I herniated a disc in my back and had sciatica 20 years ago so I've been stretching my back for years. After my stroke I was worried my back pain would come back. It did. I had to shorten my walks on the boardwalk at Point Pleasant because my back ached. A recent bout of back spasms taught me stretching by leaning forward with my legs straight while sitting in bed was not enough.
I was shocked to learn I repeatedly arch my back because the abdominal muscles on my hemiplegic (paralyzed) side are weak. This weakness lets my pelvis tilt forward (bottom half of red line on left) so I stop myself from falling by leaning back (top half of red line). My back is arched every time I lift my leg. To lift the leg, hip muscles (arrow in diagram on right) need a stable base to pull on. Abdominal and back muscles (triangles on right) have to be strong to hold the pelvis and spine straight (white line on left).
It gets worse. My PT discovered I arch my back when I lean down to pick up an object, like when I reach down to get a pot from a bottom cabinet, get milk from the bottom shelf of the refrigerator, or pick up something from the floor that I've dropped. It gets worse. When I rinse a dish and brush my teeth I arch my back so I can lean my stomach on the edge of the counter for support. I arch my back when I stand with one foot in front of the other in the check-out line when I go shopping.
Thank goodness a PT showed me how to add abdominal strengthening to my morning routine.