Changes in Laryngeal Diadochokinetic Rate and Aerodynamic Variables During the Fluid Interval Test for Voice (FIT-V)

Introduction: Perceived exertion responses to vocal exercise have received considerable attention in voice science. However, perceived fatigability comprises only half of the fatigue construct (Enoka & Duchateau, 2016); measurable declines in task performance comprise the other half. This study evaluates changes in several potential markers of performance fatigability during the Fluid Interval Test for Voice (FIT-V), a novel vocal exercise task founded on fluid-resisted laryngeal diadochokinesis (LDDK).

Methods: Thirty vocally healthy, untrained participants performed both non-resisted (FIT-V0) and resisted (FIT-V5) Fluid Interval Tests for Voice in counterbalanced order on separate days. Each task lasted 30 minutes. Laryngeal diadochokinetic rate was extracted from a Phonatory Aerodynamic System airflow trace, along with a suite of aerodynamic variables, including airflow peak prominence, exhaled volume, breath group duration, and mean airflow per breath group. Performance changes were assessed both across the 30-minute trial and within 30-second intervals.

Results: We observed no substantial decline in LDDK rate across intervals, despite within-intervals rate declines of roughly 10%. Contrasting aerodynamic responses to the FIT-V0 and FIT-V5 were apparent: airflow peak prominence increased by 15% across intervals in the FIT-V5, yet decreased by 15% across intervals in the FIT-V0. Although breath group variables could not be measured in the FIT-V5 due to current technical limitations of the FIT-V apparatus, within-intervals breath group duration and exhaled volume decreased by as much as 40% in the FIT-V0.

Discussion: The results highlight the dynamic and at times confounding interplay between true performance fatigability, as exemplified by changes in laryngeal diadochokinetic rate, and biomechanical adaptations, as exemplified by changes in aerodynamic variables. Although the results affirm that transient ad/abductory impairments of the intrinsic laryngeal muscles are possible during high-intensity contraction (e.g., the 10% decline in LDDK rate noted within intervals) they demonstrate equally compellingly that these muscles are resistant to performance declines on a 30-minute timescale when short periods of vocal rest are interspersed with exercise. Aerodynamic adaptations may play critical roles in “buffering” performance when laryngeal muscle contractility is impaired.