Breathing and Singing: Objective Characterization of Breathing Patterns in Classical Singers

Abstract

Singing involves distinct respiratory kinematics (i.e. movements of rib cage and abdomen) to quiet breathing because of different demands on the respiratory system. Professional classical singers often advocate for the advantages of an active control of the abdomen on singing performance. This is presumed to prevent shortening of the diaphragm, elevate the rib cage, and thus promote efficient generation of subglottal pressure during phonation. However, few studies have investigated these patterns quantitatively and inter-subject variability has hindered the identification of stereotypical patterns of respiratory kinematics. Here, seven professional classical singers and four untrained individuals were assessed during quiet breathing, and when singing both a standard song and a piece of choice. Several parameters were extracted from respiratory kinematics and airflow, and principal component analysis was used to identify typical patterns of respiratory kinematics. No group differences were observed during quiet breathing. During singing, both groups adapted to rhythmical constraints with decreased time of inspiration and increased peak airflow. In contrast to untrained individuals, classical singers used greater percentage of abdominal contribution to lung volume during singing and greater asynchrony between movements of rib cage and abdomen. Classical singers substantially altered the coordination of rib cage and abdomen during singing from that used for quiet breathing. Despite variations between participants, principal component analysis revealed consistent pre-phonatory inward movements of the abdominal wall during singing. This contrasted with untrained individuals, who demonstrated synchronous respiratory movements during all tasks. The inward abdominal movements observed in classical singers elevates intra-abdominal pressure and may increase the length and the pressure-generating capacity of rib cage expiratory muscles for potential improvements in voice quality.

Fig 1. Illustration of rib cage (RC), abdominal (AB) and total lung volumes during three breath cycles of a classical singer performing a singing task (task 1: Waltzing Matilda).

Parameters assessed from respiratory waveforms are indicated: respiratory frequency (Fres), time of inspiration (Ti), RC volume and time shift between peak volume of RC and AB.

Fig 2. Example of extraction of typical breathing patterns using Principal Component Analysis (PCA).

In A, rib cage (RC) and abdominal (AB) volumes are shown for three consecutive breath cycles of a classical singer performing a singing task (task 1: Waltzing Matilda). These waveforms were used to calculate the PCA components and PCA coefficients shown in B. In this example, three components explained more than 98% of the total variability of the original signals. The PCA representations in C were obtained by weighting the PCA components by the corresponding PCA coefficients. The typical breathing pattern for this subject (not shown) was obtained by weighting the PCA components by the average PCA coefficients across all breath cycles. a.u.: Arbitrary units.

Fig 3. Representative recordings of rib cage (RC), abdominal (AB) and total lung volumes of one classical singer and one untrained individual performing each experimental task.

Volume waveforms are shown for five consecutive breath cycles, with the corresponding Konno-Mead plots representing the coordination between AB and RC movements (in the x- and y-axis respectively).

Fig 4. Respiratory frequency (Fres), time of inspiration (Ti), percentage contribution of rib cage to total lung volume (%RC), phase angle, time shift, and linear correlation coefficient between rib cage (RC) and abdomen (AB) volume waveforms of classical singers and untrained individuals during each of the three tasks assessed.

Mean + SEM are shown. * P < 0.05, ** P < 0.001 vs. untrained individuals. † P < 0.05, †† P < 0.001 vs. quiet breathing.

Fig 5. Percentage of time and volume in paradoxical motion of rib cage (RC) and abdomen (AB) of classical singers and untrained individuals during each of the three tasks assessed.

Paradoxical motion is defined here as outward movements of the volume compartment during the expiratory phase of each breath cycle. Mean + SEM are shown. * P < 0.05, ** P < 0.001 vs. untrained individuals. † P < 0.05, †† P < 0.001 vs. quiet breathing.

Fig 6. Peak airflow, mean airflow, and volume excursion of classical singers and untrained individuals during each of the three tasks assessed.

Volume excursion was assessed as the difference between the volume at initiation and termination of expiratory phase of each breath cycle. Mean + SEM are shown. * P < 0.05 vs. untrained individuals. † P < 0.05 vs. quiet breathing.

Fig 7. Typical breathing patterns of classical singers and untrained individuals extracted using principal component analysis.

The group’s typical patterns are represented in the large axes, whereas patterns of individual participants are represented in small axes. Volume waveforms are shown with the corresponding Konno-Mead plots of RC and AB movements. The arrowheads in the Konno-Mead plots illustrate the time course, i.e. ascending and descending arrows correspond to inspiratory and expiratory phases, respectively. The start of expiration phase is marked in green both in the time plots and Konno-Mead plots. Note: The raw data shown in Fig 3 were recorded from classical singer #1 and untrained individual #4.