(Reuters) - In the first week of the 2011 NFL season, football fans were asked to get used to the league's controversial new rule on kickoffs, introduced to reduce player injuries.

In Week Two, which begins on Saturday, many surprised fans will get their first introduction to another potentially controversial rule imposed by the league with safety in mind: the enhanced pat-down.

The National Football League confirmed to Reuters on Thursday that it had asked the league's 32 teams to dramatically increase the physical screening spectators are required to undergo before they enter the stadium.

Some of the stepped-up security measures that stadiums rolled out on Sunday on the 10th anniversary of the September 11, and which fans may have assumed were temporary, are here to stay.

The NFL has told the teams it wants them to search all spectators at their games from the ankles up before allowing them to reach their seats.

That's a change in the NFL's long-standing pat-down policy, first introduced in 2005, which only required that fans be searched from the waist up.

By increasing the amount of touching spectators have to undergo before they're allowed to go to their seats, the new rule on pat-downs will increase the time that millions of fans spend in line during the season and could trigger a backlash.

Those fans are already digesting a rule to move the kickoff line up five yards, which reduced the number of returners who ran the ball out of the end zone in Week One and made the game a little less exciting for some.

Brian McCarthy, a spokesman for the NFL, acknowledged the new pat-down policy would require some getting used to. But he said the change would "further increase the safety of fans."

"We encourage fans to come early," McCarthy said, "enjoy their tailgating tradition and be patient as they enter the stadium.

(Reporting by James B. Kelleher in Chicago; Editing by Cynthia Johnston)