The NFL has good reason for the implementation of its oft-discussed helmet rule this season.

Information compiled by engineers and doctors in the medical community has concluded that a collision when the head is down greatly increases injury risk.

"The data is compelling," said referee John Hussey, who held a rules clarification meeting with the media and later the Cardinals players on Friday afternoon. "We need to teach this action where they hit with their head up."

It might be an easy sell to youth football leagues, but NFL players must learn to adapt on the fly after years of playing the game a certain way.

The new rule will penalize a player 15 yards if he lowers his head to initiate and make contact with his helmet against an opponent. The foul is not reserved for contact to the head and neck area, as initiating contact to the torso, hips or lower body is also a foul. Furthermore, if a hit with the helmet is delivered in an intentional way when the player had other options, it could result in an ejection.

While linebackers and defensive backs immediately come to mind as possible culprits, anyone on the field can get penalized. Running backs must keep their head up when crashing into a defender to gain extra yards and the players in the trenches must abide by the rule. Center A.Q. Shipley spoke with the media before the conversation with the officials and was eager to get clarification.

"You (media members) all report that I got short arms, so obviously I lead with my head quite often," Shipley said. "You just don't know when it's going to be called. There's a lot of verbiage. There's a lot of words on what it is supposed to be. In the trenches, O-line/D-Line play in particular, I think it's going to be very hard to see. You've got to throw a flag every time, because defensive linemen come with their head down every play. That's the clarification we're going to try to get."

Coach Steve Wilks would not be surprised if helmet-rule penalty flags were thrown at a higher rate in the preseason as the officials work to clarify the infractions. Wilks is attempting to educate his players and teach the proper technique to avoid the penalties.

"You still want those guys to be physical, but we're not trying to take shots that aren't what we think are acceptable to this game," Wilks said. "We're going to take that out of the game and keep the game safe."

Defensive end Chandler Jones said the players can't let the threat of ejection change the way they play, but they must be aware of the rules.

"You can't go out there thinking, 'I don't want to get ejected,'" Jones said. "But it's a possibility, so you want to play smart and play the game correctly."

The officials' video presentation also reiterated the clarification of the catch rule, which Hussey explained as the NFL getting back to its roots of what a catch used to be.

There were also points of emphasis in the video, which included a renewed focus on calling pass interference penalties. While no rules changes have been made, Hussey said it's important players be penalized when they illegally impede the progress of the opponent.