Throwing kinematics and elbow varus torque relative to ball size in junior baseball players.
Naoki Tanaka, Yasutomo Sakai, Yosuke Maruyama and 3 others
PMID 35035074WHAT IT FOUND
Junior baseball players threw faster and with more shoulder rotation using a smaller ball of the same weight.
While raw elbow torque did not change, the torque relative to ball speed was lower, suggesting a potential reduction in injury risk per pitch.
Key findings
01Players achieved significantly higher ball speed and shoulder external rotation angles when using the small ball compared to the standard ball.
02The maximum elbow varus torque itself did not differ significantly between the two balls, but the torque divided by ball speed was significantly lower for the small ball.
03Elbow flexion angles were significantly larger with the small ball, which the authors suggest may help buffer valgus stress.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study did not track actual injury incidence, so the link between reduced torque-to-speed ratio and injury prevention is theoretical. The analysis did not include detailed finger kinematics or the relationship between fingers and the ball during release, which could influence grip and torque. The sample size was small (26 players) and consisted mostly of males, limiting generalizability. The participants were throwing at maximum speed in a controlled laboratory setting, which may not reflect game-day fatigue or varied throwing conditions.
Declared interests
There are no conflicts of interest.
The easy way to misread this
Do not conclude that the small ball reduces absolute elbow torque, as the raw maximum varus torque values were not significantly different between the two balls. The benefit identified is a reduction in torque relative to the increased ball speed.