Brief activity breaks may benefit children's health
Children spend about six hours a day either seated or in a reclining position. Such sedentary behaviors have been associated with obesity and insulin resistance. Recent findings suggest that interrupting sitting time with brief bouts of walking improves glucose metabolism in adults, but little is known about the effects in children.
A team of researchers from several National Institute of Health (NIH) components set out to assess whether interrupting sitting with short, moderate-intensity walking bouts could improve glucose tolerance in children. The team enrolled 28 healthy, normal-weight 7- to 11-year-old children.
The children came to the NIH Clinical Center in Bethesda, Maryland, after an overnight fast. During one visit, they remained seated for 3 hours (except to use the bathroom) with limited movement. They watched movies, read, did homework, or engaged in other sedentary activities. On another visit, they interrupted their sitting by walking on a treadmill for 3 minutes at a moderate-intensity pace every 30 minutes. They walked 6 times for a total of 18 minutes during the 3-hour time frame. The order of the conditions (sit or sit plus walk) was randomized and took place from 1 to 4 weeks apart.
The visits were performed under carefully controlled conditions that included monitoring heart rate and activity levels. During each visit, the children drank a glucose solution at the start and then had blood samples taken periodically. This procedure, known as an oral glucose tolerance test, measures the body's ability to use glucose and is often used to test for diabetes. Results appeared online on Aug. 27 in the Journal of Clinical Endocrinology and Metabolism.
The researchers found that during the interrupted sitting day, the children averaged 7 percent lower glucose levels and 32 percent lower insulin levels compared to when they sat for 3 hours continuously. Their blood levels of free fatty acids (high levels of which are linked to type 2 diabetes) were also lower. So were levels of C-peptide, an indicator of how hard the pancreas is working to control blood sugar.
At the end of each visit, the children were allowed to choose their lunch from food provided on a buffet table. The researchers calculated the calorie and nutrient content of what each child ate. They found that the children consumed roughly the same amounts of calories and kinds of foods after each of the sessions. This suggested that the brief walking sessions didn't stimulate the children to eat more than they normally would.
"We know that 30 minutes or more of moderate physical activity benefits children's health," says senior author Dr. Jack A. Yanovski of NIH's National Institute of Child Health and Human Development (NICHD). "It can be difficult to fit longer stretches of physical activity into the day. Our study indicates that even small activity breaks could have a substantial impact on children's long-term health."
The researchers note that further studies will be needed to confirm these findings and to determine if fitting such breaks into school class time could be part of effective strategies to prevent obesity-related illnesses.
--From the National Institute of Health
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