Epidemiologic Comparison of Pitching Mechanics, Pitch Type, and Pitch Counts Among Healthy Pitchers at Various Levels of Youth Competition.

PURPOSE: To determine differences among healthy pitchers at various levels of competition regarding pitching history, pitching mechanics, and prevalence of breaking pitches.

METHODS: Demographic, anthropometric, pitching history, and kinematic data were collected on healthy youth pitchers using dual orthogonal high-speed video analysis. Players were grouped by maturity level (9 to 12 [prepubescent], 13 to 15 [pubescent], 16 to 17 [mature], and 18 to 22 years [adult]). Groups were compared regarding pitch counts, pitching mechanics, and use of breaking pitches. Mechanics were assessed for favorable observational parameters (e.g., closed foot orientation at foot-strike) and measurable parameters at cocking, foot-strike, and ball release (e.g., knee flexion).

RESULTS: Two hundred ninety-five pitchers were included. Sixty-three were 9 to 12, 130 were 13 to 15, 78 were 16 to 17, and 24 were 18 to 22 years of age. Older pitchers threw more pitches per game (41, 52, 69, and 50 by age group; P < .001), per season (766, 975, 1,079, and 881; P = .017), and per year (901, 1,343, 2,064, and 1,302; P < .001). They were more likely to pitch for multiple teams, for more than 9 months, in showcases, and in violation of pitch count recommendations. Older pitchers were more likely to maintain their hand on top of the ball, maintain closed shoulders at foot-strike, achieve hip and shoulder separation, and lead with their hips. Older pitchers achieved greater relative stride-length, greater knee flexion at front-foot contact, and increased lead hip flexion at ball release. Pitchers began throwing curveballs and sliders at 12.6 and 13.5 years, respectively.

CONCLUSIONS: As pitchers age, they throw more pitches per game, per season, and per year and are more likely than younger pitchers to violate pitch count recommendations. Older pitchers tend to pitch with improved mechanics and velocity. The proportion of pitchers throwing breaking pitches increases with age, with the greatest increase occurring between ages 12 and 13.

LEVEL OF EVIDENCE: Level II, cross-sectional study.