The study done in collaboration with Little League Baseball and Softball, and USA Baseball, concluded there was no clear evidence that throwing breaking pitches at an early age was an injury risk factor.
Little League president Stephen Keener said the findings don't support a ban on breaking balls for young pitchers. The study stressed the importance of pitch counts and educating players about potential risks in throwing in multiple leagues.
Little League called the research the first substantive work in the area. Researchers also said it was important for doctors, trainers and coaches to stress proper stretching, warm-up and postgame cool-down routines.
A ban on breaking balls "would not be simple to put into practice," Keener said in a statement. "With such a wide range of aptitude and ability, it's practically impossible to judge if any youth pitcher intended to throw a curveball or if that's just how the ball came out of the pitcher's hand."
Little League does have a pitch-count system intended to reduce wear on the arms of youth pitchers.
Funding for the five-year study that began in 2006 was provided through a grant from the Yawkey Foundation, named after the family that formerly owned the Boston Red Sox. Findings were released two weeks before the start of the Little League World Series, which begins Aug. 18 in South Williamsport.