As you are reading this, are you sitting in a chair that you have been sitting in for longer than three hours? Do you drive a lot for work? Are you experiencing a lower back pain? If you answered yes to these questions, then you probably have tight hip-flexors. Our main hip flexor, which is the psoas muscle is located deep on the side of the vertebral column.. The Psoas muscle may be the most important muscle in your entire body. It is the cause of imbalances in the hips, low