As NFL teams open their training camps over the next week, players are resuming the summer tradition of slamming into one another in bids to impress coaches and earn roster spots.

Fans may want to see it now, because those practice field collisions could become increasingly rare as soon as next year.

NFL practice routines are likely to be overhauled as the league and the players’ union turn their attention to reducing practice-field hitting in an effort to curb the number of concussions sustained by players.

“I don’t know exactly what the timetable will be,” said Thom Mayer, medical director of the NFL Players Association. “I’ve been consistent in telling the league if we’re serious about reducing concussions, a 20 to 25 percent reduction in concussion-prone incidents is necessary.”

While modifications appear inevitable, the specifics remain to be worked out. But Mayer said the changes are likely to reflect some experts’ belief that players face harm from repeated minor shots to the helmet as well as severe hits that result in concussions.

Changes would affect offseason and regular season practices, as well as training camp.

“When you start to have this discussion about player safety, I think all things should be on the table at the start,” said Atlanta Falcons President Rich McKay, co-chairman of the NFL’s competition committee. “You have to take the medical data, the considerations about the enhanced season and everything else, and see what works. What the final answers are, I don’t know.”

The discussions come as the league and union negotiate a possible 18-game regular season, a move that also would alter practice schedules.

The NFL has been criticized by some medical experts and Capitol Hill lawmakers in recent years for its handling of player head injuries. But NFL Commissioner Roger Goodell imposed a series of concussion-related measures last season. He banned a player who suffers a concussion or shows symptoms of one from re-entering a game or rejoining a practice. And he required that a player who suffers a concussion be cleared by an independent physician before participating in another practice or game.

In the offseason, the rule-making competition committee extended protections during games for “defenseless” players, and Goodell has said more changes are likely. Former coach and broadcaster John Madden is overseeing a coaches’ committee that is studying safety issues.

The league and union have had discussions about reducing the number of offseason practices and limiting hitting in some practices during training camp and the regular season.

On Friday, the NFL sent teams the results of a study of 16 helmets, three of which researchers concluded had performed best in laboratory tests simulating the forces of open-field collisions associated with concussions. But players are free to wear any certified helmet. The study, conducted by two independent labs, was sponsored by the league and supported by the union. “One area where we don’t have a difference is player safety,” said Jeff Pash, the NFL’s executive vice president of labor.

Vani Rao, the medical director of the brain injury clinic in the Department of Psychiatry at Johns Hopkins University, said that any reduction in the number of blows to the head absorbed by players would reduce their risk of suffering brain injuries with possible long-term health consequences. But it’s difficult to assess how much that would help, she said.

“What we know is that one concussion is bad, and more than one is really bad,” Rao said. “What’s missing is the long-term longitudinal studies about the number of concussions that a person suffers and the consequences of that.”

It is a combative time for the NFL as the league and union attempt to negotiate a new labor deal, but the two sides have continued to work cooperatively on player safety issues.

Mayer said his discussions with the league’s medical representatives about practice-field hits have been positive.

“I think they get it,” Mayer said. “There are still a lot of details to be worked out: How do you enforce it? Do you film practices? From our end, we have the players to monitor it. We can ask them, ‘Are you being exposed to fewer concussion-prone incidents?’ ”

Greg Aiello, the NFL’s senior vice president of public relations, said that discussions on the issue are ongoing, but declined to comment on the specifics.

NFL teams practice virtually year-round, with a series of offseason practices followed by a break of about a month before training camp, which features one or two practices a day.

The amount of contact varies from team to team. Some believe hitting is the best way to prepare for the rigors of games. Others try to lessen wear and tear on players and their risk of injury. But for unproven players, delivering an eye-catching hit in training camp can mean the difference between making a team and being cut.

During the offseason, league rules restrict the number of practices, the time players can spend in a team’s facility and the amount of contact permitted.

Coaches have more leeway about hitting during training camp and the regular season. During the season, teams generally have their most strenuous practices on Wednesdays and Thursdays, with lighter practices on Mondays and Fridays and no-contact walkthroughs on Saturdays. Players are given Tuesday off in the standard NFL work week, and may not practice on some Mondays.

Leaguewide, 408 players were on the season-ending injured reserve list last season, according to the union.

Former NFL coach Dan Reeves said there already is much less practice-field contact than there was when he played from 1965 to 1972.

“You only go out in pads about every other time,” Reeves said. “Back when I first came in the league, you were always in pads.”

Reeves said his experience as a coach was that nearly all concussions were suffered during games, not practices.

“Because of the limited number (of players) on the roster, you’re scared to death to hit in practice because you might get someone hurt,” he said.

But Mayer cited research that an accumulation of sub-concussive hits can put players at risk. He suggested that there “could be pretty strong pushback” from some coaches, but said the union believes practice restrictions won’t affect competition because each team will operate under the same rules.

Players tell the union that one problem with supposedly lighter practices is that on days when they wear helmets but aren’t in full pads, there is often more helmet-to-helmet hitting because players don’t have the protection of shoulder pads, Mayer said.

A possible remedy is that players might be barred from wearing helmets during light-hitting practices.

Mayer said the union isn’t necessarily seeking to reduce the amount of time that players spend at practice during training camp and the season.

“To me, it’s not the amount of time spent on the field,” Mayer said. “It’s the number of times they’re exposed to concussion-prone incidents. ... Whether it’s in training camp, whether it’s in the season, that’s not as important as getting the overall number (of hits to the head) down.”

Team owners appear to strongly favor a switch to an 18-game regular season, up from the current 16, and shortening the preseason from four games to two. Players and the union have said that the new arrangement would be more taxing on starting players.

A longer season and shorter preseason also could affect the way training camp is scheduled.

“When you talk about training camp, you have to deal with three things: You have to get ready for the season. You have to develop younger players. And you have to evaluate players,” McKay said. “You have to look at a schedule that allows you to do all those things.”

Nevertheless, Mayer said he’s confident there will be substantial changes to NFL practices in the next year or so.

“It’s the right thing to do for the players,” he said, “and therefore it’s the right thing to do for the league.”