The NFL players union, led by DeMaurice Smith, ratified the new 10-year collective bargaining agreement Thursday. In it is a measure allowing blood-testing to detect human growth hormone. (Louis Lanzano/AP)

The NFL will become the first U.S. professional sports league to blood-test its athletes for human growth hormone with their union’s consent after players agreed to the measure Thursday as they ratified a new labor pact with owners.

Despite last-minute reservations about the testing program, players approved the new 10-year collective bargaining agreement late Thursday afternoon, officially giving the sport a decade of labor peace after a nearly 41 / 2-month lockout.

The ratification also allowed hundreds of recently signed free agents to take the field for the first time at NFL camps across the country.

Arizona Cardinals place kicker Jay Feely called it a “good day,” writing on Twitter that the 10-year agreement “will mean we don’t have to talk about this anymore.”

League officials hope to begin blood-testing players for HGH in the first week of the regular season, which opens Sept. 8. Several people familiar with the negotiations confirmed the HGH testing provision, but said the league and union must continue discussions in coming weeks to develop procedures. Both sides declined to comment publicly.

The agreement for HGH blood-testing nearly fell apart when player representatives from the 32 teams expressed concerns during a conference call Wednesday night. They focused on the reliability of the blood tests and the players’ input into the way the program was being put in place.

But the objections gradually dissipated during Thursday’s deliberations and players approved the testing as they ratified the labor agreement around 4:30 p.m.

NFL players will join other athletes around the world — including those in Olympic sports under the auspices of the World Anti-Doping Agency — in submitting to blood tests for HGH. Gary Wadler, immediate past chairman of WADA’s prohibited list and methods subcommittee, said the NFL was overdue to enact such testing and other U.S. pro sports leagues should follow suit.

“It’s a big step forward, long overdue,” Wadler said. “I just hope it’s done consistent with the international standards for properly conducted testing.”

Major League Baseball last summer implemented random HGH blood-testing of minor league players, who are not represented by a union. Major league players, who are unionized, are not tested. “The blood test has been validated and is sound scientifically,” Wadler added. “The time has come.”

But another drug-testing expert, Charles Yesalis, said players’ reservations might be well-founded.

“There are people who still question how reliable that test is,” said Yesalis, a professor emeritus of health police and administration at Penn State University. “If I were a unionized player, I wouldn’t want to have my livelihood depend on it, from what I know.”

HGH already was on the NFL’s list of banned performance-enhancing substances but players have not been tested for it. Gene Upshaw, the union’s late executive director, was a strong proponent of the sport’s steroid-testing program, saying often that he wanted to get cheaters off the field so players who competed legally were not at a competitive disadvantage.

But Upshaw, who died in 2008, drew the line at having players blood-tested. He cited privacy issues, saying HGH testing would come to the NFL only when a reliable urine test was developed.

Under its new leadership, the union expressed a willingness to listen to the NFL’s blood-testing proposal during this round of negotiations. The NFL pointed to advances in blood-testing.

Under the NFL’s policy on performance-enhancing drugs, a player is suspended for four games without pay for a first positive test for a banned substance. A second positive test results in an eight-game suspension without pay, and a third offense brings a suspension of at least a year.

“We’ve all had blood taken,” Wadler said. “The amount of blood taken is so small that it doesn’t affect performance. . . . The Players Association should be worrying about a level playing field and the health of its work force.”

The labor deal also allows for a possible change in the appeal process for players disciplined by the league under the drug policy. Deliberations on that subject will continue, but the league has offered to allow appeals to an independent arbitrator. Currently, appeals are made to Commissioner Roger Goodell or a person designated by him.

The labor agreement makes no change in appeals of discipline imposed for personal conduct. Those appeals still will be made to Goodell or his designee. The players made gains in disability provisions, one person familiar with the talks said.

The league office was notified at 4:54 p.m. of the players’ final ratification of the labor deal. The deadline for that approval was Thursday. The NFL announced plans soon after to shut down its labor Web site. Teams must be in compliance with the salary cap by Friday.

Goodell and DeMaurice Smith, the union’s executive director, are scheduled to sign the labor deal Friday on the steps of the Pro Football Hall of Fame in Canton, Ohio, according to an NFL spokesman.