Acute Decrease in Glenohumeral Internal Rotation During Repetitive Baseball Pitching Is Associated with Transient...

Area of Science:

• Biomechanics of pitching
• Sports medicine
• Orthopedics

Background:

• Pitching effectiveness relies on ground reaction force (GRF) transfer.
• Medial longitudinal arch (MLA) breakdown may correlate with shoulder internal rotation (IR) deficits.
• Understanding stride leg mechanics is crucial for pitching performance and injury prevention.

Purpose of the Study:

• To investigate the association between stride leg foot morphology, soft tissue characteristics, and loss of IR during repeated pitching.
• To identify predictors of IR range of motion (IRROM) change in college pitchers.
• To explore the relationship between GRF, MLA support, and pitching velocity.

Main Methods:

• Fifteen college pitchers performed 60 simulated game pitches.
• Assessed IR range of motion (IRROM) pre- and post-pitching.
• Measured navicular height, abductor hallucis (AbH) mechanical properties, plantar fascia, and GRF at multiple time points.

Main Results:

• Mean IRROM decreased by -21.9° ± 8.4° over the pitching sequence.
• Significant decreases in IRROM and navicular height were observed.
• Increased AbH elasticity was noted throughout pitching.
• Higher vertical GRF (p=0.021) and increased AbH elasticity (p=0.046) correlated with greater IRROM loss.
• Anteroposterior GRF correlated with fastball velocity (p=0.038).

Conclusions:

• Stride leg morphological and mechanical changes, especially MLA support, impact IRROM.
• Reducing vertical GRF and AbH stress may preserve IRROM without compromising pitching velocity.
• This research highlights the importance of the stride foot's biomechanical integrity in maintaining pitching arm health and performance.