Overuse is to blame for arm injuries among youth baseball players, but throwing curve balls at an early age still increases risk, according to a new report by researchers at the University of North Carolina.1
Key findings
- Pitchers with a previous history of injury are at 5 times greater risk of elbow and shoulder injuries, which the study attributed to inadequate rest, medical treatment, and recovery time after an initial arm injury;
- The average number of innings pitched per game is a risk factor for shoulder injury in youth baseball pitchers;
- Pitch count programs* cut by half the risk of shoulder injury in youth baseball pitchers age 8 to 13;
- Pitching in travel ball "elite" or "select" programs, and pitching in "showcase" events, were associated with increased risk of elbow and shoulder injury for those who also pitched in Little League Baseball and among high school pitchers;
- The number of pitching-related injuries doubled between Little League (ages 8- to 13) and high school, mostly due to the higher number of innings and pitches thrown; and
- The relationship between age, type of pitch, and injury risk is complex, but researchers found "no clear evidence" that throwing breaking pitches at an early age was as much an injury risk factor as innings pitched or previous history of shoulder or arm injuries.
Travel ball increase overuse injuries
The study was critical of travel ball.
"The creation and evolution of 'elite' or 'select' baseball teams and leagues, if coupled with little or no regulation or regard for the health of the adolescent athlete, has the potential to increase the risk of invasive treatment and/or surgery [e.g. Tommy John surgery], once reserved for adults," the study states.
- Nearly one fourth of youth pitchers threw on travel ball teams and in Little League at the same time;
- Pitching in multiple programs simultaneously increases the risk of injury;
- Nearly one out of every five Little League pitchers (19%) reported elbow and/or shoulder pain in the previous 12 months, with a strong correlation between pain and travel ball participation; and
- Twenty percent of the players throwing for travel ball teams or pitching in showcase events reported pain.
End to curveball debate?
The Little League report, as well as articles in the media since its release, appear to downplay the injury risk from curveballs, but a close look at the study reveals no categorical statement that throwing curve balls at an early age is not an injury risk factor; it says only that "baseline risk factors for injury to Little League-age pitchers did not point directly to throwing curveballs."
Indeed, the very next sentence in the report - that children who pitched a higher number of innings pitched and had a previous history of shoulder or arm injuries "all were at higher risk for suffering arm injuries" - suggests that throwing curve balls is still a risk, not just among the those factors that place youth pitchers at the highest risk. 
Likewise, a chart included with the study, shows that throwing a slider was second only to pitching after a prior shoulder injury in terms of increasing the injury risk, with throwing curve balls at an older age in practice, throwing curve balls at an older age in games, and throwing curve in general all increased injury risk to varying degrees. The finding that a slider was second only to previous shoulder injury as a risk factor is consistent with earlier biomechanical studies reporting that throwing the pitch places more strain
Perhaps this is why the Little League press release accompanying the report is not only carefully worded on the subject of curveballs but takes pains to emphasize the practical difficulties Little League would encounter in enforcing any curveball ban.
"Some within the baseball community have advocated for a ban on curveballs," Stephen D. Keener, President and Chief Executive Officer for Little League Baseball and Softball, said. "However, the study conclusions do not clearly support such a ban."
"Furthermore, a ban on breaking balls would not be simple to put into practice," Mr. Keener said in the Little League statement. "With such a 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. To task our dedicated volunteers with judging the type of pitch thrown is not only unfair, it would be impractical."
"Even if Little League were to find a practical way to ban curveballs in our program, they would remain a part of the game for children playing outside our program, as they have been for decades," Mr. Keener, a Little League graduate, said. "For coaches and parents, armed with the information in this report, the decision on when and how to teach the curveball is a matter of preference and education."
The new report appears consistent with a 2010 ASMI study2 which attempted to study the risk of serious injury from throwing curveballs before age 13. But, while that study, like the new one, seemed to show a slight increased risk associated with starting curveballs at a young age, it had far too few participants to determine such an association. Thus, the authors, including Drs. Glenn Fleiseg and James Andrews of the American Sports Medicine Institute, concluded that the true risk of serious injury from starting to throw curveballs at an early age was, despite years of study, still unknown. Nevertheless, commenting on that study, and earlier studies,3, 4, 5, 6, Dr. Fleisig told the New York Times in 2009, that he didn't "think throwing curveballs at any age is the factor that is going to lead to an injury." 7
As for the Little Study, Dr. Fleiseg noted that, "Part of the confusion is that the pitchers that throw curveballs tend to be the ones that throw a lot. So it's hard to separate those factors. But when you do separate them statistically, the pitchers who pitch too mucy are the ones who get hurt, whether they throw a curveball or not."
