Stretching middle deltoid

Hi everybody,

I just realized that i'm not sure about how to stretch the middle/side  fibers of the deltoid

To stretch the front delts you have to put your humerus into extension (behind your torso)
To stretch the rear delts you have to pu your humerus into flexion and across your torso ( i mean bringing one arm towards the opposite shoulder and slightly upward at about 45 degree)

But for the side fibers i'm not sur how to do it, any tips ?

Are they actually stretchable ?

Thank you in advance

UP

There are many way , one of them is is to use 90° of shoulder flexion un the sagittal planche , externally rotate the upper arm so that inner elbow is facing the ceiling and then perform and adductiong accross the sagittral plain.