High levels of HPA hormones increase risk for mental health conditions and high cortisol may 207 be toxic to the brain (Frodl & O’Keane, 2013). Dehydroepiandrosterone (DHEA) is another hormone made by the adrenal cortex, it is modified by addition of sulphate to be DHEA-sulphate (DHEA-S), a hormone with a longer life in the bloodstream. DHEA protects against the neurotoxic effects of cortisol, and it is known to promote brain growth. DHEA is also converted to testosterone in many body tissues including the underarm and pubic area skin. Blood levels of DHEAS show an interesting developmental pattern (Figure 8-1). Levels are high before birth, decline in the first year and then remain low when at about age 6 the DHEA producing cells become active again. The renewed secretion of DHEAS around age 6 is called adrenarche; and its mechanism is not known. As middle childhood progresses DHEAS levels rise slowly eventually causing pubic and underarm hair growth and also propensity for body odor. DHEAS levels continue to rise until early adulthood and then decline over the rest of the lifespan. DHEAS levels parallel important events in brain development and the role of this hormone in brain development and behavior is still being studied. Preliminary studies link early adrenarche with mental health issues in girls (Byrne et al., 2017). Among primates adrenarche is only found in the larger-brained hominins (Cumberland et al., 2021). Growth Patterns During Middle Childhood Age Height Height Girls Dimorphism Weight Weight Girls Dimorphism (Years) Boys (in) (in) (% ifference) Boys (lbs) (lbs) (%difference) 6 45.82 44.83 -0.57% 45.82 44.83 -2.17% 7 51.09 50.41 -0.22% 51.09 50.41 -1.34% 8 56.78 56.80 0.13% 56.78 56.80 0.04% 9 63.24 64.25 -0.45% 63.24 64.25 1.60% 10 71.44 73.67 -0.44% 71.44 73.67 3.12% 11 79.53 82.44 0.37% 79.53 82.44 3.66% 12 89.24 92.24 1.46% 89.24 92.24 3.36% Table 8-1. Average height and weight for boys and girls from CDC data. Dimorphism is percent difference between girls and boys. A positive (red) difference indicates the value for girls is greater. During middle childhood height increases at a rate of 2-3 inches per year. The change in height over time is called the height velocity. Similarly, children gain about 5 pounds per year, and this rate of change is called the weight velocity. The prepubertal growth spurt occurs during middle childhood when both height and weight velocity reach a lifetime maximum. Peak height occurs a year before first menstruation for girls (Iuliano-Burns et al., 2001). Girls gain body fat during middle childhood to prepare for sexual maturation. The average girl spends two years less time in middle childhood than the average boy if middle childhood is defined as ending with menarche for girls and first ejaculation for boys. The mean age for the beginning of the growth spurt for girls is nine, while for boys it is eleven. Table 8-1 shows that by the end of middle childhood girls (on average) are 1% taller and 3% heavier than boys. Girls are also 208 slightly taller at age 8 possibly due to earlier adrenarche. Clinicians monitor children’s height and weight at least yearly to watch for the growth spurt. Motor Skills and Athletics “Use it to grow it” is an important developmental theme that applies to all skills throughout the lifespan. Genes program the brain to be ready to respond to environmental challenges. The brain is shaped by the sensations it processes and the responses it generates. What individuals do can both magnify and reduce inborn genetic differences and so motivation is an important factor in determining individual differences. An interaction between nature and nurture is apparent for sex differences in motor skill development (Thomas & French, 1985). Regarding physical motivation, boys are more physically active than girls from an early age and this sex difference is large (Eaton & Enns, 1986). As a result of increased activity and other sex differences, boys’ gross motor skills are better developed. In one thorough meta- analysis of 20 motor skills, sex differences in 15 skills were accounted for by practice and were small to medium. For one skill, throwing distance and speed, large biologically based sex differences appear at age 3 and increase with age and boys’ greater practice. This sex difference is likely a relic of the human ancestral past where boys and men hunted with tools they threw. The CDC recommends that children enjoy 60 minutes or more of moderate-to-vigorous physical activity daily. But less than 25% get this recommended amount (CDC, 2022). During middle childhood many children have health problems related to lack of motor skill development. “More than 70% of the children aged 6–11 years in the United States do not meet the recommended levels of physical activity, and less than half of the youth achieve adequate fundamental motor skills and