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Measuring 3D In-vivo Shoulder Kinematics using Biplanar Videoradiography
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Intersegmental dynamics of 3D upper arm and forearm longitudinal axis rotations during baseball pitching
Kozo Naito1, Hiroyasu Takagi2, Norimasa Yamada3
1Department of Sports Sciences, Japan Institute of Sports Sciences, Tokyo, Japan.
Human Movement Science
|October 11, 2014
Summary
Baseball pitchers generate rapid shoulder internal rotation (IR) through muscular torque. Forearm pronation (PR) relies on interactive torques, not muscular effort, highlighting 3D movement mechanics.
Area of Science:
- Biomechanics of baseball pitching
- Human movement analysis
- Sports science
Background:
- Shoulder internal rotation (IR) and forearm pronation (PR) are critical for baseball pitching velocity.
- The specific mechanisms driving rapid IR and PR, particularly the roles of muscular torques and inter-segmental forces, remain unclear.
Purpose of the Study:
- To elucidate how muscular torque and interactive torques maximize IR and PR angular velocities.
- To detail inter-segmental interactions within the kinetic chain during pitching.
Main Methods:
- Induced-acceleration analysis applied to motion capture data from eight collegiate baseball pitchers.
- Quantification of muscular (MUS) and interactive torques (GYR, COR, CEN) contributions to maximum IR (MIRV) and PR (MPRV).
Main Results:
- Muscular torque explained 98.0% of the variance in MIRV.
- Muscular torque contributed negatively (-48.1%) to MPRV.
- MPRV was primarily influenced by interactive torques (GYR, CEN), with negligible effects of GYR, COR, and CEN on MIRV.
Conclusions:
- Rapid forearm pronation in pitching is a passive effect, arising naturally from 3D throwing motion.
- Understanding these biomechanical contributions can inform pitching performance enhancement and conditioning strategies.
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