Download Childhood Physical Growth

Childhood Physical Growth
Written by Joseph Lao, Ph.D.
2-11 Years
The years between 2-6 used to be called the play years, because children didn't start school
until about five years of age and kindergarten was mostly a play time. Now, the period between
2-4 is called either early childhood, toddlerhood or the preschool years. The period between
4-7 is sometimes called middle childhood, or the early school years. And the period between
7-11 is often called the late childhood period. Body Growth
The physical growth of children is not smooth. Instead, it is characterized by growth spurts
followed by periods of slower growth. Overall, the rate of physical growth slows down after
infancy. The height of the average child increases by 2-3 inches per year until about 7 years of
age. In addition, the cephalocaudal pattern of growth that characterizes infancy is now
reversed, with the rest of the body now growing faster than the head. Starting at about 8 years
of age many children experience what is referred to as a preadolescent growth spurt. During
this period, it is common for children to grow between 4-6 inches per year. It is also common
for girls to experience this growth spurt sooner than boys (the female body tends to mature
more quickly than the male body). As a result, the late childhood period is the only time in the
human lifespan when the average female is taller than the average male.
Although the weight of the average child increases by 3-5 lbs per year until about age 7, 2-3
year olds have the smallest weight gain of the entire life-span. This is partly because during
these years they have smaller appetites. (Appetite tends to fluctuate with our growth cycles). Also, children have a very high metabolic rate during the early childhood period. In fact, at three
years of age the human metabolic rate is the highest of the entire lifespan. In practical terms
this means children at this age have a very high level of physical energy. And boys tend to
have higher activity levels than girls. This means they really need to move around. Not surprisingly, during the early childhood period the percentage of body fat decreases and
muscle tissue increases. Children get thinner. Sometimes parents get concerned that their
children are too thin and try to force them to eat, even when they don't want to. If you wish to
go to the section on nutrition please click here. For now, focus on providing nutritious foods. Also try to accept their preferences as long as they are healthy (e.g., within normal limits for
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Childhood Physical Growth
Written by Joseph Lao, Ph.D.
their height and weight). Most children resume a normal appetite by about 8 years of age. The bones of the child continue to grow. The arms and legs get longer. Since the legs now
grow faster than the torso, the legs constitute a growing percentage of the height of the child. The bones in the hands and feet also grow, but in a different way. While the one year old
typically has only three bones in their wrist, this number will increase to nine by around 51
months (or just over four years) of age. Similar developments occur in the ankle. On the other
hand, the bones of the skull fuse together, so that the three plates that are evident at birth
become completely fused by about 18 months of age. Still another characteristic of bone
growth is that the bones of all parts of the body tend to get harder, and a little more brittle. The
softness of neonatal bones facilitates the process of birth. However, it is helpful to have
relatively hard bones in order to facilitate lifting heavy objects, and especially walking and
running. Two other interesting patterns have been detected with respect to group differences in
the rate of bone growth. First, the bones of females tend to grow faster than those of males. Second, the bones of African American children tend to grow faster than those of Caucasian
American children.
Another important area of physical growth concerns the muscles of the child. At birth, we have
all the muscles we will ever have. However, as Helen Bee has observed, the neonates muscles
tend to be relatively short, thin, and watery. As children progress through the childhood years
their muscles tend to grow longer, thicker, and less watery. These changes are correlated with
increased muscle strength.
Brain Growth
Once the basic structures of the brain are formed, by birth, subsequent growth of the brain
consists of the multiplication and growth of glial cells, branching out of dendrites, the
establishment of connections (synapses) between neurons, and dying out of unused neurons. The early pattern of cephalocaudal growth continues during infancy but reaches its peak in early
childhood before reversing so that the rest of the body can catch up to the growth of the brain. For instance, by 5 years of age the human brain has reached 90 % of adult weight, but the body
has reached only 30 % of adult weight. The rest of the body will soon catch up.
When we are born the human brain is still not completely developed. Those parts of the brain
that perform vital functions, e.g., mediating breathing and reflexes, are filled with neurons that
are partly covered by a fatty sheath that greatly speeds of the processing and transmission of
information. Most of these regions are in the hindbrain, the most ancient part of the human
brain. The type of cell that makes up this fatty sheath is called a glial cell. During the early
postnatal period the number of glial cells in the human brain increases dramatically, typically
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Childhood Physical Growth
Written by Joseph Lao, Ph.D.
reaching a peak by the end of the second year of life. As we mature the proliferation of glial
cells enables them to wrap their myelin sheaths around neurons in higher and higher parts of
the brain. Although the myelination process is not completed during childhood, it is partly
responsible for a dramatic increase in the speed with which children can process information
and respond to stimuli. It turns out that growth does not proceed at the same pace in all of the different parts of the
brain. During the early childhood period we find a dramatic developments in the language
centers of the brain. These developments are correlated with experience and the emergence of
linguistic skills. The cerebellum is responsible for coordinating physical movements. This part
of the brain continues to mature (e.g., via myelination) after infancy, apparently reaching adult
levels by about four years of age. In addition, the frontal lobe (the part that handles the
organization and planning of behavior), is the last part of the human brain to fully mature. Indeed, some evidence suggests that this part of the brain may not reach complete maturity
until our late thirties. One of the most exciting discoveries about the developing brain is that it is responsive to
experience. In a way, the brain records all of our experiences in the form of alterations in the
number of neurons available and connections between them. Those parts of the brain that are
stimulated, through experience, tend to grow more branches (but not more neurons), and form
more synapses between nearby neurons. This facilitates communication between neurons in
the parts of the brain that mediate experiences. At the same time, those parts of the brain that
are not used tend to experience a reduction in the number of neurons and synapses. In this
respect, it is reasonable to say that experience sculpts the human brain. How Can I Nurture the Growth of My Child?
As in infancy, a healthy diet is one key. It is important for children to receive all of the vitamins
and nutrients that are necessary for healthy normal growth. In addition, the importance of
exercise cannot be overestimated. Exercise stimulates the growth of the muscles, bones, and
vital organs. Mental stimulation is also important for the growth of the brain. Age appropriate
challenges, and a supportive environment, enable the growing child to exercise their mental
capacities, which, together with physical exercise, nurtures the growth of the brain. Finally,
emotional warmth must be mentioned here. Children thrive in a warm, friendly, stimulating
environment much more easily than in a cold, tough, unstimulating environment, whether at
home or in school. Children whose emotional needs are not satisfied simply do not grow as
well as when those needs are satisfied.
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Childhood Physical Growth
Written by Joseph Lao, Ph.D.
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