Impact of ball weight on medial elbow torque in youth baseball pitchers

Abstract

Our hypothesis was that an increase in ball weight would result in an increase in medial elbow torque during the pitching motion. Youth pitchers were recruited for this study and instructed to throw 5 maximum-effort fastballs from ground level using baseballs of 4 different weights: 85 g (3 oz), 113 g (4 oz), 142 g (5 oz), and 170 g (6 oz). The validated Motus sensor was used to assess medial elbow torque, arm speed, arm slot, and shoulder rotation for each pitch. Pitch velocity was measured using a radar gun. Relationships between baseball weight and pitching kinetics and/or kinematics were evaluated using linear mixed-effects analysis. An exit survey was conducted detailing the pitcher's evaluation of the ball weights used. A total of 19 youth baseball pitchers (average age, 11.8 ± 1.1 years; age range, 9-14 years) completed the study. For every 1-oz (28-g) increase in ball weight, ball velocity decreased 2.0 ± 0.1 mph (χ2 = 52.68, P < .001), medial elbow torque increased 0.92 ± 0.37 newton meters (χ2 = 5.36, P = .02), and arm speed decreased 8.52 ± 3.68 rpm (χ2 = 5.03, P = .02). Shoulder rotation and arm slot were not significantly impacted by ball weight (P > .05). Survey results indicated that the 85-g(3-oz) baseball was most favored (8 of 19 pitchers) and believed to result in the highest pitch velocity (15 of 19 pitchers). The 170-g(6-oz) baseball was least favored (17 of 19 pitchers) and believed to result in the slowest pitch velocity (18 of 19 pitchers). No adverse outcomes were reported with the use of any ball weight or the mobile sensor. Among youth pitchers, an increase in ball weight correlated with greater medial elbow torque, decreased pitch velocity, and decreased arm speed.