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UW researchers discover value of rest

More rest may do a growing body good, according to a recent study conducted by University of Wisconsin researchers.

The study, which analyzed growth spurts in young lambs, showed most of the lambs’ growth occurred when they were sleeping or resting, according to the researchers who conducted it. The researchers also said the findings of the study will likely apply to other animals, including human children.

Their work was published in the November and December issue of the Journal of Pediatric Orthopedics.

Specially made sensors designed to record growth measurements every few minutes over the course of several weeks were implanted in the lambs’ legs.

Video cameras monitoring the lambs’ behavior also allowed researchers to determine when the lambs were standing or walking, and when the lambs were resting or sleeping.

“[The tiny sensors] measured growth very precisely, almost continuously,” said Norman Wilsman, a professor for the School of Veterinary Medicine and co-author of the study. “You could see how the bones would grow and [when] they would stop growing.”

The main issue the researchers sought was whether growth in children or adolescent animals is continuous or episodic, Wilsman said.

“We were surprised to find that essentially, the only times they were growing was when the lambs were lying down,” he said.

After taking readings from the sensors, the researchers found 90 percent of the lambs’ growth occurred while they were recumbent.

Wilsman also said it is likely that growth in humans happens in the same way.

“At the end of your bones, there are these soft cartilage disks called growth plates,” said Dr. Kenneth Noonan, an orthopedic surgeon and contributor to the study. “When the animals are standing, the growth plates are compressing — the weight of the animal is preventing the cartilage from elongating. When they lay down, the pressure is released.”

Wilsman said the results of the study are not necessarily related to sleep.

“It is not associated with sleep and it is not associated with night,” Wilsman said. “But that is when the bones are growing in children because that is a long period of recumbency.”

Wilsman said this study also provides information on how and why growing children experience “growing pains.”

These pains, which often occur at night, are common in children. But until now, doctors were unsure of why kids got them, Wilsman said.

“We’ve never really had an explanation for [growing pains],” Wilsman said. “We’ve sort of had an intuition about it, but this is the first piece of science that shows that intuition was right.”

Wilsman said this research may provide insight to researchers studying bone growth, and may eventually lead to treatments for children who have bone-growth disorders.

“Growth plates can be affected by many different ways, from fractures, tumors, trauma or medicines,” Noonan said. “This technology will allow us to look at how certain drugs could be used for children because we can prove that it has no effect on growth.”

While he stressed the importance of a balanced lifestyle, Wilsman said, “This study suggests there are probably good reasons for us to rest every once in a while.”