Posture.

[Tinker28]

Can poor posture make your upper back really sore? My back from time to time gets sore for a few days then goes away then after a while comes back. I have been doing more and more siting and I do slouch a lot. anyone have an idea?

[Jmac]

Slouching can absolutely cause your back - both upper and lower - to be sore. Sit up. It's helps with confidence, too.