Jacksonville Jaguars wide receiver Lamaar Thomas (center) is hit in the head by Tampa Bay Buccaneers linebacker Brandon Magee as cornerback Kip Edwards helps make the tackle a 2014 preseason game. Magee was penalized for the hit.
Phelan M. Ebenhack/AP
A growing number of pediatric sports medicine groups warn that when a child focuses on a single sport before age 15 or 16, they increase their risk of injury and burnout — and don't boost their overall success in that sport.
Hero Images/Getty Images