Thyroarytenoid muscle and vocal fry: a literature review

The work of speech-language pathologists uses exercises such as the vocal fry (VF), which originates from the great contractile activity of the intrinsic laryngeal thyroarytenoid muscle (TA). The aim of this study was to review the literature related to TA and VF. A literature review of the last 20 years on the subject was performed in the databases LILACS, SciELO, PUBMED, Web of Science and Google Scholar. It was found that the internal beam of the TA has slow twitch fibers, isotonic, resistant to fatigue; the external beam provides fast twitch, fatigable and isometric fibers. The VF is characterized by the perception of the vibration of the glottal pulses during the emission of the lowest frequencies in the vocal range (crackling in bass or vocal fry), mainly by the action of the TA, especially its inner portion, which shows evident shortening, dropping the mucosa in great volume along the free edge, increasing subglottic pressure and jitter, shimmer and noise levels, and reducing the airflow. Based on the literature, the isometric exercise with the external TA happens with VF sustained in the lowest possible frequency to the subject (maximum contraction), for six seconds, five to ten times daily, consistent with its predominance of fast twitch fibers. In the isotonic exercise with the internal TA, high sounds must be to stretch the muscle, alternating emissions by VF (concentric contraction) and in modal register and falsetto head (high-pitched sounds) (eccentric contraction) with several daily series of eight to 12 repetitions, consistent with the predominance of slow twitch fibers.

Voice; Laryngeal muscles; Phonation; Rehabilitation; Speech therapy