The term medial applies to that side of a limb that is nearest the midline in the anatomical position.
It does not matter what position you move your arms to, this side of your limb is always called the medial side.
Think of this green area of your arm or leg as being painted.
No matter what position you put your arm in – above your head, behind your back or even stand on your hands this side of your arm will always be green!
It is the same with the term medial.