Expiratory Reserve Volume – Voice Science

Definition

Expiratory reserve volume (ERV) is the additional volume of air that can be forcefully exhaled after a normal tidal expiration—the respiratory reserve below quiet breathing that professional singers access to complete extended phrases. Typical values range from 1000–1200 mL in males and 700–1100 mL in females, constituting approximately 20–35% of vital capacity depending on posture. John Hutchinson designated this volume as “reserve air” in his foundational 1846 spirometry paper. ERV is calculated mathematically as functional residual capacity minus residual volume (ERV = FRC − RV).

Context

Relevance to Voice Production

Professional classical singers routinely access ERV during phrase completion, terminating at 30–50% of vital capacity—well below the 40% VC typical of conversational speech termination. Thomasson and Sundberg (1997) documented that operatic singers use lung volume ranges from 70–80% VC down to 30–50% VC, with demanding exercises like the messa di voce extending below 20% VC. This expanded range requires active engagement of expiratory musculature that remains quiescent during normal breathing.

The physiological distinction is significant: at functional residual capacity (approximately 38% VC), the elastic recoil forces of lung and chest wall precisely balance. Accessing ERV below this equilibrium point demands active expiratory muscle contraction to generate positive pressure, fundamentally different from the inspiratory muscle “checking action” used at higher lung volumes.

Genre Considerations

Classical singing demands sustained ERV access for phrases spanning 6–8+ seconds. Contemporary Commercial Music styles, including country singing, typically employ speech-like patterns with minimal ERV utilization (Hoit et al., 1996). Belt technique paradoxically requires a “relatively small amount of air” with precision more critical than volume—excessive inspiration creates counterproductive subglottal pressure.

Scientific Basis

Physiological Mechanisms

ERV access requires coordinated activation of expiratory muscles typically quiescent during tidal breathing:

• Abdominal wall: transversus abdominis, internal oblique, external oblique, rectus abdominis
• Rib cage: internal intercostals, triangularis sterni

These muscles increase [[intra-abdominal pressure]] and compress the chest cavity to drive air from the lungs below the resting equilibrium point.

Posture significantly affects ERV magnitude. Craig’s 1960 study established that ERV “is the most variable subdivision of the lung volume,” with sitting yielding approximately 34% of VC versus only 18% supine—a reduction of 500–700 mL due to cephalad displacement of abdominal contents. This has direct implications for voice assessment protocols requiring standardized positioning.

Measurement

The ATS/ERS standardization documents (2005, updated 2023) establish the “linked maneuvers” protocol: FRC measurement first via body plethysmography or gas dilution, followed immediately by ERV measurement, then slow inspiratory vital capacity—all performed without disconnecting from the mouthpiece. The GLI 2021 equations provide validated reference values across age ranges.

Pedagogical Considerations

Watson and Hixon’s landmark 1985 study identified the rib cage as the “pressure-flow generating element” regulating expiratory drive—the primary structure controlling ERV utilization. The appoggio technique maintains inspiratory posture during phonation precisely to control the rate of descent through the ERV range, using managed elastic recoil rather than abrupt expiratory muscle contraction.

Clinical relevance: Voice disorder patients, particularly teachers with vocal fatigue, demonstrate measurably reduced lung volumes at breath group initiation and termination (Lowell et al.). Hunter and Maxfield found that female teachers with vocal fatigue symptoms showed reduced ERV compared to asymptomatic peers—a finding with occupational health implications. Respiratory lung volume training (RLVT) protocols targeting expanded ERV utilization have shown promising results for muscle tension dysphonia (Lowell et al., 2025).

Related Terms

Also known as: ERV, Reserve air (historical)

See also: Lung Capacity (parent concept), Vital Capacity, Functional Residual Capacity (equilibrium point above ERV), Residual Volume (volume below ERV), Inspiratory Reserve Volume (complementary volume above tidal), Appoggio (technique governing ERV utilization)

References

Craig, A. B. 1960. “Effects of Position on Expiratory Reserve Volume of the Lungs.” Journal of Applied Physiology 15(1): 59–61. https://doi.org/10.1152/jappl.1960.15.1.59.

Hoit, Jeannette D., Christine L. Jenks, Patricia J. Watson, and Thomas F. Cleveland. 1996. “Respiratory Function During Speaking and Singing in Professional Country Singers.” Journal of Voice 10(1): 39–49. https://doi.org/10.1016/S0892-1997(96)80017-8.

Hutchinson, John. 1846. “On the Capacity of the Lungs, and on the Respiratory Functions.” Medico-Chirurgical Transactions 29: 137–252.

Thomasson, Monica, and Johan Sundberg. 1997. “Consistency of Phonatory Breathing Patterns in Professional Operatic Singers.” Journal of Voice 11(4): 373–383. https://doi.org/10.1016/S0892-1997(97)80033-8.

Wanger, Jack, et al. 2005. “Standardisation of the Measurement of Lung Volumes.” European Respiratory Journal 26(3): 511–522. https://doi.org/10.1183/09031936.05.00035005.

Watson, Peter J., and Thomas J. Hixon. 1985. “Respiratory Kinematics in Classical (Opera) Singers.” Journal of Speech and Hearing Research 28(1): 104–122. https://doi.org/10.1044/jshr.2801.104.