- Email: [email protected]
Aerobic Exercise as a Warm-up for Singing: Acoustic Impacts
ARTICLE IN PRESS Aerobic Exercise as a Warm-up for Singing: Acoustic Impacts *Monica A. McHenry and †Joseph Evans, *Valhalla, New York, and †Houston, Texas Summary: Objectives. In a previous work, it was found that a 30-minute aerobic workout significantly increased singers’ sound pressure level and airflow during voicing, suggesting a shift to flow phonation. This companion study was designed to assess the impact of the same workout on pitch accuracy, vibrato rate, extent and regularity, and the singing power ratio. Study Design. This study is a cohort experimental study. Methods. Twenty-two students in an academic vocal performance program participated. They performed an aerobic workout for 30 minutes. Before and after the workout, they sang the first seven notes of the “Star-Spangled Banner” on /pa/, producing seven /pa/s on the last note. The students then sang an ascending and descending scale to the ninth on “ah.” The following measures were obtained from the “Star-Spangled Banner”: pitch accuracy calculated on the seventh note (“by”); and vibrato rate, regularity, and extent, calculated on the most sustained sixth note (“see”). For the scale, the following measures were calculated from each note: pitch accuracy; vibrato rate, regularity, and extent; and the singing power ratio. Results. There were no significant differences from pre- to postworkout across any measures. Conclusions. It appears that an aerobic workout positively impacts the respiratory driving force for voice production but does little for phonation. Critical for performance is the fine tuning and balancing across the respiratory, laryngeal, and resonance systems. It appears that this can only be achieved with vocalization exercises, facilitating coordination within and across the physiological systems involved in the complex art of bel canto. Key Words: Vibrato–Singing power ratio–Pitch accuracy–Workout–Bel canto.
INTRODUCTION Warming up before any physical activity is typically recommended. Based on exercise physiology, a physical warm-up facilitates muscle contraction and relaxation speed, movement efficiency as a result of reduced viscous resistance in active muscles, oxygen delivery and use, nerve transmission, and blood flow.1 Applying these principles to vocal warm-up, Elliot et al2 speculate that increased blood flow in the laryngeal muscles would result in decreased vocal fold viscosity, enhancing effortless production. There are many detailed investigations of the ideal warm-up to optimize specific types of physical performance. One issue addressed is the specificity of the warm-up.3 Investigators stressed the importance of discipline-specific warm-ups, with a goal of preparing the muscles that could potentially limit performance. Another work focuses on the importance of warm-up to reduce muscle damage that may contribute to delayed-onset muscle soreness.4 These investigators also highlighted the importance of cool-down to increase circulation, facilitating the removal of cellular waste products resulting from exercise. Another aspect to be considered is the timing of the physical warm-up. As expected, longer elapsed times have a detrimental effect on performance, although this has only been studied Accepted for publication October 27, 2016. Presented at the 45th Annual Symposium: Care of the Professional Voice, June 5, 2016, Philadelphia, PA. From the *New York Medical College, Valhalla, New York; and the †School of Music, University of Houston, Houston, Texas. Address correspondence and reprint requests to Monica A. McHenry, Department of Speech-Language Pathology, New York Medical College, 30 Plaza West, Ste. 214, Valhalla, NY 10595. E-mail: [email protected] Journal of Voice, Vol. ■■, No. ■■, pp. ■■-■■ 0892-1997 © 2016 The Voice Foundation. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jvoice.2016.10.023
under limited conditions.5 All of the variables impacting the effectiveness of warm-up for a physical activity are relevant to vocal warm-ups as well. DeFatta and Sataloff6 emphasized the importance of individualization based on the singers’ Fächer, anticipated performance demands, individual response to warmup exercises, and general fitness level. These recommendations are, for the most part, based on knowledge of muscle physiology and anecdotal evidence, rather than on empirical data. One of the challenges in translating the exercise physiology literature to vocal hygiene is the complexity of the vocal fold tissues. Knowledge of muscle tissue is relevant to the body of the vocal folds, as well as the supporting musculature, but does not address the viscoelastic properties of the superficial layer, critical for effortless vocal fold vibration.7 Subtle details of the investigations drastically impact the interpretation of results. For example, Sandage et al7 measured phonatory threshold pressure immediately after completion of submaximal exercise, whereas in a previous work, we obtained aerodynamic measures only after rest, hydration, and a return to resting pulse rate.8 Finally, a much neglected consideration in optimizing performance and minimizing delayed negative effects of performance is coolingdown vs vocal rest. Gottliebson9 found that a systematic cooldown routine resulted in reported improved vocal function compared to vocal rest or conversation. The cool-down consisted of glides, arpeggios, and humming, designed to return to an optimal pitch for speech. It was difficult to determine the source of the reported benefit. The author speculated that cooling down could have increased awareness of optimal resonance, or may simply have been a psychological benefit. In a previous work on the delayed effect of performance, we found a benefit of vocal rest.10 Specifically, individuals who did not sing in a choir on the morning after performing demonstrated better vocal function
