I am posed the question often of “why is my back bothering me during planks? I must have a weak “core.” Individuals may have a weak lumbo-pelvic region. However, it may be the tightness of the psoas causing the discomfort.
Where is the Psoas?
The psoas is located from T12-L4 in its origin of the spine. It then crosses the lumbo-pelvic region and inserts on the femur in the posterior aspect. The psoas is the primary flexor of our “core”. Additionally, it assist in side flexion.
Why Would the Psoas Potentially Cause Low Back Discomfort When Planking?
The function (flexion) and location (lumbar origins) of the psoas can become counter to the hip extension needed for planking. Simply getting into “parallel” or "spinal neutral" for planking can become uncomfortable in the lumbar spine as the sheering forces from gravity are applied with a tight psoas. The psoas will begin to pull on the lumbar spine from the sheering and compression forces.
Here are Some Exercises and Stretches for Psoas Tightness:
Standing Hip extensions
Single Leg Romanian Dead Lift
Hip Flexor/Psoas- This stretch is low load with a stretch in the chain (including the quad).
Lastly, the plank itself is a great way to stretch the psoas while strengthening the core.