"What is the purpose of learning how to properly use the iliopsoas muscle, and how does this affect exercise technique from a Pilates perspective?"
This was the question asked of me, which led to an interesting few days of contemplation about how I think, what I teach, how I originally learned many of the Pilates exercises, and how my teaching has evolved as I've grown and deepened my understanding of human movement and the work of Joseph H. Pilates.
With much to say on the topic, I foresee an Iliopsoas: Part 2, to continue discussion of techniques to facilitate finding the psoas and releasing the rectus femoris as the primary hip flexor. Understanding this muscles action and purpose can help teachers, and students develop effective ways to tweak Pilates technique and gain greater benefits from their Pilates workouts.
A Brief Anatomical Introduction to the Iliopsoas
The psoas major connects the ribcage and torso with the legs. A large multi-joint muscle it attaches to six joints (T12, L1 - L5) and passes over two (SI joint, Ball & Socket of the Hip) It passes through the front of the pelvic bowl and attaches on the inner side of the thigh on the lesser trochanter.
The iliacus is a fan-shaped muscle that lies on the inside of the pelvic bowl, attaching below the inner rim of the pelvic bones (Ilium.) The fibers blend with the psoas and insert on the lesser trochanter along a shared tendon.
Because both the iliacus and psoas muscles have the same action for movement of the thigh they are commonly referred to as a single muscle, the "iliopsoas."
The primary action of the iliopsoas: Hip flexion
- If the spine is stabilized the resulting movement will be flexion at the hip joint.
- If the thigh (hip joint) is held still and the psoas is contracted bilaterally, the result will be flexion of the lumbar spine which results in anterior tilt of the pelvis.
- The psoas muscle is also activated in both lateral flexion (side bending) and rotation of the lumbar spine.
The Benefits of Pilates for Efficient Muscle Action
Pilates technique done well, teaches the body how to open all the joints and improve muscle length while moving through a full range of motion. Without open joints, movement will either be restricted, or movement will be deflected to the joint above or below the closed joint space creating additional strain on our skeletal and muscle systems.
Our muscles have the ability to contract or shorten, as well as stretch or lengthen, depending on the required task and the habits we have developed for movement and muscle recruitment. The iliopsoas plays a key role for understanding the relationship of the spine and pelvis, to the legs and then learning how to develop safe, healthy, and efficient movement patterns.
Thinking About the Action of the Psoas During Exercise
An example of the importance of the iliopsoas can be seen in the Pilates mat exercise The Hundred. Ideally, the legs should be held off the floor, in hip flexion at eye level. (Most beginners don't have the strength to begin with the legs at this angle, so the exercise is usually taught with the legs starting at 45 degrees or a higher angle off the floor.)
If the legs are held in flexion by using the quadriceps, particularly the rectus femoris, movement at the hip joint will be restricted and the front of the hip will be closed. To lower the legs further, if the hip cannot move freely, the lower back will engage to pull the pelvis into a greater anterior tilt to achieve the result of holding the legs at a lower angle. However, managing the movement this way means that the lower back muscles are doing more work than the abdominals to support the correct position. When the lower back moves into extension in this manner, it closes the joints of the lumbar spine, places strain on the entire spine and the proper curl cannot be maintained. This is a very dangerous way to work, and reinforces poor habits for movement and support for Pilates, or any other exercise program if the body is trained in this manner.
Ideally, the pelvic floor anchors the base of the spine to allow lengthening and movement of each segment apart helping to maintain open joint space while in the flexed position. Posterio-lateral breathing helps to pull the ribcage away from the pelvis so that the torso curl can be lengthened (opening the spine) and deepened (increasing both the stability of the lumbar segments, and the flexion of the thoracic spine) with each breath. By utilizing the illiopsoas to support the low back in a lengthened and stable position (against the contraction of the pelvic floor), the lumbar spine stays safely in relative flexion while the pelvis continues to "lengthening away" from the upper torso. When the flexed hip (to support the legs) is held with the psoas, and higher portion of the hamstrings, the entire hip joint is open and free to easily lift or lower the legs. This helps to maintain the leg position, without losing the support, or "grabbing" the front of the thighs. In this manner, holding the position for The Hundred is supported by the back of the body, against the resistance of the front of the torso creating the flexed spine. The exercise breathes, is maintained as an energetic whole without undue strain on either the front or the back, and balanced muscle development is achieved.
