Physical Development

Although it may be tempting to think that physical development is the concern of physical education teachers only, it is actually a foundation for many academic tasks. In first grade, for example, it is important to know whether children can successfully manipulate a pencil. In later grades, it is important to know how long students can be expected to sit still without discomfort—a real physical challenge. In all grades, it is important to have a sense of students’ health needs related to their age or maturity, if only to know who may become ill, with what illness, and to know what physical activities are reasonable and needed.

Trends in Height and Weight

Typical height and weight for well-nourished, healthy students are shown in Table 3.3.1. The table shows averages for several ages from preschool through the end of high school. But the table does not show the diversity among children. At age 6, for example, when children begin school, the average boy or girl is about 115 centimeters tall, but some are 109 and others are 125 centimeters. The average weight at age 6 is about 20 kilograms but ranges between about 16 and 24 kilograms—about 20% variation in either direction.

Table 3.3.1. Average height and weight of well-nourished children
Age	Height (cm)	Weight (kg)
2	85	7.0
6	115	20.0
10	135	31.0
14	162	52.0
18	169	60.5

There are other points to keep in mind about average height and weight that are not evident in Table 3.1. The first is that boys and girls, on average, are quite similar in height and weight during childhood, but diverge in the early teenage years, when they reach puberty. For a time (approximately age 10–14), the average girl is taller, but not much heavier, than the average boy. After that, the average boy becomes both taller and heavier than the average girl—though there remain individual exceptions (Malina, et al., 2004). The pre-teen difference can, therefore, be awkward for some children and youth, at least among those who aspire to look like older teenagers or young adults. For young teens less concerned with “image,” though, the fact that girls are taller may not be especially important, or even noticed (Friedman, 2000).

A second point is that as children get older, individual differences in weight diverge more radically than differences in height. Among 18-year-olds, the heaviest youngsters weigh almost twice as much as the lightest, but the tallest ones are only about 10 percent taller than the shortest. Nonetheless, both height and weight can be sensitive issues for some teenagers. Most modern societies (and the teenagers in them) tend to favor relatively short women and tall men, as well as a somewhat thin body build, especially for girls and women. Yet neither “socially correct” height nor thinness is the destiny for many individuals. Being overweight, in particular, has become a common, serious problem in modern society (Tartamella, et al., 2004) due to the prevalence of diets high in fat and lifestyles low in activity. The educational system has unfortunately contributed to the problem as well, by gradually restricting the number of physical education courses and classes in the past two decades.

The third point to keep in mind is that the average height and weight are related somewhat to racial and ethnic background. In general, children of Asian background tend to be slightly shorter than children of European and North American backgrounds. The latter in turn tend to be shorter than children from African societies (Eveleth & Tanner, 1990). Body shape differs slightly as well, though the differences are not always visible until after puberty. Asian youth tend to have arms and legs that are a bit short relative to their torsos, and African youth tend to have relatively long arms and legs. The differences are only averages; there are large individual differences as well, and these tend to be more relevant for teachers to know about than broad group differences.

Puberty and Its Effects on Students

A universal physical development in students is puberty, which is the set of changes in early adolescence that bring about sexual maturity. Along with internal changes in reproductive organs are outward changes such as the growth of breasts in girls and the penis in boys, as well as relatively sudden increases in height and weight. By about age 10 or 11, most children experience increased sexual attraction to others (usually heterosexual, though not always) that affects social life both in school and out (McClintock & Herdt, 1996). By the end of high school, more than half of boys and girls report having experienced sexual intercourse at least once—though it is hard to be certain of the proportion because of the sensitivity and privacy of the information. (Center for Disease Control, 2004b; Rosenbaum, 2006).

At about the same time that puberty accentuates gender, role differences also accentuate for at least some teenagers. Some girls who excelled at math or science in elementary school may curb their enthusiasm and displays of success in these subjects for fear of limiting their popularity or attractiveness as girls (Taylor & Gilligan, 1995; Sadker, 2004). Some boys who were not especially interested in sports previously may begin dedicating themselves to athletics to affirm their masculinity in the eyes of others. Some boys and girls who once worked together successfully on class projects may no longer feel comfortable doing so—or alternatively may now seek to be working partners, but for social rather than academic reasons. Such changes do not affect all youngsters equally, nor affect any one youngster equally on all occasions. An individual student may act like a young adult one day, but more like a child the next. When teaching children who are experiencing puberty, teachers need to respond flexibly and supportively.