health-related fitness levels” (Gu et al., 2021, p. 64). Children who are not active do not practice their motor skills. Lack of motor skills then discourages them from being active or playing sports because they do not perform well. Lack of motor skills becomes a reason for low health-related fitness and risk of becoming overweight. Participation in Organized Sports Social class determines participation is organized sports in many WEIRD nations (Andersen & Bakken, 2019). In the United States, youth athletics is big business and is also a source of developmental privilege for White children living in the suburbs. The youth sports industry in the US generates $17 billion in revenue; which is more than professional baseball (Thompson, 2018). Families may spend $1000 a month or more on travel teams and this travel is a source of tourism dollars for communities (Brychta et al., 2021). With this commercialization it is not surprising that family income determines children’s opportunities. Gender, race/ethnicity, and income all predict sports participation (Figure 8-2); the gender gap is largest for Asians. Baseball is the most popular sport for 6-year-old boys and girls. By age 12, basketball is the most popular sport followed by baseball, soccer, volleyball and football (Sabo & Veliz, 2008). 209  Children's Organized Sports Participation 70 60 50 Girls Boys % Participating 40 30 20 10 0 Caucasian African American Hispanic Asian Figure 8-2. Children’s organized sports participation by gender and ethnicity; Girls – Caucasian (n=425); African-American (n=106); Hispanic (n=124); Asian (n=55); Boys – Caucasian (n=435); African-American (n=127); Hispanic (n=123); Asian (n=99) (Sabo & Veliz, 2008). Learn more about the commercialization of youth athletics. Benefits of Organized Sports Participation The American Academy of Pediatrics (AAP) produced a position statement regarding free play and children’s participation in organized sports (Logan et al., 2019). Free play is important for development and children can build motor skills (running, leaping, throwing, catching, and kicking) that way. The AAP states ”organized sports programs for preadolescents should complement, not replace, the regular physical activity that is a part of free play, child-organized games, recreational sports, and physical education programs in the schools. Regular physical activity should be encouraged for all children whether they participate in organized sports or not” (Committee on Sports Medicine and Fitness and Committee on School Health, 2001). Unfortunately, many neighborhoods are not safe for unsupervised children and adults may not be available to provide supervision. Organized sports can provide opportunities for activity that children would not otherwise have. The benefits of organized sports participation include: 1. Development of fundamental motor skills. 2. Better cardiovascular fitness and higher levels of energy expenditure and physical activity. 3. Improved academic performance (verbal, numeric, and reasoning domains). 4. Increased use of self-regulatory skills, such as planning, self-monitoring, evaluation, reflection, and effort. 5. Enhancement of social skills and social identity. 210  6. Heightened sense of self-worth. 7. Improved mental health. Risks of Organized Sports Participation Organized sports can be a source of stress for some children. Coaches may be untrained and may not understand that abilities may be limited by developmental readiness. “Adults' involvement in children's sports activities may bring goals or outcome measures that are not oriented toward young participants. Tournaments, all- star teams, most valuable player awards, trophies, and awards banquets are by- products of adult influences” (Committee on Sports Medicine and Fitness and Committee on School Health, 2001). Physical injury is also a risk with organized sports and sports injury is the second leading cause of emergency room visits for children. The highest number of injuries are from football, wrestling, cheerleading, and ice hockey (Caine et al., 2008). Sport-related concussion is a serious concern for children, but experts struggle with how to define and diagnose the condition. According to the AAP sport-related concussion (SRC) is “a traumatic brain injury induced by biomechanical forces” and also includes 1) a direct blow to the head or a shaking of the brain within the skull; 2) rapid onset (minutes to hours) of neurologic symptoms that resolve with time; 3) injuries not seen in brain scans; and 4) a range of symptoms with or without loss of consciousness (Headache (86% to 96%), dizziness (65% to 75%), difficulty concentrating (48% to 61%), and confusion (40% to 46%). (Halstead et al., 2018). The highest risk of SRC for boys is football, followed by lacrosse and ice hockey. For girls soccer, lacrosse and field hockey are most risky. (For a complete