Metabolic and Phonatory Responses to Anaerobic Vocal Capacity Tasks With and Without Back Pressure

To examine the metabolic (blood lactate) and phonatory responses to two vocal tasks involving short duration and high vocal demand based on laryngeal diadochokinesis.

The study has a crossover design. Thirty-one normophonic females (mean age: 20.94 ± 1.89) performed two 90-second Vocal Capacity Anaerobic Task (VCAT) exercises: VCAT⁹⁰ without back pressure and VCAT^90BP with back pressure, which was applied using a tube submerged in 10 cm of water. Both tasks required producing the /ʌ/ as rapidly as possible in a single breath. In the VCAT⁹⁰ task, laryngeal resistance was set within the target range of SPLeq@30 cm = 75-80 dBA. In VCAT^90BP, participants phonated through back pressure at the highest possible vocal intensity. Sessions were conducted 2 days apart at the same time of day. Immediately before and after each task, acoustic (fundamental frequency [f_o], soft phonation index [SPI], and cepstral peak prominence [CPP]), electroglottographic (EGG) (contact quotient [CQ]), perceptual (Borg CR-100 perceived exertion scale), and metabolic (capillary blood lactate) measurements were taken. Acoustic and EGG measures were derived from 5-second sustained /a/ phonations.

Following VCAT⁹⁰, blood lactate increased from 0.887 to 1.294 mmol/L, corresponding to an approximately 46% increase with a large effect size (P = 0.001; r = -0.933). Significant increases were also observed in f_o (P = 0.018), CQ (P = 0.002), and Borg CR-100 scores (P = 0.001), whereas CPP (P = 0.013) and SPI (P = 0.011) decreased significantly. Following VCAT^90BP, Borg CR-100 scores increased significantly (P = 0.001). No significant changes were observed in metabolic, EGG, or most acoustic measures (P > 0.05). However, CPP showed a small but statistically significant increase following VCAT^90BP (P = 0.043; d = -0.38), the functional significance of which remains uncertain.

The findings provide preliminary evidence that VCAT⁹⁰ elicited increases in blood lactate and perceived vocal exertion, alongside measurable phonatory changes. In contrast, although VCAT^90BP was perceived as demanding, it did not produce comparable metabolic or phonatory responses. These differences may reflect variations in task demands rather than the effects of back pressure alone. The results provide preliminary insight into the use of VCAT⁹⁰ for examining vocal anaerobic metabolic responses, although further research is needed to clarify underlying mechanisms and potential applications.