Stavanger University College. School of Arts Education. N-4068 Stavanger, Norway
Introduction. Sporadic electromyographic (EMG) investigations have earlier been performed on classical singers (1-3). To further survey muscle activation levels and muscular patterns during inhalation and phonation, we have the last five years performed surface EMG recordings on primary and auxiliary breathing muscles of classical singers.
Material and Methods. Singers in their first or second year of conservatory study, advanced student singers and professional opera singers served as subjects. Muscle activity was recorded from the shoulder and neck region (the upper trapezius (TR), the stenocleidomastoideus (STM) and the scalenus muscles (SC), and the muscles in the posterior neck (PN)), and the trunk (the intercostals (INT), the lateral abdominal muscles (OBL) and the rectus abdominis muscle (RC)). In some studies EMG biofeedback (BF) was used to lower the activity in the TR and STM muscles, and the activity levels before and after BF were compared in the analyses.
1: In a study of the student singers, in their first or second year of conservatory study, it was discovered that during phonation, these students had higher EMG activity levels in TR than required by postural needs. BF was in this study shown to lower especially TR activity, but also, to some extent, STM activity (4).
2: Professional opera singers’ EMG activity was recorded from TR, STM, SC, PN, INT, OBL and RC. It was concluded that STM and SC showed correlated activity patterns during inhalation and phonation. Substantial muscle activity was observed at the PN site during inhalation and phonation. BF performed on TR and STM had a secondary effect of lowering EMG activity in SC and PN (5, 6), while INT, OBL and RC activity were not influenced by BF to TR and STM (7).
3. In a follow-up study of professional opera singers and advanced student singers, the phasing of TR activity to upper and lower thorax movement and to the phasing of activity in INT and OBL was investigated. A phasing of upper TR activity to INT and OBL activity was shown, all muscles supporting the expiration phase. The group results from both opera singers and student singers showed that TR EMG activity was significantly lowered after BF. Lowered TR activity resulted in an expanded upper TX circumference and less TX respiratory movement after BF. Thus, during phonation the upper TR contributed in the compression of upper TX, serving as an accessory muscle of expiration (8).
The main finding in these studies is that TR supports exhalation by classical singers. The high resolution of the recordings made the number of data points entered in the correlation analyses high (600-1000), thereby reaching statistical significance for quite low correlations. However, visual inspection of the EMG recordings confirmed that the TR, INT and OBL support exhalation and had a consistent activity pattern for the individual breaths, ensuring that the results are trustworthy (8).
The finding of relatively high neck and shoulder activity by the student singers, could be explained as lack of vocal technique in an early stage of their individual development (4). Nevertheless, this assumption was contradicted by a study on professional opera singers, showing activity peaks during inhalation and also high STM and SC activity during start of phonation (5). With non-singers, both muscles have been shown to support inhalation (9-12). With singers, the term “muscles of inhalation”, could be expanded from mainly the diaphragm (13) and the external intercostals (14) to include STM and SC. As the recruitment of these muscles was required during both inhalation and phonation, they could be included in the term “muscles of inhalation” by classical singers. When a balancing of the subglottal pressure during phonation is needed, the interplay in the upper trunk area would be between STM, SC and the upper external intercostal muscles, supporting inhalation forces, and the expiratory phased upper internal intercostals and TR supporting exhalation forces. Thus, the interplay between these muscles has for upper TX movement a similar function to the interplay between the lower external intercostals and the diaphragm vs. the lower internal intercostals and the abdominal muscles in the control of lower TX.
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