Effects of Back Pressure on the Feasibility and Tolerability of Laryngeal Diadochokinetic Exercise: A Pilot Study

Background: The term vocal demand response refers to how speakers meet vocal demands. Vocal loading tasks with predetermined demand parameters (duration, pitch, loudness, etc) have been used in research to study the vocal demand response; these have historically consisted of loud sustained vowel and loud speech tasks. Tasks founded on laryngeal diadochokinesis (LDDK) may be viable alternatives, especially if demand parameters such as exercise-rest ratio and fluid back pressure are concurrently modulated. Objectives: To explore the effects of four fluid back pressure conditions (0, 5, 10, and 15 cm H₂O) on several measures of subjective participant experience, feasibility, and tolerability during intervallic laryngeal diadochokinetic exercise. Methods: Participants (n = 12) completed 15-minute trials of LDDK in 30-second rest and exercise intervals against four counterbalanced back pressure conditions: 0, 5, 10, and 15 cm H₂O. The effects of back pressure on (1) ratings of perceived vocal exertion, (2) prevalence of adverse effects such as shortness of breath or lightheadedness, (3) subjective difficulty of sustaining LDDK, (4) number of exercise intervals completed, (5) rankings of participant-preferred back pressure levels, and (6) expert ratings of auditory-perceptual diadochokinetic strength were assessed descriptively. Results: Perceived vocal exertion, lightheadedness, and subjective laryngeal diadochokinetic difficulty increased as back pressure increased. Number of intervals completed, auditory-perceptual diadochokinetic strength, and participant rankings of back pressure conditions, by contrast, decreased as back pressure increased. 0 and 5 cm H₂O were the most preferred back pressure conditions overall. Discussion: Fluid back pressure was feasible and broadly tolerated during 15-minute trials of vocal exercise. However, the transition from 5 → 10 cm H₂O appeared to represent an inflection point in our results: a minority of participants did not tolerate exercise at 10 cm H₂O, becoming a majority at 15 cm H₂O. We conclude that fluid back pressure should be restricted to values between 0 and 10 cm H₂O during LDDK.