http://www.ebp-clients.co.uk/c1/wordpress/?p=73

“local, ipsilateral pain, occasionally extending into the thigh with pain and decreased range of motion in extension and rotation both standing and sitting.” They add that the pain could be relieved by walking, lying with knees bent, using ice packs and taking non-steroidal anti-inflammatory drugs and aggravated by prolonged standing or resting. They also stated that there would be no signs of neurologic involvement or antalgic posture, so posture that reduces pain such as leaning to one side, and no aggravation of pain from sitting, flexion or coughing/sneezing.

The study is this one:
The clinical aspects of the acute facet syndrome: results from a structured discussion among European chiropractors

Lise Hestbaek, Alice Kongsted, Tue Secher Jensen and Charlotte Leboeuf-Yde
Nordic Institute of Chiropractic and Clinical Biomechanics, Forskerparken 10B, DK-5230 Odense M, Denmark

And is spot on.

Always start with 6 cycles of these to ‘neurologically’ warm up your low-back:

http://www.youtube.com/watch?v=CXRsjICsGnc

then start the core stability exercise itself:

http://www.youtube.com/watch?v=9Ar2iRusnnc

Each plank/bridge position you do should be done to the point that you start shuddering (a neurological control issue rather than a fatigue problem) or until you reach the 20 second point and rest for a bit and then do it again, and again.

The next time try to increase the time you are in the bridge position. You can do these as often as you like.

Repeat this exercise till you can crack 30 seconds in the plank.

Then come and tell me and we can go further. Hope this helps.