As the weather gets hotter, preschoolers get less exercise outside, research finds.

The findings, published last week in the Journal of the American Medical Association Pediatrics, may seem obvious to anyone who’s watched their little ones wilt and turn red-faced on the playground. But researchers approached the question in a novel way: they used advanced wearable activity monitors to follow specific children in a specially designed laboratory school for studying child behavior and development.

“Given that we’re seeing an increasing number of hot days,” says Andrew Koepp, lead author of the paper and PhD candidate in human development and family sciences at the University of Texas at Austin, “it’s important to understand how young children’s activity changes so that we can take steps to make sure they are getting the physical activity they need to be healthy.”

The study looked at children ages three to six who are enrolled at the Priscilla Pond Flawn Child and Family Laboratory School on campus. The study used digital wearable activity monitors on each child for a week in April 2022 as the children played on the school’s partially shaded playground. Ambient air temperatures were between 72 degrees and 95 degrees Fahrenheit.

When temperatures were at 72 degrees, children engaged in moderate to vigorous physical activity (MVPA) for 27% of their outdoor play time. MVPA is defined as raising the heart rate to the point where a person can speak, but would have a hard time singing. When temperatures rose to 95 degrees, MVPA dropped to 21% of outdoor play time. Additionally, sedentary time, where children were sitting or still, rose on hotter days from 62% on play time at 72 degrees to 70% of playtime at 95 degrees.

The Centers for Disease Control recommends that children between the ages of three and five be physically active throughout the day, as physical activity improves young children’s development, academic performance and learning, and helps build strong muscles and bones, contributes to healthy weight and blood sugar levels, and improves cardiovascular, lung, and mental health.

The sample at the laboratory school is made up of healthy, middle- and upper-income children, but, as laboratory school director Amy Bryan, an associate professor of practice in human development and family sciences, explains: “These effects would likely be amplified in more vulnerable children who had health issues or other risk factors for low activity, as would the impacts on their development.”

Read the full article about preschoolers by Esther Robards-Forbes at Futurity.