Introduction

Professional voice users, typically singers, teachers, and actors are expected to sustain prolonged, variable, and often intense vocal demands, often with minimal opportunity for rest or recovery. Despite the combined need for endurance and high-intensity output in voice use, clinical voice care has traditionally emphasized laryngeal techniques, vocal economy, vocal efficiency, and symptom management, with less attention to the systemic capacity required to sustain vocal performance over time (Johnson & Sandage, 2021; Nanjundeswaran et al., 2017; Nanjundeswaran & VanSwearingen, 2025).

Vocal fatigue is one of the most common and functionally limiting conditions reported by professional voice users (McCabe & Titze, 2002; Nanjundeswaran et al., 2015). Voice therapy improves awareness of voice use and vocal behaviors, but it does not fully explain a recurring clinical pattern: Why do some individuals fatigue quickly under relatively modest vocal demands, while others tolerate similar or even greater demands with minimal effort? This suggests that vocal fatigue cannot be explained solely by laryngeal factors. Instead, it requires broader consideration of physiological constraints related to energy availability, endurance, and recovery in voice use (Hunter & Titze, 2009; Nanjundeswaran et al., 2017; Nanjundeswaran & VanSwearingen, 2025).

This perspective highlights the need to approach vocal fatigue not as a voice-specific phenomenon, but as a manifestation of whole-body system performance capacity, shaped by bioenergetic efficiency, vocal efficiency, and recovery processes that may be influenced by cardiovascular fitness, and strength training (Nanjundeswaran et al., 2017; Sandage & Smith, 2017; Morton-Jones et al., 2024).

Voice can be viewed through the lens of an endurance–strength system. Professional voice use typically requires prolonged, moderate effort interspersed with brief periods of higher vocal demand. Sustained teaching or singing repertoire may require prolonged output (endurance— sustained energy), whereas loud projection or expressive phrasing may require brief periods of increased power or speed (strength—quick bursts of energy).

When the bioenergetic supply of sustained energy or rapid energy bursts does not meet task demands, the voice tends to compensate locally at the level of the larynx, leading to increased effort, changes in vocal quality, and vocal fatigue. What is often labeled clinically as a “voice problem” may instead reflect a capacity limitation, where the body is being asked to perform beyond its available bioenergetic physiological reserves.

To better understand mismatches between demand and supply, it is necessary to consider the bioenergetic pathways underlying voice use (see Morton-Jones et al., 2024). Two primary metabolic systems support voice production: aerobic metabolism, which sustains prolonged vocal activity, and anaerobic metabolism, which supports high-demand vocal output.

Bioenergetic Pathways Supporting Voice Use

The aerobic (oxidative) energy system supports prolonged, submaximal activity through efficient oxygen delivery and mitochondrial energy production (McArdle et al., 2015). For professional voice users, aerobic metabolism may play a central role in sustaining extended periods of speaking or singing (e.g., teaching, rehearsals), long performances with relatively stable vocal output, and repeated vocal tasks across a full workday (Nanjundeswaran & Shembel, 2022, Morton-Jones, Gladden, Kavazis, & Sandage, 2024).

When aerobic capacity is limited, vocal demands may rely more heavily on anaerobic resources, approaching an individual’s maximal physiological capacity and resulting in increased perceived effort and vocal fatigue. In contrast, greater aerobic conditioning may regulate the metabolic cost of voice use, allowing vocal demands to feel more sustainable and less effortful, reflecting a closer match between energy supply and task demand (Nanjundeswaran & VanSwearingen, 2025). From this perspective, endurance is not simply about “lasting longer,” but about supporting more economic, efficient and sustainable vocal effort.

While aerobic capacity primarily supports duration, anaerobic pathways support intensity. Professional voice users routinely engage in brief, high-demand vocal behaviors such as loud projection, rapid vocal onsets, emotionally expressive speech, or climactic singing passages. These behaviors require rapid energy availability and greater reliance on anaerobic metabolism (Morton-Jones et al., 2024).

In systems with limited cardiovascular conditioning, repeated anaerobic reliance may increase metabolic stress (e.g., increased oxygen debt) and slow recovery between vocal bouts (e.g., increased excess post-exercise oxygen consumption). Over time, this pattern may contribute to instability, increased effort, and cumulative vocal fatigue. The ability to transition efficiently back to aerobic dominance may therefore be critical for minimizing fatigue across performances or long workdays (McArdle et al., 2015; Nanjundeswaran & VanSwearingen, 2025).

Highlighting Cardiovascular Fitness in Vocal Fatigue Research

Our work on cardiovascular conditioning and vocal fatigue is grounded in a bioenergetic framework that conceptualizes vocal fatigue as a whole-system phenomenon shaped by physiological capacity and recovery, rather than an isolated laryngeal impairment (Nanjundeswaran et al., 2017; Nanjundeswaran & VanSwearingen, 2025). Building on this framework, this line of research examines how aerobic capacity and metabolic efficiency influence perceived vocal effort, fatigue progression, and recovery during sustained voice use.

Using controlled vocal demand tasks, objective indices of cardiovascular fitness, and validated self-report measures such as the Vocal Fatigue Index, this work demonstrates that individuals with greater aerobic conditioning tend to exhibit lower perceived vocal effort, greater tolerance to repeated vocal demands, and more efficient recovery trajectories following vocal demand tasks (Nanjundeswaran & VanSwearingen, 2025). These findings support a model in which vocal fatigue emerges from the dynamic interaction between task demands, physiological capacity, and recovery processes, and suggest that fatigue-related symptoms may signal constraints in whole-system performance rather than isolated laryngeal dysfunction (Nanjundeswaran et al., 2017; Nanjundeswaran & VanSwearingen, 2025).

