When first doing the exercises

When first doing the exercises, be cautious and don’t hurry. If your lower back pain is of such intensity that you can move around only with difficulty and cannot find a position in which to lie comfortably in bed, you should approach the exercises in an especially cautious and unhurried manner.
When you begin any of the exercises, you may at first experience an increase in pain. This initial increase of pain is common and can be expected. As you continue to practice, the pain should quickly diminish, at least to the level you experienced before beginning the exercises. The reduction of pain, at least to the original level, usually occurs during the first exercise session. In the first exercise session or a later one, the reduction of pain should be followed by centralization of pain.
Once the pain no longer spreads outward and instead is felt only at the midline, the intensity of pain will decrease rapidly over a period of two to three days. In one to four weeks, your pain should disappear entirely.
If, following an initial increase in pain, the pain continues to increase or spreads to places farther away from the spine, immediately stop exercising. Seek advice from a health professional. In other words, do not continue with any of the exercises if your symptoms are much worse immediately after exercising and remain throughout the day. Also stop the exercises if, during exercise, you experience symptoms in the leg below the knee for the first time or if you experience a worsening in symptoms that you already had below the knee.
If your symptoms have been present more or less continuously for many weeks or months, you should not expect to be pain-free in two or three days. The response will be slower than if your symptoms were recent, but if you are doing the correct exercises, it will usually be only a week before improvement begins. If you are lucky, it will be faster than that.