Answer:
65%
Step-by-step explanation:
American football is a physically demanding sport due the fact that The players of NFL are required to constantly involved in a body impact with another equally strong athletes.
This strong impact often creates some sort of damage to their bones or brains. Since NFL teams have to do a match every week , the players often have to do the matches again even before the damage that they accumulated previously haven't truly healed. This is why large portion of the players got some form of permanent disability after they retire.