Origin in the transverse processes of lumbar vertebrae (L1-L5) and the lateral aspect of the vertebral bodies from T12 to L5. His insertion into the lesser trochanter of the femur.
Of all the muscles, probably the most controversial in terms of their function is the psoas. In the only function that seems to be no controversy is in its main action: hip flexor. In fact it is by far the primary hip flexor, could itself perform the full range of travel of the hip flexion ... Or maybe not?
In this study of Hai Hu, Hodges and colleagues evaluates the activity of the various hip flexors straight leg raising ( SLR). And again the graph of this article when we discuss the component tilted, but the 4 hip flexors, by far the most powerful was the iliac crest, followed by adductor greater rectus femoris and finally the psoas major.
At least if there's any consensus on which is the largest hip flexor, we can say that its most important action is flexion of the hip. Where much consensus there is in other functions.
Impact Lumbar
Lordosante "or Cifosante?
Classically, the psoas lordosantes has properties. In numerous articles and books listed as a contributor to muscle lumbar extension taking fixed point in the hip. This was the proposal of an anatomical view. Seen in profile, psoas fibers descend vertically and anteriorly, beyond the pelvis to the address change to the rear to anchor the lesser trochanter, as if the pelvis serve pulley to increase the time of lumbar lordosis.
Later, some authors, such as Janda, began to postulate that the psoas contributed significantly in lumbar flexion. It was then that the paradox of the psoas, which stated that the psoas behaved both flexor and lumbar extensor function of the position of the column. If it was based on a marked lordosis (spinal erectors shortening) the psoas and behaved as if he was lordosante contrribuía flexural bending. The video is well appreciated the paradox of the psoas: hip flexion with knee extension increases the lordosis, the lever arm, and passes from flexor to extensor. Resorting back to the article of Hu Hai, increased lordosis in straight leg raises could be explained by the action of the iliac, very strong in the SLR, which causes pelvic anteversion, and is the one who carries the lumbar pelvis.
Still later, it was suggested that perhaps the action of the psoas was to maintain the physiologic lordosis and began to talk about their stabilizing role. Bogduk in their analysis showed that in the anatomical position, the psoas generated an extensor moment in high lumbar and lower thoracic and lumbar bending moment in low.
Rotator "back?
In this blog: it is devoted several entries to the psoas. The psoas dogmatic III defends the idea of \u200b\u200bthe psoas and lumbar rotator and tilter. Less consistent in research, lumbar rotation psoas has its advocates, some of the theories, supported by the multi-costitución psoas muscle bundles with a length of between 3 and 8 cm and originating at the segmental level.
Tilt "trunk?
Provision psoas side invites us to think that may have a lateral component tilter.
studies Santaguida show that the psoas not control the lordosis, or extend or flex the lumbar spine, or buffered the rotations, but exerts a compressive force by associating a lateral bending motion on lumbar spine, and contributes to the stabilization of the lumbar segments.
If the psoas had a lateral bending component of the psoas should be understood as an antagonist of himself to the role of lateral tilter. Proposed Peninou psoas contraction to reciprocal inhibition of its antagonist, the psoas on the opposite side, in his role as lumbar lateral bending.
Returning to study Hu Hai, published in Spine last year, see this chart. The contralateral psoas is activated even more strongly that performing hip flexion. Based on this study, the reciprocal inhibition for the psoas, your action should be main antagonist: ipsilateral hip extension, and not to the contralateral psoas activation in elevation of the leg in supine.
To roll a little more the thing Andersson (1995) established that the psoas major lumbar controls lateral movement eccentrically
lumbar stabilizer.
In recent years, several authors have been giving more weight to the role of stabilizer and is now considered that the psoas has no component relevant to the movements on the spine.
is based on the idea that the direction of the fibers is too vertical, and more than a movement of lumbar flexion or extension, is an axial compression of the vertebrae, which keeps them aligned. Bogduk was the first to say that the psoas could hardly generate movement on the lumbar spine,
Santaguida studies with EMG showed psoas activation when performing flexion with arms, as with the transversus and multifidus , supporting the idea of \u200b\u200bpostural stabilization.
showed Bogduk that the psoas was little action on the lumbar motion, even if eregi as a postural muscle that maintains the physiologic lordosis. Postural muscle function is well understood with the changes in length. The iliopsoas should allow hip extension. A limitation of 10 ° in most muscles is not a big problem. However, a limitation of 10 degrees in the iliopsoas prevents proper gear.
Gibbons, in his model of the role of the psoas major, dismisses any rotation, tilt or flexion and extension of the lumbar spine and determine its role in stabilizing back as the main action.
Pelvic Stabilizer
is the head of the pelvic alignment in the anteroposterior plane. The psoas slows the anterior displacement of the pelvis. In the position of "sway back" the weakness of the psoas and gluteus maximus cause an anterior translation of the pelvis and sacroiliac pain. (Lower crossed syndrome Janda)
impact on the hip
Adductor and Abductor "?
seems to be no consensus even on the component or spacer adductor muscle. It is clear that the psoas can not have a great time abductor or adductor. If you have any contribution to these movements depend, again, from the initial position of the hip. While in add may abduct and adduct may abd being in the midline, and only from the theory.
or "External Rotator Internal Rotator?
Most texts exposes the psoas and external rotator. For some a more important component than others, but most considered external rotator (flippers). However, some authors argue that the psoas is a component of internal rotator (dove feet).
Here , another entry in the same blog: The psoas dogmatic I.
others on both sides and suggest something similar to the paradox of psoas in lordosis: the psoas is internal or external rotator function of the position to leave.
Here , Psoas as the study of hip rotator depends on your starting position.
An analysis of the role of the psoas in a newborn shows illustratively as the psoas is rotator cuff internal and external expansion hip flexion. Click here , to read the full article.
hip stabilizer.
one hand, makes a coaptation of the head against the acetabulum and on the other side stops the anterior displacement of the femoral head, and has the tendon anterior to the head of the femur.
Following the role model of Gibbons psoas major, psoas takes a shortening of the coaptation FAI member, but this was taken into account before limb differences in ratings lower limbs.
This no longer a matter of debate for anatomists, and with respect to physical therapists and clinicians, it is worth an anatomic view, but in the end everything is translated into the practical aspect of functional and global motion and perhaps not as analytical anatomy ... but it's fun!.
If at the end of this reading has been made clear the role of the psoas, sorry, it was not my intention.
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