The Psoas Muscle in a Runner: An Endurance Savy Muscle ?

 We received a question yesterday from a doctor. We felt it was worthy of sharing. Here it is, followed by our response.

Doctor:  I do have a question about one of my athletes in particular.  He is a fairly good (All-State in IL) high school track distance runner that has some left sided femoral acetabular impingement.  He gets some capsular hip pain that also will ‘tighten up’ his low back during speed endurance/threshold running only.  Moderate and easy distance runs cause no problem and neither do track/speed workouts.  Only during speed endurance does he have issues.  Upon evaluation after these sessions he does seem to have some low back QL tightness, but joint mobility is fairly good in his lumbar spine.  He does show marked hypertonicity through his left hip joint.  I’m not quite sure the mechanism here- why he would only flare up with speed endurance running- any insights?
Thanks a bunch and I look forward to hearing from you!

The Gait Guys response:

 You state “only during speed endurance” does he have issues. We will assume you mean a long, hard anaerobic workout, which would tax type II b fibers. You also mention he has hypertonicity through his hip joint.  Since the psoas crosses this joint it should be considered in sprinting and long, hard endurance activities, especially if the patient is flexor dominant. The psoas major muscle is composed of type I, IIA and IIX muscle fibers. It has a predominance of type IIA muscle fibers. The fiber type composition of the psoas major muscle was different between levels of its origin starting from the first lumbar to the fourth lumbar vertebra. The psoas major muscle has dynamic and postural functions, which supports the fact that it is the main flexor of the hip joint (dynamic function) and stabilizer of the lumbar spine, sacroiliac and hip joints (postural function). The cranial part of the psoas major muscle has a primarily postural role, whereas the caudal part of the muscle has a dynamic role. This is all very much supported in this journal article here (link) ( and making it work in an endurance capacity would certainly cause issues. Flexor dominance is a common scenario we see clinically, due to insufficient extensor activity (and decreased vestibulo and reticulo spinal drive to extensors) and increased cortico spinal drive (to the flexors, including the iliopsoas). This would fuel the “bail out” (lack of stability) of the lower abs. The anterior tippage of the pelvis would drive the femur posteriorly, binding the joint (the opposite of an anterior femoral glide).

Video footage and some pix of your athlete would provide more insight for us to help.

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