first some theory:
the two muscles stabilizing your lumbar region are the multifidus and the transvers abdominis which is the deepest of the abdominals. clinically it has been found when someone is exhibiting low back pain, the nervous system has lost it's ability to contract the multifidus and/or tranverse abdominis.
the transverse abdominis originates on th iliac crest(hip bone), the lateral inguinal ligiment( where you give your self an inguinal hernia), the thoracolumbar fascia(broad sheet of tnedon like material that covers your lower back and your lats also attach to it) and the cartilage of the lower 6 ribs . it insert to the abdominal aponeurosis( which is what your six pack is embeded in-hahahahah) to the linea alba( a tendon that runs from your xiphoid process on the bottom of your sternum to your pubic symphysis,the bony part just behind your nut sack,there is actually a joint there).
the mutifidus are part of the transversospinalis group which also contain the rotatores and the semispinalis up in the upper thoracic and cervical area. the multifidus originate on the sacrum for the lower lumbar vertebrae and the transverse(wing like projection of each side of the vertabrae) processes of the rest of the vetebral column. they insert into the spinous process( thew spikey part that sticks straight back) 2 to 3 vertabrae above their origins.
the interesting thing about the multifidus is the fact that there is a gadzillion of them along your spine and each and every one of them is seperately innervated, that is to say they are controlled by the central nervous system each as their own entity, they are not batch fired. skeletal muscle are supposed to be voluntary but the small stabilizers are not really. when you get up of the toilet let's say, the cns fires the multifidus first to stiffen up the spine, then the next layer of muscles fire up until the prime movers go and move your big burly strong man physique into the standing position. some ghoulish researchers took apart some bodies spine, removed the the musculature but left all the ligaments and such alone then side loaded a lumbar joint segment(2 vertabrae) and blam, they got to about 18 pounds and there was catastrophic failure of the segment.
my instructor rick jemmett( google him,he is one of the gurus of low back pain) likened the onset of injury to the spine to a computer glitch. the stabilisers for whatever reason fail to fire first and the prime movers fire anyways and without support your spine sees more than 18 pounds and pop, your are face down on the ground wondering why it hurts so much and how you got hurt bending over to pick up a bag of cheetos. i am sure you all have had an incident like this, doing not much but getting a most hanus injury,i have certainly have had it happen.
now for whatever reason the cns forgets about your little mutifidi and they atrophy very quickly, for some reason when all this happens your transverse abdominis shuts down thereby comprimising the lumbar spine even more. the mechanism behind this is not clearly understood but if you do not learn to reactivate those 2 muscles you are up for a life time of reoccuring episodes of back pain. interestingly enough,rick has told me he has looked at x-rays of someone who's spine looks so bad from arthritis that the guy should not have been able to get out of bed let alone walk but felt no pain. multifidus and transverse abdominis were working as they should. others he has looked at,spine looks healthy but atrophy of multifidus on one side and guy is crippled. one last thing, if you are suffering from a bout of severe lumbar pain, regardless if you do something or nothing the pain will most likely resolve in 4 to 6 weeks but if you do not do the proper rehab it will occur again and again. the one thing you can do for your self other that rehab is do not sit down for anything. sitting puts an enourmous amount of stress on the lumbars , if you can arrange your life so you either lie or stand, the pain will most likely subside sooner.
so what is causing your pain,it is most likely that your bigger prime movers are now trying to stabilise your spine as your multifidus are now doing nothing. the bigger muscles do a crap job as they are not designed to do fine little movements like the stabilizers and just crank on everything and pull it up tight. we now have to learn how to actually control the stabilizers. first the transvers abdominis. you must find your anterior superior iliac spine(asis) . lie on your back with a knees bent and stick your thumbs onto the iliac crest on both sides, the bones in your waist at about the belt line. slide your thumbs forward followiing the curve down, it will drop off abruptly, this is where you wanna be,slide your thumbs medial and down an inch. this is the best place to feel your transverse abdominis. what you want to do now is flex transvese with out firing anything else. it takes an obscene amount of concentration to do this. do not flex your abs. good luck,this one takes time. you might try thinking of lifting your pelvic floor towards your navel. if you yous your fore fingers to palpate the transvers thaen you can lay your thumbs on your abs to check if you are flexing them. use any combination of sets and time till you master flexing transverse and you can just hold it whenever you like. and yes it is difficult to master this.
once you got this under control,it is time for the for the multifidus. flex the area just above your gluteal cleft( your ass crack). again this take moocho concentration. start in the same position as the transverse exercise and concentrate on just flexing the muscles in that area. if you reach back and feel around you will find it is pretty devoid of much muscle mass. try and keep everything else quiet, do not flex your glutes and do not flex your erectors. try it standing, just tighten the area with out flexing anything else. again it is obscene amounts of concentration to get this right. once you mastered this, combine the 2 exercises so you can do them together at any time and be diligent. do them whilst lying in bed, in the tub, standing in line, develop the ability to do them while driving to work. rick told me that this 2 exercises brought him great sucess in his clinical practice so work on them and see what they do for you.