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Babies can fall asleep and wake up in a different body.
Careful measurements of a baby’s length every day, together with sleep diaries, document that increased sleep is a sign of a growing child. Often described as “growth spurts,” children can experience a surge in length/height by more than half an inch in one day and then not grow for days to weeks. This suddenly taller body can be a challenge. The typical experience of a “growth spurt” for an infant is observable as they now bump into a table edge that only the day before they walked beneath. Unfortunately, the effort is often repeated as the infant comes to recognize that something has changed and walking under the table is no longer an option. Adjusting to their suddenly bigger bodies can be frustrating as longer arms and legs alter the distance-to-target for reaching and stepping, resulting in clumsiness. For parents, their child’s suddenly bigger bodies mean that pants and shoes that fit yesterday are abruptly too small.
“Simply put, growth is everything.”
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90 to 95% of the time healthy babies aren’t growing at all.
Children grow by saltation and stasis, named for the Latin saltare, to leap, and stasis, to stand. When measured daily, babies and children are documented to grow in bursts of up to a centimeter in length/height (saltations) within a day, separated by lulls in growth (stases) of such long duration that more than 90 percent of the time they are not growing at all. This contrasts with the growth charts we see in doctors' offices showing an uninterrupted curve of increasing size across age. Normal growth is not continuous but occurs only when chemical signals either trigger or permit cell division and/or cell expansion. We are beginning to understand the complex factors that contribute to this biological mechanism and to the influences from sleep, nutrition, changes in body chemistry and even behavior and illness. The presence of saltation and stasis is a profound part of human development.
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What is a “growth spurt”?
A growth spurt commonly means the obvious event of noticeable growth, “the baby can’t fit into her onesie anymore!” The discovery of saltation and stasis as the cellular foundation for growth goes beyond recognition to understanding the timing of saltatory growth as it interrupts routine stasis and, most importantly, the mechanisms of these two key events in infant and child development. Of practical value to parents is the recognition of their child’s changing dynamic in eating, sleeping, and behavior before, during, and immediately after a “growth spurt.”
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When do “growth spurts” happen?
Parents often ask at what ages they can expect “growth spurts.” The simple answer is that it depends on the child. Recent research has shown similarity in the timing of “growth spurts” between identical twins, suggesting a genetic basis, with influences from diet, illness, stress and a number of environmental factors. The number of days between “growth spurts” varies within and between individual children, ranging from 3 to 60 days in the first year of life, increasing to several months at older ages. Every parent learns when their individual child is growing by his/her behaviors.
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Babies WHISper loudly when they grow.
How can parents know when their child is experiencing a “growth spurt”? Babies share their discomfort loudly, and need emotional support, comforting and temporary increased food intake. The abrupt saltatory elongation of bones can turn even a calm and good-humored child into a Whiney, Hungry and Irritable person with Sleep perturbations. It likely takes only minutes to hours for bone elongation, but effects from the chemistry involved in organizing the saltatory growth event and putting the finishing touches on the newly built bone may last for 2 or 3 days. The underlying biological processes include hormones, chemicals associated with energy utilization and conservation, inflammation, and immune responses, each of which can have disruptive effects on behavioral state.
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Gaining weight versus ‘growing’.
Gaining weight is not necessarily a sign of healthy growth, as an overabundant increase in weight due to energy imbalance is not the same thing as developmentally accruing lean body mass. Variability in time since last feeding, amount consumed, a baby’s urinary and fecal content, and overall hydration can significantly influence measurement values. This is important as the first year of life is a critical time for the expansion of fat cell number, and once accumulated, fat cell numbers are rarely reduced, with higher numbers among overweight and obese individuals for life. Protecting babies from overabundant fat cell development does not mean not feeding them when they are hungry. Protecting babies from inappropriate fat tissue development does involve being wary of product claims that promote “healthy growth” with the use of nutritional supplements when this means promoting weight gain among otherwise healthy children.
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Surely, he can’t be hungry again…
Ah, but he is hungry again. Babies’ frenzied eating demands prior to a saltatory “growth spurt” are part of the biological sequence that prepares the body to grow. Short-term energetic strategies include a “stock-up” option characterized by short-lived behavioral disruptions. The intense cries to eat again often raise parental concerns, ranging from fears of over-feeding to worries about whether nursing mothers can “keep-up” with their baby’s “bottomless pit” appetite and hourly requests for another snack. Repeated initiations and longer feeds, however, increase maternal milk production. Parents also receive guidance from numerous sources on how-to react to their demanding, fussy babies, with admonitions about the need to teach infants early to wait for “meal times.” The facts are that in the throes of growing, babies are not heedful of “waiting” and the good news is that appetites decline after several days as growth occurs, often accompanied by weight and fat reduction.
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Cells “pop” in size and babies grow longer.
Saltatory growth in total body length occurs predominantly in the legs. The biological mechanism for this includes chemicals that trigger specialized cells near the end of long bones to act in unison. These cells undergo a series of divisions, until 8-16 cells emerge as a small unit. Many such units cluster together, become synchronized and await the moment when they will undergo expansion in size. The moment these clustered units ”pop” is the biological saltation we witness as our baby’s “growth spurt.”
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“Growth spurts” are not just for babies…
The body grows in size by saltation and stasis at all ages from earliest prenatal life to the attainment of adulthood. The frequency of saltatory growth declines with age as the short durations between saltations in infancy give way to longer durations of stasis with age. Regardless of age, individuals experience both the chemistry of the growing body and the reaction to sudden changes in body size. Saltatory growth episodes are manifest by surly behavior among children, the ‘bottomless pit’ consumption patterns of adolescents, and the inconvenient days when pants and shoes suddenly do not fit. The clumsy child and adolescent are unaccustomed to where their body is in three-dimensional space after a saltation; tripping is not uncommon as their suddenly longer legs hit the ground unexpectedly sooner today than they did yesterday. Overall, the time between growth saltations changes with age and is shorter in both infancy and adolescence by comparison with the childhood years. Yet, the underlying mechanisms of saltation and stasis are a continuing reality of the developmental process of growing up human.
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Children do not grow like the growth charts.
The growth charts we see in our pediatrician’s office give the impression that our children should grow both continuously and by equal daily increments. No wonder parents can become alarmed when their child goes through a check-up with little growth or a sudden great leap. Not to worry. The science of saltation and stasis explains why individual babies and children do not follow the simple paths of the curves. While it is often said that there is a “right” size and a “right” path to get to that size, in reality individuals grow according to their own timing. It is normal for a child not to track along a single line on the growth charts because the lines do not illustrate the biology of growing children.
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If children don’t grow like the growth charts why do we have them?
Growth charts were designed to summarize the variability in size found among children at certain ages, specific times, and locations. They are designed to answer the question of who is relatively small and who is relatively tall. A growth chart presents information in terms of percentiles that summarize size, not growth. These charts demonstrate the data conclusions on, for example, the size of the relatively small children (the size at which only 5% of children are smaller, the 5th percentile), the size of the relatively tall children (the size at which only 5% are larger, or the 95th percentile), and the ‘average’ size child (the 50th percentile). Healthy children come in all sizes. But they do not grow continuously.