What is the ideal ER:IR ratio?

For shoulder health, the external rotation to internal rotation ratio should be approximately 0.66-0.75 (ER is typically weaker than IR). Throwing athletes often have lower ER:IR ratios on the dominant arm.

Why is ER weakness problematic for throwers?

External rotators (infraspinatus, teres minor) decelerate the arm after ball release. Weakness increases eccentric loading per throw, contributing to rotator cuff tendinopathy and labral injuries.

How is ER:IR ratio improved?

External rotation exercises with bands or cables (side-lying ER, prone Y-T-W, face pulls) improve ER strength. A ratio of ER:IR approaching 0.75 is the target for overhead athletes.

Shoulder Internal-External Rotation Ratio

Calculate the shoulder internal-to-external rotation strength ratio to assess rotator cuff balance and guide preventive training for throwing, swimming, and overhead athletes.

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Frequently Asked Questions

What is the ideal ER:IR ratio?

Why is ER weakness problematic for throwers?

How is ER:IR ratio improved?