To investigate the change in fundamental frequency range and vocal fold stability achievable with vocal fold stretching exercise in human populations with high and low vocal activity

The vocal ligament is part of the layered structure of the vocal fold. It is a thin band of tissue near the superior medial edge of the vocal fold. The cord-like appearance of the ligament gave rise to the traditional term "vocal cord". The ligament connects the arytenoid cartilage (lower broad dark region) to the anterior portion of the thyroid cartilage (upper dark region). The slightly thickened endpoints are known as the anterior and posterior macula flava. In the medial-lateral direction, the vocal ligament comprises the intermediate and deep layer of the lamina propria.

The physiological functions of the vocal ligament are not fully understood. One function is to limit mechanical strain (elongation), a general function of most ligaments in the body. A second function may be to produce a firm closure of the glottis by forming a straight edge along the membranous (vibrating) portion of the vocal fold. A strong ligament that can be tensed with exercise is likely to help straighten the edge of the folds. Vocal fold bowing, for example, is a pathological condition often associated with advanced age, but it can also occur in young adults who press their arytenoid cartilages together excessively in speech. Atrophy of the thyroarytenoid muscle, which lies lateral to the ligament, causes the middle of the membranous vocal fold to be retracted from the midline of the glottis. The result is a weak voice because airflow cannot be suddenly shut off for efficient acoustic excitation of the vocal tract. For self-sustained vocal fold vibration, the superficial layer must be very pliable and deformable for mucosal surface-wave motion. The role of the ligament is then to stabilize the vertical motion when large pressures are applied to vocal fold surfaces. The most important known function of the ligament, however, is to widen the fundamental frequency range. The stiffer the ligament, the greater the likelihood that several octaves of fo range can be achieved.

Inclusion Criteria:

• Participants must be 18 years or older
• no current voice disorder
• no history of performance or professional vocal training

Exclusion Criteria:

• history of head/neck cancer, laryngeal surgery, current voice disorder requiring medical management
• cognitive limitations that would prevent them from successfully and safely participating in the study.
• history of gastrointestinal disease or surgery w
• no known neurological or structural abnormalities of vocal folds
• previous laryngeal surgeries;
• allergies to local anesthetics (used to suppress a sensitive gag reflex during laryngeal endoscopic examination);
• cardiac abnormalities;
• recent history of smoking (must be completely smoke-free for six months prior to study commencement because of the effect of smoking on the voice and laryngopharyngeal reflux severity).