Spastic dystonia refers to the tonic contraction of a muscle or a muscle group when the subject is at rest. It can be described as a relative inability to relax muscles . Spastic dystonia can alter resting posture contributing to the hemiplegic posture: the upper limb is flexed and adducted; the lower limb is extended . Although not induced by muscle stretch, spastic dystonia is sensitive to muscle stretch and length. It can be triggered by muscle stretch, even though prolonged stretch can reduce it . The common view is that spastic dystonia is an efferent phenomenon, mediated by an abnormal pattern of supraspinal descending drive . The inability to relax the muscle (i.e., spastic dystonia) is a central feature in spastic patients and is likely to be connected to the prolonged firing of -motoneurons, a well-documented phenomenon in patients with UMNS . We think that this inability to relax the muscle is present not only after a voluntary contraction or after an involuntary event (for instance yawning, sneezing, and coughing), but also after a reflex contraction, possibly having a role in the isometric tonic muscle contraction often seen in spastic patients after the dynamic phase of stretch reflex. We do think that this issue warrants further studies.