If you suffer from stiff shoulders it can be useful to try out arm movements while lying in semi supine. Lying down means that your arm movements won't affect the rest of your body so much and you can find the arm muscles in the back and chest and release the weight of the arms back into the shoulders to ease stiffness in the shoulder blades and rotator cuff muscles. Don't do anything that is painful, work within your easy range of movement.
Before you lie down to do the exploration please check videos 1, 2 and 3 which explain what semi supine is, how to get up from semi supine and the arm movements you will do when lying down.
1. Semi Supine.
2. How to get up from Semi Supine
3. The arm movements in seated position
4. Ten minute semi-supine with arm movements: