AAROM GHjt ER(90) with stick in supine (bi-lateral) (Shoulder external rotation 90 to 180° AAROM, with stick, arms out to side, supine)

Lie on your back holding a stick in both hands.
Bring both arms out to lie on the floor by your sides at shoulder height.
Your elbows should be at 90 degrees holding the stick with your forearms vertical.
Keeping your upper arms rested on the floor, rotate the stick overhead as though trying to reach the backs of your hands to the floor overhead.
Control the movement as you bring your forearms back to the vertical position and repeat.