Whether young pitchers should delay throwing curve balls because they pose an increased and unnecessary risk of arm injuries has long been the subject of debate.1 But despite the fact that baseball is the most widely studied youth sport in the United States, the jury is still out on the role of breaking pitches in overuse injuries. 
While some experts are "now moving away from [such] long-held and perhaps largely anecdotal belief,"1 others - both leading experts and at least one leading sports medicine group - continue to urge caution
The most recent to weigh in: the American Academy of Pediatrics, which, in a February 2012 Policy Statement,8 continues to recommend against throwing curveballs until age 14 and sliders until age 16.
Less stressful on arm?
To be sure, the studies send mixed messages.
A 2002 study2 found associations between breaking pitches and arm pain; however, it was (unexpectedly) the slider which correlated with increased risk of elbow pain and the curveball that was linked with increased risk of shoulder pain.
Three biomechanical studies, one published in 20083 and two in 2009, 4,5 found a curveball less stressful to the elbow than the fastball for high school and youth pitchers. They thus appeared to pour cold water on earlier studies, and the conventional wisdom that throwing curveballs leads to increased risk of arm injury in young pitchers.
In the wake of the studies, Glenn Fleisig, chairman of research at the American Sports Medicine Institute (ASMI) in Birmingham, Alabama and co-author of one of the 2009 studies,4 told the New York Times6 flatly that he didn't "think throwing curveballs at any age is the factor that is going to lead to an injury."
Carl Nissen, the author of the other 2009 study,5said in the sameTimes article that he could "comfortably stand up and say the curveball is not [part of the injury] problem."
Andrews not persuaded
The studies, however, were not enough to persuade Dr. James Andrews of the ASMI, and one of the most highly respected sports medicine physicians in the country, to soften his long-held stance against pitchers throwing curveballs before age 14. In the same interview with the Times,6 he warned that the new findings "may do more harm than good" because he feared parents and coaches would interpret the findings improperly as a license to teach kids to throw too many curves or begin when they were too young.
Dr. Andrews also cautioned that the study he co-authored with Fleiseg, his longtime ASMI colleague,4 had limitations because it was conducted under laboratory, not game conditions.
Continuing to believe that, when young pitchers are tired, throwing curves could still be dangerous, Dr. Andrews cited the story of a 12-year-old on whom he performed so-called "Tommy John" surgery the day of the interview when, following an outing in which he threwing 30-something curveballs in a row, the last tore the ulnar collateral ligament in his elbow in two.6
A more recent 2010 ASMI study7 attempted to study the risk of serious injury from throwing curveballs before age 13. But, while it seems 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. Fleiseg and Andrews, concluded that the true risk of serious injury from starting to throw curveballs at an early age was, despite years of study, still unknown.
Caution urged
All of which led the National Athletic Trainers' Association, in its 2011 position statement on overuse injuries,1 to urge caution, essentially siding with Dr. Andrews in the ongoing curve ball debate. Like Dr. Andrews, the NATA pointed to potential flaws in the two biomechanical studies: "It is important to note that the participants in these studies were healthy, with no history of arm injury, and in the case of the [2009] study, perhaps slightly older than the players who are generally the target of the recommendations against throwing breaking balls."
Thus the NATA recommended that parents and coaches restrict the use of breaking ptiches in order to prevent pitching-related arm injuries.
If an individual pitcher can throw breaking pitches on a limited basis and remain symptom free, the NATA said, then it may be allowed. But, if any throwing-related symptoms of overuse injury develop, the NATA says, throwing breaking pitches should be immediately terminated and medical attention sought.
Little League study: curveball not direct injury factor
Adding further fuel to the fire is a 2011 study by researchers at the University of North Carolina, commissioned by Little League Baseball, which appears to come down on the side of those who argue that throwing curveballs is not the primary cause of arm injuries in Little League pitchers, but that such injuries are principally the result of overuse: pitchers throwing before they are fully recovered from a previous injury, throwing too many innings, and too many pitches, and playing on more than one team at a time. But even that study shows that curveballs increase the injury risk, if only slightly, and throwing sliders is second only to previous injury in increasing injury risk.
Commenting on the study for USA Today, 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 much are the ones who get hurt, whether they throw a curveball or not."
Pediatricians add their two cents
The most recent group to weigh in on the subject of curveballs is the American Academy of Pediatrics. In its 2012 Policy Statement on Baseball and Softball8, the AAP acknowledges the recent studies challenging the theory that the curveball and slider are stressful to the young elbow, but, on the basis of other studies showing increased injury among those who throw curve balls and sliders at early ages, continues to recommend that introduction of the curve ball be delayed until after age 14, or when pubertal development has advanced to the stage when the athlete has started to shave, and that sliders not be thrown until age 16.
Stay tuned for more developments in this ongoing debate.
1. Valovich McLeod TC, Decoster LC, Loud KJ, Micheli LJ, Parker JT, SandreyMA, White C. National Athletic Trainers' Association Position Statement: Prevention of Pediatric Overuse Injuries. J Ath. Tr. 2011;46(2):206-220.
2. Lyman S, Fleisig GS, Andrews JR, Osinski ED. Effect of pitch type, pitch count, and pitching mechanics on risk of elbow and shoulder pain in youth baseball pitchers. Am J. Sports Med 2002;30(4):463-468.
3. Shouchen, Dun et. al., A Biomechanical Comparison of Youth Baseball Pitches: Is the Curveball Potentially Harmful? Am.J. Sports Med. 2008;36(4):686-692.
4. Fortenbaugh D, Fleiseg G, Andrews J. Baseball Pitching Biomechanics in Relation to Injury Risk and Performance. Sports Health: A Multidisciplinary Approach 2009;1:314-320.
5 Davis, J.T., et. al. The Effect of Pitching Biomechanics on the Upper Extremity in Youth and Adolescent Baseball Pitchers. Am. J. Sports Med. 2009;37(8):1484-1491.
6. Hyman, Mark, "StudiesShow That the Curveball Isn't Too Stressful for Young Arms," NewYork Times (July 26, 2009).
7. Fleisig G, Andrews J, Cutter G, Weber A, Loftice J, McMichael C, Hassel N, Lyman S. Risk of Serious Injury for Young Baseball Pitchers: A 10-Year Prospective Study. Am. J. Sports Med. 2010;20(10): 1-5.
8. American Academy of Pediatrics Council on Sports Medicine and Fitness, Baseball and Softball Policy Statement (doi 10.1542/peds 2011-3593)(www.pediatrics.org/cgi/doi/10.1542/peds2011-3593 (accessed February 26, 2012).
Posted March 16, 2011; Revised August 14, 2011; further revised and updated February 26, 2012
