Effects of Inhalatory Abdominal Wall Movement on Vertical Laryngeal Position during Phonation – Jenny Iwarsson Journal of Voice: Volume 15 No.3 2001 pp384 – 394
This study is perhaps useful to the singing community on a number of levels: Firstly it addresses the issue of ‘respiratory posturing’ (2001:384) and seeks to provide some definitional clarity as to the nature of these postures and their possible impact on voicing. According to Iwarsson (2001) the respiratory posture refers to the shape of the torso during the inhalation and subsequent phonation. ‘Belly in’ is where the abdominal wall is drawn in and ‘belly out’ is where the abdominal wall is brought ‘downward and outward’ (2001:385). Iwarsson (2001) argues that the belly in method results in the activation of rib cage muscles. With this method, the position ‘is usually accompanied by a highly domed shaped diaphragm and an elevated, outward rib cage wall positioning’ (2001:385). Conversely, the ‘belly out’ position is a result of a contraction of the diaphragm. It is assumed later on the study that this expansion enables the diaphragm to descend deeper into the torso.
Iwarsson (2001) considers the mechanical advantages of the two positions. She explores whether a thoracic breathing pattern optimizes the performance of the diaphragm. This position can be achieved by expanding the rib cage and keeping the abdomen constant. This according to Estenne et al (1990) facilitates the stretching of the muscle fibres of the diaphragm to an optimal length. She also cites Colton and Casper (1996) to emphasise the lack of scientific support for the claim that thoracic breathing is linked to voice problems.
According to Iwarsson the ‘abdomino-diaphragmatic type of breathing has been assumed to be associated with certain advantages.’ (2001:385). She cites Kotby (1995) when discussing the Accent Method and draws attention to a lack of evidence for this method at the time of this particular study. Kotby (1995) argues that ‘abdomen out’ allows for greater control and timing compared with upper thoracic breathing although according to Iwarsson (2001), there is no supporting evidence for this claim. In contrast, Estenne et al (1995) highlight the physiological advantages of thoracic breathing as the intercostal muscles are supplied by a larger number of muscle spindles.
This is itself is an interesting, unbiased and useful exploration of the two opposing methods bringing some definitional clarity to this controversial area and perhaps exposing some myths related to the controversial thoracic breathing pattern.
Although this information may prove to be illuminating, it was not the purpose of the study. ‘The aim of this investigation was to test the hypothesis that inhalation with an expanding abdominal wall induces a lower position of the larynx in the neck during the subsequent phonation, as compared to the paradoxical inward abdominal movement’ (386).
The lowering of the position of the larynx caused by an expanding abdominal wall is known as ‘tracheal pull’. This was first put forward by Zenker (1964) who asserts that during the inhalation, the diaphragm contracts and descends and this in turn creates a downward pull on the larynx due to the elastic structure of the trachea. This study sought to discover whether the ‘abdomen out’ condition affects the diaphragm and in turn results in the tracheal pull. It was thought that this might result in a lowering of the larynx. According to Iwarsson (2001) this may well be a specific aim of a singing teacher or clinical voice therapy. ‘A high position of the larynx is typically associated with a hyperfunctional voice source. Therefore, a lowering of a habitually elevated larynx is sometimes a specific goal in singing pedagogy as well as voice therapy.’ (2001:386).
The study examined 34 subjects, 17 males and 17 females and all subjects were healthy, non-smokers, non-singers and were unaware of the purpose of the study. They were all examined using a respiratory inductive plethysmograph. This consisted of a number of elastic transducers (respibands) with one placed around the subject’s rib cage and the lower respiband around the abdominal wall with its upper edge at the level of the navel. During the entire experiment, the subjects were in a standing position.
The results of the study were surprising ‘a clear effect of the inhalatory strategy was found: the abdomen-out condition was associated with a clearly higher position of the larynx in the neck as compared to the abdomen-in condition, thus contrary to the expectations based on the tracheal pull effect. Hence, the hypothesis that an expansion of the abdominal wall lowers the VLP by means of a greater tracheal pull, must be rejected.’ (2001:389)
A post-hoc experiment with six subjects after the experiment found that the impact of the posture resulted in a protruding chin with the abdomen out position. This happened in all six subjects and may explain the unexpected higher laryngeal position. According to Iwarsson (2001), this may be because expansion of the abdomen doesn’t result in tracheal pull or that competing forces caused by postural effects prevents the larynx from being lowered.
Perhaps this study challenges some of the myths surrounding thoracic and clavicular breathing as it does not advance any supporting evidence to demonstrate links to vocal harm. This was not the primary purpose of the study but it does raise interesting questions. The study was conducted in 2001 and I may discover some studies that prove this on my journey.
With regards to the nature of tracheal pull, the study has clear implications for voice therapy. In her earlier study Iwarsson et al (1998) explores Zenker (1964) a little further and she cites ‘a caudally directed force on the larynx widens the glottis and hence can be assumed to generate a mechanically abducted force component.’ (Zenker 1964:22) Tracheal pull could therefore be desirable where a client exhibits symptoms of a hyperfunctional voice because of the nature of the glottal abduction brought about by the tracheal pull. It could also be harnessed where a singer is presenting with a pressed tone. If a clear link between ‘abdomen-out’ breathing and the tracheal pull could be established then a clearer breathing strategy could be harnessed. This study was unable to establish this link perhaps due to postural effects.
Cited in Iwarsson
Colton RH, Casper JK. Understanding Voice Problems. A Physiological Perspective for Diagnosis and Treatment. 2nd ed. Baltimore, Md: Williams and Wilkins: 1996: 308 – 309
Estenne M, Zoochi L, Ward M, Macklem P Chest wall motion and expiratory muscle use during phonation in normal humans. J Appl Physiol. 1990;68 (5): 2075-2082.
Kotby MN. The Accent Method of Voice Therapy. San Diego, Calif: Singular Publishing Group, Inc: 1995; 39 -79.
Zenker W. (1964) Questions regarding the function of external laryngeal muscles. In: Brewer D, ed. Research Potentials in Voice Physiology. Syracuse, NY: State University if New York; 1964: 20 – 40.