ARTICLE IN PRESS 2 than those who did. It is clear that both warm-up and cooldown exercises warrant further investigation, specifically regarding their impact on vocal performance. Warming up before vocal performance is considered standard practice. Students learn warm-up strategies in voice lessons, and customize and adapt the most beneficial for regular practice. Typically, singers complete vocal exercises to prepare for performance. The majority of singers report some sort of warmup, although its duration varies markedly.11 Anecdotally, the greatest warm-up challenge appears to be for individuals with higher Fächer who were required to perform early in the morning, such as at a church service. Preparation for such a performance requires more extensive vocalization because of the typically increased mass of the vocal folds in the morning secondary to fluid accumulation in the superficial layer. A number of years ago, Titze12 detailed the specific physiological benefits of what he considered to be the five best vocal warm-up exercises. These exercises are ideally designed to prepare for bel canto. Bel canto is a term used to describe a style of classical singing characterized by a well-rounded tone with very smooth and effortless productions throughout the vocal range, with no evidence of register shifts.13,14 In the first recommended exercise, semi-occluded vocal tract exercises optimize vocal fold configuration and lowered phonation threshold pressure. Twooctave pitch glides stretch the vocal folds and optimized the interaction between the thyroarytenoid and cricothyroid muscles, facilitating the negotiation of passaggio, a key component of bel canto. Vowel sequence /a/-/i/ scales loosen the tongue and jaw. Messa di voce serves to coordinate laryngeal musculature with changing lung pressure. Finally, staccato on arpeggios establishes an ideal vocal onset. Vocalization exercises are focused on preparing and coordinating the respiratory and laryngeal systems for the exacting requirements of performances in the genre of bel canto. They do not, however, engage the entire body in the warm-up. In previous work, it was speculated that a physical, aerobic warm-up may prove as beneficial as a purely vocal warm-up.8 The reader is referred to the previous study8 for more details on the benefits of both vocal and aerobic warm-up strategies. The earlier findings focused on the aerodynamic contributions to voice production. Sixteen graduate and six undergraduate students completed a 30-minute treadmill workout in their aerobic heart rate range. Aerodynamic data were collected before and after the warm-up. It was found that the workout significantly increased mean sound pressure level and mean airflow during voicing, suggesting a shift to flow phonation, or an optimization of airflow. It is recognized that simply increasing airflow in isolation can lead to a weak, breathy production. The interpretation of the presence of flow phonation was based on the concomitant increase in mean sound pressure level, which may have reflected not only increased airflow but also an optimization of vocal tract configuration.15 It was concluded that an aerobic workout had beneficial effects on the aerodynamics of voice production. The present work represents an acoustic analysis of the samples obtained pre- and postworkout. It was hypothesized that singers would improve in the following: pitch accuracy; vibrato rate, extent and regularity; and the singing power ratio (SPR).
Journal of Voice, Vol. ■■, No. ■■, 2016
METHODS The study was approved by the Institutional Review Board, and all participants completed a consent form. Singers were assessed after having been awake for at least two hours, with minimal voice use. Before aerobic exercise, their resting heart rate was established. Maximum heart rate was calculated as 220 − age. Finally, the target aerobic heart rate was calculated as 60%–80% of their maximum heart rate. Participants Twenty-two students in an academic vocal performance program participated. There were 16 graduate and six undergraduate students. Voice types were 11 sopranos, 1 mezzo soprano, 5 tenors, 2 bass-baritones, and 3 baritones. Ages ranged from 18 to 38 years, with a mean of 24 years. Fitness levels were obtained using the NASA Physical Activity Scale, shown to be moderately well correlated with objectively measured physical activity values.16 Reported fitness levels were highly varied, ranging from 0 (avoid walking or exertion) to 8 (running 16–20 mi/wk or walking 21–26 mi/wk or spending 6–8 h/wk in comparable physical activity). The mean activity level across all participants was 6.1 (standard deviation [SD] = 1.8). A rating of 6 represents running 6–10 mi/wk, walking 7–13 mi/wk, or spending 1–3 h/wk in comparable physical activity, suggesting that the majority of singers were relatively