list see the AAP SRC publication.) It is important for children who have a concussion to stop playing the sport for a time. Repeat concussions close together can cause serious problems for some children. Health During Middle Childhood During middle childhood children should visit a health care provider yearly whether or not they are sick. One of the purposes of these visits is screening for health problems and developmental disorders. Despite recommendations that clinicians use validated screening tools many do not; and so developmental disorders are often missed (Ebert et al., 2020). Mental health clinicians should not assume that because a child sees a medical practitioner regularly developmental problems have been discovered. Clinicians who are treating a child/family should communicate about the child’s needs. This interdisciplinary communication is called integrated care (Harrington, 2019). While most children do not have health problems, 40% are diagnosed with a chronic condition such as obesity, asthma, diabetes, or epilepsy (Managing Chronic Health Conditions in Schools | Healthy Schools | CDC, 2022). Overweight is defined as a body mass index in the 85-95th percentile of the reference range. Overweight can be associated with health problems depending on the child. Obesity is defined as the 95th percentile and above 211 because this amount of body fat poses risk for health problems. The prevalence of obesity in children was ∼5% in 1970, 17% in 2004 and is currently 18.4% in children between 6 and 11 years. The highest obesity prevalence is in Black girls (24%) and Mexican American boys (22%) (Barlow & and the Expert Committee, 2007). Obesity impacts psychological and physical health. Approximately 9-13% of overweight children have high blood pressure. Other medical problems include asthma hyperlipidemia, type 2 diabetes, sleep apnea, poor self-esteem, and depression. Both the AAP and American Psychological Association (APA) have published clinical practice guidelines for the assessment and treatment of overweight and obesity. The APA recommends family-based, multicomponent behavioral interventions to treat obesity and overweight in children 2 to 18 (Weir, 2019). The guidelines recommend counseling on diet, physical activity and “teaching parents strategies for goal setting, problem-solving, monitoring children’s behaviors, and modeling positive parental behaviors,” (p. 32). The guidelines recommend 26 contact hours with the family. Unfortunately, for many families cost, location, and time commitment make it difficult for them to receive the interventions. The APA recommends that behavioral treatment be offered in primary care offices to encourage greater participation. The AAP guideline gives the following recommendations that are supported by evidence and expert opinion: 1. Limiting consumption of sugar-sweetened beverages; 2. Encouraging consumption of diets with recommended quantities of fruits and vegetables; the current recommendations from the US Department of Agriculture (USDA) (www.mypyramid.gov) are for 9 servings per day, with serving sizes varying with age; 3. Limiting television and other screen time to no more than 2 hours of television viewing per day); 4. Eating breakfast daily; 5. Limiting eating out at restaurants, particularly fast-food restaurants; 6. Encouraging family meals in which parents and children eat together; 7. Limiting portion size; 8. Eating a diet rich in calcium (the USDA provides recommendations about serving size and daily number of dairy product servings); 9. Eating a diet high in fiber; 10. Eating a diet with balanced macronutrients (energy from fat, carbohydrates, and protein in proportions for age, as recommended by Dietary Reference Intakes) ; 11. Promoting moderate to vigorous physical activity for at least 60 minutes each day ; 12. Limiting consumption of energy-dense foods (high fat/high sugar). 212 Sleep and Sleep problems Children between 6 and 12 years need 9-11 hours of sleep each night (How Much Sleep Do Babies and Kids Need?, 2020). Longitudinal studies show that the average 6 y/o sleeps 9h40min, 8 y/o sleeps 9h15min, 10 y/o sleeps 9h, 12 y/o sleeps 8h20min (Ranum et al., 2019). Children normally sleep longer on the weekends compared to week days and in the winter months as compared to summer months (Nixon et al., 2008). For 6-8 y/o children consistently sleeping less than 9 hours a night is associated with obesity, mood problems, and behavioral problems (Nixon et al., 2008; Ranum et al., 2019). About 8% of children in this age group have sleep problems (Williamson et al., 2019). For children less than 7, waking during the night is the most common sleep problem, after age 7, difficulty falling asleep is more common (Williamson et al., 2019). Causes of Death in Middle Childhood Death Rates for Children and Youth Under 24 Age Group 15–24 69.7 5–14 13.4 1–4 23.3