Wrestling can also be classified in terms of what is required to win. These categories can be graded on an ascending scale of violence as follows: break-stance sports are those that require forcing the opponent to relinquish a certain posture or position; toppling requires that the standing opponent be forced to touch the ground with some part of his body other than his feet; touch-fall wrestling requires that the opponent be forced into a certain position, usually supine, for a brief instant; pin-fall wrestling requires that the opponent be held in such a position for a measurable length of time; and submission wrestling requires the opponent to vocally or visually signal defeat by his own choice.