Back ache and pain are a symptom, not the cause, of a problem.  Just as a fever is the result of an infection and not the cause of the illness, backaches, spasms and pains are a symptom.

Damage and stress to the spinal joints and discs irritate the same nerves which control muscle contraction in the back, so when the nerves are irritated, they produce pain and reflex spasm. A spasm is the body's way of stopping motion to protect an injured joint.

Back and spinal injury may come from one big trauma (such as an auto accident) or by the buildup of many small traumas (such as long term unbalanced posture from working on a computer, lifting, or other activity).

For pain relief and correction the prefered professionals are Doctors of Chiropractic.  Chiropractors relieve back pain from nearly all kinds posture and mechanical problems, and should also recommend specific exercises to strengthen posture and prevent future pain.  See Low Back Pain; Mid Back Pain; Neck Pain