"If kids don't have axillary (underarm) or pubic hair, they aren't ready to play," said Dr. Robert Cantu, a neurosurgeon at Emerson Hospital in Massachusetts and author of a new book, "Concussion and Our Kids."
"And I have absolutely no problem with parents who want to hold a child out for longer, say 16 or 18."
No tackling? No body checking before 14?
Heading a soccer ball before 14 in soccer might be sacrificed -- if studies eventually bear out the debatable link to concussion -- but tackling and body checking essentially define football and hockey.
In Cantu's words, "These are sports in which smashing into your opponent isn't just a possibility -- it's the object of the game."
And there is some substance behind the argument for waiting until 14, says Cantu, not the least of which is protecting young, developing brains. At 14, he says, several things enhance the body's ability to protect against head trauma.
Before 14, there is a size disparity between the head and the body, causing what concussion experts call a "bobble-head" effect -- the head snaps back dramatically after it is hit.
"Our youngsters have big heads on very weak necks and that combination sets up the brain for greater injury," said Cantu, a clinical professor of neurosurgery at Boston University School of Medicine.
However, around age 14, a child's skull is about 90% the size of an adult's, and the neck and body are strong enough to steel the head against the force of a blow, according to Cantu. The more developed the neck muscles, the less dramatically the head (and thus the brain) is rocked after a tackle or a body check.
Image: Child with football, via Shutterstock