This study found that open-chain (OKC) abduction promotes the recruitment of rotator cuff muscles, highlighting their role in responding to medial deltoid activity.

On the contrary, closed-chain (CKC) abduction poses less demands on the rotator cuff, given that the movement is performed with external stabilization.

Thus, it can be started earlier in the rehabilitation process. Of all the muscles studied, only the activity of the middle deltoid was similar across exercise type and different loads.