Athletic development specialists dedicated to the art and science of excellence in movement

The Psoas...Length, Strength, and Timing

The psoas...still not fully understood and often overlooked.  Generally the psoas is believed to work in hip flexion and lumbar stabilization, with possible contributions to hip rotation.  

Regev (2011) noted “the human psoas major has architectural and physiologic features that support its role as both a flexor of the hip and a dynamic stabilizer of the lumbar spine.”

Yoshio (2002) writes, “We concluded that the PMM works phasically: (1) as an erector of the lumbar vertebral column, as well as a stabilizer of the femoral head in the acetabulum at 0 degrees -15 degrees flexion at the hip joint; (2) less as a stabilizer, in contrast to maintaining its erector action, at 15 degrees -45 degrees; and (3) as an effective flexor of the lower extremity, at 45 degrees -60 degrees.”

Often the psoas is linked to low back issues and hip problems, yet is frequently overlooked in prevention and treatment strategies, in part because it’s hard to find manually and in part because chasing symptoms is quicker and easier....

What are some movement impairments related to the psoas?  

Hip mobility – Almost seems like a chicken-or-the-egg problem…does a stiff psoas create hip problems or does poor motor control in the hip aggravate the psoas?  

Lumbar instability – One theory is the brain relies on the psoas for stability to compensate for an underlying motor control dysfunction.  Whether or not this results in the neurological perception of pain will vary by individual, but it’s certainly not a biomechanically advantageous arrangement.

Respiration - The psoas is not directly involved in respiration, but can be affected as part of overall breathing dysfunction.  

Pain – Pain, regardless of source, can do funky things to the body.  Even if pain did not originate mechanically, the end result may be the same if you neglect the psoas!    

Self-maintenance and training for the psoas…

Address the psoas in four stages...soft tissue, length, strength, and timing (credit to Dr. John Mullen for the Length-Strength-Timing trilogy)






Regev GJ, Kim CW, Tomiya A, Lee YP, Ghofrani H, Garfin SR, Lieber RL, Ward SR.  Psoas muscle architectural design, in vivo sarcomere length range, and passive tensile properties support its role as a lumbar spine stabilizer. Spine (Phila Pa 1976). 2011 Dec 15;36(26):E1666-74.

Yoshio M, Murakami G, Sato T, Sato S, Noriyasu S.  The function of the psoas major muscle: passive kinetics and morphological studies using donated cadavers.J Orthop Sci. 2002;7(2):199-207.



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