As we all know, deltoids are the muscles that are often overtrained, and for which there is a high risk of serious injury, precisely because they are involved in most of the movements and exercises for the upper body, just as in many daily activities, adduction and abduction of the humerus, extension of the same, and of intra and extra rotation.
So as you can well understand, in most of our daily workouts for the upper body, the shoulder is still stressed.
It is however stressed even if there is a tendency, especially in many agonists, to neglect the training of the posterior deltoid, which is likely to bring up the athlete's front vision as impressive, complete with wide collar bone, wide shoulders, while in turn on the back, especially on stage, we are likely to see this major failing in the posterior deltoid and then we will find a back that does not have the details that it should have.
So the training today will have a particular focus on posterior deltoid.
What I propose are 4 exercises, to be repeated 4 times.
I combine them together in a giant set, you obviously can do one at a time and also choose the recovery mode you want according to your case.