After you spend 1 or 2 seconds in the slouched position, it is time to perform the overcorrect position of the exercise. To do this, try to sit up with upright posture as straight as you can.
When you sit upright, a forward curve in your spine, called a lordosis, should be accentuated. Your posture should be so upright that you feel unnatural, and you should feel slight strain on your low back, neck, or shoulders.
Once you are in the full upright and overcorrected posture, hold the position for 1-2 seconds, and then slowly release your posture about 10 to 15%. You should feel the stress and strain that was in your neck, shoulders, or low back go away. The forward curve in your low back should still be present, just not fully accentuated.
You should now be sitting in proper posture for your back. This position may feel unnatural at first, but as you progress with the slouch-overcorrect procedure, it will start to feel more and more natural. Once you have attained proper sitting posture, the use of a lumbar roll or small pillow behind your low back for support can help keep your spine in optimum position.
You can repeat the slouch-overcorrect procedure for 10 repetitions, and it can be performed several times each day to practice attaining and maintaining proper sitting posture.
Exercises and proper sitting posture are proven methods to help decrease low back and neck pain. By performing the slouch-overcorrect procedure, you can teach your spine to be in optimum posture to help decrease and eliminate pain and keep the pain away.
Source: McKenzie, R., & May, S. (2003). The lumbar spine mechanical diagnosis and therapy. (2nd ed.) Waikanae: Spinal Publications New Zealand.