How is muscle spasm different from normal muscle activity?
In normal muscle activity, muscle fibers alternately elongate and contract. When a muscle is over stimulated by trauma or overuse, the resultant muscle contractions are not followed by the normal relaxation. The muscle remains shortened and is unable to lengthen, as it should. This occurs because the nervous system receives signals from the overused muscle and, as a mechanism of defense against further muscle overuse and injury, the nervous system will trigger a “protective muscle spasm reflex” in the affected muscle. Neural impulses from the spastic muscle will feed into the central nervous system. This barrage of neural activity originating in the spastic muscle will result in further stimulation of the spastic muscle by the central nervous system, reinforcing the muscle spasm and preventing muscular relaxation and elongation. This positive feedback loop prevents muscle relaxation in the spastic muscle and is called the hyperactive reflex arc. In this reflex arc, neural impulses from
