Eccentric anterior deltoid short lever (Shoulder flexion strengthening eccentric, bending arm from overhead, standing; 01)

Stand straight holding a broom-stick or rod in both hands.
Lift your symptomatic arm up as far as you can using your good arm to drive the movement.
Do not allow your shoulder to hunch.
Remove the support of the stick and slowly lower your arm, keeping your elbow bent and your hand close to your face.
Relax and repeat.