From Reflexes to Voluntary Motor Development

Every basic motor skill (any movement ability) develops over the first two years of life. The sequence of motor skills first begins with reflexes. Infants are equipped with several reflexes, or involuntary movements in response to stimulation. Some of these reflexes are necessary for survival, such as breathing reflexes (this includes hiccups, sneezing, and thrashing reflexes), reflexes to obtain food (such as rooting and sucking). Other reflexes are not necessary for survival, often called primitive reflexes, but signify the state of brain and body functions. Some of these include the Babinski reflex (toes fan upward when feet are stroked), the stepping reflex (babies move their legs as if to walk when feet touch a flat surface), the palmar grasp (the infant will tightly grasp any object placed in its palm), and the Moro reflex (babies will fling arms out and then bring to the chest if they hear a loud noise). These movements occur automatically and are signals that the infant is functioning well neurologically. Within the first several weeks of life, these reflexes are replaced with voluntary movements or motor skills.

Video 3.3.1. Reflexes in Newborn Babies highlights some of the reflexes present at birth. Most of these reflexes will disappear or be replaced with voluntary motor skills within the first months of life.

Motor development occurs in an orderly sequence as infants move from reflexive reactions (e.g., sucking and rooting) to more advanced motor functioning. This development proceeds in a cephalocaudal (from head-down) and proximodistal (from center-out) direction. For instance, babies first learn to hold their heads up, then sit with assistance, then sit unassisted, followed later by crawling, pulling up, cruising, and then walking. As motor skills develop, there are certain developmental milestones that young children should achieve. For each milestone, there is an average age, as well as a range of ages at which the milestone should be reached. An example of a developmental milestone is a baby holding up its head. Babies on average are able to hold up their heads at 6 weeks old, and 90% of babies achieve this between 3 weeks and 4 months old. If a baby is not holding up his head by 4 months old, he is showing a delay. On average, most babies sit alone at 7 months old. Sitting involves both coordination and muscle strength, and 90% of babies achieve this milestone between 5 and 9 months old (CDC, 2018). If the child is displaying delays on several milestones, that is a reason for concern, and the parent or caregiver should discuss this with the child’s pediatrician. Some developmental delays can be identified and addressed through early intervention.

Gross Motor Skills

Gross motor skills are voluntary movements that involve the use of large muscle groups and are typically large movements of the arms, legs, head, and torso. These skills begin to develop first. Examples include moving to bring the chin up when lying on the stomach, moving the chest up, and rocking on hands and knees. But it also includes exploring an object with one’s feet as many babies do, as early as 8 weeks of age, if seated in a carrier or other device that frees the hips. This may be easier than reaching for an object with the hands, which requires much more practice (Berk, 2007). And sometimes an infant will try to move toward an object while crawling and surprisingly move backward because of the greater amount of strength in the arms than in the legs!

During middle childhood, physical growth slows down. One result of the slower rate of growth is an improvement in motor skills. Children of this age tend to sharpen their abilities to perform both gross motor skills such as riding a bike and fine motor skills such as cutting their fingernails.

Early childhood is a time when children are especially attracted to motion and song. Days are filled with moving, jumping, running, swinging, and clapping, and every place becomes a playground. Even the booth at a restaurant affords the opportunity to slide around in the seat or disappear underneath and imagine being a sea creature in a cave! Of course, this can be frustrating to a caregiver, but it’s the business of early childhood. Children may frequently ask their caregivers to “look at me” while they hop or roll down a hill. Children’s songs are often accompanied by arm and leg movements or cues to turn around or move from left to right. Running, jumping, dancing movements, etc. all afford children the ability to improve their gross motor skills.

Video 3.3.2. Early Childhood Gross Motor Development demonstrates some of the motor skills expected of children during the preschool years.

