This exercise should be mandatory for people who sit at desks.
It's called the Band dislocate.
When you sit at a desk for long periods of time your shoulders start rounding forward and your chest caves in.
Band dislocates help mobilize your rotator cuffs while stretching out your chest muscles.
How to do them:
You can use a band, a towel or a broom handle. Resistance band is best.
Hold the band in front of your waist. Rotate your arms up & over your head down to your low back.
Reverse the process. That is one rep.
Do this for 6 to 12 reps.
Do this a few times a week and your shoulders and chest will thank you.