Don't let this stretch to more than an hour. Get up, walk around, swing your arms. Do something else for at least 10 minutes. Simple exercises can prevent pain. Please check with your doctor first.
Neutral position means sitting up, head straight with eyes looking forward.
Hunch your shoulders toward your ears, then relax. Pull your elbows back as if you want them to meet in back. Do strengthening exercises for the upper body, with light weights. Ask your doctor, physical therapist, or gym personnel for recommendations. You should see a doctor for serious, long-lasting pain.