A state of increased muscle tension when the muscle is lengthened. Spasticity often involves an exaggeration of the tendon reflexes. In more details, spasticity is a feature of altered skeletal muscle performance in muscle tone involving hypertonia. Spasticity is also referred to as an unusual tightness, stiffness, or pull of muscles. Clinically, spasticity is defined as velocity dependent resistance to stretch where a lack of inhibition results in excessive contraction of the muscles. This ultimately leads to hyperflexia, or overly flexed joints. Spasticity mostly occurs in disorders of the central nervous system by impacting the upper motor neurons.