Continued change characterizes children’s bodies during middle and late childhood, and their motor skills improve. As children move through the elementary school years, they gain greater control over their bodies and can sit and keep their attention focused for longer periods of time. Regular exercise is one key to making these years a time of healthy growth and development.
BODY GROWTH AND CHANGE
The period of middle and late childhood involves slow, consistent growth (Hockenberry, Wilson, & Rodgers, 2017). This is a period of calm before the rapid growth spurt of adolescence. During the elementary school years, children grow an average of 2 to 3 inches a year until, at the age of 11, the average girl is 4 feet, 10 inches tall, and the average boy is 4 feet, 9 inches tall. During the middle and late childhood years, children gain about 5 to 7 pounds a year. The weight increase is due mainly to increases in the size of the skeletal and muscular systems, as well as the size of some body organs.
Synaptic pruning is an important aspect of the brain’s development, and the pruning varies by brain region across children’s development. Connect to “Physical Development in Infancy.”
Proportional changes are among the most pronounced physical changes in middle and late childhood. Head circumference and waist circumference decrease in relation to body height (Kliegman & others, 2016; Perry & others, 2018). A less noticeable physical change is that bones continue to ossify during middle and late childhood but yield to pressure and pull more than mature bones.
The development of brain-imaging techniques such as magnetic resonance imaging (MRI) has led to increased research on changes in the brain during middle and late childhood and links between these brain changes and cognitive development (Khundrakpam & others, 2018; Mah, Geeraert, & Lebel, 2017). Total brain volume stabilizes by the end of late childhood, but significant changes in various structures and regions of the brain continue to occur. In particular, the brain pathways and circuitry involving the prefrontal cortex, the highest level in the brain, continue to increase during middle and late childhood (see Figure 1). These advances in the prefrontal cortex are linked to children’s improved attention, reasoning, and cognitive control (de Haan & Johnson, 2016; Wendelken & others, 2016, 2017).
image2 FIGURE 1 The Prefrontal Cortex. The brain pathways and circuitry involving the prefrontal cortex (shaded in purple) show significant advances in development during middle and late childhood. What cognitive processes are linked to these changes in the prefrontal cortex?
Leading developmental neuroscientist Mark Johnson and his colleagues (2009) proposed that the prefrontal cortex likely orchestrates the functions of many other brain regions during development. As part of this neural leadership role, the prefrontal cortex may provide an advantage to neural networks and connections that include the prefrontal cortex. In their view, the prefrontal cortex coordinates the best neural connections for solving a problem at hand.
image3 What characterizes children’s physical growth in middle and late childhood? ©Chris Windsor/Digital Vision/Getty Images
Changes also occur in the thickness of the cerebral cortex (cortical thickness) in middle and late childhood (Thomason & Thompson, 2011). One study used brain scans to assess cortical thickness in 5- to 11-year-old children (Sowell & others, 2004). Cortical thickening across a two-year time period was observed in the temporal and frontal lobe areas that function in language, which may reflect improvements in language abilities such as reading. Figure 6in “Physical Development in Infancy” shows the locations of the temporal and frontal lobes in the brain.
As children develop, some brain areas become more active Page 268while others become less so (Denes, 2016). One shift in activation that occurs as children develop is from diffuse, larger areas to more focal, smaller areas (Turkeltaub & others, 2003). This shift is characterized by synaptic pruning, a process in which areas of the brain that are not being used lose synaptic connections and areas that are used show increased connections. In one study, researchers found less diffusion and more focal activation in the prefrontal cortex from 7 to 30 years of age (Durston & others, 2006).
Increases in connectivity between brain regions also occurs as children develop (Faghiri & others, 2018). In a longitudinal study of individuals from 6 to 22 years of age, connectivity between the prefrontal and parietal lobes in childhood was linked to better reasoning ability later in development (Wendelken & others, 2017).
During middle and late childhood, children’s motor skills become much smoother and more coordinated than they were in early childhood (Hockenberry, Wilson, & Rodgers, 2017). For example, only one child in a thousand can hit a tennis ball over the net at the age of 3, yet by the age of 10 or 11 most children can learn to play the sport. Running, climbing, skipping rope, swimming, bicycle riding, and skating are just a few of the many physical skills elementary school children can master. In gross motor skills involving large muscle activity, boys usually outperform girls.
Increased myelination of the central nervous system is reflected in the improvement of fine motor skills during middle and late childhood. Children can more adroitly use their hands as tools. Six-year-olds can hammer, paste, tie shoes, and fasten clothes. By 7 years of age, children’s hands have become steadier. At this age, children prefer a pencil to a crayon for printing, and reversal of letters is less common. Printing becomes smaller. At 8 to 10 years of age, the hands can be used independently with more ease and precision. Fine motor coordination develops to the point at which children can write rather than print words. Cursive letter size becomes smaller and more even. At 10 to 12 years of age, children begin to show manipulative skills similar to the abilities of adults. They can master the complex, intricate, and rapid movements needed to produce fine-quality crafts or to play a difficult piece on a musical instrument. Girls usually outperform boys in their use of fine motor skills.
