Sitting Wrecks Your Hip Action

In the video below, Kelly Starrett discusses how sitting throughout the day places the hip joint in a poor position for normal daily movements. In the video he discusses how prolonged sitting places the psoas muscle in a short, contracted position. As an individual attempts to stand from this position, he/she hyper-extends the lumbar spine. Biomechanically, a tight psoas and shortened lumbar paraspinals draw the pelvis into an anterior pelvic tilt and the lumbar vertebrae into extension. Be aware: the chest may appear upright- giving the impression of natural movement,- but a closer look at the L-spine reveals movement beyond the neutral range.    

The problem with sitting exists beyond the chair as well. Normal standing posture requires little muscular action to maintain an upright position. In the presence of a hip flexor contracture due to prolonged sitting, forces are placed anteriorly across the hip requiring the hip extensors to counteract the force. Increased muscular action and metabolic cost creates the desire to sit, perpetuating the circumstance which initiated the hip flexion contracture (Neumann 2010). 

Quick facts regarding the hip joint:
-Normal hip flexion AROM: 120 degrees; extension AROM: 10-15 degrees
-Unmodified, ovoid ball and socket joint with 3 deg of freedom
-Capsular pattern (as defined by Cyriax): hip flexion > restricted hip ABDuction > restricted IR
-Closed packed position: Hip extension, ABDuction, IR
-Open packed position: 30 deg flexion, 30 deg abduction, 20 deg ER    

Quick facts regarding the psoas muscle:
-The psoas attaches proximally along the transverse process of T12 and all lumbar vertebrae
-The muscle attaches distally on the less trochanter of the femur
-The iliopsoas is a stong hip flexor and tilts the pelvis anteriorly as well
-If the pelvis is not stabilized the psoas will pull the lumbar spine into excessive lordosis

The Student Physical Therapist Advice: 
Engage the Transversus abdominus (TrA) prior to moving from sitting to standing. The TrA provides a posterior pelvic tilt to counteract the force of the psoas muscle. Additionally a posterior tilt does not allow the lumbar paraspinals to contract as readily. With proper cueing, the gluteus maximus can then be engaged and stress will be taken off the low back.  

Enjoy the video-  Jim 

References: Neumann, Donald. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. 2nd edition. St. Louis, MO: Mosby Elsevier, 2010. 341-342. Print.