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Relationship between maximum shoulder external rotation angle during throwing and physical variables.

Koji Miyashita1, Yukio Urabe, Hirokazu Kobayashi

  • 1Dept. of Sport Rehabilitation, Division of PT & OT Sciences, Graduate School of Health Sciences, Hiroshima University, Kasumi1-2-3 , Minami-ku, Hiroshima, Japan.

Journal of Sports Science & Medicine
|October 24, 2013
PubMed
Summary

Controlling maximum shoulder external rotation (MER) is key to preventing throwing injuries in baseball players. Shoulder internal rotation and extension angles at foot contact, along with internal rotation strength and external rotation range of motion, are significant factors influencing MER.

Keywords:
Throwingelbowinjury preventionshoulder

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Area of Science:

  • Sports Medicine
  • Biomechanics
  • Orthopedics

Background:

  • Throwing motions in baseball place significant stress on the shoulder and elbow joints.
  • The degree of maximum shoulder external rotation (MER) is directly correlated with this stress, increasing the risk of injury.
  • Identifying factors that influence MER is crucial for developing effective injury prevention strategies.

Purpose of the Study:

  • To investigate the correlation between MER and kinematic variables at stride foot contact (SFC).
  • To examine the relationship between MER and passive range of motion (ROM) and shoulder strength.
  • To identify potential risk factors for shoulder and elbow injuries in baseball players.

Main Methods:

  • Forty high school baseball players performed maximum effort throwing tasks.
  • Three-dimensional analysis was used to measure MER and shoulder angles (external rotation, extension, abduction) at SFC.
  • Shoulder internal rotation (IR) and external rotation (ER) passive ROM and muscle strength were measured.

Main Results:

  • Significant moderate linear correlations were found between MER and ER at SFC (r = -0.32), extension angle at SFC (r = 0.35), IR strength (r = -0.30), and passive ROM of ER (r = 0.46).
  • Shoulder IR and extension angles at SFC were found to determine the degree of MER.
  • Weak IR muscle strength and excessive ER ROM were identified as potential risk factors.

Conclusions:

  • Shoulder internal rotation and extension angles at stride foot contact are key determinants of maximum shoulder external rotation.
  • Weak internal rotation strength and excessive external rotation range of motion may increase the risk of shoulder and elbow injuries in baseball players.
  • Findings can inform the development of targeted prevention and rehabilitation strategies for throwing-related injuries.