Children’s fundamental motor skills are already developing when they begin kindergarten, but are not yet perfectly coordinated. Five-year-olds generally can walk satisfactorily for most school-related purposes (if they could not, schools would have to be organized very differently!). For some fives, running still looks a bit like a hurried walk, but usually, it becomes more coordinated within a year or two. Similarly with jumping, throwing, and catching: most children can do these things, though often clumsily, by the time they start school, but improve their skills noticeably during the early elementary years (Payne & Isaacs, 2005). It is important to notice if a child does not keep more or less to the usual developmental timetable, and to arrange for special assessment or support if appropriate. Common procedures for arranging for help are described in the chapter on “Special education.”

Even if physical skills are not a special focus of a classroom teacher, they can be quite important to students themselves. Whatever their grade level, students who are clumsy are aware of that fact and how it could potentially negatively affect respect from their peers. In the long term, self-consciousness and poor self-esteem can develop in a child who is clumsy, especially if peers (or teachers and parents) place a high value on success in athletics. One research study found, for example, what teachers and coaches sometimes suspect: that losers in athletic competitions tend to become less sociable and are more apt to miss subsequent athletic practices than winners (Petlichkoff, 1996).

Fine Motor Skills

Fine motor skills are more exact movements of the hands and fingers and include the ability to reach and grasp an object. These skills focus on the muscles in the fingers, toes, and eyes, and enable coordination of small actions (e.g., grasping a toy, writing with a pencil, and using a spoon). Newborns cannot grasp objects voluntarily but do wave their arms toward objects of interest. At about 4 months of age, the infant is able to reach for an object, first with both arms and within a few weeks, with only one arm. Grasping an object involves the use of the fingers and palm, but no thumbs. Stop reading for a moment and try to grasp an object using the fingers and the palm. How does that feel? How much control do you have over the object? If it is a pen or pencil, are you able to write with it? Can you draw a picture? The answer is, probably not. Use of the thumb comes at about 9 months of age when the infant is able to grasp an object using the forefinger and thumb (the pincer grasp). This ability greatly enhances the ability to control and manipulate an object, and infants take great delight in this newfound ability. They may spend hours picking up small objects from the floor and placing them in containers. By 9 months, an infant can also watch a moving object, reach for it as it approaches, and grab it. This is quite a complicated set of actions if we remember how difficult this would have been just a few months earlier.

Figure 3.3.1. This baby is working on his pincer grasp.

Fine motor skills are also being refined in activities such as pouring water into a container, drawing, coloring, and using scissors. Some children’s songs promote fine motor skills as well (have you ever heard of the song “itsy, bitsy, spider”?). Mastering the fine art of cutting one’s own fingernails or tying their shoes will take a lot of practice and maturation. Fine motor skills continue to develop in middle childhood, but for preschoolers, the type of play that deliberately involves these skills is emphasized.

Table 3.3.2. Timeline of Developmental Milestones.
~2 months	Can hold head upright on own    Smiles at sound of familiar voices and follows movement with eyes
~3 months	Can raise head and chest from prone position Smiles at others Grasps objects Rolls from side to back
~4-5 months	Babbles, laughs, and tries to imitate sounds· Begins to roll from back to side
~6 months	Moves objects from hand to hand
~7-8 months	Can sit without support· May begin to crawl Responds to own name Finds partially hidden objects
~8-9 months	Walks while holding on· Babbles “mama” and “dada” Claps
~11-12 months	Stands alone Begins to walk Says at least one word Can stack two blocks
~18 months	Walks independently· Drinks from a cup· Says at least 15 words Points to body parts
~2 years	Runs and jumps Uses two-word sentences Follows simple instructions Begins make-believe play
~3 years	Speaks in multi-word sentences· Sorts objects by shape and color
~4 years	Draws circles and squares    Rides a tricycle Gets along with people outside of the family Gets dressed
~5 years	Can jump, hop, and skip     Knows name and address Counts ten or more objects

Sensory Development

As infants and children grow, their senses play a vital role in encouraging and stimulating the mind and in helping them observe their surroundings. Two terms are important to understand when learning about the senses. The first is sensation, or the interaction of information with the sensory receptors. The second is perception, or the process of interpreting what is sensed. It is possible for someone to sense something without perceiving it. Gradually, infants become more adept at perceiving, making them more aware of their environment and presenting more affordances or opportunities to interact with objects. With improved sensory-perceptual abilities also comes the ability to navigate their environment. At the same time, movement through the environment seems to scaffold the development of sensory-perceptual abilities.

