Starting next spring, Maine will restrict pitch counts rather than innings pitched in high school baseball.

The National Federation of State High School Associations, which establishes playing rules for high school athletics across the country, announced the change Tuesday.

Driving the change is a concern for safety, partly because of the rise in ligament-replacement elbow surgeries (known as Tommy John) among adolescents.

“We’ve had an inning rule for a number of years,” said Mike Burnham, an assistant executive director of the Maine Principals’ Association, “but during any given inning the number of pitches can fluctuate so much that this is just a better way of protecting those young arms.”

The MPA will be required to come up with a policy detailing the number of pitches that a player can throw in a game. Under the NFHS guidelines, each state will be allowed to come up with its own policy.

“We’re giving states lots of latitude on how they’re going to do this,” said Dr. William Heinz, a Portland-based orthopedist who is the chair of the NFHS medical advisory board and serves on the MPA’s sports medicine committee.

“What we’re trying to do is generate awareness, that you’ve got to pay attention to these arms and not let them throw forever.”

Participation numbers for high school baseball in Maine have held steady over the past five years, with a low of 3,309 in 2015 and a high of 3,366 in 2014. A 2015 study by the American Academy of Orthopaedic Surgeons showed that more than half (57 percent) of the 790 Tommy John surgeries performed between 2007 and 2011 involved high school pitchers aged 15 to 19, with an average annual increase among that age group of 9 percent.

In order to comply with the new policy, Burnham said Phil St. Onge, the Nokomis High assistant principal who is chair of the MPA baseball committee, will attend the next MPA sports medicine committee meeting in August before convening the MPA’s baseball committee in October.

“We want to make sure that both of those committees are on the same page,” Burnham said. “The baseball committee typically wouldn’t meet until after the new year, but knowing this is coming and needs to go before the full membership for a vote, they’re meeting (on Oct. 18).”

Burnham cited USA Baseball’s Pitch Smart program, which recommends pitch limits according to the age of the pitcher as well as prescribed rest between appearances. For example, a 15- or 16-year-old should max out at 95 pitches in a game and rest four days if throwing more than 75 pitches, three if between 61 and 75, two if between 46 and 60 and one if between 31 and 45. No rest is required for pitchers throwing up to 30 pitches in a game. For those aged 17-18, the recommended rest requirements are the same, but the maximum per game rises to 105.

Vermont, which has been using pitch count limits for a decade, doesn’t do it by age. Instead, a varsity pitcher is limited to 120 pitches, a junior varsity pitcher to 110 and a middle school pitcher to 85.

“Everybody’s different,” said Ray Petit, who recently resigned from Thornton Academy after six years as head baseball coach and 11 as an assistant. “I just don’t think pitch count is the way to go. You have different sizes and different strengths.”

Petit pointed to his pitching staff this spring, which included a freshman, a sophomore and a senior who plans to continue pitching in college.

“(Senior) Ben Lambert can go 100 pitches,” Petit said. “(Freshman) Luke Chessie can’t. He can maybe go 75-80. Everybody’s strength and size should go into it but I don’t know how you would do that.”

Josh Stowell, who recently completed his second year as head coach for Deering High, said he thinks pitch counts offer a better measure of fatigue than innings. Someone with poor control and plentiful walks can throw many more pitches than an efficient strike-thrower, who under current guidelines would have to take a day off even if he throws only 10 pitches in two innings.

“I think a pitch count is definitely the way to go,” he said. “It won’t be a big adjustment.”

Whether umpires, scorekeepers or some central agency keeps tabs on each pitcher has yet to be determined.

“I don’t see this as being a huge controversy,” said the MPA’s Burnham, “as long as it’s very clearly defined how we’re going to track it.”