SOUTH WILLIAMSPORT, Pa. – For the two biggest outs of his team’s Little League World Series run, Louisiana manager Scott Frazier called for his 12-year-old pitcher’s new curveball.

Conner Perrot learned how to throw it – middle finger on the horseshoe seam of the baseball, thumb directly beneath it, release the pitch the way you’d spiral a football – six months before this Aug. 17 game and spent four more months tinkering with it until it was ready for action.

Now, from the same slot where Perrot throws his fastball, the curveball came looping out instead, starting down the middle of the strike zone even with a hitter’s belt before exiting stage left at his ankles.

Breaking pitches have dominated here at the Little League World Series, where once the very thought of a child throwing a curveball or slider was met with disapproval.

Wailuku, Hawaii’s Isaac Imamura pitches at the top of the sixth inning of a baseball game against Elizabeth, New Jersey at the Little League World Series tournament. Associated Press/Gene J. Puskar

Hawaii relief pitcher Isaac Imamura used it to shut down New Jersey hitters who had prepared to fend off scorching fastballs. Canada’s Timmy Piasentin at times used breaking balls for the majority of at-bats against Curaçao. In the same game, Curaçao’s Keven Rosina buried his curveball in the dirt as a swing-and-miss pitch for strike three. Perrot threw his curve to close down Oregon rallies with a strikeout to end one inning and a double play groundball to end the next.

“The curveball is the atomic bomb,” said Tommy John, a chiropractor, former minor league pitcher and the son of a former major league pitcher by the same name. “Nobody can touch it and the coach loves it because they win.”

For generations, curveballs were considered too dangerous for young pitchers. The force on the shoulder and elbow involved with throwing such a pitch was thought to be too much for a child’s developing arm. Throwing too many curveballs or throwing curveballs improperly could lead to ligament damage, coaches and doctors claimed, specifically tears to the ulnar collateral ligament, the tissue in the elbow that connects the upper arm to the inside part of the lower arm.

Tears to that ligament are often called “Tommy John” injuries, named for the former MLB pitcher who in 1974 was the first to undergo reconstructive surgery for a UCL tear and return to a productive career.

Curveballs, especially the wrist-flicking motion required to spin them effectively, were thought to exacerbate the force on the UCL, which acts like a slingshot in a throwing motion, said Glenn Fleisig, research director at the American Sports Medicine Institute in Birmingham, Ala.

That’s why at the start of the spring Perrot ditched his conventional curveball, one he’d thrown for years, for what he calls his “football pitch.” The seemingly more natural release, letting the ball roll off the fingers instead of flicking the wrist, makes the ball behave the same way as his old curve.

“I was always taught to snap the wrist for a curveball, but [my coach] said that puts a lot of stress on your elbow,” Perrot said before his team defeated Minnesota on Aug. 19. “Ever since I started throwing [a curveball], it was just snap the wrist, snap the wrist and get rotation on the ball, and then he just taught me a different philosophy where you throw it like a football.”

And at this Little League World Series, which concludes Sunday, debate persists over whether breaking pitches are safe for young pitchers. Years of worry fueled by anecdotal evidence have dissuaded some coaches and parents from teaching the pitch, or at least certain versions of it, to developing players.

But researchers who study the biomechanics of pitching have shown the pitch that coaches and medical professionals have fretted over for years is no more dangerous to throw than a fastball.

Fleisig and other researchers at ASMI followed 500 baseball players ages 9 to 14 in the spring of 1999 and hypothesized that the rotational force, or torque, necessary to throw a curveball was harmful to young pitchers.

The study, published in 2002 in the American Journal of Sports Medicine, did find a relationship between arm pain and breaking pitches. Curveballs were associated with a 52% increased risk of shoulder pain. And sliders, another type of breaking pitch that sweeps across the strike zone at high velocity, showed an 86% increase in elbow pain.

But it also found a stronger relationship between the number of pitches thrown in a game and elbow and shoulder pain.

“Although muscle soreness is normal and necessary in the development of a pitcher, joint pain is not,” the researchers, Fleisig, Stephen Lyman, E. David Osinski and renowned orthopedic surgeon James Andrews, wrote.

They resolved that the topic needed more examination, so ASMI researchers conducted a biomechanical study in 2006 that did not find any significant differences in joint stress between fastball and curveballs. The researchers also tracked the same study subjects from 1999 for 10 years and released new findings in 2011 that disproved their original hypothesis: “The study was unable to demonstrate that curveballs before age 13 years increase risk of injury,” they wrote.

Instead, they found the number of innings pitched was the greatest predictor of which pitchers would experience joint pain after outings and which pitchers would suffer elbow and shoulder injuries later in their playing careers.

So why were breaking pitches so closely related to joint pain that was actually caused by overuse?

“The kid who has the good curveball is more likely to be overused,” said Eric Cressey, a strength and condition specialist who consults with MLB pitchers. “He’s more likely to be left in the game because the coach wants to win.”

And in an age of sport specialization, when kids play the same sport – and use the same ligaments and groups of muscles – in all seasons, young pitchers’ arms often don’t get the rest they need after a strenuous season.

“We set out to prove curveballs are dangerous and it didn’t really turn out, but we got slapped in the face by how strong the amount of pitching was a factor,” Fleisig said in an interview. “In this generation, we have a lot more kids getting [Tommy John] surgery, but this is not the first generation to throw the curveball.

“. . . But this generation of specialization, whether it’s baseball, soccer or gymnastics, kids are being steered to play one sport all year. That’s not with bad intentions. The kids say, ‘This is my favorite sport and I want to keep playing.’ But the underdeveloped body is incapable of accommodating the same motions year-round.”

Little League and other baseball governing bodies have instituted pitch count limits to protect young arms and established mandatory rest periods between appearances on the mound.

But that’s not enough, said Frazier, the Louisiana manager. Especially in his state, where playing 12 months of nonstop baseball is routine for some kids, he encourages players to take four months off and go play another sport.

Perrot, the pitcher, plays football in the fall and basketball in the winter. Every few days in the offseason, he said, he’ll throw a baseball around the yard just for fun, but nothing serious. The routine helps his arm stay fresh and in command of his pitches, like that “football” curve.

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