Many scientists believe aging muscles or muscles deprived exercise go through shortening. It is not simply a matter of unstreched muscles staying too short the muscles actually become shorter, the longer they put more and more pressure on the nerves running through the muscle sheaths. This causes the muscle to stiffen for protection. The muscle forms a rigid, natural splint. When the shortened muscles set off the splinting relax, however, the contraction of the muscles increases until they are knotted up in a uncontrollable spasm, exactly the kind of spasm people experience with lower back pain.
Muscle spasm is the body s reaction to tissue injury.
Calcium reacts with ATP to produce muscle contraction. Simultaneously the accumulating leuktrienes combine with histamine in another chemical reaction to release substance-p. Substance-p stimulates nerve endings located throughout the muscle. This stimulation or axon to the nerve cell or neuron located in the spinal cord. A normal muscle, completely relaxed, shows no electrical activity, while a muscle in spasm or tensed with pain have electrical activity.