I read a Frederic Delavier’s book « Strength Training Anatomy » and there is good stuff.
Sitting on a bench with your back straight. Your arms bend with your elbows forward. A dumbbell in each hand in supinated grip (thumbs inwards) and at the level of shoulders :
Inhale and press your arm vertically by rotating your wrists at 90° to have your hands in pronation (thumbs outwards).
Exhale at the end of the movement
This exercise work deltoid muscles, mainly the anterior bundles and the clavicular bundle of the pectoralis major, triceps brachial, trapezius and anterior serratus.
We can do this exercise :
Sitting with a backrest to prevent excessive arching of the back
Alternatively, one arm after other
Train with elbows forward, we limit excessive friction at the elbows joint, which can trigger inflammations than can lead to severe pathologies. This movement is recommended to people with fragile shoulders. This is to replace traumatic exercises like back press or dumbbell press.