Vision

What can young infants see, hear, and smell? Newborn infants’ sensory abilities are significant, but their senses are not yet fully developed. Many of a newborn’s innate preferences facilitate interaction with caregivers and other humans. The womb is a dark environment void of visual stimulation. Consequently, vision is the most poorly developed sense at birth. Newborns typically cannot see further than 8 to 16 inches away from their faces, have difficulty keeping a moving object within their gaze, and can detect contrast more than color differences. If you have ever seen a newborn struggle to see, you can appreciate the cognitive efforts being made to take in visual stimulation and build those neural pathways between the eye and the brain.

Although vision is their least developed sense, newborns already show a preference for faces. When you glance at a person, where do you look? Chances are you look into their eyes. If so, why? It is probably because there is more information there than in other parts of the face. Newborns do not scan objects this way; rather, they tend to look at the chin or another less detailed part of the face. However, by 2 or 3 months, they will seek more detail when visually exploring an object and begin showing preferences for unusual images over familiar ones, for patterns over solids, faces over patterns, and three-dimensional objects over flat images. Newborns have difficulty distinguishing between colors, but within a few months are able to discriminate between colors as well as adults. Infants can also sense depth as binocular vision develops at about 2 months of age. By 6 months, the infant can perceive depth perception in pictures as well (Sen, Yonas, & Knill, 2001). Infants who have experience crawling and exploring will pay greater attention to visual cues of depth and modify their actions accordingly (Berk, 2007).

Visual Pathways

Have you ever examined the drawings of young children? If you look closely, you can almost see the development of visual pathways reflected in the way these images change as pathways become more mature. Early scribbles and dots illustrate the use of simple motor skills. No real connection is made between an image being visualized and what is created on paper.

At age 3, the child begins to draw wispy creatures with heads and not much other detail. Gradually pictures begin to have more detail and incorporate more parts of the body. Arm buds become arms and faces take on noses, lips, and eventually eyelashes. Look for drawings that you or your child has created to see this fascinating trend. Here are some examples of pictures drawn by girls from ages 2 to 7 years.

Figure 3.3.3. These drawings demonstrate the progression in both drawing skill and visual processing during early childhood. The top left drawing is done by a 2-year old, and the bottom right image is drawn by a 7-year old.

Hearing

The infant’s sense of hearing is very keen at birth. If you remember from an earlier module, this ability to hear is evidenced as soon as the 5th month of prenatal development. In fact, an infant can distinguish between very similar sounds as early as one month after birth and can distinguish between a familiar and non-familiar voice even earlier. Babies who are just a few days old prefer human voices, they will listen to voices longer than sounds that do not involve speech (Vouloumanos & Werker, 2004), and they seem to prefer their mother’s voice over a stranger’s voice (Mills & Melhuish, 1974). In an interesting experiment, 3-week-old babies were given pacifiers that played a recording of the infant’s mother’s voice and of a stranger’s voice. When the infants heard their mother’s voice, they sucked more strongly at the pacifier (Mills & Melhuish, 1974). Some of this ability will be lost by 7 or 8 months as a child becomes familiar with the sounds of a particular language and less sensitive to sounds that are part of an unfamiliar language.

Touch

Immediately after birth, a newborn is sensitive to touch and temperature, and is also sensitive to pain, responding with crying and cardiovascular responses. Newborns who are circumcised (the surgical removal of the foreskin of the penis) without anesthesia experience pain, as demonstrated by increased blood pressure, increased heart rate, decreased oxygen in the blood, and a surge of stress hormones (United States National Library of Medicine, 2016). According to the American Academy of Pediatrics (AAP), there are medical benefits and risks to circumcision. They do not recommend routine circumcision, however, they stated that because of the possible benefits (including prevention of urinary tract infections, penile cancer, and some STDs) parents should have the option to circumcise their sons if they want to (AAP, 2012).

