Psoas is a major hip flexor which attaches the hip to the upper lumbar spine so will either pull the spine down or the hip up when it is flexed. If the muscles supporting your spine are strong the spine will remain in its natural alignment while you raise your hip, however, if the spine is weak you will end up bending both the hip and spine which will ultimately lead to chronic back pain. When we sit for long periods Psoas is continually contracted and shortens causing a tight lower back.

Psoas is a major hip flexor which attaches the hip to the upper lumbar spine so will either pull the spine down or the hip up when it is flexed. If the muscles supporting your spine are strong the spine will remain in its natural alignment while you raise your hip, however, if the spine is weak you will end up bending both the hip and spine which will ultimately lead to chronic back pain. When we sit for long periods Psoas is continually contracted and shortens causing a tight lower back.

Original article and pictures take https://backpainninjars.com site