Scapular kinematics during the shoulder flexion motion of asymptomatic baseball players with scapular dyskinesis

Abstract

Objective: Our study aimed to quantitatively evaluate scapular kinematics during shoulder flexion in baseball players with scapular dyskinesia (SDK).

Methods: Participants were 51 asymptomatic college and professional-level baseball players. Measurement was a shoulder flexion motion with a 2 kg weight for 6 seconds per a cycle using a motion capture system. The evaluation criteria for the SDK were as follows: the SDK was visually classified into four types (type I-IV), the abnormal group with type I, and control group with type IV. For the analysis section, scapular angles were calculated every 30°during shoulder flexion from 30° to 120°.

Results: There were 23 people in the abnormal group and 22 in the control group. The scapula posterior tilt during the elevation phase from 30° to 90°in shoulder flexion of the abnormal group was significantly decreased than that of the control group (p＜0.05). scapular anterior tilt at the 30° and 60°during the lowering phase of shoulder flexion during in the abnormal group was significantly increased than in the control group (p＜0.01).

Conclusion: This study showed that SDK type I in asymptomatic baseball players was associated with an understated scapular posterior tilt during the elevation phase from 30° to 90°of shoulder flexion and an excessive anterior tilt during lowering phase from 30° to 60°.