The deepest group of muscles in the spine are called Multifidus and Rotatores. These are short muscles attaching vertebra to vertebra (see image). They do not have the length to extend when stretched deeply. Due to their short length, they are at high risk for injury.
You do not have to lift heavy weights to pull or tear these muscles.
Often, a simple movement like twisting, or leaning forward while seated in a chair to pick up a pen off the floor, can tear a Multifidus off its attachments. Once it happens, the muscles go into a spasm creating a knot, or multiple knots. The tissues around the muscle tear contract to protect the area from further damage.
This spasm reaction limits the blood flow. The area becomes very sensitive to touch, and any spinal movement causes severe pain.
Typically, with rest, the tear heals and the pain subsides. We forget about it for a while. But the spasm remains. The muscle tissues, once torn, are more susceptible to another injury. After a hard workout, a long flight, or a stressful event, the pain comes back.
The only way to break the cycle of pain is to release the spasm.
There is no better way to release the spasm than hands-on massage therapy. A skillful massage therapist will examine all the muscles involved (Multifidus, Rotatores, Semispinalis, and others), find the knots and trigger points, and release the spasms.
Not only does massage release the spasm, it helps restore health to all surrounding tissues: massage creates blood flow, relaxes muscle tension from any compensation patterns, and improves range of motion in the vertebral joints so this injury does not happen again.