active. Tasks Before the aerobic workout, the participants wore a mask attached to a pneumotachograph to capture airflow, with a pressure sensing catheter placed behind the lips to capture intraoral air pressure (Phonatory Aerodynamic System, PENTAX Medical, Montvale, New Jersey, USA). The participants then sang the first seven notes of the “Star-Spangled Banner” (SSB) on /pa/, in a key appropriate for their Fächer. The singers produced a syllable train of seven /pa/s on the seventh note of the SSB. They repeated the abbreviated SSB three times. They then sang an ascending and descending scale to the ninth on “ah,” again in an appropriate key, recorded in a quiet room on an iPad (Apple, Cupertino, California, USA). For the scale, the singers were given only the starting pitch and were not accompanied further. After initial data acquisition, the singers’ pulse rates were monitored as they walked or ran on a treadmill. The treadmill speed was adjusted as needed to maintain the target heart rate range for 30 minutes. After completion of the workout, the singers drank ½ L of water. When the singers’ heart rates had returned to their preworkout level, data acquisition was repeated. Data analysis The audio recording of the SSB /pa/ productions were analyzed using Praat.17 Pitch accuracy was obtained from the second of three trials, and was averaged across the second through sixth repetitions of the seventh highest note. Pitch accuracy was determined by comparing the target fundamental frequency with the singer’s actual fundamental frequency, and converting the hertz difference to semitones. All measures of vibrato were obtained from the sixth note (“see”) in the second trial, because the singers sustained that note longer than they did the repeated
ARTICLE IN PRESS Monica A. McHenry and Joseph Evans
Impact of Aerobic Exercise as a Warm-Up for Singing
/pa/ productions of the seventh note. Vibrato rate was determined by counting the number of vibrato cycles in the stable portion of the vowel and dividing by time in seconds. Vibrato regularity was determined by obtaining the SD of each period of vibrato in the stable portion of the vowel. Vibrato extent was calculated by determining the lowest and highest frequencies in a vibrato cycle and converting those values to a semitone extent. Pre- and postvibrato data were not obtained if the singer produced a straight tone in either condition. Two singers were eliminated because of straight tone production. The ascending and descending scale to the ninth was obtained for only 10 singers because of technical problems. Pitch accuracy and vibrato rate, extent, and regularity were obtained for each note in the scale as described earlier. Additionally, the SPR18 was determined by subjecting each note to a spectral analysis. The difference in the highest amplitude from 0 to 2000 Hz and the highest amplitude from 2000 to 4000 Hz was calculated. The values were averaged across all notes in the scale. All data were subjected to a paired t test to compare pre- and postworkout values. Because there were nine comparisons of interest, the Bonferroni correction was applied to an alpha level of .05. To be significant, a p value of .006 was required. Intrajudge reliability Reliability was determined by remeasuring all data for a male and a female participant. Reliability data were averaged across participants and pre- and postconditions. Differences between original and repeated measures were SSB pitch accuracy = .17 semitones, SSB vibrato rate = .09 cycles/second, SSB vibrato variability = .001 second, SSB vibrato extent = .07 semitones, scale pitch accuracy = .008 semitones, scale vibrato rate = .001 cycles/ second, scale vibrato variability = .002 second, scale vibrato extent = .02 semitones, and scale SPR = .5. RESULTS Pitch accuracy for the SSB was calculated based on the difference (above or below) from the target note to the actual note on the seventh note (ie, “by”). The values in hertz were converted to semitones. The mean pitch accuracies were −.13 (SD = .4) preworkout and −.23 (SD = .4) post workout. There was no significant difference (t = 2.1, df = 20; p = 0.29). Ten participants were less accurate post workout by more than .1 semitone; six were within .1 semitone pre- to post workout; and five were better post workout by more than .1 semitone. Pitch accuracy for the scale was determined for 10 singers and was calculated for each note in the ascending and descending scale to the ninth. The differences in semitones between the actual and target pitches were calculated. The individual differences of all notes across singers were input for statistical analysis. The mean pitch differences were −.32 (SD = .47) preworkout and −.29 (SD = .57) post workout. There was no significant difference (t = −.5, df = 162, p = 0.57). Inspection of the means for each singer revealed the following patterns pre- to post workout: five became more flat in pitch, one became less flat, three moved from flat to slightly sharp, and one moved from sharp to flat. It should be noted that target accuracies were not uniform across notes, although there was a tendency for singers who were flat
3
