Contact sport

Where there is a limit as to how much contact is acceptable most sports have a mechanism to call a foul by the referee, umpire or similar official when an offence is deemed to have occurred.

[6][7] Full contact rules differentiate from other forms of the same sports that may otherwise restrict blows to the head and the use of elbows or knees.

[2] The American Academy of Pediatrics policy statement was revised in 2008 to include the following definition: In collision sports (e.g. boxing, ice hockey, American football, lacrosse, and rodeo), athletes purposely hit or collide with each other or with inanimate objects (including the ground) with great force.

In limited-contact sports (e.g. softball and squash), contact with other athletes or with inanimate objects is infrequent or inadvertent.

Defeating an opponent generally takes place using in isolation or combination actions such as striking and grappling depending on the rules of the sport.

Several sports' governing bodies began changing their rules in order to decrease the incidence of serious injuries and avoid lawsuits.

At the professional level, America's professional football league, the National Football League, implemented The Concussion Protocol in 2011, banning concussed players from re-entering the same game in which they were injured in order to reduce the risk of further injury and damage.

Rowan Stringer died in 2013 of second-impact syndrome, "...the result of suffering multiple concussions playing rugby three times in six days.