Rationale. The majority of muscles in the hip flexor group originate at the lumbar spine, cross the pelvis and attach to the top of the femur (an exception is the iliacus muscle, which originates on the pelvis). When these muscles become chronically shortened from constant hip flexion (prolonged sitting), the lumbar spine tends to be pulled toward the top of the leg and the pelvis drops down and forward. This disrupts correct functioning of the entire lumbopelvic hip girdle and can lead to pain in the lower back and hips. This exercise stretches the hip flexors so that the spine, hips and pelvis move back into alignment. Movement Cues. Kneel on one knee, placing your other foot in front of you. Lift your torso upright as you tuck your pelvis and contract the gluteal muscles. Feel the stretch in the front of the hip and leg of the kneeling side. Perform this exercise at least once a day for 30 seconds to 1 minute on both sides. Progression. Raise the arm on the same side as the kneeling leg. Regression. Round the lower back slightly to reduce the arch in your lower back. Tip. Keep the center of the hips aligned over the knee so the hips don't shift to the side. Precaution. Avoid arching the lower back as you lift the arm overhead.