The professional sports locker room is a sanctuary, a place that is supposed to be free of outside distractions. At halftime of an N.B.A. game, for instance, players sit attentively, absorbing the coach’s instructions. They rehydrate, and maybe even change into a fresh uniform. Their focus for those 15 minutes rests entirely on what must be done in the second half to win the game.

Except when they’re flicking through their smartphone notifications on the sly.

The habit of monitoring mobile devices officially now has no bounds, not even at the locker room door. In a league populated by athletes who have grown up with a ball in one hand and a mobile device in the other, players are increasingly returning to the court only after taking a few quick swipes through some messages.

“I don’t think you should necessarily be coming in at halftime and start going through your mentions, but it’s just become habitual,” said Spencer Hawes of the Charlotte Hornets, who are playing the Miami Heat in the first round of the N.B.A. postseason. “What do you do when you’ve been away from your phone in any situation? You come in, check it, check if anyone texted you. I think halftime is kind of no different.”

The ritual has challenged the popularly held perception of the professional sports locker room as a scene of intense focus on the task ahead. It may not affect performance on the court, but it nonetheless signals a significant cultural shift for the veteran players who remember older times and a place, the locker room, that was free of digital distractions.