Publications

Objective: To examine whether experimentally increasing vocal demand with a Vocal Loading Task (VLT) elicits a coordinated vocal demand response across multiple physiological domains and whether this response is differentially modulated by immediate recovery interventions.

Methods: This study was designed as a prospective, repeated-measures crossover study. Twenty-nine normophonic female participants (age range: 18–25 years) completed a 1-hour VLT across four sessions (48-hour intervals), each followed by one of four interventions: transcutaneous electrical nerve stimulation (TENS), therapeutic ultrasound (US), semi-occluded vocal tract exercises (SOVTE), or vocal rest. Assessments at baseline (T0), post loading (T1), and post intervention (T2) included perceived vocal effort, electroglottographic measures (contact quotient [CQ], fundamental frequency [Fo]), anterior neck thermography, and muscle biomechanics. Data were analyzed using a two-way repeated-measures ANOVA.

Results: Increasing vocal demand with the VLT was associated with consistent increases in perceived effort, Fo, temperature, and muscle tone, along with decreased CQ, indicating a coordinated vocal demand response across multiple physiological domains. All interventions reduced perceived effort, TENS and US produced greater reductions than SOVTE and vocal rest. Muscle tone decreased following intervention, whereas stiffness showed limited responsiveness. CQ patterns varied by intervention, with TENS and US trending toward baseline and SOVTE associated with further decreases.

Conclusions: Increasing vocal demand with a VLT elicited a reproducible, multidimensional vocal demand response across perceptual, vibratory, thermal, and biomechanical domains. Recovery appeared to involve multiple, partially independent physiological processes that were differentially associated with the intervention applied. These findings support the use of multidimensional, non-invasive assessment for investigating vocal demand responses and recovery under controlled experimental conditions.

Keywords: vocal demand, thermography, myotonometer, therapeutic US, TENS, SOVTE

The present study demonstrates that increasing vocal demand with a VLT elicits a coordinated, multidimensional vocal demand response across perceptual, vibratory, thermal, and biomechanical domains. Specifically, increases in perceived vocal effort, fundamental frequency, anterior neck temperature, and perilaryngeal muscle tone, together with decreases in electroglottographic contact quotient, were observed consistently across sessions. Taken together, these findings indicate that experimentally increased vocal demand is associated with reproducible physiological and perceptual responses, supporting the use of the VLT as a reproducible experimental paradigm for investigating vocal demand responses under controlled laboratory conditions. In addition to characterizing the vocal demand response, the findings provide insight into the nature of recovery following VLT. Recovery was not uniform across the assessed physiological domains, suggesting that different components of the vocal demand response may return toward baseline at different rates. Although all interventions were associated with reductions in perceived vocal effort, their effects on physiological measures varied, indicating that recovery involves multiple, partially independent processes. These findings support a multidimensional view of recovery following increased vocal demand rather than a single, global recovery mechanism. It should also be acknowledged that the effects observed following TENS and therapeutic US cannot be fully disentangled from those of the concurrent vocal rest incorporated into these interventions. Accordingly, these findings should be interpreted with appropriate caution and confirmed in future studies employing designs that isolate intervention-specific effects.

More broadly, these findings highlight the importance of adopting a multidimensional, systems-level approach to the study of vocal function. By examining perceptual, vibratory, thermal, and biomechanical responses within a single experimental framework, the present study provides a more comprehensive account of how the vocal system responds to and recovers from increased demand. This perspective may help inform future research aimed at identifying domain-specific mechanisms of vocal loading and recovery, as well as the development of targeted approaches for assessment and intervention.