Is Throwing a Curveball Dangerous to our Youth Baseball Pitchers?


Over the last few weeks, there has been some debate regarding the release of two recent studies that showed that curveballs may not be as damaging to our youth baseball pitchers as we had once thought.

I tried to let this die down a bit before discussing it, as the general press really picked up on this and started a debate with absolutely no medical background.  The New York Times discussed this recently and  I even saw a couple of sportscasters on ESPN discussing this on TV.  A lot of people have flat out disagreed with these studies, but consider the following:

  • Both studies, from two different institutions here and here from AJSM in 2008 and 2009, showed that the curveball does not increase force on the throwing arm in comparison to a fastball.  One of these studies was from the prestigious American Sports Medicine Institute who were the leaders in learned the majority of what we know about throwing mechanics.
  • Notice how they don’t say that throwing a curveball is safe or does not cause injuries.

These are simply biomechanical studies.  But lets take a step back and think about this, maybe they are right.  Maybe curveballs are safe?  Consider the argument from the perspective of the scientist, clinician, pitching coach, and the player:

  • Pitching is really just a physics equation, force = mass x acceleration, right?  Force = injury.  So if the mass of the ball and the acceleration of the arm are similar, why would we expect force to be higher?  This is purely the scientific thought process.  Taking this to the next step, the angular velocity of the arm during a curveball is slower than a fastball, hence the studies that show lower force on the body.
  • Clinically, I would say that because the forearm position is different between the curveball and fastball, that there could be consequences.  The static stabilizers (the bones, joint, and ligaments) are the same, but alter the forearm position alters the position of the forearm muscles and potentially decreases the mechanical advantage of the dynamic stabilizers (the muscles) to protect the elbow.  So the curveball will have the same force, yes, but may be less able to stabilize to protect the arm.  This may increase the incidence of injury.
  • The next thing to consider is youth mechanics.  My bet would be that if we studied this, there would many youth that are not taught the correct mechanics to throw a curveball, this would certainly increase injury risk.
  • From the player perspective, one thing is certain: A Little League pitcher that can throw an effective curveball is going to be good, they are going to then throw a lot, and they have a high chance of being abused.  It has been proven in a couple of other studies here and here that one of the highest predictors of injury in Little League pitchers is the amount of pitching that they perform, or they abuse that they endure.

I think it is definitely still a good recommendation to limit the development of a curveball in our youth baseball players, I would still say that pitchers who throw a curveball are more susceptible to injury due to the above rationale, but the curveball itself may not be as evil as once thought.

Bottom line, teach your kids how to throw an effective fastball and changeup and stick to the recommended pitch count restrictions in youth baseball.  Locating strikes and changing speeds will be just as effective in Little League baseball and a changeup has actually been show to be LESS forceful on the throwing arm.  As they mature, both physically and mechanically, learn to develop more advanced pitching.

Dr. Andrews summarized this best in the NY Times article:

“It may do more harm than good — quote me on that,” Andrews said during an interview in his Birmingham clinic. He fears that parents and coaches may interpret the findings improperly, as a license to teach kids to throw too many curves or begin when they are too young. “There are still some unknown questions.”

Photo by Wildernice

Dun S, Loftice J, Fleisig GS, Kingsley D, & Andrews JR (2008). A biomechanical comparison of youth baseball pitches: is the curveball potentially harmful? The American journal of sports medicine, 36 (4), 686-92 PMID: 18055920

6 replies
  1. ronbethjohnson
    ronbethjohnson says:

    The Dun study did show that the curveball produced significantly greater wrist flexion
    torque and forearm supination torque among
    the 3 pitches. This does indicate increased stresses to the elbow when throwing a curveball. They seemed to not mention this. Are these forces enough for injury. We don't know.

  2. Chad Ballard, PT
    Chad Ballard, PT says:

    If regular throwing (outfield) puts enough stress to tear the UCL, my money would be on poor cuff and scapular strength eventually leading to mechanical changes that put increased stress on the UCL.

  3. Mike Reinold
    Mike Reinold says:

    Thanks Greg and Trevor. Greg I will likely be at ASMI, but havent confirmed yet. Now that I think about it, this will be my 10th consecutive year!

    Scott, each throw does stress the UCL significantly, even of from an outfielder. While these are not as common as pitchers, probably due to the lack of repetition that you mention, it is not impossible. Especially if player has a history of pitching etc.

  4. sportdpt4
    sportdpt4 says:

    Hey Mike,
    Thanks for posting the articles, I am a PT/ATC in an hospital based pediatrics/adolescent sports medicine practice. I first received the NYT article and subsequently the research articles that prompted the news piece. I agree with you completely that this information is specifically a biomechanical study regarding velocity. In the ASMI research the subjects were healthy little leaguers throwing 5 pitches (15 total). The study findings should not be generalized to game situation pitches as mentioned in the research article, and it does not include little leaguers who have had pain or experience pain in the elbow/shoulder with pitching. The take away message I took, solidified the importance of pitch counts (a simple method of recommending pitch count: (1/2 pitchers age)x10, emphasizing mechanics (>50% of pitching velocity is driven from the trunk and legs, and to protect the pediatric athlete so that they may enjoy their sport without unnecessary harm. I have a quick case study question from a patient last week who underwent Tommy John surgery….He played outfield….what were the mechanical factors that lead to his 50% tear of his UCL requiring surgery?….(hint: it wasn't the curve ball) Similar to your point regarding (F=m x a) velocity,force+repetition=tissue failure/injury.
    Scott McInturff, PT, DPT, ATC

  5. Trevor Winnegge DPT
    Trevor Winnegge DPT says:

    Very interesting articles Mike. I would be interested to see how the kids threw a curveball in these studies. There are a few ways to throw a curveball, including arm slot and wrist angle. I think a 12-6 curveball thrown over the top with a rapid radial deviation to ulnar deviation snap of wrist while in flexionwould be more harmful than more of a sidearm curve with RD-UD in wrist neutral position. I just think intuitively with the wrist in flexion you are shortening the wrist flexors and ulna deviators and then asking them to provide a forceful concentric contraction in that shortened position. I feel this definitely leads to overuse injuries-little league elbow. I will have to read these studies a bit more to see what position the wrist is in during curveballs. thanks Mike!

  6. Greg Arnold, DC, CSCS
    Greg Arnold, DC, CSCS says:

    Thanks for bringing attention to this. I reported on this as well to my patient first here:

    and most recently here:

    IT IS ALL ABOUT MECHANICS….young throwers/pitchers have such inconsistent mechanics that torque on the elbow changes with changing arm slot and body position.

    Thanks, Mike. Will you be be at the 2009 ASMI Conference?

Comments are closed.