Curveballs, sliders and pitch counts: Surviving life as a pitcher with your arm intact

Pitchers get hurt. That’s a fact of baseball. And anyone who’s played the game has an opinion about why: the pitching motion is unnatural, curveballs and split-finger fastballs ruin elbows, pitch counts are too high, some pitchers aren’t built to last.

Three UNC researchers were a little more scientific about it. They surveyed thousands of players from youth leagues, high schools, and colleges. Turns out that the type of pitch a player throws doesn’t matter nearly as much as how often the player throws any type of pitch.

The curveball has long been blamed for arm injuries because it requires the pitcher’s forearm to twist right before the ball is released. A lot of parents and coaches don’t let their Little Leaguers throw curveballs. Some parents have even pressured Little League Baseball to ban the pitch. The organization has never taken that step, but it did want to find out why its pitchers were complaining of achy, tired, and injured arms. Little League Baseball teamed up with researchers from Yale and UNC, including Johna Register-Mihalik, who collected and analyzed much of the data.

Between 2006 and 2010, the researchers recruited and surveyed hundreds of Little Leaguers. Register-Mihalik also worked with athletic trainers to survey several hundred high school and college players. The anonymous surveys included questions about the ages of pitchers, their injury histories, which pitches they threw, how many innings they pitched, how many pitches they threw each outing, how many years they had pitched, and how many leagues they played in each season.

Register-Mihalik’s team found that Little Leaguers who threw curveballs didn’t experience pain or get injured any more than the Little Leaguers who didn’t throw curveballs. But another pitch seemed to be causing trouble.


Parents and coaches don’t want young kids to throw curveballs because the technique requires pitchers to twist their wrists. It’s like turning a doorknob hard while throwing. The idea is to make the ball drop dramatically as it approaches home plate. The curveball is slower than a fastball, so it has a second level of deceptiveness. But throwing a curveball puts torque on the elbow.

The uninitiated might think that a curveball moves to the side. Nope. That’s a slider. It’s a pitch that’s thrown much like a fastball, except that the pitcher’s wrist flicks inward just before the ball is released. The idea is to make the ball move to the side just as the batter is about to hit it. Three decades ago, kids weren’t throwing sliders. Now some are.

“Kids who threw the slider were at three times the risk of getting injured,” Register-Mihalik says. They reported more pain more often than other pitchers. One reason could be the mechanics necessary to throw a good slider. It requires a more violent arm motion; it’s like a combination of a curve and a fastball. “And that means it’s a more risky pitch than a curveball, especially for kids at a young age when their muscles and bones are not fully developed,” Register-Mihalik says. Yet her surveys revealed that not many Little Leaguers throw sliders. And kids who don’t throw curveballs or sliders still get hurt. Some even develop tendinitis.

Register-Mihalik’s team found two main culprits: high pitch counts and pitching too often. A pitch count is the number of pitches a player is allowed to throw in a game. “When we first started our study, pitch counts weren’t mandatory in Little League Baseball,” Register-Mihalik says. “About half the leagues used pitch counts and half didn’t. We found that pitchers in leagues with pitch counts were at a much lower risk of getting injured.” About 50 percent lower.

Since the researchers released their findings, Little League Baseball has put the report to good use, showing it to coaches and parents to back up the organization’s decision to make pitch counts mandatory.

Still, there’s only so much one organization or league can do.


Some kids play on two teams at the same time—a traditional summer league team, for instance, and a travel team. One league’s rules don’t apply to the other league. Also, the best youth players often participate in fall travel leagues and attend special baseball tournaments called showcases where college coaches and professional scouts look for future players. The surveys that Register-Mihalik’s team used show that Little Leaguers and high schoolers who pitched on travel teams or in showcases were at a much greater risk of getting injured.

The researchers also found that compared to Little Leaguers, high school pitchers were at double the risk of developing arm problems. And college pitchers faced twice the risk than that of high school players. Sixty percent of college pitchers reported taking pain relievers in order to pitch through elbow or shoulder pain. Over 80 percent of college pitchers reported pitching when their arms were tired. All this is despite the fact that college coaches have much tighter control than high school and Little League coaches over what their pitchers do at the gym, on the practice field, during games, and in the off-season.

Register-Mihalik’s team found that college pitchers were much more prone to get hurt if they had suffered arm injuries during Little League or high school. She also found that college players who’d been pitching for a greater number of years faced a lower risk of getting injured. This might seem counterintuitive; you’d think that the more someone pitches, the more wear and tear. That might be true for some pitchers. “But so many players have been weeded out by the time they get to college,” Register-Mihalik says. Only the really good pitchers are still playing in college. A lot of them have proven over the course of years that they can handle heavy a work load.

The lessons of this study are clear. If kids want to pitch, don’t let them just sling the ball however they want. Teach them proper mechanics, limit their pitch counts, and be leery of them pitching too much in secondary leagues or during the fall and winter. There’s still no guaranteeing a healthy future. Baseball may not be a violent game, but don’t tell that to elbows and shoulders.


Johna Register-Mihalik is a postdoctoral research associate in the Department of Exercise and Sport Science in the College of Arts and Sciences. The five-year study was developed and implemented by Fred Mueller, the director of the National Center for Catastrophic Sport Injury Research at UNC; Stephen Marshall, a professor of epidemiology in the UNC Gillings School of Global Public Health; and Barry Goldberg, the former director of sports medicine at Yale University.


By Mark Derewicz, Endeavors magazine