This chapter discusses muscular performance in the intact organism, which involves the cooperative activity of not only skeletal muscles but also at least the bones, joints and ligaments. The vertebral column consists of a series of vertebrae separated from one another by intervertebral discs. Movements of the spine involve various muscles and ligaments. Ligaments are moderately stretchable, and the extent to which they can be stretched imposes a safe limit on movement. The ribs join the vertebral column to the sternum forming a rigid cylinder. Minimum disc pressure in the sitting posture is achieved while sitting on a seat with a backrest which is inclined slightly backwards and is furnished with a lumbar support. People who spend long hours driving a vehicle are more prone to backache. Lack of physical exercise weakens the muscles of the back and abdomen, and thereby increases the compressive load on the intervertebral disc.