INDIANAPOLIS (AP) - The NCAA banned the horse-collar tackle from college football.

Following the lead of the NFL and acting on a proposal made by its Football Rules Committee, the NCAA will assess a penalty this season when a runner is yanked to the ground from the inside collar of his shoulder pads or jersey.

Other changes announced Wednesday include a clarification of rules on chop blocks, or tackling below the knees, and implementation of a 40-second play clock that will start as soon as the ball is ruled dead. Previously, a 25-second clock began only on the referee's signal.

The NCAA also will emphasize consistency in officiating, including blending crews from different conferences.

Rogers Redding, NCAA football secretary-rules editor and coordinator of football officials for the Southeastern Conference, said the horse-collar ban may result in fewer back injuries.

"What we're hearing from trainers and physicians is we're getting some back injuries when the ball carrier is immediately snapped to the ground by being jerked quickly," he said. "If the ball carrier is grabbed by the shoulder or jersey and just ridden to the ground over a couple of yards, that's not going to be a foul."

The chop block will now be defined as any high-low combination block by any two players against an opponent other than the runner, anywhere on the field, anytime in the game and with or without a delay between the hits, Redding said.

Football officials support the change, said Dave Parry, head of College Football Officiating and coordinator of officiating for the Big Ten.

"We'll err on the side of safety. We'll defend the official who may be a little more strict, because that's a major point of emphasis," Parry said.

A video on avoiding helmet-to-helmet contact has been developed by the NCAA Committee on Competitive Safeguards and Medical Aspects of Sports.

"This is a short DVD that focuses on proper injury-prevention tackling techniques," said Ron Courson, a member of the committee and director of sports medicine at the University of Georgia. "It's been distributed to every college in the nation, and we encourage every football program to show this to the student-athletes."

The NCAA also modified the procedure for restarting the game clock after a runner has gone out of bounds. Except during the final two minutes of each half, the game clock will be restarted on the referee's signal, rather than when the ball is snapped.

AP-ES-08-20-08 1557EDT