CHICAGO — Strict rest may not be the best medicine for kids with concussions, a Canadian study found, challenging the idea that physical activity should be avoided until symptoms disappear.

A month after their concussions, ongoing or worse symptoms were more common in children and teens who were inactive during the week following injury, compared with those who engaged in physical activity during that first week. Activity was mostly light exercise including walking and swimming.

The results were similar even among those who early on had three or more concussion symptoms, which can include nausea, headaches and confusion. Physical activity still seemed to reduce chances for lingering symptoms a month after the concussion.

“It’s still important to have caution in the immediate post-injury period,” said lead author Dr. Roger Zemek, an emergency medicine specialist at Children’s Hospital of Eastern Ontario. After a sports-related concussion, kids “should always be removed from play and not return that day.”

To avoid re-injury, kids should generally be sidelined from the sport or activity that led to the concussion until a doctor clears them to return, he said. But the study results suggest they can resume sports or other physical activities sooner than previously thought, he said.

The researchers surveyed about 2,400 kids aged 5 to 18 treated for concussions in nine emergency departments in Canada. Most were sports-related injuries and most kids had at least one concussion symptom in the first week.

Results from the 2013-2015 study were published Tuesday in the Journal of the American Medical Association .