NFL players ratified a new, 10-year collective bargaining agreement Thursday, hours after it was finalized, and two people familiar with the negotiations told The Associated Press the contract allows the NFL to become the first major U.S. professional sports league to use blood testing for human growth hormone.

They spoke on condition of anonymity because no formal announcement had been made about the details of the CBA.

Players eventually would be subject to random testing for HGH, in addition to annual checks — as is the case for all banned substances in the league's drug-testing program — only after the union is confident in the way the testing and appeals process will work.

"We have to see if we agree with the test," Jacksonville Jaguars cornerback Rashean Mathis said. "If we agree with the test, then it's legit. If not, they have to come up with another one."

Most of the deal to end the NFL's 4½-month lockout was agreed to last month, but certain elements still needed to be ironed out after the NFL Players Association re-established itself as a union. The union — which dissolved itself in March, when the old CBA expired, allowing players to sue the league in federal court — was again formed by last weekend. Final CBA language was in place Thursday afternoon in talks between the sides' lawyers in Washington.

Before 5 p.m. ET, players voted to approve the final agreement. That allowed players who signed contracts July 26 or after — and had been forced to sit out practices by NFL rules — to finally join teammates in drills Thursday, as the new "league year" officially began.

Among the other CBA elements that were settled this week: parameters for penalties associated with on-field discipline and new disability program guidelines. Under a new neuro-cognitive disability benefit, for example, players do not have to prove that their mental disability was related to playing football.

For on-field offences — which grabbed headlines last season when the league made a point of enforcing existing rules about illegal hits more strictly — the NFLPA must be consulted before a player is suspended or fined more than $50,000. And players now will be able to argue on appeal that a fine is excessive if it exceeds 25 per cent of one week's pay for a first offence or 50 per cent of a week's pay for a second offence.

The off-field conduct policy remains largely unchanged and in the hands of NFL Commissioner Roger Goodell.

The most significant new item in Thursday's agreement, though, is the HGH testing, which was the last topic holding things up.

Goodell has been keen to have players tested for HGH, saying in an interview with the AP in August 2010: "It's about the integrity of the game."

"We think it's important to have HGH testing, to make sure we ensure that we can take performance-enhancing substances out of the game," Goodell said then.

Preventing athletes from using HGH is considered a key target in the anti-doping movement. The substance is hard to detect, and athletes are believed to choose HGH for a variety of benefits, whether they be real or only perceived — including increasing speed and improving vision.

Last year, Major League Baseball implemented random blood testing for HGH in the minors, making it the first U.S. professional sports league to take that aggressive step against doping. Baseball was able to impose that on players with minor-league contracts because they are not members of the players' association, which means blood testing is not subject to collective bargaining.