to be so across notes. Although one might expect the greatest difference in the highest note of the scale, often the greatest differences occurred earlier in the ascending scale, with the highest note typically the most accurate. The vibrato rate for the SSB was calculated based on the most sustained sixth note (ie, “see”). The mean vibrato rate both preand post workout was 5.7 (preworkout SD = .8, post workout SD = .5). There was no significant difference (t = 2.1, df = 18, p = 0.51). Three singers, who demonstrated what would be considered a slow vibrato rate, increased it to a more appropriate rate. These values in vibrato cycles per second were 4.6–5.5, 4.1–5.3, and 4.9–6.3, moving to within the optimal vibrato range.19 Vibrato regularity for the sustained sixth note of the SSB was calculated by determining the SD of the period of each vibrato cycle. The mean vibrato regularities were .015 (SD = .008) preworkout and .012 (SD = .009) post workout. There was no significant difference (t = 2.1, df = 18, p = 0.41). For seven individuals, the vibrato rate became more regular, four by .01, and three by .02. Vibrato regularity for seven individuals was unchanged, whereas four singers demonstrated increased irregularity by .01 and one increased by .02. The vibrato extent for the SSB was calculated by determining the lowest and highest frequencies in a cycle of vibrato, and converting this value to semitones. The mean vibrato extent preworkout was 2.3 (SD = .9) and post workout was 2.4 (SD = 1.0). The vibrato extent is greater than ideal (roughly one semitone around the target pitch18) and may reflect overdriving in response to singing while wearing a mask over the nose and mouth. There was no significant difference in the pre- to postworkout values (t = .69, df = 12, p = 0.5). The vibrato rate for the scale, averaged across notes, was 5.6 for both pre- and post workout. There was no significant difference (t = .2, df = 9, p = 0.8). Vibrato regularities, averaged across notes, were .04 preworkout (SD = .1) and .001 post workout (SD = .004). There was no significant difference in the pre- to postworkout values (t = .99, df = 9, p = 0.4). Vibrato extents for the scale, averaged across notes, were 1.3 preworkout (SD = .6) and 1.6 post workout (SD = .4). This difference approached significance (t = 2.5, df = 9, p = 0.04). It should be noted that the difference was due to some extent to three singers producing straight tones in the preworkout condition. Two singers decreased vibrato extent in the post condition, but did so only slightly. The SPR was calculated only for the scale because of the presence of the mask during the SSB condition. The pre-SPR was 19.4 (SD = 6.9), whereas the post-SPR was 17.0 (SD = 7.6). This difference was not significant (t = 2.2; df = 9; p = 0.06). Because there were virtually no significant acoustic differences before and after the workout, and the majority of singers exercised frequently, there was no attempt to relate physical fitness to vocal performance. DISCUSSION The present study was designed to expand previous work3 that demonstrated positive vocal and respiratory changes with an aerobic workout. In the earlier work, singers demonstrated a significantly increased sound pressure level, and as an important
ARTICLE IN PRESS 4 concomitant, increased airflow during voicing. It appears, however, that improvements with exercise are limited to aerodynamic changes. In the present work, singers overall showed virtually no improvement in target pitch accuracy, vibrato rate, extent, and regularity, and the SPR. Some individual changes are of interest nonetheless. Our findings for three individuals demonstrated a normalization of the vibrato rate from slow to within normal limits, comparable to changes noted by Moorecroft and Kenny.20 It is possible that the aerobic workout increased activation across their physiological systems, an effect that has also been achieved by vocalization alone.5 In an earlier work,21 the effects of a vocal warm-up in isolation were compared with a vocal warm-up combined with a 5-minute workout in an aerobic heart rate range. Participants were nonsingers, however, and the vocal warm-up was one designed to prepare actors for the stage. Thus, measures critical for singers such as pitch accuracy and features of vibrato were not obtained. Nonetheless, it was found that a combined approach reduced phonation threshold pressure and decreased noise in the voice (ie, jitter and noise-to-harmonics ratio). Thus, a warmup strategy that combines vocalization with an aerobic workout remains appealing. CONCLUSIONS It appears that an aerobic workout positively impacts the respiratory driving force for voice production. The singer has an easier time generating increased airflow during voicing, resulting in a healthy increase in sound pressure level. This is especially crucial for classical opera and concert singers, who are required to perform without amplification or sound enhancement in large theaters with full orchestras. An aerobic workout has been shown to reduce phonation threshold pressure, but this is a relatively isolated physiological change in the vocal fold tissues. Although there are clear aerodynamic benefits, data from the current work demonstrate that a purely aerobic workout is not adequate to prepare the voice for classical performance. The vocal loads sustained during successful projection with orchestral accompaniment necessitate careful preparation. Exercises designed for vocal fold flexibility at very full amplitudes and sustained pitches at the extremes of the range are essential both for immediate bel canto vocalism and for rapid recovery and continued vocal health after such performances. Critical for performance is the fine tuning and balancing across the respiratory, laryngeal, and resonance systems. It appears that these can only be achieved with vocalization
