Perceived Exertion and Vocal Fold Vibratory Dose Responses to the Fluid Interval Test for Voice (FIT-V)

Objective: This study explores perceived exertion and vocal fold vibratory dose responses to the Fluid Interval Test for Voice (FIT-V; Apfelbach et al., 2023), a novel vocal exercise task that uses fluid-resisted laryngeal diadochokinesis as the primary source of vocal demand, and contrasts them with those elicited by a standard loud oral reading task (see, e.g., Solomon & DiMattia, 2000).

Methods: Thirty vocally healthy, untrained participants completed a loud oral reading task, a resisted FIT-V task (FIT-V5), and a non-resisted FIT-V task (FIT-V0) in counterbalanced order on separate days. Each task lasted 30 minutes. Vocal fold cycle and distance doses were measured with an Ambulatory Phonation Monitor, while overall perceived exertion was assessed once per minute using the Borg CentiMax scale. At the end of exercise, participants rated anatomically specific perceived cognitive, laryngeal, articulatory, thoracic, and abdominal exertion.

Results: Both FIT-V tasks imposed roughly half the vocal fold vibratory dose of the loud oral reading task (p < .001). Overall perceived exertion was qualitatively higher in the FIT-V0 (58) and FIT-V5 (61) tasks relative to the loud oral reading task (50), despite a non-significant task × time interaction (p = .068). The FIT-V tasks elicited significantly higher perceived thoracic (p = .037, FIT-V0 = 24; p = .002, FIT-V5 = 32; LOR = 17) and abdominal exertion (p = .002, FIT-V0 = 23; p = .004, FIT-V5 = 22; LOR = 12); the loud oral reading task, significantly higher laryngeal exertion (p = .007, FIT-V0 = 34; p = .040, FIT-V5 = 38; LOR = 46).

Discussion: The FIT-V tasks have lower vocal fold vibratory doses relative to existing tasks, a positive indicator for their safety as vocal loading protocols. However, their divergent perceived exertion responses underscore potential mechanistic differences between FIT-V and loud oral reading tasks. These differences, both advantageous and disadvantageous, will be appraised through the lenses of vocal fatigue and vocal effort to propose future directions for the Fluid Interval Test for Voice.