LOS ANGELES — A group of Colorado Rockies players visited Treyarch Studios, the Santa Monica headquarters of the global video game developer, on Tuesday. Call of Duty: Black Ops 4 won’t be released until October, but the players hunkered down in a dark, glossy room encircled with screens and dove into the new game.There was a baseball game that night too, and first pitch at Dodger Stadium was still several hours away. Playing video games wasn’t a part of everyone’s game-day routine, but iPads were waiting in the dugouts, a standard tool for major league teams in 2018. Televisions hung in the players’ cafeterias. Smartphones were ubiquitous. Just by going about his day, the average baseball player took in more screens than your company’s HR department.A new book claims this is a serious problem.The author is Tommy John, a chiropractor based in San Diego. He is less famous than the elbow ligament replacement surgery that also bears his father’s name. In “Minimize Injury, Maximize Performance,” John attempts to reverse a recent explosion in surgeries through a set of guidelines for youth athletes designed to, well, minimize their injuries and maximize their performance. The guidelines are not catchy. They aren’t specific to any one sport. The book probably won’t make Tommy John the author more famous than Tommy John the pitcher or Tommy John the surgery.“Nobody can sell the stuff that it takes,” the author said in a recent telephone interview. “It’s a bunch of mundane acts over and over. It’s constantly doing the small things over and over. But you can’t sell that. It’s not easy. It’s not one thing.”The “Tommy John solution,” as he calls it, offers a lot of nuggets culled from hard research and John’s own anecdotal evidence working with youth, college and pro athletes. John himself had a brief pro career as a pitcher before transitioning to chiropractics. He said his father never gave him a pitching lesson until he asked for one as a 12-year-old.“It was just ‘here, throw the ball here.’ Back up, ‘throw the ball here.’ It was so basic,” John said. “I wanted more.”The idea of not specializing in one sport year-round, and not focusing on any one sport-specific activity before puberty, is not new. Youth injuries are rising nonetheless. John cited a 2013 interview with Dr. James Andrews in which America’s most famous orthopedic surgeon estimated 40 percent of his patients were youth, up from 15 percent in the span of a decade. Newsroom GuidelinesNews TipsContact UsReport an Error Andrews is on MLB’s “Pitch Smart” committee, formed by the league to combat the youth injury epidemic. If the program is successful, MLB hopes, the bodies of future major leaguers will not be on the verge of collapse by the time they reach their 20s. Many of its guidelines overlap with the Tommy John Solution.So far, prolonged screen exposure is not an area of overlap.“We have looked at this issue with interest and further research is needed before definitive recommendations,” the league said in a statement.In “Minimize Injury, Maximize Performance,” John does not tread so lightly. He treats screen exposure like a Trojan horse, a subversive attack on the human brain.“Each time people answer a text, surf social media, use the latest app, or battle online against others, their brain is being bombarded by stimuli,” he writes. “Every bright color, high-definition pixel, pop-up ad, or unexpected sound is a trigger their brain has to react to, yet they can only process so much.”John says these stimuli throw our sympathetic nervous system – the body’s so-called “fight or flight” response – into overdrive, and being in a constant state of overdrive ultimately weakens the body’s immune system.The average healthy adult might not notice the consequences the same as someone who participates in a punishing physical activity – for example, throwing a baseball. John focuses on youth athletes, but he believes the consequences are the same for major leaguers.“I’ve worked with the highest level of professionals. The same rules apply,” John said. “You are at a detriment when you expose yourself to something like a screen. Your sympathetics are going to ramp up. We can’t use age groups. The 20-year-old today is not the 20-year-old of 20 years ago.”Keith Dugger, the Rockies’ head athletic trainer, said he’s tried educating players about the consequences of screen exposure. His staff might have control over players’ physical movements for several hours a day, for eight months a year. He can monitor things like stretching routines and weightlifting programs. But playing video games or using a smartphone?“We want them to limit the amount of time they’re in front of their gaming devices when they get home after a game,” he said. “We want a cutoff period. We’re not putting a curfew on them but we’re saying, ‘be responsible. Don’t stay up all night.’”Does he think they’re listening?“I think they listen a little bit, especially if there’s science that’s out there, documentation showing there’s an ill effect toward them or their gameplay. In reality, they’ll do anything if it’s not affecting their gameplay.”Rockies pitcher Bryan Shaw was among the group that visited Treyarch Studios on Tuesday. He already has the release date for Call of Duty: Black Ops 4 circled on his calendar.“October 20,” he said. “I’m ready. I’m excited. I think all of us that went are.”Shaw described the role of video games in his life in anything but dire terms. When the Rockies are on the road, he said, it’s a regular part of his pre- and postgame routine.“Usually we get back to the hotel, relax, play some games until you fall asleep,” he said. “I played some today. You wake up at 10 o’clock, whatever it is, go eat breakfast and sit in your room until you come to the field at 2, so yeah I jumped on today.”Shaw doesn’t think gaming impedes his sleep schedule, though traveling from coast to coast over the course of 162 games might. An eight-year veteran, Shaw is 30 years old and says he’s been playing video games all his life. He’s averaged 63 games and 59 innings a season and has never been placed on the disabled list.If convincing major leaguers to limit their screen exposure is any indication, John will face an uphill battle with teenagers.“That’s a fallacy,” Dodgers pitcher Walker Buehler said. “I don’t like it. I don’t believe it.”“I think I would almost argue the opposite, that we already do it so much that it can’t really (harm) us, or maybe it almost warms us up,” Dodgers pitcher Ross Stripling said. “But there’s a chance. I’ve got to think it depends on what you’re doing – playing a violent video game or watching a thriller probably burns you more than if you’re sitting there reading a Kindle.”Screen exposure might not be on the front lines of MLB’s injury-prevention battle yet. But if it ever gets there, medical staffs could be in for a battle.