- Prolonged failure of muscle relaxation after contraction. This may occur after voluntary contractions, muscle percussion, or electrical stimulation of the muscle. Myotonia is a characteristic feature of myotonic disorders.
Definition from: MeSH via Unified Medical Language System at the National Library of Medicine
- Tonic spasm of one or more muscles; also: a condition characterized by such spasms.
Definition from: Merriam-Webster's Medical Dictionary by Merriam-Webster Inc.
See also Understanding Medical Terminology.