Stabilising your shoulders
Just try something for me... all I want you to do is sitting at your desk, keep your elbows by your sides bent, and turn your palms upwards to the sky. Then try palms down...
....can you feel the difference in your upper back??
You should be able to feel your upper back muscles contracting and stabilising your shoulder blades when your palms are upwards.
Now every time you go to type. Turn your palms to the ceiling activate your upper back muscles. Then turn palms down to type. This improves your posture, helps to protect your upper back and shoulders. Simple, but effective.