This perspective helps explain why traditional voice therapy, while essential for improving vocal behaviors, vocal economy, and vocal efficiency, may not fully resolve vocal fatigue in some professional voice users. In such cases, fatigue may be driven less by laryngeal mechanics and more by broader systemic limitations in endurance, metabolic regulation, and recovery capacity, highlighting the relevance of cardiovascular fitness and bioenergetic efficiency in both assessment and intervention.

Clinical and Translational Implications

Viewing vocal fatigue through a bioenergetic lens supports a more integrated model of voice care, complementing technique-focused therapy with conditioning-informed strategies. This approach does not replace traditional voice therapy; rather, it extends and strengthens it, particularly for professional voice users whose occupational demands exceed what technique alone can sustain (Johnson & Sandage, 2021). This framework may also be useful for habilitation and training in professional voice users as a means of preventing fatigue-related symptoms.

From a clinical standpoint, providers can consider whether a client’s fatigue reflects a technique limitation, a capacity limitation, or a combination of both. Over time, voice assessment for both habilitation and rehabilitation may benefit from incorporating markers of endurance, fatigue resistance, and recovery, alongside acoustic, perceptual, and laryngeal measures.

Conclusion

Professional voice use must be understood through the lens of energy supply, metabolic flexibility, and recovery, instead of solely a matter of coordination, control, or efficiency. Vocal fatigue may signal not just a failure of effort or technique, but a mismatch between vocal demand and systemic capacity.

By integrating aerobic and anaerobic bioenergetic pathways into voice research and clinical practice, work on cardiovascular conditioning and vocal fatigue advances a mechanism-driven framework for understanding, preventing, and rehabilitating fatigue in professional voice users. Treating voice users as vocal athletes, capable of adaptation, conditioning, and long-term performance growth opens new possibilities for sustaining vocal health, artistic excellence, and career longevity.

For Further Reading
Bioenergetics, Endurance, Recovery

Morton-Jones, M. E., Gladden, L. B., Kavazis, A. N., & Sandage, M. J. (2024). A Tutorial on Skeletal Muscle Metabolism and the Role of Blood Lactate: Implications for Speech Production. Journal of Speech, Language, and Hearing Research, 67(2), 369–383. https://doi.org/10.1044/2023_JSLHR-23-00531

Morton-Jones, M. E., Kavazis, A. N., & Sandage, M. J. (2025). Blood Lactate as a Metabolic Biomarker of Anaerobic Vocal Capacity: A Pilot Study. Journal of Voice. https://doi.org/10.1016/j.jvoice.2024.11.044

Nanjundeswaran, C., VanSwearingen, J., & Verdolini Abbott, K. (2017). Metabolic Mechanisms of Vocal Fatigue. Journal of Voice, 31(3), 378.e1–378.e11. https://doi.org/10.1016/j.jvoice.2016.09.014

Guntupalli Nanjundeswaran, C., & VanSwearingen, J. (2025). Self-Reported Fatigue and Bioenergetic Pathways Secondary to Interventions for Vocal Fatigue: A Feasibility Study. Journal of Voice. https://doi.org/10.1016/j.jvoice.2025.02.027

References

Guntupalli Nanjundeswaran, C., & VanSwearingen, J. (2025). Self-Reported Fatigue and Bioenergetic Pathways Secondary to Interventions for Vocal Fatigue: A Feasibility Study. Journal of Voice. https://doi.org/10.1016/j.jvoice.2025.02.027

Johnson, A. M., & Sandage, M. J. (2021). Exercise Science and the Vocalist. Journal of Voice, 35(3), 376–385. https://doi.org/10.1016/j.jvoice.2019.09.007

Hunter, E. J., & Titze, I. R. (2009). Quantifying vocal fatigue recovery: Dynamic vocal recovery trajectories after a vocal loading exercise. Annals of Otology, Rhinology & Laryngology, 118(6), 449–460. https://doi.org/10.1177/000348940911800606

McArdle, W. D., Katch, F. I., & Katch, V. L. (2015). Exercise physiology: Nutrition, energy, and human performance (8th ed.). Wolters Kluwer.

McCabe, D. J., & Titze, I. R. (2002). Chant therapy for treating vocal fatigue among public school teachers: A preliminary study. American Journal of Speech-Language Pathology, 11(4), 356–369. https://doi.org/10.1044/1058-0360(2002/040)

Morton-Jones, M. E., Gladden, L. B., Kavazis, A. N., & Sandage, M. J. (2024). A Tutorial on Skeletal Muscle Metabolism and the Role of Blood Lactate: Implications for Speech Production. Journal of Speech, Language, and Hearing Research, 67(2), 369–383. https://doi.org/10.1044/2023_JSLHR-23-00531

Nanjundeswaran, C. D., Jacobson, B. H., Gartner-Schmidt, J., & Verdolini Abbott, K. (2015). Vocal Fatigue Index (VFI): Development and validation. Journal of Voice, 29(4), 433–440. https://doi.org/10.1016/j.jvoice.2014.09.012

Nanjundeswaran, C. D., VanSwearingen, J. M., & Verdolini Abbott, K. (2017). Metabolic and respiratory correlates of vocal fatigue. Journal of Voice, 31(6), 736.e1–736.e13. https://doi.org/10.1016/j.jvoice.2017.03.004

Sandage, M. J., & Smith, A. G. (2017). Muscle Bioenergetic Considerations for Intrinsic Laryngeal Skeletal Muscle Physiology. Journal of Speech, Language, and Hearing Research, 60(5), 1254–1263. https://doi.org/10.1044/2016_JSLHR-S-16-0192

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