WASHINGTON — Back in August 2011, the NFL and the players' union signed off on a new labor deal that set the stage for the league to test for human growth hormone, perhaps as soon as a month later.

Nearly two full seasons now have gone by and nothing's happened.

The NFL Players Association won't concede the validity of a test that's used by Olympic sports and Major League Baseball, and the sides haven't been able to agree on a scientist to help resolve that impasse.

Cue Congress. The House Oversight and Government Reform Committee is holding a hearing Wednesday to take a look at the science behind tests for HGH.

It's a substance that is hard to detect and believed to be used by athletes for a variety of benefits, whether real or only perceived — such as increasing speed or improving vision.

"The players are claiming that the testing is questionable. What's bothering me about all of this is that the players made an agreement in 2011 ... that they would begin the human growth hormone testing, and it seems to me that they have thrown roadblocks and found excuses not to do it. And that concerns me. An agreement is an agreement," said Rep. Elijah Cummings of Maryland, the ranking committee Democrat, who noted that he expects there will be additional hearings.

"We also want to make sure that the players are treated fairly," Cummings said in a telephone interview. "We want to hear the science, so we can make some valid judgments as to the players' allegations that this may not be valid."

A memo sent by committee staff members last week to lawmakers says: "Every week of football played without a test for HGH endangers the game and sends a message to young athletes that HGH is tolerated at the game's highest level."

The memo closes by saying: "This hearing will examine the science behind current HGH testing and highlight the fact that this testing is available to use in the NFL."

In a statement issued Tuesday previewing the hearing, committee chairman Darrell Issa, a California Republican, sent something of a warning to the NFL and players.

"There has been a frustrating lack of progress on testing. The possibility that federal legislation could eventually be adopted to address this problem may be unlikely at this point, but the league and its players would be unwise to ignore it," Issa said.

The committee did not ask anyone from the league or union to testify Wednesday. Scheduled witnesses include Pro Football Hall of Fame member Dick Butkus, U.S. Anti-Doping Agency Chief Science Officer Larry Bowers, and National Institutes of Health Deputy Director Lawrence Tabak.

In written testimony submitted to the committee, Bowers says "there is a broad consensus among scientific experts who regularly work in the growth hormone field" that the test is reliable and valid, and that "the chances of an athlete who has not used synthetic growth hormone testing positive are comparable to the chance of that same athlete being struck by lightning during his or her lifetime."

Bowers writes that World Anti-Doping Agency records show that as of late August, 12 positive results showed up from 12,764 HGH tests around the world.

"I would like to point out that the only people who are still questioning the methodology and validity of the ... test are lawyers, not scientists," his testimony reads.

Tabak's written testimony says many studies vouch for the reliability of HGH testing, even though the naturally occurring hormone and the artificial form are "virtually indistinguishable." He adds: "Questions can always be raised about whether a given test, even one whose reliability has been established under most circumstances, also has universal validity. ... In science, universal validity is almost never achievable. ..."

He also discusses the "serious risks" athletes who give themselves HGH are taking, and estimates some use doses 10 times higher than those prescribed for medical purposes.

Even once scientific issues are resolved, there will be other matters the league and union need to figure out, including who administers the test and what the appeals process will be. The latter could be of particular import in the aftermath of the decision in the New Orleans Saints' bounty case Tuesday, when NFL Commissioner Roger Goodell's suspensions of four players were tossed aside by former Commissioner Paul Tagliabue.

The collective bargaining agreement that ended the NFL lockout 16 months ago included a provision for HGH testing — but only once the NFLPA approved the process.

"The players agreed to HGH testing in the CBA because they believe in a clean game. They did not, however, agree to an artificial timeline to impose a testing protocol that has no transparency in the underlying science nor a fair due process that is outlined," union spokesman George Atallah said.

NFL senior vice president Adolpho Birch, who oversees the league's drug program, said the sport has been "trying to do whatever needed to be done to advance the ball" on HGH testing.

"I am hopeful because, among other things, the hearing presumably will put to rest the questions of whether the test is safe, practical, reliable and appropriate for NFL players," Birch said. "If that occurs, it may present an opportunity for the parties to resume serious discussions on how to implement it, rather than being sort of lost in the trenches discussing the questions about its reliability."