If you want to work your shoulders, upper arms, and upper back all at the same time, you've got to try doing a two-minute headstand. It's ok if you've never done one in your life or if you can't balance upsidedown. Check out this yoga how-to video tutorial and do your headstand in front of the wall. You can rest your feet against the wall and focus on staying like this for two minutes. If you want, work on moving your feet away from the wall and balance for two minutes. Whichever variation you do, you'll still feel it in your upper body, but the trick is that you have to hold it for two minutes. It will be one of your favorite yoga exercises to do.