The main issue with back pain is that even when you are not straining or exercising, the muscles of the back still play a support function. This means that an injury or condition can still cause major discomfort even though you are not moving or exerting stress on that part of the body. Falling asleep might even become a major struggle.
The most important muscles for posture, balance and support of the upper body are wrapped in layers across the midsection (your core) as well the entire back. Accordingly, even a minor injury in these areas can stop you dead in your tracks. Reaching onto a shelf or bending over to tie your shoe — it all becomes painful. This includes chronic pain that has been with you for months or years, to acute pain and injuries from this morning.
Back pain can have especially wide ranging effects and consequences. It is often so intricate and deeply rooted that it radiates well beyond the back and into the limbs. This is nerve related.