Effects of Sustained Semi-Occluded Vocal Tract Exercises in Non-Disordered Populations

Semi-occluded vocal tract (SOVT) exercises, including straw phonation therapy, are effective for treating vocal disorders and increasing ease of phonation by decreasing phonation threshold pressure (PTP) and increasing subglottic pressure. While the short-term effects of SOVT straw phonation therapy have been demonstrated, the sustained and lingering effects remain largely unexplored. This study aims to assess the effects of sustained daily SOVT exercises (SOVTEs) across three different straw lengths by evaluating aerodynamic parameters, including PTP, mean flow rate (MFR), subglottic pressure (P_S), laryngeal resistance (R_L), and phonation power (PW) to help guide optimized straw phonation usage and configurations.

Twenty-two normophonic participants completed a 4-week daily protocol of SOVT straw phonation exercise with a randomly assigned straw length (7.50, 15.00, or 30.00 cm). Aerodynamic measurements were recorded via mechanical interruption and electroglottography (EGG) at week zero (baseline), week two (mid-therapy), week four (post therapy), and week five (post therapy).

A significant main effect of time was observed for PTP, with post hoc tests showing significant and gradual decreases in PTP from week zero to week four, with PTP returning to baseline at week five. All three straw lengths generated the same statistical results. No significant main effects of time and straw length were observed for MFR, P_S, R_L, or PW, indicating that these parameters did not change in non-disordered participants following 4-week SOVTEs.

Sustained SOVT straw phonation therapy in a non-disordered population significantly reduces PTP, demonstrating improvements in ease of phonation over time. Lingering effects of daily SOVTEs lasted greater than one and less than seven days in terms of PTP. No significant differences were observed between straw lengths, suggesting that straw lengths tested do not impact sustained phonatory outcomes in a non-disordered population.