The iliopsoas is another powerful hip flexor that begins in two distinct regions proximally. The iliacus has a broad origin, arising from the inner table of the iliac wing, the sacral alae, and the iliolumbar and sacroiliac ligaments. The psoas originates at the lumbar transverse processes, the intervertebral discs, and the adjacent bodies from T12 to L5, in addition to the tendinous arches between these points. Distally, the two large muscular bodies converge to become one distinct structure—the iliopsoas—and subsequently jointly insert at the lesser trochanter of the proximal femur. The nerve to the iliopsoas (i.e., the anterior division of L1 to L3) supplies the iliopsoas muscle.
The hip flexors help balance the posterior pelvic muscles. Three key muscles often become tight and shortened as a result of activities of daily living. These are the iliacus, psoas major, and the rectus femoris. The iliacus and the psoas major are often referred to as the iliopsoas because they share the same insertion at the lesser trochanter of the femur. The psoas minor inserts on the superior ramus of the pubis bone and mainly supports the natural lordotic curvature of the spine, but is only found in about 40% of the population. The psoas major originates on the anterior surface of the lumbar vertebrae and runs over the pubis bone and inserts into the lesser trochanter of the femur. This muscle not only helps to flex the hip, but also has an effect on the lordotic curvature of the lumbar vertebrae. The rectus femoris has a proximal attachment at the acetabulum and inserts into the tibial tuberosity. This long muscle plays a role in both hip flexion and leg extension (Figure 9-4).
Kneel on your mat with your thighs perpendicular to the floor and tops of your feet facing down. Bring your inner knees together. Slide your feet apart so they are slightly wider than your hips and press the tops of your feet evenly into the mat. Slowly sit down between your feet. Use your hands to turn the top of your thighs inward. Then, lean back onto your forearms and slowly lower torso to floor. Hold for at least 30 seconds.
The good news is that there are plenty of good hip stretches out there that you can do to relieve discomfort, decrease tightness, and increase mobility in your hips. Since your hips are involved in so many of the movements you make (both inside and outside of the gym) stretching them is a great way to keep them feeling good and ready to work for you. Add some of the 12 hip stretches Atkins demos below to the end of your workout, or spend 10 minutes each day just doing a few of them, to improve mobility in your hips.