Too much tension and too little exercise greatly increase the natural loss of muscular fitness with age.
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.