Hypothesis: College pitchers with increased external rotation gain (ERG) produce increased 5 medial elbow torque (elbow stress), while those with reduced total rotational range of motion 6 (TROM) have reduced medial elbow torque, during pitching. 7
Methods: Pitchers were recruited from three college baseball teams. Players with prior injury or 8 on pitching restrictions due to pain were excluded. Players were evaluated within two weeks 9 before their first game of the season. Pitchers completed an intake survey and shoulder and arm 10 measurements were taken. Pitchers were fitted with a baseball sleeve which included a sensor at 11 the medial elbow. The sensor calculated elbow torque, arm speed, arm slot, and shoulder rotation 12 for each pitch, while a radar gun measured peak ball velocity. After adequate warmup, pitchers 13 threw 5 fastballs in a standardized manner off the mound at game-speed effort. The primary 14 outcome was to evaluate the relationship between shoulder range of motion (ROM) and medial 15 elbow torque. Additional outcomes evaluated pitcher characteristics and demographics in the 16 context of shoulder ROM. 17
Results: Twenty-eight pitchers were included in the preseason analysis. The average [standard 18 deviation] age and playing experience was 20.1 [1.3] years and 15.3 [1.8] years, with 2.5 [1.2] 19 years playing at collegiate level. The dominant shoulder demonstrated decreased internal rotation 20 (IR) and increased external rotation (ER) relative to the non-dominant side (p < 0.001). The 21 average glenohumeral internal rotation deficit (GIRD) and ERG were 11.3° [9.87] and 5.71° 22 [8.8] degrees, respectively. ERG>5° was found to be a significant predictor of elbow stress Predictors of Elbow Stress in College Pitchers 23 during pitching (47.4 [0.7] vs 45.1 [0.6] Nm, P=.014). Univariate associations demonstrated each 24 additional degree of ER resulted in increased elbow torque (beta estimate = 0.35Nm +/- 0.06, 25 P=.003). Conversely, decreased medial elbow torque was found in pitchers with reduced 26 shoulder ROM (GIRD>20°: 43.5 [1.1] vs 46.6 [0.5] Nm, P=.011; loss of TROM>5°: 43.6 [1.1] 27 vs 46.6 [0.5] Nm, P=.013), and in those with greater arm length (P < .05).
Conclusions: College pitchers with increased external rotation produce greater medial elbow 29 torque during the pitching movement. Each degree of increased external rotation was found to corelate with increased elbow torque and ball velocity. On the contrary, arm length and reduced 31 shoulder range of motion were associated with reduced medial elbow torque. This study suggests 32 that increased external rotation in pitchers is associated with greater elbow stress during pitching.