Researchers have found that people with low back pain demonstrate weakness of their multifidus muscles (deepest layer of your back muscles that span 1-3 spinal segments and continue from your neck to your sacrum) on the same side of their pain almost immediately. Unfortunately, the multifidus muscles do not spontaneously recover once the pain subsides.
The multifidus muscles are thought to create extension of the spine over a couple of spinal levels. Activating all of your multifidus will create extension or backward bending of the entire spine.
To activate the lower spinal levels of your multifidus, lie on your stomach, on a mat or over 1-2 pillows. Arch your back by thinking about bringing your tailbone toward your head - of course you cannot touch your tail to your head - it is the image of the type of movement you are trying to create- which is a small arch that is felt deep in your spine. This will activate both sides of your multifidus.
Keep in mind if you had low back pain on the left your left multifidus would be weaker than your right multifidus. To activate your left mutifidus, think about bringing your tailbone toward your left ear. Once again this is a small movement but now there is a bit more focus on the left side of your low back. Hold the contraction for 3 seconds and then fully relax. Start with 5 repetitions and work up to 25 repetitions.
Work in your pain-free range. Do not continue if you have increasing pain. Seek medical attention. Not every exercise is good for every body!