The Impact of Fatigue on Baseball Pitching Mechanics in Adolescent Male Pitchers

Purpose: To determine if shoulder and elbow kinematics, pitching velocity and accuracy, and pain change during a simulated baseball game in adolescent pitchers. Methods: Adolescent male pitchers aged 13 to 16 years were included. Pitchers were excluded if they had undergone previous shoulder or elbow surgery, currently had a known shoulder or elbow injury, or were unable to complete the simulated game for any reason. Shoulder range of motion was assessed before and after the game. Velocity and accuracy were measured for every pitch, and every 15th pitch was videotaped from 2 orthogonal views in high definition at 240 Hz. Quantitative and qualitative mechanics were measured from these videos. Perceived fatigue and pain were assessed after each inning using a visual analog scale. Data were statistically analyzed using a repeated-measures analysis of variance. Results: Twenty-eight elite adolescent pitchers were included. These pitchers, on average, were aged 14.6 +/- 0.9 years (mean +/- standard deviation), had been pitching for 6.3 +/- 1.7 years, and threw 94 +/- 58 pitches per week. Our experimental model functioned as expected in that pitchers became progressively more fatigued (0.3 +/- 0.6 to 3.5 +/- 2.1), had more pain (0.1 +/- 0.4 to 1.6 +/- 2.2), and pitched with a lower velocity (73 +/- 5 mph to 71 +/- 6 mph) as pitch number increased (P < .001, P = .001, and P < .001, respectively). Knee flexion at ball release progressively increased (49 degrees +/- 15 degrees to 53 degrees +/- 15 degrees) with pitch number (P = .008). Hip-to-shoulder separation significantly decreased as pitch number increased, from 90% +/- 40% at pitch 15 to 40% +/- 50% at pitch 90 (P < .001). Upper extremity kinematics remained unchanged (P > .271 in all cases, 91% power for elbow flexion at ball release). External rotation and total range of motion in the pitching shoulder significantly increased after pitching (P = .007 and P = .047, respectively). Conclusions: As pitchers progress through a simulated game, they throw lower-velocity pitches, become fatigued, and have more pain. Core and leg musculature becomes fatigued before upper extremity kinematics changes.