Let’s explore why your hip flexors get so tight anyway... The main contributing factor is excessive sitting, which puts your hip flexor muscles in a shortened position. You drive to work, sit for 8 hours, drive back home, eat dinner, watch TV on the couch, and curl up to sleep. Short hip flexors are also a major contributor to low back pain as it can increase your anterior pelvic tilt (excessively arched low back curve).