Aerodynamic Demand Responses to the Fluid Interval Test for Voice: A Laryngeal Diadochokinetic Vocal Loading Task

Vocal loading tasks are useful for studying vocal demand responses-the unique sets of biomechanical, aerodynamic, and acoustic adaptations that speakers employ to meet the vocal demands of communication. We discuss aerodynamic demand responses to the Fluid Interval Test for Voice (FIT-V), a vocal loading task founded on resisted laryngeal diadochokinesis (LDDK), to determine how aerodynamic factors may influence LDDK performance.

Participants (N = 30) produced loud abductory LDDK (/hʌ hʌ hʌ/) for 30 min, alternating 30-s intervals of exercise and rest. Depending on the task condition, fluid back pressure of 0 or 5 cm H₂O was imposed to modulate respiratory demand. Airflow data were captured continuously and analyzed using a two-way analysis of variance (Task × Time) to characterize aerodynamic adaptations in both LDDK pulses and whole breath groups.

Instantaneous LDDK rate did not change significantly within trials or intervals-unlike the aerodynamic variables, which exhibited task- and time-dependent changes. Large increases in mean airflow and expiratory volume within trials were characteristic of the resisted FIT-V₅ task, whereas the nonresisted FIT-V₀ task exhibited declining mean airflow and expiratory volume. Irrespective of task, all breath groups grew shorter within trials, and all aerodynamic variables decreased dramatically within intervals.

Voice users actively modulated their aerodynamic output at multiple levels throughout the FIT-V tasks, although it is unclear whether these modulations were responsible for participants' ability to maintain rapid LDDK rates. Future work will examine how different vocal demand responses influence perceived fatigue, performance fatigability, and laryngeal pathology risk.