A weak and overstretched psoas will allow the pelvis to be thrust forwards, coming in front of the ribs.
This gives the appearance of a flat back and flat bottom which then pulls the hamstrings too tight and leaves the lumbar spine in a vulnerable position. If this sounds like you, chances are your Psoas has switched off and your pelvis is not functioning correctly.
It is also possible to have the Psoas on one side being too tight, and the other side being too stretched. This can pull the pelvis and lumbar spine into all sorts of wonky positions, so it is useful to know how to release it ( click here http://www.dbmuscletherapy.com/2017/06/29/the-mighty-psoas/ ) and to strengthen it.
Strengthening the Psoas
A simple exercise to help fire up the Psoas looks like this:
Sit on the edge of a chair with your feet flat on the floor and bring your arms up in front of you at shoulder height.
Slowly lean your upper body back but don’t touch the back of the chair.
Once your upper body moves beyond vertical, gravity is trying to pull it downwards. Your Psoas will fire up to counteract the effect.
This gives it a symmetrical contraction on both sides. Hold for 10-20 seconds, return to upright and repeat 3 times.