As the NFL moves into the playoffs, the league is searching for a safer helmet and considering offseason rule changes to provide more protection from concussions.

Congress is still on the NFL's case, too, and will examine head injuries in football again Monday, a day after the regular season ended and Miami Dolphins quarterback Pat White was carted off the field because of a helmet-to-helmet collision in a game.

One researcher who recently conducted crash-dummy tests on five manufacturers' helmets for the NFL worries about what good will come of efforts to measure how much safer players are than they were a decade ago and understand where improvements could be made.

"There's some really frightening potential for how this data is used," David Halstead of the Southern Impact Research Center said in a telephone interview. "In other words — and the NFL, I'm sure, wouldn't like me saying this — my concern is that somebody makes a direct comparison and says, 'This helmet performed 40 percent better, so you're 40 percent less likely to be injured.' That's absolutely incorrect."

Halstead is particularly concerned the study will be construed by high schools or youth leagues as recommending a particular helmet, even if the NFL insists that's not its intention.

Instead, NFL officials say the goal is to do basic scientific research that will give players and equipment managers more information about helmets and will help manufacturers know where they could improve equipment.

"The majority of players are still wearing helmets designed in the '90s," NFL spokesman Greg Aiello wrote in an e-mail to The Associated Press. "That's a key reason we wanted to initiate more research on helmets."

The NFL and Riddell have had a licensing/sponsorship arrangement since 1990, and teams have been eligible for price breaks from the company, although that discount provision will be eliminated next year under a deal set to expire after the 2013 season. Each player can choose what helmet he wears; most go with Riddell, whose Web site notes it's the "Official Helmet of the NFL."

Another possible result of testing: The league could use the data to "see if there are potential rules changes that should be made," said Jeff Pash, NFL executive VP and chief counsel. "This study can be used by our competition committee and others to find, for example, that there are certain impacts that are particularly difficult to attenuate the forces. Maybe that can go into consideration of how you set up the rules of the game and how you enforce those rules."

The first round of the NFL's helmet testing, done from October to December at Halstead's lab and a lab in Canada, looked at how two helmet models made 10 years ago and present-day models responded to blows at various angles and speeds, up to about 22 mph.

Specific data won't be released before March, but Halstead did offer this summary: "Some of the new helmets, not surprisingly, tested significantly better in certain locations than the 10-year-old helmets. Some of the new helmets didn't perform any better than a 10-year-old helmet, which is a little surprising."

The league also is paying attention to tests being done on mouth guards to see whether they could play a role in helping prevent concussions. The NFL's Aiello said the league has not ruled out making use of mouth guards mandatory.

Halstead is scheduled to testify at a congressional hearing at Detroit's Wayne State University School of Medicine on Monday, the House Judiciary Committee's second recent look at football head injuries.

Other witnesses slated to appear include former NFL players Kyle Turley and Ted Johnson, as well as Ira Casson, a doctor who resigned as co-chairman of the NFL's concussion committee amid accusations of bias. The House panel had hoped Casson would testify at its Oct. 28 hearing; he did not attend and later said he was not formally invited.

"That was the voice that was missing, the dog that didn't bark," NFL Players Association medical director Thom Mayer said.At that session, NFL commissioner Roger Goodell was grilled by some lawmakers about his league's concussion policies and connections between head injuries and brain disease. Since then the league has instituted stricter return-to-play guidelines for players showing concussion symptoms, and required each team to enlist an independent neurologist as an adviser. Goodell will not appear Monday.

"There's been good progress," Mayer said. "Our intention is to keep the pedal to the metal and make sure we continue to move forward."

Mayer said the NFL is close to agreeing that reports team doctors and trainers deliver to the league about individual players' concussions will be simultaneously given to the NFLPA.

"After all," Mayer said, "they're our players."

Casson's resignation was announced in November, and the league aims to select a replacement before the Super Bowl. There are five finalists, according to Mayer, who said he will help the NFL's medical adviser recommend a new leader of the concussion committee.

Lawmakers also plan to ask an NCAA representative about Texas Tech coach Mike Leach, who was fired after allegations surfaced that he mistreated a player diagnosed with a concussion.

"If true, this suggests there needs to be a culture change, where coaches and players understand and abide by concussion diagnoses and recommendations," committee chairman John Conyers, D-Mich., planned to say in his opening remarks.

In Turley's written testimony, obtained in advance by the AP, he speaks candidly about having multiple concussions, saying his "faculties continue (to) degenerate and my life continues to change."

Turley, who played for the Saints, Rams and Chiefs from 1998-2007, also writes that "the egregious negligence of NFL team medical staff is fairly universal, that its effects are perpetuated and magnified by the NFL disability committees, comprised of the owners and the players union representatives, which continually deny retired players' disability claims wrongfully, and that active players continue to be put into the game after suffering concussions."