Introduction: Vocal demand response (VDR) refers to the physiological and behavioral adaptations of the phonatory system in response to a communication scenario. A vocal loading task (VLT) is a vocal stress test of the phonatory system used to elicit and study VDR following a vocally demanding situation. While VLTs are widely used to assess vocal fatigue and disorders, consensus is lacking on optimal task parameters and sensitive outcome measures. This systematic review and meta-analysis aimed to examine the relationship between VDR and VLT, identify modalities used to assess VDR, and determine which measures best detect vocal changes post-VLT.

Method: Following PRISMA guidelines, a systematic search across seven databases yielded 10,233 records. After removing duplicates, 6,959 unique articles underwent abstract screening. 88 were selected for full-text review, and 73 studies were included in the final analysis. Extracted data encompassed VLT characteristics (e.g., task type, duration, target loudness, etc.), participant demographics (e.g., age, sex, sample size), evaluation modalities (e.g., acoustic, aerodynamic, self-ratings, endoscopic imaging, auditory-perceptual assessments, etc.), and specific outcome measures. Frequency distributions were computed for each factor to identify prevailing trends in literature.

Results: A notable increase in VLT-related publications has occurred since 2020, accounting for 33% of included studies. The Journal of Voice was the most frequent publication outlet (53%), followed by Folia Phoniatrica et Logopaedica (12%) and JSLHR (5%). Reading tasks were the predominant VLT type (79%) followed by singing (11%) and sustained vowel phonation (8%). The average VLT duration was 61.9 ± 43.8 minutes. Acoustic analysis was the most common modality (78%), followed by self-rating (63%), aerodynamic (29%), and endoscopic imaging (23%). Ongoing analyses will explore trends in target sound pressure levels, background noise, and measure sensitivity.

Conclusion: Interest in VLTs as tools for evaluating VDR has grown substantially. Reading tasks of approximately 1 hour are most frequently used, with acoustic measures as the primary evaluation method. Notably, 37% of studies omitted self-ratings, despite their value in capturing perceived vocal fatigue and effort. This review informs future research by identifying sensitive measures and optimal VLT parameters for assessing VDR.