Long hours at the computer can take it's toll on our posture muscles. I found over the years I developed a hunch and had to slowly correct it. One of the best ways is working out either at the gym or in your own home. All muscles groups are best to hit, but ones you want to focus on at the start if you're a computer user like me is the core muscles and the back. I started getting shoulder pain a lot, and the way I fixed this was back exercises.
Single-Arm Dumbbell Row - This exercise has been one of the best. It strengthens your back while stretching out your arms and shoulder at the same time. It helps pull your shoulders back when at the computer to prevent that hunch. Get a dumbell and
Planks - Get on the ground and you just want to hold yourself up in a held pushup position. This will strengthen your abs and core muscles that hold you up, this is important with the long hours at the computer as these muscles hold you up and stop you slouching.
Push Ups - Not only does this help the chest and triceps but will help build your core as well and a little of your back
Sit Ups -This will hit your abs, you also want to add a twist to hit the obliques on the sides.
Squats and Deadifts - This hits your legs well which you need to do when spending many hours without using your legs I find they become stiff and sore.
Remember to take care of yourself as well, the training will help but you also need to try sit up as well.