After approximately three decades of "Flexion Stress", in combination with general lack of strenuous use of trunk musculature for dynamic activity (sedentary lifestyle and / or work), muscles of the (human) abdominal wall / torso become weaker and less responsive.
Painful conditions can occur when large myofascial structures become less capable of absorbing force or performing quick movements. Acute articular dysfunction ("I threw my back out") or chronic dysfunction (from various types of disc degeneration) are more likely to occur. These conditions do not resolve well or are resistant to treatment unless muscle re-education and training are introduced.
Exercises that strengthen abdominal / torso muscles (which connect the major body regions of the thorax and pelvis) have been recognized for more than a thousand years. These are called (in English) "Plank" and "Side-Plank" and involve isometric contraction (muscle contraction without shortening the muscle) for extended periods of time, allowing development of strength and especially endurance. Such muscle activity--whether isometric or dynamic-- tends to maintain integrity of spine-to-pelvis relationships while the torso is moved. Such maintenance of relationships is essential to preventing painful low back conditions and to managing any type of existing low back pain.
Please refer to this website's explanations and illustrations of technique for more information on how to safely perform such exercises.