The muscles of the back play a key roles in lower back pain. The muscles are responsible for keeping the body upright and allow movement of the trunk in different directions. Experts have linked poor muscular strength to development of the development of low back pain. It is now evident that muscle endurance and spinal flexibility could play major roles in the prevention of back pain. This study therefore provides the reference values as a baseline for proper interpretation of the back extensors endurance and spinal extension flexibility in patients with back dysfunction.