Journal of Voice, Vol. ■■, No. ■■, 2016
exercises, facilitating coordination within and across the physiological systems12 involved in the complex art of bel canto. REFERENCES 1. McArdle WD, Katch FL, Katch VL. Exercise Physiology. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2001:575. 2. Elliot N, Sundberg J, Gramming P. What happens during vocal warm-up? J Voice. 1995;9:37–44. 3. Sanders A, Keiner M, Schlumberger A, et al. Effects of functional exercises in the warm-up on sprint performances. J Strength Cond Res. 2013;27:995– 1001. 4. Olsen O, Sjøhaug M, van Beekvelt M, et al. The effect of warm-up and cool-down exercise on delayed onset muscle soreness in the quadriceps muscle: a randomized controlled trial. J Hum Kinet. 2012;35:59–68. 5. Spitz MG, Wenefick RW, Mitchell JB. The effects of elapsed time after warm-up on subsequent exercise performance in a cold environment. J Strength Cond Res. 2014;28:1351–1357. 6. DeFatta RA, Sataloff RT. The valuye of vocal warm-up and cool-down exercises. Questions and controversies. J Singing. 2012;69:173–175. 7. Sandage MJ, Connor NP, Pascoe D. Voice function differences following resting breathing versus submaximal exercise. J Voice. 2013;27:572– 578. 8. McHenry M, Evans J. Aerobic exercise as a warm-up for singing: aerodynamic changes. J Voice. 2015;doi:10.1016/j.jvoice.2015.08.011. [Epub ahead of print]. Retrieved 4/1/16. 9. Gottliebson RO. Efficacy of cool-down exercises in the practice regimen of elite singers [doctoral dissertation]. Cincinnati, OH: University of Cincinnati; 2011. 10. McHenry MA, Evans J, Powitzky E. Vocal assessment before, after, and the day after opera performance. J Voice. 2015;30:186–191. 11. Gish A, Kuncuk M, Sims L, et al. Vocal warm-up practices and perceptions in vocalists: a pilot survey. J Voice. 2012;26:e1–e10. doi:10.1016/ j.voice.2010.10.005. Retrieved 7/1/2014. 12. Titze IR. Voice research: the five best vocal warm-up exercises. J Singing. 2001;57:51–52. 13. Tommasini A. Bel canto: audiences love it, but what is it? New York Times, Nov 28, 2008:AR22. 14. Lani J. Bel canto and the art of singing. Opera J. 2003;36:3–36. 15. Titze I. On flow phonation and airflow management. J Singing. 2015;72:57– 58. 16. Sieminski DJ, Cowell LL, Montgomery PS, et al. Physical activity monitoring in patients with peripheral arterial occlusive disease. J Cardiopulm Rehabil. 1997;17:43–47. 17. Boersma P, Weenink D. Praat: Doing phonetics by computer (Version 5.3.35). Amsterdam, ND: U Amsterdam. Available at: http://www.fon.hum.uva.nl/ praat. Accessed December 8, 2012. 18. Omori K, Ashutosh K, Carroll L, et al. Singing power ratio: quantitative evaluation of singing voice quality. J Voice. 1996;10:228–235. 19. Isherwood N. Vocal vibrato: new directions. J Singing. 2009;65:71–283. 20. Moorecroft L, Kenny DT. Vocal warm-up produced acoustic change in singers’ vibrato rate. J Voice. 2012;26:667, e13-8. doi:10.1016/j.voice .2011.10.007. Retrieved 7/5/2014. 21. McHenry M, Johnson J, Foshea B. The effect of specific versus combined warm-up strategies on the voice. J Voice. 2009;23:572–576.
INTRODUCTION Warming up before any physical activity is typically recommended. Based on exercise physiology, a physical warm-up facilitates muscle contraction and relaxation speed, movement efficiency as a result of reduced viscous resistance in active muscles, oxygen delivery and use, nerve transmission, and blood flow.1 Applying these principles to vocal warm-up, Elliot et al2 speculate that increased blood flow in the laryngeal muscles would result in decreased vocal fold viscosity, enhancing effortless production. There are many detailed investigations of the ideal warm-up to optimize specific types of physical performance. One issue addressed is the specificity of the warm-up.3 Investigators stressed the importance of discipline-specific warm-ups, with a goal of preparing the muscles that could potentially limit performance. Another work focuses on the importance of warm-up to reduce muscle damage that may contribute to delayed-onset muscle soreness.4 These investigators also highlighted the importance of cool-down to increase circulation, facilitating the removal of cellular waste products resulting from exercise. Another aspect to be considered is the timing of the physical warm-up. As expected, longer elapsed times have a detrimental effect on performance, although this has only been studied Accepted for publication October 27, 2016. Presented at the 45th Annual Symposium: Care of the Professional Voice, June 5, 2016, Philadelphia, PA. From the *New York Medical College, Valhalla, New York; and the †School of Music, University of Houston, Houston, Texas. Address correspondence and reprint requests to Monica A. McHenry, Department of Speech-Language Pathology, New York Medical College, 30 Plaza West, Ste. 214, Valhalla, NY 10595. E-mail: [email protected] Journal of Voice, Vol. ■■, No. ■■, pp. ■■-■■ 0892-1997 © 2016 The Voice Foundation. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jvoice.2016.10.023
