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Humeral torque in professional baseball pitchers
Michelle B Sabick1, Michael R Torry, Young-Kyu Kim
1Steadman-Hawkins Sports Medicine Foundation, 181 West Meadow Drive, Vail, CO 81657, USA.
The American Journal of Sports Medicine
|May 20, 2004
Summary
Throwing athletes may experience humeral shaft fractures due to high axial torque during the cocking phase. This torque, near maximum shoulder external rotation, can exceed 48% of the humerus
Area of Science:
- Sports Medicine
- Biomechanics
- Orthopedic Surgery
Background:
- Spontaneous humeral shaft fractures are a known risk for throwing athletes.
- The exact biomechanical mechanism and timing of these fractures during pitching remain unclear.
Purpose of the Study:
- To investigate the biomechanics of humeral shaft fractures in professional baseball pitchers.
- To determine the role of humeral axial torque during the pitching motion.
Main Methods:
- Calculated the torque acting on the long axis of the humerus in 25 professional baseball pitchers during game situations.
- Measured peak humeral axial torque and related it to the pitching phase.
Main Results:
- Peak humeral axial torque averaged 92 +/- 16 Nm near maximum shoulder external rotation (end of cocking phase).
- This torque promotes external rotation of the distal humerus, consistent with observed fracture patterns.
- Peak torque reached 48% of the humerus' theoretical torsional strength, indicating a role for repetitive stress.
Conclusions:
- Humeral shaft fractures are most likely to occur during peak humeral torque at maximum shoulder external rotation.
- Pitchers with more extended elbows at stride foot contact exhibited lower peak humeral torques.