Walking to relieve Back Pain

Increases blood flow. Decreased physical activity can cause the small blood vessels of your spine to become constricted, reducing blood flow to the spinal muscles. Walking helps open up the blood vessels, increasing the supply of oxygen and nutrients to these muscles.
Flushes out toxins. Muscles produce physiologic toxins when they contract and expand. Over time, these toxins can accumulate within the lower back muscle tissues and cause stiffness. Walking helps flush out these toxins and improve flexibility.
These factors combine to help build strength in the muscles of your lower back, adding to the strength and integrity of your lower back .Walking increases your flexibility by stretching the muscles and ligaments in the back, legs, and buttocks. When you walk, specific muscles, such as your hamstrings, erector muscles of the spine, and hip flexor muscles are activated and stretched. The flexibility of your spinal ligaments and tendons is also increased, improving the overall range of motion in your lower back.While walking can help improve function in your lower back, it also has other health benefits. Committing to a regular walking program may help
Reduce and/or maintain an optimal weight
Keep blood pressure under control
Improve the levels of total cholesterol
Decrease anxiety and depression
Reduce the risk of heart disease and dementia
Walking also helps increase the production of endorphins (natural pain-inhibiting hormone), decreasing the overall perception of pain
https://www.spine-health.com/blog/2-reasons-why-walking-good-your-lower-back