You’re an avid runner, and now Junior has decided he’d like to start, too. Is it OK? Sure, with a few caveats.

• Factor in age. Kids who run too much too soon can burn out. There’s no hard and fast rule, but try a mile or so for kids 9 to 13, one to three miles in junior high and three to five miles in high school, says Dr. Rebecca Demorest of the American Academy of Pediatrics (aap.org).

• Beware of overheating. Kids heat up faster than adults and don’t sweat as efficiently. Make sure they hydrate every 15 to 20 minutes.

• Don’t overdo it. Overuse injuries are common in repetitive sports. It’s not clear whether excessive running can harm growth plates, but use common sense.

• Think balance. More than one in six kids are overweight, but make sure runners take in enough healthy calories for all their energy output. Watch out for girls who stop getting their periods or don’t get a period by 16, which may put them at risk for fractures and weak bones.

• Finally, make sure running isn’t interfering with schoolwork. But know this: physically fit kids tend to perform better on tests.