FILE - In this May 4, 2012, file photo, Dallas Cowboys' Morris Claiborne (24) walks the field during NFL football rookie camp at the team's training facility in Irving, Texas. As part of a symposium designed to ease their transition as pros, NFC rookies attended a seminar on health and safety hosted Monday, June 25, by Cleveland Browns team physician Dr. Mark Schickendantz. Schickendantz spoke on a number of topics, including concussions and potential long-term effects of head injuries, which have become a major focus for the league in recent years. (AP Photo/Tony Gutierrez, File)