(Reuters Health) - More than half of U.S. children may not be getting the recommended amount of physical activity and doctors can help by making exercise one of the “vital signs” assessed in routine health checks, researchers say.

“We need to start asking children and their parents questions about physical activity on a routine basis. Exercise guidelines for families should be specific, and education about what counts as ‘moderate to vigorous physical activity’ should be included,” said the lead author of a study presented November 3 at the American Academy of Pediatrics annual conference in Orlando, Florida.

Julie Young, an athletic trainer at Nationwide Children’s Hospital Division of Sports Medicine in Dublin, Ohio and her colleagues reviewed electronic medical records of 7,822 children ages 5 to 18 in their hospital’s pediatric sports medicine clinic, who were asked about their physical activity by their doctors. One of the researchers’ goals was to understand whether kids were meeting physical activity guidelines.

They found that 5 percent of the children were completely inactive, registering zero minutes of exercise per week. Nearly 50 percent were not active enough to meet guidelines, exercising less than the recommended 420 minutes per week. The remaining 45 percent of patients were sufficiently active, exercising more than 420 minutes per week.

Further questioning revealed that even the group getting sufficient physical activity still fell short in one sense. Only about 12 percent of the active kids, or 5.2 percent of the total study group, got the recommended 60 minutes of activity each day, while the rest were getting longer bouts of activity on fewer days per week. Exercising longer and for fewer days puts these kids at risk for burnout or repetitive injury, the researchers said in a statement.

Other notable findings include further evidence that boys exercise more than girls. The boys in this study averaged 61 minutes more exercise per week than girls, and as a result were 39 percent more likely to meet the guidelines.

The difference in activity levels between boys and girls was mostly a result of the number of days per week kids participated in physical activity, Young noted.

Another insight from the study is that physical activity appears to increase with age, with younger kids reporting the least exercise.

“While pediatricians often ask if children are physically active, many don’t ask specifically if children are meeting current exercise guidelines of 60 minutes on daily physical activity,” Young told Reuters Health in an email.

“There are vast benefits of physical activity,” she added. “Children who are physically active are more likely to be active as adults - lifelong (physical activity) can decrease risks of common diseases.”

“To me, the important finding is that older kids are more active,” said Dr. William Phillips, who wasn’t involved in the study. “This may be due to the greater availability of school related sports programs which may be less costly than many of the ‘private’ sports leagues/programs that younger children participate in,” said Phillips, a pediatric orthopedic surgeon at Texas Children’s Hospital in Houston.

“Defining a child’s activity level as a ‘vital sign’ is a great way to emphasize its importance,” Phillips said.

SOURCE: bit.ly/2zNyX2Z American Academy of Pediatrics National Conference & Exhibition, November 3, 2018.