under limited conditions.5 All of the variables impacting the effectiveness of warm-up for a physical activity are relevant to vocal warm-ups as well. DeFatta and Sataloff6 emphasized the importance of individualization based on the singers’ Fächer, anticipated performance demands, individual response to warmup exercises, and general fitness level. These recommendations are, for the most part, based on knowledge of muscle physiology and anecdotal evidence, rather than on empirical data. One of the challenges in translating the exercise physiology literature to vocal hygiene is the complexity of the vocal fold tissues. Knowledge of muscle tissue is relevant to the body of the vocal folds, as well as the supporting musculature, but does not address the viscoelastic properties of the superficial layer, critical for effortless vocal fold vibration.7 Subtle details of the investigations drastically impact the interpretation of results. For example, Sandage et al7 measured phonatory threshold pressure immediately after completion of submaximal exercise, whereas in a previous work, we obtained aerodynamic measures only after rest, hydration, and a return to resting pulse rate.8 Finally, a much neglected consideration in optimizing performance and minimizing delayed negative effects of performance is coolingdown vs vocal rest. Gottliebson9 found that a systematic cooldown routine resulted in reported improved vocal function compared to vocal rest or conversation. The cool-down consisted of glides, arpeggios, and humming, designed to return to an optimal pitch for speech. It was difficult to determine the source of the reported benefit. The author speculated that cooling down could have increased awareness of optimal resonance, or may simply have been a psychological benefit. In a previous work on the delayed effect of performance, we found a benefit of vocal rest.10 Specifically, individuals who did not sing in a choir on the morning after performing demonstrated better vocal function
ARTICLE IN PRESS 2 than those who did. It is clear that both warm-up and cooldown exercises warrant further investigation, specifically regarding their impact on vocal performance. Warming up before vocal performance is considered standard practice. Students learn warm-up strategies in voice lessons, and customize and adapt the most beneficial for regular practice. Typically, singers complete vocal exercises to prepare for performance. The majority of singers report some sort of warmup, although its duration varies markedly.11 Anecdotally, the greatest warm-up challenge appears to be for individuals with higher Fächer who were required to perform early in the morning, such as at a church service. Preparation for such a performance requires more extensive vocalization because of the typically increased mass of the vocal folds in the morning secondary to fluid accumulation in the superficial layer. A number of years ago, Titze12 detailed the specific physiological benefits of what he considered to be the five best vocal warm-up exercises. These exercises are ideally designed to prepare for bel canto. Bel canto is a term used to describe a style of classical singing characterized by a well-rounded tone with very smooth and effortless productions throughout the vocal range, with no evidence of register shifts.13,14 In the first recommended exercise, semi-occluded vocal tract exercises optimize vocal fold configuration and lowered phonation threshold pressure. Twooctave pitch glides stretch the vocal folds and optimized the interaction between the thyroarytenoid and cricothyroid muscles, facilitating the negotiation of passaggio, a key component of bel canto. Vowel sequence /a/-/i/ scales loosen the tongue and jaw. Messa di voce serves to coordinate laryngeal musculature with changing lung pressure. Finally, staccato on arpeggios establishes an ideal vocal onset. Vocalization exercises are focused on preparing and coordinating the respiratory and laryngeal systems for the exacting requirements of performances in the genre of bel canto. They do not, however, engage the entire body in the warm-up. In previous work, it was speculated that a physical, aerobic warm-up may prove as beneficial as a purely vocal warm-up.8 The reader is referred to the previous study8 for more details on the benefits of both vocal and aerobic warm-up strategies. The earlier findings focused on the aerodynamic contributions to voice production. Sixteen graduate and six undergraduate students completed a 30-minute treadmill workout in their aerobic heart rate range. Aerodynamic data were collected before and after the warm-up. It was found that the workout significantly increased mean sound pressure level and mean airflow during voicing, suggesting a shift to flow phonation, or an optimization of airflow. It is recognized that simply increasing airflow in isolation can lead to a weak, breathy production. The interpretation of the presence of flow phonation was based on the concomitant increase in mean sound pressure level, which may have reflected not only increased airflow but also an optimization of vocal tract configuration.15 It was concluded that an aerobic workout had beneficial effects on the aerodynamics of voice production. The present work represents an acoustic analysis of the samples obtained pre- and postworkout. It was hypothesized that singers would improve in the following: pitch accuracy; vibrato rate, extent and regularity; and the singing power ratio (SPR).