American children and adolescents are not getting enough exercise (Powers & Dodd, 2017; Powers & Howley, 2018). Increasing children’s exercise levels has a number of positive outcomes (Dumuid & others, 2017; Walton-Fisette & Wuest, 2018).
image4 What are some good strategies for increasing children’s exercise? ©Randy Pench/Zuma Press/Newscom
An increasing number of studies document the importance of exercise in children’s physical development (Dowda & others, 2017; Martin & others, 2018; Pan & others, 2017; Yan & others, 2018). A recent study of more than 6,000 elementary school children revealed that 55 minutes or more of moderate-to-vigorous physical activity daily was associated with a lower incidence of obesity (Nemet, 2016). Further, a research review concluded that exercise programs with a frequency of three weekly sessions lasting longer than 60 minutes were effective in lowering both systolic and diastolic blood pressure (Garcia-Hermoso, Saavedra, & Escalante, 2013).
Experts recommend that preschool children engage in two hours of physical activity per day. Connect to “Socioemotional Development in Early Childhood.”
Aerobic exercise also is linked to children’s cognitive skills (Best, 2010; Lind & others, 2018; Martin & others, 2018). Researchers have found that aerobic exercise benefits children’s processing speed, attention, memory, effortful and goal-directed thinking and behavior, and creativity (Chu & others, 2017; Davis & Cooper, 2011; Davis & others, 2011; Khan & Hillman, 2014; Lind & others, 2018; Ludyga & others, 2018; Monti, Hillman, & Cohen, 2012; Pan & others, 2017). A recent meta-analysis concluded that sustained physical activity programs were linked to improvements in children’s attention, executive function, and academic achievement (de Greeff & others, 2018). Also, a recent study found that a 6-week high-intensity exercise program with 7- to 13-year-olds improved their cognitive control and working memory (Moreau, Kirk, & Waldie, 2018). Further, in a recent fMRI study of physically unfit 8- to 11-year-old overweight children, a daily instructor-led aerobic exercise program that lasted eight months was effective in improving the efficiency of neural circuits that support better cognitive functioning (Kraftt & others, 2014).
Parents and schools play important Page 269roles in determining children’s exercise levels (Brusseau & others, 2018; de Heer & others, 2017; Lind & others, 2018; Lo & others, 2018; Solomon-Moore & others, 2018). Growing up with parents who exercise regularly provides positive models of exercise for children (Crawford & others, 2010). In addition, a research review found that school-based physical activity was successful in improving children’s fitness and lowering their fat levels (Kriemler & others, 2011).
Screen time also is linked with low activity, obesity, and worse sleep patterns in children (Tanaka & others, 2017). A recent research review found that a higher level of screen time increased the risk of obesity for low- and high-activity children (Lane, Harrison, & Murphy, 2014). Also, a recent study of 8- to 12-year-olds found that screen time was associated with lower connectivity between brain regions, as well as lower levels of language skills and cognitive control (Horowitz-Kraus & Hutton, 2018). In this study, time spent reading was linked to higher levels of functioning in these areas.
Here are some ways to encourage children to exercise more:
· Offer more physical activity programs run by volunteers at school facilities.
· Improve physical fitness activities in schools.
· Have children plan community and school activities that interest them.
· Encourage families to focus more on physical activity, and encourage parents to exercise more.
HEALTH, ILLNESS, AND DISEASE
For the most part, middle and late childhood is a time of excellent health. Disease and death are less prevalent at this time than during other periods in childhood and in adolescence. However, many children in middle and late childhood face health problems that harm their development.
Accidents and Injuries Injuries are the leading cause of death during middle and late childhood, and the most common cause of severe injury and death in this period is motor vehicle accidents, either as a pedestrian or as a passenger (Centers for Disease Control and Prevention, 2017c). For this reason, safety advocates recommend the use of safety-belt restraints and child booster seats in vehicles because they can greatly reduce the severity of motor vehicle injuries (Eberhardt & others, 2016; Shimony-Kanat & others, 2018). For example, one study found that child booster seats reduced the risk for serious injury by 45 percent for 4- to 8-year-old children (Sauber-Schatz & others, 2014). Other serious injuries involve bicycles, skateboards, roller skates, and other sports equipment (Perry & others, 2018).
Overweight Children Being overweight is an increasingly prevalent health problem in children (Blake, 2017; Donatelle, 2019; Smith & Collene, 2019). Recall that being overweight is defined in terms of body mass index (BMI), which is computed by a formula that takes into account height and weight—children at or above the 97th percentile are included in the obesity category, at or above the 95th percentile in the overweight category, and children at or above the 85th percentile are described as at risk for being overweight (Centers for Disease Control and Prevention, 2017b). Over the last three decades, the percentage of U.S. children who are at risk for being overweight has increased dramatically. Recently there has been a decrease in the percentage of 2- to 5-year-old children who are obese, which dropped from 12.1 percent in 2009–2010 to 9.4 percent in 2013–2014 (Ogden & others, 2016). In 2013–2014, 17.4 percent of 6- to 11-year-old U.S. children were classified as obese, essentially the same percentage as in 2009–2010 (Ogden & others, 2016).
