BACKGROUND

Sustained vocal emission during singing generates an increase in intrathoracic pressure resembling that produced during the Valsalva manoeuvre (VM), with potential implications for cardiovascular autonomic control [1,2]. Although evidence exists on cardiorespiratory synchronisation during singing [3] and previous work from our group has documented the interaction between vocal fundamental frequency and cardiovascular variables [4], no studies have characterised the heart rate (HR) pattern and autonomic tone during individual sustained vocalisation as a function of specific vocal parameters [5]. This gap constitutes the starting point of the present study.

AIMS

To obtain an initial characterisation of the cardiovascular and autonomic response during sustained vocalisation at different vocal frequencies and intensities in adults with healthy voice.

METHODS

Quasi-experimental repeated-measures study. Two adult participants with musical training (1 male, 1 female) completed a standardised protocol including: 1) physiological stabilisation and baseline recording, 2) sustained emission of the vowel /a/ (10 s) at 3 pitches (A–E–B, adapted to the relevant octave by sex) × 3 intensities (piano, mezzo-forte, forte) × 2 repetitions (n = 36 observations). ECG (lead II), pulse signal, and glottal microphone signal were continuously recorded (Biopac MP160, AcqKnowledge). Instantaneous HR was derived from RR intervals. HR was normalised as a percentage change from individual baseline and compared across 5-time windows using Friedman and Wilcoxon tests (α = 0.05). HR variability was also analysed using BaroWavelet (LF/HF ratio across three phases: baseline, emission and post-emission) [6].

RESULTS

A biphasic pattern of HR increase —two peaks separated by a decrease— was identified consistently across all 36 observations: 1st peak before or at the onset of vocalisation (+30.5 ± 8.8%), decrease during sustained emission (+9.0 ± 9.5%), 2nd peak of greater amplitude at the end of emission (+40.1 ± 17.2%) and post-emission drop (−3.0 ± 6.7%). The Friedman test showed significant differences across the five time points of the pattern (χ² = 120.2; p < 0.001) and the Wilcoxon test confirmed the consistency of all four transitions (W = 0; p < 0.001). Neither acoustic intensity nor pitch significantly modified the pattern (p > 0.05). Autonomic analysis showed a significant increase in the LF/HF ratio during vocalisation compared to baseline (2.14 ± 1.16 vs. 6.09 ± 2.83; p < 0.001), with a partial decrease in the post-emission phase (3.70 ± 2.07; p < 0.001 vs. emission).

CONCLUSIONS

These preliminary findings suggest that sustained vocalisation generates a biphasic HR pattern whose profile resembles that of the VM, accompanied by an increase in sympathetic tone during phonation and a partial decrease during post-emission recovery. The pattern was consistent across all 36 observations regardless of pitch, intensity, or participant, supporting its potential as a reference profile in healthy voice within a broader comparative study.

ETHICAL APPROVAL

The study was approved by the Ethics Committee of the University of Malaga (CEUMA; ref. 107-2025-H), conducted in accordance with the Declaration of Helsinki. All participants provided written informed consent prior to inclusion.

KEYWORDS

Sustained vocalisation; heart rate; autonomic nervous system; Valsalva manoeuvre; BaroWavelet; heart rate variability