The short hip flexors comprise of two muscles, the psoas and iliacus.
They form one of the largest and thickest muscle bulks in the human body and are sometimes referred to as the ‘tenderloins’!
The psoas muscle is made up of a superficial and a deep layer. The superficial originates from the lateral borders of the T12 to L1-4 and the adjacent intervertebral discs. The deep layer of the psoas muscle stems from the transverse processes of L1-4. Between these layers rests the lumbar neural plexus. If there is over activity in the muscle layers, or inflammation present, then the neural branches may possibly be compromised, leading to sensory or motor dysfunction about the front of the hip and thigh.
The psoas passes downward and laterally over the small bowel, through the pelvis and over the pubic rami to join the iliacus muscle; thus forming the iliopsoas. Collectively, they continue distally to attach at the lesser trochanter of the femur. The muscle layers are covered with a thick layering of myofascia, which can itself result in tightness and adhesions. Where these muscle layers traverse bony areas, sits a bursa to act as a cushioning between soft and hard structures. The iliopectoneal bursa lies between the iliopsoas and hip joint capsule, with the subtendinous bursa resting between the lesser trochanter and iliopsoas tendon. In the event of irritation to the bursae, inflammation occurs causing localised pain on activation of the short hip flexors and results in bursitis. When this happens, we should aim to reduce over-activity of the iliopsoas thus preventing further aggravation of the bursae.
The psoas acts to flex and externally rotate the hip joint, or if working in reverse origin insertion, will act to laterally flex the trunk when working unilaterally and flex the trunk sagittally when working bilaterally.
In humans, the hip-flexors are made up of fast and slow twitch fibers, having the capacity for endurance as well as ballistic contractions. Interestingly, 50% of humans will be shown to have an additional hip flexor – the psoas minor. Are you one of the lucky ones?
In the western world, with our somewhat sedentary lifestyle and work practices, the iliposoas muscle group is simply held in a shortened position much of the time and becomes ‘tight’. This creates an anterior pelvic tilt, thus leading to an increased lumbar lordosis, which in turn creates undue pressure on the lower vertebrae. To prevent us from toppling forward, the gluteal and hamstring group of muscles then overwork to counterbalance the anterior pull; thus locking the hip joint so to speak. One may develop trigger points through the quadratus, lumborum, piriformis, gluteus medius/minimus, hamstrings and the erector spinae.
A key to creating quality movement function is to ensure that the iliopsoas can eccentrically lengthen with ease. This is very functional, allowing femoral head on acetabulum-disassociated movement and spacing through the hip joint, without the detrimental shearing of the lumbo-pelvic region. In addition, we should ensure that the deep hip external rotators and adductors are released to reduce the ‘need’ for the iliopsoas to counter-pull. This area is part of our primitive ‘fight and flight’ response, so we can run away from the cheetah. The tensions of the modern day can now create this same tension response in the hip flexors. We must learn to let go!
Of course our primary goal is to activate our transversus abdominis firstly, followed by the iliopsoas in sequence. Any lift of the leg must utilise the hip flexor. We do not want it to be just the driving force, and as stated above, eccentric lengthening is as important. Cues such as: ‘deepen the femoral head into the acetabulum’; ‘allow the femur to feel heavy in the socket’; ‘allow the layers of hip flexors to glide over the pubic rami’; ‘initiate the movement form the deep abdominals’; and ‘soften through the hip flexors’ are all useful. When the feet are grounded, cuing the ‘anchor the feet to the ground’ or ‘allow the back of the femur to feel heavy into the ground’ will activate a little more hamstring and glute, thus causing a reciprocal softening of the hip flexors.
Correct activation of the iliopsoas, as little as possible, will reduce trigger point tension in the antagonistic muscle groups, reduce a pull into anterior pelvic tilt and lumbar extension shearing, reduce the irritation to the associated bursae and create the ‘length’ required of hip flexors. This combined with some good old-fashioned rolling on your Franklin or spiky ball will make life a whole lot easier.
On a clinical note, iliopsoas asymmetry may be related to a more structural component such as scoliosis, leg length discrepancy or pelvic torsion. If you find that you cannot achieve the correct goal for your client, perhaps refer them to their allied health practitioner for a check.
Until next time, Happy Pilates to all!
Jen Guest
Physiotherapist/Polestar Pilates Senior Educator.
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