The best exercise for shoulder health and mobility

I cannot recommend this exercise enough. It is brilliant for improving your shoulder range of motion and strengthening the entire shoulder especially rear delts and the rhomboids and lower trap muscles - if done correctly. One of the keys is to externally rotate your hands (face palms up) and really try to keep the straps tight through the whole movement.

Start with your arms out front so that the rotation is easy then progressively move further forward to force your hands further behind your head which will really challenge your mobility and you should feel a nice burning sensation in your mid-upper back. It's ok to arch your back and lift your chest as this will help open on your thoracic spine. Do it as a standalone exercise or as a warmup and especially do it if you spend a lot of time hunched over a computer.