Journal of Voice, Vol. ■■, No. ■■, 2016
METHODS The study was approved by the Institutional Review Board, and all participants completed a consent form. Singers were assessed after having been awake for at least two hours, with minimal voice use. Before aerobic exercise, their resting heart rate was established. Maximum heart rate was calculated as 220 − age. Finally, the target aerobic heart rate was calculated as 60%–80% of their maximum heart rate. Participants Twenty-two students in an academic vocal performance program participated. There were 16 graduate and six undergraduate students. Voice types were 11 sopranos, 1 mezzo soprano, 5 tenors, 2 bass-baritones, and 3 baritones. Ages ranged from 18 to 38 years, with a mean of 24 years. Fitness levels were obtained using the NASA Physical Activity Scale, shown to be moderately well correlated with objectively measured physical activity values.16 Reported fitness levels were highly varied, ranging from 0 (avoid walking or exertion) to 8 (running 16–20 mi/wk or walking 21–26 mi/wk or spending 6–8 h/wk in comparable physical activity). The mean activity level across all participants was 6.1 (standard deviation [SD] = 1.8). A rating of 6 represents running 6–10 mi/wk, walking 7–13 mi/wk, or spending 1–3 h/wk in comparable physical activity, suggesting that the majority of singers were relatively active. Tasks Before the aerobic workout, the participants wore a mask attached to a pneumotachograph to capture airflow, with a pressure sensing catheter placed behind the lips to capture intraoral air pressure (Phonatory Aerodynamic System, PENTAX Medical, Montvale, New Jersey, USA). The participants then sang the first seven notes of the “Star-Spangled Banner” (SSB) on /pa/, in a key appropriate for their Fächer. The singers produced a syllable train of seven /pa/s on the seventh note of the SSB. They repeated the abbreviated SSB three times. They then sang an ascending and descending scale to the ninth on “ah,” again in an appropriate key, recorded in a quiet room on an iPad (Apple, Cupertino, California, USA). For the scale, the singers were given only the starting pitch and were not accompanied further. After initial data acquisition, the singers’ pulse rates were monitored as they walked or ran on a treadmill. The treadmill speed was adjusted as needed to maintain the target heart rate range for 30 minutes. After completion of the workout, the singers drank ½ L of water. When the singers’ heart rates had returned to their preworkout level, data acquisition was repeated. Data analysis The audio recording of the SSB /pa/ productions were analyzed using Praat.17 Pitch accuracy was obtained from the second of three trials, and was averaged across the second through sixth repetitions of the seventh highest note. Pitch accuracy was determined by comparing the target fundamental frequency with the singer’s actual fundamental frequency, and converting the hertz difference to semitones. All measures of vibrato were obtained from the sixth note (“see”) in the second trial, because the singers sustained that note longer than they did the repeated
ARTICLE IN PRESS Monica A. McHenry and Joseph Evans
Impact of Aerobic Exercise as a Warm-Up for Singing
/pa/ productions of the seventh note. Vibrato rate was determined by counting the number of vibrato cycles in the stable portion of the vowel and dividing by time in seconds. Vibrato regularity was determined by obtaining the SD of each period of vibrato in the stable portion of the vowel. Vibrato extent was calculated by determining the lowest and highest frequencies in a vibrato cycle and converting those values to a semitone extent. Pre- and postvibrato data were not obtained if the singer produced a straight tone in either condition. Two singers were eliminated because of straight tone production. The ascending and descending scale to the ninth was obtained for only 10 singers because of technical problems. Pitch accuracy and vibrato rate, extent, and regularity were obtained for each note in the scale as described earlier. Additionally, the SPR18 was determined by subjecting each note to a spectral analysis. The difference in the highest amplitude from 0 to 2000 Hz and the highest amplitude from 2000 to 4000 Hz was calculated. The values were averaged across all notes in the scale. All data were subjected to a paired t test to compare pre- and postworkout values. Because there were nine comparisons of interest, the Bonferroni correction was applied to an alpha level of .05. To be significant, a p value of .006 was required. Intrajudge reliability Reliability was determined by remeasuring all data for a male and a female participant. Reliability data were averaged across participants and pre- and postconditions. Differences between original and repeated measures were SSB pitch accuracy = .17 semitones, SSB vibrato rate = .09 cycles/second, SSB vibrato variability = .001 second, SSB vibrato extent = .07 semitones, scale pitch accuracy = .008 semitones, scale vibrato rate = .001 cycles/ second, scale vibrato variability = .002 second, scale vibrato extent = .02 semitones, and scale SPR = .5. RESULTS Pitch accuracy for the SSB was calculated based on the difference (above or below) from the target note to the actual note on the seventh note (ie, “by”). The values in hertz were converted to semitones. The mean pitch accuracies were −.13 (SD = .4) preworkout and −.23 (SD = .4) post workout. There was no significant difference (t = 2.1, df = 20; p = 0.29). Ten participants were less accurate post workout by more than .1 semitone; six were within .1 semitone pre- to post workout; and five were better post workout by more than .1 semitone. Pitch accuracy for the scale was determined for 10 singers and was calculated for each note in the ascending and descending scale to the ninth. The differences in semitones between the actual and target pitches were calculated. The individual differences of all notes across singers were input for statistical analysis. The mean pitch differences were −.32 (SD = .47) preworkout and −.29 (SD = .57) post workout. There was no significant difference (t = −.5, df = 162, p = 0.57). Inspection of the means for each singer revealed the following patterns pre- to post workout: five became more flat in pitch, one became less flat, three moved from flat to slightly sharp, and one moved from sharp to flat. It should be noted that target accuracies were not uniform across notes, although there was a tendency for singers who were flat
