a pain in the lower back ranging from slight to extreme; can result from heavy lifting, bending awkwardly, being overweight, or sitting in one position too long; may be caused by a slipped disk, arthritis, or other conditions in which the body is imbalanced; pain results from pressure on the root of a nerve or from muscle or ligament strain, often causing muscle spasms; treatment for minor cases may include rest, painkillers, a firm mattress, and application of heat; severe pain may need a spinal injection, brace, or surgery.