What characterizes a block in the back?

A block in the back is characterized by the initial contact being made in the back of the opponent, specifically within the area defined by the shoulders, below the helmet, and above the waist. This definition is important because it outlines the specific zone where the contact must occur for it to be considered a block in the back.

This type of foul is penalized because it can lead to dangerous situations, where a player is susceptible to injury from unexpected contact while in a vulnerable position. The rule aims to promote player safety and fairness on the field. The emphasis on the area of contact—between the shoulders and above the waist—also helps officials determine if the block was legal or if it falls under the category of illegal blocking.

The other choices do not define a block in the back accurately. Initial contact on the shoulder does not indicate a violation, a block occurring in the end zone does not necessarily constitute a block in the back, and a block made on a runner can be legal unless it meets the specific criteria for being a block in the back. This understanding helps players, coaches, and officials recognize and enforce the rules effectively.