The study I referenced used the following criteria:

"Pain was categorized as “chronic” when it was perceived for more than three months. Studies concerning specific CLBP, e.g., pain arising from scoliosis, tumors, or other known pathologies were excluded."

I find stenosis is variable. Some studies lump stenosis into non-specific LBP and some exclude it. Herniations are usually included in non-specific LBP. MRI studies show many findings are not associated with pain.

Walking won't change stenosis, but it can improve symptoms. Most LBP resolves on its own. Walking is a great low-intensity activity to encourage movement and help the body resolve pain.