It is not just in the United States that children are becoming more overweight (Thompson, Manore, & Vaughan, 2017). For example, a study found that general and abdominal obesity in Chinese children increased significantly from 1993 to 2009 (Liang & others, 2012). Further, a recent Chinese study revealed that high blood pressure in 23 percent of boys and 15 percent of girls could be attributed to being overweight or obese (Dong & others, 2015).
Conditions, Diseases, and Disorders
Metabolic syndrome has increased in middle-aged adults in recent years and is linked to early death. Connect to “Physical and Cognitive Development in Middle Adulthood.”
Causes of Children Being Overweight Heredity and environmental contexts are related to being overweight in childhood (Insel & Roth, 2018; Yanovski & Yanovski, 2018). Genetic analysis indicates that heredity is an important factor in children becoming overweight (Donatelle, 2019). Overweight parents tend to have overweight children (Pufal & others, 2012). For example, one study found that the greatest risk factor for being overweight at 9 years of age was having an overweight parent Page 270(Agras & others, 2004). Parents and their children often have similar body types, height, body fat composition, and metabolism (Pereira-Lancha & others, 2012). In a 14-year longitudinal study, parental weight change predicted children’s weight change (Andriani, Liao, & Kuo, 2015).
Environmental factors that influence whether children become overweight include the greater availability of food (especially food high in fat content), energy-saving devices, declining physical activity, parents’ eating habits and monitoring of children’s eating habits, the context in which a child eats, and heavy screen time (Ren & others, 2017). In a recent Japanese study, the family pattern that was linked to the highest risk of overweight/obesity in children was a combination of irregular mealtimes and the most screen time for both parents (Watanabe & others, 2016). Further, a recent study found that children were less likely to be obese or overweight when they attended schools in states that had a strong policy emphasis on healthy foods and beverages (Datar & Nicosia, 2017). Also, a behavior modification study of overweight and obese children made watching TV contingent on their engagement in exercise (Goldfield, 2012). The intervention markedly increased their exercise and reduced their TV viewing time.
image5 What are some of the health risks for overweight and obese children? ©Image Source/Getty Images
Consequences of Being Overweight The high percentage of overweight children in recent decades is cause for great concern because being overweight raises the risk for many medical and psychological problems (Powers & Dodd, 2017; Schiff, 2019; Song & others, 2018). Diabetes, hypertension (high blood pressure), and elevated blood cholesterol levels are common in children who are overweight (Chung, Onuzuruike, & Magge, 2018; Martin-Espinosa & others, 2017). Research reviews have concluded that obesity was linked with low self-esteem in children (Gomes & others, 2011; Moharei & others, 2018). And in one study, overweight children were more likely than normal-weight children to report being teased by their peers and family members (McCormack & others, 2011).
Intervention Programs A combination of diet, exercise, and behavior modification is often recommended to help children lose weight (Insel & Roth, 2018; Martin & others, 2018; Morgan & others, 2016). Intervention programs that emphasize getting parents to engage in healthier lifestyles themselves, as well as to feed their children healthier food and get them to exercise more, can produce weight reduction in overweight and obese children (Stovitz & others, 2014; Yackobovitch-Gavan & others, 2018). For example, one study found that a combination of a child-centered activity program and a parent-centered dietary modification program helped overweight children lose pounds over a two-year period (Collins & others, 2011).
Cardiovascular Disease Cardiovascular disease is uncommon in children. Nonetheless, environmental experiences and behavior during childhood can sow the seeds for cardiovascular disease in adulthood (Schaefer & others, 2017). Many elementary-school-aged children already possess one or more of the risk factors for cardiovascular disease, such as hypertension (high blood pressure) and obesity (Chung, Onuzuruike, & Magge, 2018; Zoller & others, 2017). In a recent study, the combination of a larger waist circumference and a higher body mass index (BMI) placed children at higher risk for developing cardiovascular disease (de Koning & others, 2015). A recent study found that high blood pressure in childhood was linked to high blood pressure and other heart abnormalities in adulthood (Fan & others, 2018). Also in a longitudinal study, high levels of body fat and elevated blood pressure beginning in childhood were linked to premature death from coronary heart disease in adulthood (Berenson & others, 2016). Further, one study found that high blood pressure went undiagnosed in 75 percent of children with the disease (Hansen, Gunn, & Kaelber, 2007).
Cancer Cancer is the second leading cause of death in U.S. children 5 to 14 years of age. One in every 330 children in the United States develops cancer before the age of 19. The incidence of cancer in children has increased slightly in recent years (National Cancer Institute, 2018).
Childhood cancers mainly attack the white blood cells (leukemia), brain, bone, lymph system, muscles, kidneys, and nervous system. All types of cancer are characterized by an uncontrolled proliferation of abnormal cells (Marcoux & others, 2018). As indicated in Figure 2, the most common cancer in children is leukemia, a cancer in which bone marrow manufactures an abundance of abnormal white blood cells that crowd out normal cells, making the child highly susceptible to bruising and infection (Kato & Manabe, 2018; Shago, 2017).