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Updated: Aug 8, 2026
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Measuring 3D In-vivo Shoulder Kinematics using Biplanar Videoradiography
Published on: March 12, 2021
Electromyographic Analysis of the Shoulder During Isokinetic External Rotation in Baseball Players With
Yasuyuki Ueda1,2, Jun Umehara2,3, Noriaki Ichihashi2
1Department of Physical Therapy, Takarazuka University of Medical and Healthcare, Hyogo, Japan.
Journal of Athletic Training
|August 7, 2026
Summary
Athletes with throwing shoulder pain show lower eccentric external rotation strength, potentially linked to reduced posterior deltoid activity and infraspinatus muscle atrophy. This finding aids in understanding pitching-related shoulder impairments.
Area of Science:
- Sports Medicine
- Orthopedics
- Biomechanics
Background:
- Shoulder-rotator weakness is noted in athletes with impaired throwing shoulders.
- Specific muscle activity deficits in these athletes remain unclear.
Purpose of the Study:
- To compare isokinetic external rotation torque and muscle activity in baseball players with and without pitching-related shoulder impairments.
- To identify specific muscle deficits associated with throwing-related shoulder pain.
Main Methods:
- A cross-sectional study involving 42 collegiate baseball players (pain group, n=18; control group, n=24).
- Isokinetic concentric and eccentric shoulder external rotation torque measurements at 90° abduction.
- Surface electromyography of infraspinatus (ISP), posterior deltoid (PD), and middle trapezius (MT) muscles.
- Measurement of ISP muscle thickness.
Main Results:
- No significant differences in concentric external rotation torque or muscle activity between groups.
- Lower eccentric external rotation torque in the pain group compared to the control group (P=.03).
- Reduced posterior deltoid (PD) muscle activity (P=.009) and infraspinatus (ISP) muscle thickness (P=.02) in the pain group.
Conclusions:
- Eccentric shoulder external rotation torque is diminished in athletes with throwing-related shoulder impairments.
- This deficit may be associated with reduced posterior deltoid activity and infraspinatus muscle atrophy.
- Findings highlight potential targets for rehabilitation and injury prevention in baseball players.
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