We need to be able to get our arms overhead for a variety of reasons; putting stuff in high cupboards, shoulder/overhead press, olympic lifting, tennis, yoga/gymnastics, pull ups etc. Not having adequate range in the shoulder to do this means that somewhere else has to do the work, usually the back!
Do this workout if you'd like your shoulders to be able to shoulder press and for your back to not have to do their job!
Equipment:
elevated surface (chair, box etc.)