The iliopsoas muscle is the missing link in a lot of people that have low back pain.
The iliopsoas muscle attaches from the hip to the lumbar spine/low back region. When it is too tight from prolonged sitting it pulls the lumbar spine/low back region into excess extension. Prolonged extension of the spine can irritate and compress the intervertebral discs.
To feel relief from back pain a great treatment strategy may be to stretch the iliopsoas muscles on both sides.
This is called the hip flexor/or iliopsoas stretch. Perform 3 x 60 seconds , 2 x a day, 5 x a week 8 weeks. Try to warm up the muscles first by doing a bike exercise or jogging for 15 minutes.