During Which Pilates Exercises Is It Important To Think About The Use of the Psoas?
In all exercises where the legs extend away and return to the body, any exercise involving movement of the hip joint for flexion & extension, exercises requiring stabilization of the spine, or movement of the pelvis, flexion/extension, side-bending, lumbar rotation, and exercises that require multi-directional movement or actions in more than one plane. (Most, if not all, exercises in the Pilates repertoire!)
The Benefits of Working with the Pilates System
It is very difficult to change the habits of an overused rectus femoris, and adaptively shortened psoas by doing exercises that require unsupported leg work. The benefit of utilizing the Reformer, Cadillac, and Chairs is the assistance provided by the foot bar, straps, and springs to learn how to stabilize the length of the spine, and open the hips for free movement, using the psoas as the primary hip flexor. This "supported from underneath" feeling, should then transfer to Matwork, and exercises that challenge the psoas in less supported positions as the body gets stronger.
Gaining mastery over efficient action of the psoas in non-weight bearing positions cues the muscles for both length and strength. With practice, this will reinforce learning how to keep the psoas active for daily life and standing activities. In vertical positions, when the bones of the spine and hips are placed under the stress of gravity and the weight of the upper body, the tendency to lose good psoas support through poor posture habits and lack of muscle use results in closing joint spaces and restricting proper range of motion for the hips and spine.
The Use of the Illiopsoas in Seated Positions
When seated, the psoas, pelvic floor, and abdominals should support the hip and spine position. In this manner the "gripping sensation" in the front of the hip is released, allowing the thigh to maintain a posterior/inferior position in the socket. (If gripped, the pelvic floor is not active enough, and the rectus femoris is overworking to hold the pelvis in place and the ball of the hip joint will sit too high in the socket.) Sit like this long enough, and the psoas will become both weak, and adaptively shortened. For movement to hinge the pelvis forward from either a seated or standing position, movement should initiate with the front of the pelvic floor against a lengthening contraction of the psoas. Done this way, the lumbar spine remains held in a relatively stabilized position, the back is supported, the hip joint remains open, and a greater range of motion will be achieved at the hip to bend forward. Rather than pulling the front of the pelvis towards the thighs, initiation comes from the back of the pelvis moving forward in space-Free and easy motion.
Lack of Good Psoas Support
Without focusing on efficient psoas use, students may "go through the motions" of doing the Pilates exercises without really finding proper psoas action to lengthen the lumbar spine and freely move at the hip joint. When this happens, the body will continue to strengthen poor movement mechanics. Some things might improve, but if the grand design is to use Pilates to develop whole body functioning as an efficient lever and pulley system optimal results will probably not be achieved until students understand the importance of the illiopsoas and are able to gain mastery over supported movement. In addition, without good psoas support, additional strain may be placed on the back and hips during exercise or movement, increasing the risk of injury.
Reinforcing Efficient Psoas Support for Daily Living
There are so many ways to practice functional use of the psoas in Pilates. Gaining mastery over this will help lumbar length, strength, and mobility, as well as help to develop more freedom of motion at the hip. The easiest place to see resulting benefits is in gait mechanics for walking. Good walking technique also continues to reinforce proper use of the psoas for Pilates. Future articles will explore tips and techniques to apply to developing exercise programs to effectively train or re-train the psoas for improved function, support, and safe and efficient movement habits.
For Further Reading:
I would recommend both of these for additional insight and education into the anatomy and function of the psoas.
The Psoas Book by Liz Koch. If you're interested in a little further reading, this resource has some good insight into the anatomy, physical, and psychological effects of proper use of the Psoas muscle.
Anatomy of Movement by Blandine Calais-Germain. This book is also a great, easy-to-read reference for understanding the anatomy and muscle action.