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to be so across notes. Although one might expect the greatest difference in the highest note of the scale, often the greatest differences occurred earlier in the ascending scale, with the highest note typically the most accurate. The vibrato rate for the SSB was calculated based on the most sustained sixth note (ie, “see”). The mean vibrato rate both preand post workout was 5.7 (preworkout SD = .8, post workout SD = .5). There was no significant difference (t = 2.1, df = 18, p = 0.51). Three singers, who demonstrated what would be considered a slow vibrato rate, increased it to a more appropriate rate. These values in vibrato cycles per second were 4.6–5.5, 4.1–5.3, and 4.9–6.3, moving to within the optimal vibrato range.19 Vibrato regularity for the sustained sixth note of the SSB was calculated by determining the SD of the period of each vibrato cycle. The mean vibrato regularities were .015 (SD = .008) preworkout and .012 (SD = .009) post workout. There was no significant difference (t = 2.1, df = 18, p = 0.41). For seven individuals, the vibrato rate became more regular, four by .01, and three by .02. Vibrato regularity for seven individuals was unchanged, whereas four singers demonstrated increased irregularity by .01 and one increased by .02. The vibrato extent for the SSB was calculated by determining the lowest and highest frequencies in a cycle of vibrato, and converting this value to semitones. The mean vibrato extent preworkout was 2.3 (SD = .9) and post workout was 2.4 (SD = 1.0). The vibrato extent is greater than ideal (roughly one semitone around the target pitch18) and may reflect overdriving in response to singing while wearing a mask over the nose and mouth. There was no significant difference in the pre- to postworkout values (t = .69, df = 12, p = 0.5). The vibrato rate for the scale, averaged across notes, was 5.6 for both pre- and post workout. There was no significant difference (t = .2, df = 9, p = 0.8). Vibrato regularities, averaged across notes, were .04 preworkout (SD = .1) and .001 post workout (SD = .004). There was no significant difference in the pre- to postworkout values (t = .99, df = 9, p = 0.4). Vibrato extents for the scale, averaged across notes, were 1.3 preworkout (SD = .6) and 1.6 post workout (SD = .4). This difference approached significance (t = 2.5, df = 9, p = 0.04). It should be noted that the difference was due to some extent to three singers producing straight tones in the preworkout condition. Two singers decreased vibrato extent in the post condition, but did so only slightly. The SPR was calculated only for the scale because of the presence of the mask during the SSB condition. The pre-SPR was 19.4 (SD = 6.9), whereas the post-SPR was 17.0 (SD = 7.6). This difference was not significant (t = 2.2; df = 9; p = 0.06). Because there were virtually no significant acoustic differences before and after the workout, and the majority of singers exercised frequently, there was no attempt to relate physical fitness to vocal performance. DISCUSSION The present study was designed to expand previous work3 that demonstrated positive vocal and respiratory changes with an aerobic workout. In the earlier work, singers demonstrated a significantly increased sound pressure level, and as an important
ARTICLE IN PRESS 4 concomitant, increased airflow during voicing. It appears, however, that improvements with exercise are limited to aerodynamic changes. In the present work, singers overall showed virtually no improvement in target pitch accuracy, vibrato rate, extent, and regularity, and the SPR. Some individual changes are of interest nonetheless. Our findings for three individuals demonstrated a normalization of the vibrato rate from slow to within normal limits, comparable to changes noted by Moorecroft and Kenny.20 It is possible that the aerobic workout increased activation across their physiological systems, an effect that has also been achieved by vocalization alone.5 In an earlier work,21 the effects of a vocal warm-up in isolation were compared with a vocal warm-up combined with a 5-minute workout in an aerobic heart rate range. Participants were nonsingers, however, and the vocal warm-up was one designed to prepare actors for the stage. Thus, measures critical for singers such as pitch accuracy and features of vibrato were not obtained. Nonetheless, it was found that a combined approach reduced phonation threshold pressure and decreased noise in the voice (ie, jitter and noise-to-harmonics ratio). Thus, a warmup strategy that combines vocalization with an aerobic workout remains appealing. CONCLUSIONS It appears that an aerobic workout positively impacts the respiratory driving force for voice production. The singer has an easier time generating increased airflow during voicing, resulting in a healthy increase in sound pressure level. This is especially crucial for classical opera and concert singers, who are required to perform without amplification or sound enhancement in large theaters with full orchestras. An aerobic workout has been shown to reduce phonation threshold pressure, but this is a relatively isolated physiological change in the vocal fold tissues. Although there are clear aerodynamic benefits, data from the current work demonstrate that a purely aerobic workout is not adequate to prepare the voice for classical performance. The vocal loads sustained during successful projection with orchestral accompaniment necessitate careful preparation. Exercises designed for vocal fold flexibility at very full amplitudes and sustained pitches at the extremes of the range are essential both for immediate bel canto vocalism and for rapid recovery and continued vocal health after such performances. Critical for performance is the fine tuning and balancing across the respiratory, laryngeal, and resonance systems. It appears that these can only be achieved with vocalization
Journal of Voice, Vol. ■■, No. ■■, 2016
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