Six-Pack Singing: On Associations Between Anterior Abdominal Muscle Activity and Vital Capacity Percentage

Breath management techniques are a key component within singing voice pedagogy, as well as clinical treatment of both hypo- and hyperfunctional voice disorders. Common assumptions regarding the relationships between anterior abdominal musculature (AAM), subglottal pressure (P_Sub), and sound pressure level (SPL) suggest a linear relationship where increased AAM activation will result in greater P_Sub causing a rise in SPL. The present study questions this tenet, utilizing simultaneous surface electromyographic, aerodynamic, and acoustic measures to contribute to this gap in understanding. Twenty-one healthy adult singers were recorded performing a slow vital capacity (VC) task and consonant-vowel repetitions (/papapa…/) from maximum inspiration to depletion, phonating on a controlled fundamental frequency at three SPLs. The results revealed a strong systematic increase in AAM activation as %VC decreased below 40% (P < 0.0005, ⍴ = -0.81). During controlled phonation, a strong %VC effect was also observed, with incrementally higher %sEMG values for respectively increasing SPL targets. Surprisingly, %sEMG was not strongly associated with either P_Sub or SPL, and immediate and sustained maximal contraction of the AAM throughout phonation did not significantly alter target vocal outputs compared with baseline measurements. The current study offers three key findings: 1) in habitual behaviors of healthy singers, AAM activates predominantly in association with decreasing %VC; 2) AAM activity is not strongly correlated with P_Sub or SPL; and 3) immediate contraction of AAM within the inspiratory reserve appears unnecessary for phonation. These data offer novel insights into relationships between respiratory and phonatory parameters and contribute to evidence-based voice pedagogy and therapy.