Safety first: this is general education, not medical advice. Nothing here says it's fine for a young pitcher to throw lots of breaking balls. If your player has arm pain, stop pitching and see a doctor.
Few topics start more sideline arguments than curveballs. Some parents say a curve will wreck a 12-year-old's elbow. Some coaches say it's harmless with good mechanics. The research is more mixed than either side admits, and the best-supported advice is simpler: protect the arm from too much pitching.
Myth: "A curveball by itself ruins a young arm"
What the research says: it's less clear-cut than that. In a one-season study of 476 pitchers aged 9 to 14, the curveball was associated with a 52% increased risk of shoulder pain and the slider with an 86% increased risk of elbow pain (Lyman et al., 2002). That measured pain, not surgery, and showed an association, not proof of cause.
A 10-year follow-up of 481 pitchers measured serious injury (elbow or shoulder surgery, or quitting because of a throwing injury). It was "unable to demonstrate that curveballs before age 13 years increase risk of injury" (Fleisig et al., 2011). "Unable to demonstrate" isn't the same as "proved safe," but it isn't a smoking gun either. A 2006 comparison of injured and uninjured pitchers also found no significant difference in pitch type frequency or the age pitches were first thrown (Olsen et al., 2006).
The American Sports Medicine Institute (ASMI) says curveballs "have been suggested as a risk factor, but the existing research does not support this concern." It adds a caution: a young pitcher may not be developed enough to throw one with good mechanics, and throwing it too early can cause arm fatigue and limit mastering the fastball (ASMI position statement).
Myth: "There's a magic age when curves become fine"
Fact: the major sources don't give one number, and none says anything goes. The American Academy of Pediatrics' HealthyChildren.org says pitchers younger than 14 "should only throw fast balls and changeups" (AAP). Pitch Smart, from MLB and USA Baseball, says ages 9 to 12 should avoid pitches other than fastballs and changeups, and ages 13 to 14 "can begin using breaking pitches after developing consistent fastball and changeup" (9-12, 13-14). The safe takeaway: wait, and build a good fastball and changeup first.
Myth: "It's all about the pitch type"
Fact: the strongest signals in the research are about how much and how tired. In the Olsen study, "the factors with the strongest associations with injury were overuse and fatigue." The injured pitchers had pitched more months, games and pitches, and more often with arm pain and fatigue. In the 10-year study, pitchers who threw more than 100 innings in a year were 3.5 times more likely to be injured. ASMI says "research points to overuse as the principle risk factor."
Myth: "It's only hard throwers who get hurt"
Fact: the Olsen study did find higher velocity and showcase pitching were associated with injury, but overuse and fatigue were the strongest factors. Anyone can throw too much. ASMI also says to avoid radar guns with adolescent pitchers.
Myth: "Pitch counts and rest don't matter if the mechanics are good"
Fact: ASMI says poor mechanics contribute to injury risk, but counts and rest matter on their own. In the Lyman study, pitches thrown in a game and in a season were significantly associated with elbow and shoulder pain. Pitch Smart says "research has shown that pitch counts are the most accurate and effective means" of limiting pitching with fatigue. The AAP says there is "a direct link between elbow pain and the number of pitches (pitch counts) and the number of games in which a young player throws," and says it's seen much more often in players who play year-round and pitch for more than one team.
What to do: a checklist for parents and coaches
- Follow pitch count and rest rules, and keep your own count. Little League's daily limits are 75 pitches for ages 9-10 and 85 for ages 11-12, with required rest days (Little League pitch count rules). See the full age tables on Pitch Smart and our ArmRules page.
- Take time off from throwing. For ages 9 to 12, Pitch Smart says at least 4 months off each year (2 to 3 in a row) and no more than 80 combined innings in any 12 months.
- Don't pitch for two teams at once. Pitch Smart and ASMI both advise against it.
- Stop at pain or fatigue. ASMI says to rest a tired pitcher, and to stop pitching for elbow or shoulder pain until a sports medicine physician evaluates it.
- Don't send a tired arm to a tournament or showcase. Showcase pitching was associated with injury in the Olsen study.
- Learn the basics first: throwing, then the fastball, then the change-up (ASMI).
- Play other sports and have fun. Pitch Smart and ASMI both recommend it.
- Build arm care habits. Our Arm Care Training section has routines. Talk to a coach or doctor about anything your player's arm is telling you.
Tracking arm health
Some families use an app to keep an eye on a pitcher's arm. One example is ArmCare. By the company's own description, its app works with a sensor and a short test (about 60 seconds) that scores arm strength, range of motion and readiness, then suggests throwing and training adjustments based on fatigue. The company also makes performance and injury-reduction claims on its site; we haven't verified those, and nothing here says any tool prevents injury. Treat it as one tool among many: tracking goes together with pitch counts and rest rules, not in place of them. If a pitcher has arm pain, stop throwing and see a doctor.
Disclosure: this is our referral link, and Ground Up Baseball may receive a benefit if you sign up.
Where the evidence is still mixed
The view has shifted since the 2002 study urged caution. These studies are observational, and many rely on questionnaires and interviews, so they show associations, not proof. That's why our advice is conservative: the clearest findings are about workload and fatigue, and the major organizations still say to hold off on breaking balls.
Looking for a safe, conservative arm-care routine? See our Arm Care Training section, and check the ArmRules pitch count and rest rules for your player's age.
Sources
Links were checked on Oct 23, 2026. The three study summaries come from the PubMed abstracts; read the full papers for the details.
- Pitch Smart (MLB and USA Baseball), Pitching guidelines, Ages 9-12, Ages 13-14
- American Sports Medicine Institute, Position Statement for Adolescent Baseball Pitchers (updated April 2013)
- American Academy of Pediatrics, HealthyChildren.org, Little League Elbow
- Little League International, Regular Season Pitching Rules
- 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. PubMed
- Olsen SJ, Fleisig GS, Dun S, Loftice J, Andrews JR. Risk factors for shoulder and elbow injuries in adolescent baseball pitchers. Am J Sports Med 2006. PubMed
- Fleisig GS, Andrews JR, Cutter GR, et al. Risk of serious injury for young baseball pitchers: a 10-year prospective study. Am J Sports Med 2011. PubMed
- ArmCare, armcare.com. This is the company's own description of its product; we have not independently reviewed it. Viewed Oct 23, 2026.