Date Published: May 9, 2016
Publisher: Public Library of Science
Author(s): Sauro Salomoni, Wolbert van den Hoorn, Paul Hodges, Charles R Larson.
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.
Breathing patterns during speaking and singing can differ from that during quiet breathing by modification of respiratory kinematics (i.e. movements of rib cage and abdomen) in response to altered task demands. Active control of breathing pattern affects the efficiency of the respiratory system and is considered essential in classical singing training for the development of optimal voice performance [1–4]. Experienced singers and teachers commonly refer to the use of abdominal muscle “support” to improve respiratory control and tone quality [4–7]. Although an agreed definition of the term “support” remains elusive [8,9], it is generally considered to involve enhanced abdominal muscle activation, which elevates intra-abdominal pressure and expands the rib cage, thus increasing the length and the pressure-generating capacity of the rib cage expiratory muscles . However, attempts to identify stereotypical patterns of respiratory kinematics in classically trained singers have been so far inconclusive [2,6,11,12], and it is unclear how the breathing pattern of classical singers differ from that of untrained individuals.
Acceptable repeatability was observed in all parameters assessed for tasks performed with and without the facemask (ICC > 0.75). This supports the absence of an effect of the facemask on breathing strategy and consistency of the measures between separate trials. No differences were found in the demographic data between groups (see Table 1, 1-way ANOVA–no effect for group: Classical vs. Control Mean(SD); age 41.9(18.2) vs. 33.7(8.8) years, F(1,9) = 0.68, p = 0.43; height 170.3(8.5) vs. 178.5(5.3) cm, F(1,8) = 2.87, p = 0.13; weight 70.0(12.7) vs. 70.5(9.3) kg, F(1,8) = 0.00, p = 0.95; BMI 23.9(2.4) vs. 22.0(1.6), F(1,8) = 1.59, p = 0.24). Fig 3 shows representative examples of raw data recorded from a typical participant in each group, together with the Konno-Mead plots, which represent the coordination between AB and RC movements in the x- and y-axis, respectively. Although there were no significant differences between groups for any parameter during quiet breathing (1-way ANOVA–no effect for group: all F(1,9) < 3.98, p > 0.08), breathing patterns during singing differed in several key aspects. During the two singing tasks, classical singers used a smaller percentage of RC contribution to lung volume than untrained individuals (Fig 4, F(1,9) > 28.87, p < 0.001). Classical singers also demonstrated greater positive phase angle and time shift between RC and AB (i.e. AB before RC, F(1,9) > 28.92, p < 0.001), as well as greater percentage of time and volume of RC in paradoxical motion (i.e. motion of RC in direction opposite to that expected for direction of airflow, Fig 5, F(1,9) > 7.6, p < 0.05) and greater percentage of AB volume in paradoxical motion (F(1,9) > 10.93, p < 0.01). As a consequence of these features, smaller correlation coefficients were found between RC and AB signals of classical singers than controls during singing (F(1,9) > 5.7, p < 0.05). During the singing of the standard piece (Waltzing Matilda), lower mean airflow and lower volume excursion were observed in classical singers than controls (Fig 6, F(1,8) > 8.9, p < 0.05), but there was no effect of group for these parameters when participants sang the piece of their choice. No significant differences were observed between the patterns of respiratory kinematics of untrained individuals and classical singers during quiet breathing, although there was a trend for greater abdominal contribution in singers than untrained individuals. In contrast, each group demonstrated distinct adaptations during singing tasks. Untrained individuals displayed minimal differences in the coordination between rib cage and abdominal movements with singing, which suggests similar respiratory patterns during both breathing and singing. Although there was some variation between participants, most classical singers demonstrated greater contribution of the abdomen to total lung volume than untrained individuals during singing tasks, and this was associated with pre-phonatory inward movements of the abdominal wall and a greater degree of independence in the movements of the rib cage and abdomen. This would increase the length and the pressure-generating capacity of rib cage expiratory muscles and elevate intra-abdominal pressure to improve the control of subglottal pressure during long utterances. These adaptations have been associated with changes in sound power spectrum and may have implications for voice quality, as commonly advocated by classical singing teachers and professionals. Source: http://doi.org/10.1371/journal.pone.0155084