The sense of touch is acute in infants and is essential to a baby’s growth of physical abilities, language and cognitive skills, and socio-emotional competency. Touch not only impacts short-term development during infancy and early childhood but also has long-term effects, suggesting the power of positive gentle touch from birth. Through touch, infants learn about their world, bond with their caregivers, and communicate their needs and wants. Research emphasizes the great benefits of touch for premature babies, but the presence of such contact has been shown to benefit all children (Stack, 2010). In an extreme example, some children in Romania were reared in orphanages in which a single care worker may have had as many as 10 infants to care for at one time. These infants were not often helped or given toys with which to play. As a result, many of them were developmentally delayed (Nelson, Fox, & Zeanah, 2014). When we discuss emotional and social development later in this module, you will also see the important role that touch plays in helping infants feel safe and protected, which builds trust and secure attachments between the child and their caregiver.

Taste and Smell

Not only are infants sensitive to touch, but newborns can also distinguish between sour, bitter, sweet, and salty flavors and show a preference for sweet flavors. They can distinguish between their mother’s scent and that of others, and prefer the smell of their mothers. A newborn placed on the mother’s chest will inch up to the mother’s breast, as it is a potent source of the maternal odor. Even on the first day of life, infants orient to their mother’s odor and are soothed, when crying, by their mother’s odor (Sullivan et al., 2011).

Health and Illness

By world standards, children and youth in economically developed societies tend, on average, to be remarkably healthy. Even so, much depends on precisely how well-off families are and on how much health care is available to them. Children from higher-income families experience far fewer serious or life-threatening illnesses than children from lower-income families. Whatever their income level, parents and teachers often rightly note that children— especially the youngest ones—get far more illnesses than do adults. In 2004, for example, a government survey estimated that children get an average of 6–10 colds per year, but adults get only about 2–4 per year (National Institute of Allergies and Infectious Diseases, 2004). The difference probably exists because children’s immune systems are not as fully formed as adults, and because children at school are continually exposed to other children, many of whom may be contagious themselves. An indirect result of children’s frequent illnesses is that teachers (along with airline flight attendants, incidentally!) also report more frequent minor illnesses than do adults in general—about five colds per year, for example, instead of just 2–4 (Whelen, et al., 2005). The “simple” illnesses are not life-threatening, but they are responsible for many lost days of school, both for students and for teachers, as well as days when a student may be present physically, but functions below par while simultaneously infecting classmates. In these ways, learning and teaching often suffer because health is suffering.

The problem is not only the prevalence of illness as such (in winter, even in the United States, approximately one person gets infected with a minor illness every few seconds), but the fact that illnesses are not distributed uniformly among students, schools, or communities. Whether it is a simple cold or something more serious, illness is particularly common where living conditions are crowded, where health care is scarce or unaffordable, and where individuals live with frequent stresses of any kind. Often, but not always, these are the circumstances of poverty. Table 3.3 summarizes these effects for a variety of health problems, not just for colds or flu.

Source: Richardson, 2005; Spencer, 2000; Allender, 2005. ​
Table 3.3.3. Health effects of children’s economic level
Health program	Comparison: Poor vs. non-poor
Delayed immunizations	3 times higher
Asthma	Somewhat higher
Lead poisoning	3 times higher
Deaths in childhood from accidents	2–3 times higher
Deaths in childhood from disease	3–4 times higher
Having a condition that limits school activity	2–3 times higher
Days sick in bed	4o percent higher
Seriously impaired vision	2–3 times higher
Severe iron deficiency (anemia)	2 times higher

As students get older, illnesses become less frequent, but other health risks emerge. The most widespread are the consumption of alcohol and the smoking of cigarettes. As of 2004, about 75 percent of teenagers reported drinking an alcoholic beverage at least occasionally, and 22 percent reported smoking cigarettes (Center for Disease Control, 2004a). The good news is that these proportions show a small, but steady decline in the frequencies over the past 10 years or so. The bad news is that teenagers also show increases in the abuse of some prescription drugs, such as inhalants, that act as stimulants (Johnston, et al., 2006). As with the prevalence of illnesses, the prevalence of drug use is not uniform, with a relatively small fraction of individuals accounting for a disproportionate proportion of usage. One survey, for example, found that a teenager was 3–5 times more likely to smoke or use alcohol, smoke marijuana, or use drugs if he or she has a sibling who has also indulged in these habits (Fagan & Najman, 2005). Siblings, it seems, are more influential in this case than parents.