Which of the following statement about 'Cadaveric spasm' is not true?

Cadaveric spasm, also known as postmoemspasm, instantaneous rigor, cataleptic rigidity, or instantaneous rigidity, is a rare form of muscular stiffening that occurs at the moment of death and persists into the period of rigor mois. In cadeveric spasm, only a pa of muscles are involved and it causes stiffening of that paicular muscles Ref synopsis of forensic laxminarayana 2e ; Krishnan vij Textbook of Forensic medicine and Toxicology 5th edtion ; pg no - 87