The existence of growth spurts and growing pains in children may be perpetually evident to parents, but their cause has lacked scientific explanation. A new study by Emory University anthropologist Michelle Lampl, M.D., Ph.D., and colleagues at the University of Wisconsin-Madison now sheds some light on this childhood phenomena.
In a five-year study using lambs, the research team found that leg growth occurred primarily when the animals were at rest. While the research does not provide a definitive link to nocturnal growth and the pain that some children experience, it does provide valuable new data and a possible explanation for growing pains, Lampl and colleagues say. Their results were recently published in the November/December 2004 issue of the Journal of Pediatric Orthopaedics.
As the first study to demonstrate actual bone growth spurts, it presents a significant leap forward in documenting the process of normal growth spurts, and suggests that infants and children may also grow when they are at rest, Lampl says.
"In children, we often view growth as a long continuous arc, especially if we look at annual growth measurements like the charts you might find in your pediatrician's office. However, growth is not so smooth, and occurs in spurts, as first shown some years ago among our studies of infants," Lampl says. "This is the first animal model to show that growth -- at the level of the bone -- is not a continuum."
To develop the animal model to test her theories, Lampl turned to Norman Wilsman, V.M.D., a professor of comparative biosciences at the University of Wisconsin-Madison's School of Veterinary Medicine, and his team. The results of their lamb study, which measured the leg bones every three minutes, showed that at least 90 percent of the bone growth occurred when the animals were at rest.
For more than a decade, Lampl has researched growth spurts and growing pains, and documented that children do grow in spurts during the course of a day, which changes the previously held maxim that child growth is constant. The next step in her research will be to identify and define the biology behind the growth, and what triggers it. "This study helps us know what kinds of questions to ask," Lampl says.
What may be occurring is that when an animal is at rest, pressure on the growth plates of long bones such as the tibia is eased, permitting the bones to elongate, she says. Growth plates are soft zones of cartilage near the ends of bones. When a young animal is standing, walking or running, pressure may compact the plate, inhibiting growth, Lampl explains.