Abstract
Objectives:
Previously, yoga volitional breathing with low inspiration to expiration ratios (i/e) (as in bhramari pranayama) improved cognition and reduced state anxiety. This study compared the effects of low, high and equal i/e ratio breathing on affect and attention.
Material and Methods:
Affect, vigor and attention were assessed in forty healthy participants (group mean age± SD; 22.58±3.83; M:F= 2.33:1) while breathing with three different i/e regulated by a visual metronome on separate days viz., (i) low i/e (28:72), (ii) equal i/e (50:50), (iii) high i/e (72:28) compared to control, without conscious breath modification. Assessments were: (i) brief mood introspection scale (BMIS), (ii) global vigor and affect scale (GVAS), (iii) Spielberger's state trait anxiety inventory-state (STAI-S) and a six letter cancellation test to assess sustained attention. Data were analyzed with repeated measures analysis of variance with Bonferroni adjusted post-hoc tests.
Results:
Pleasant feelings increased after low and equal i/e. Low i/e also increased positive feelings whereas equal i/e decreased scores in the cancellation test for sustained attention. All three breathing practices and the control session decreased state anxiety and increased vigor. High i/e breathing alone did not decrease negative feelings. For all the breath ratios the breath frequency cue was set at twelve breaths per minute.
Conclusion:
In summary, varying breath phase ratios influenced positive and pleasant feelings but did not influence state anxiety or vigor. Understanding the mechanisms underlying the findings would be improved with concurrent physiological assessments.
Keywords: Affect, attention, varying inspiration to expiration durations, vigor
Introduction
Yoga breathing volitionally modifies breath frequency, depth of breathing, and duration of breath phases to produce distinct cognitive, affective, and physiological changes.[1]
Changes in the inspiration to expiration ratio (i/e) have several psychophysiological effects.[2] In Bhramari pranayama, exhalation is prolonged, while breath frequency is reduced.[3] In a systematic review on the effects of Bhramari pranayama, stress levels reduced and attention improved.[4] Volitional breathing and attention influence each other bidirectionally.[5,6] In Bhramari pranayama, there was an increased P300 amplitude evoked by an auditory oddball paradigm and reduced anxiety in healthy volunteers,[3,6] possibly due to the lower breath frequency or low i/e ratio during Bhramari pranayama.[7] The physiological effects of breathing with low i/e have been reported.[2,8] However, to understand for the first time the effects of breathing with low, high or equal i/e in the same persons, the present randomized crossover trial compared breathing with different i/e on mood states and attention.
Methods
Participants
Forty healthy volunteers (male: female = 28:12; group average age ± standard deviation (SD): 22.6 ± 3.8 years) were recruited in North India. The Post hoc power analysis showed that the present study, with n = 40, α =0.05, Cohen's d = 0.67 (determined from changes in pleasant-unpleasant scores of the Brief Mood Introspection Scale following a low i/e session), had power = 1.00 (G*power software University of Bonn, Bonn, Germany).[9] Participants (i) aged between 20 and 45 years and (ii) having at least 6 months experience of voluntary breath regulation were included. No participants were excluded based on the predetermined criteria of diagnosed mood disorders or inability to attend assessments. Participants' baseline characteristics are presented in Table 1. Participants' signed consent was obtained and the study was approved by the Institution's Ethics Committee (PRF/YRD/022/001).
Table 1.
Baseline characteristics of the participants (n=40)
| Characteristics | Values |
|---|---|
| Age (years) | |
| Age range | 18–31 |
| Group mean age±SD | 22.58±3.83 |
| Gender (male: female) | |
| Actual values | 28:12 |
| Percentage values | 70:30 |
SD: Standard deviation
Study design
Participants were assessed for (i) mood and (ii) attention before and after three breath interventions and one control period on 4 separate days in random order. Random allocation to the sessions was carried out by a person with no other involvement in the trial using an online randomizer (www.randomizer.org). Duration of each intervention session was 13 min with a 2-min training session. The session structure is provided in Figure 1. The trial is presented following CONSORT guidelines.
Figure 1.
Schematic presentation of a study session
Assessments
Brief Mood Introspection Scale
It was used to assess the intensity of 16 mood adjectives on a four-point rating scale.[10] The scores were categorized into four mood categories: (i) pleasant-unpleasant, (ii) arousal-calm, (iii) positive-tired, and (iv) negative-relaxed.
Global Vigor and Affect Scale
It was used to assess subjective feeling of global vigor and global affect with eight Visual Analog Scales, scored between 0 and 100 points, of which four assess global vigor and four assess global affect.[11]
Spielberger's State-Trait Anxiety Inventory Subscale State
It was used to assess state anxiety.[12]
Six-letter cancellation test
It was used to assess sustained attention, selective attention, and visual scanning.[13,14] Total attempts (a total number of letters cancelled), wrong attempts, and net attempts were calculated.
Intervention
A circular, visual metronome with two concentric circles (i.e. an inner light blue circle and an outer dark blue circle) was projected on a screen. Participants were seated at a comfortable viewing distance in crossed leg position. The inner light blue circle of the metronome expands representing inspiration phase and then constricts representing expiration phase. Participants were instructed to synchronize their breathing with the metronome.
There were three intervention sessions ((i) low i/e [i.e. 28:72], (ii) equal i/e [i.e. 50:50], (iii) high i/e [i.e. 72:28]) with a respiratory frequency of 12 breaths/min and a control session (gazing at the metronome without breath modification). After the sessions, participants rated their practice on two 10 cm analog scales for (i) ability to change the i/e and (ii) ability to maintain the i/e for 10 min. Sessions were included if the rating for both questions was > 7.5 cm (all sessions were included).
Data analysis
Separate repeated measures analyses of variances with two within subjects factors, i.e. sessions (four levels) and states (two levels), followed by Bonferroni adjusted post hoc analyses, were conducted (IBM SPSS, Version 24.0, New York, USA), Family-wise error rates were controlled using sequentially rejective Bonferroni tests for states, sessions, and interactions between sessions and states.[15]
Results
Forty participants were assigned to four randomly ordered sessions on separate days. All participants completed the four sessions.
Repeated measures analysis of variance
Following Bonferroni–Holm correction, there was a significant (P < 0.05 in all cases) main effect of States for (i) pleasant-unpleasant (P-U), (ii) arousal-calm (A-C), (iii) positive-tired (P-T), and (iv) negative-relaxed (N-R) scores of the BMIS, (v) total global vigor (TGV), (vi) total global affect (TGA), (vii) Spielberger's State-Trait Anxiety Inventory-State Scores (STAI-S), and (viii) total attempted (TA) scores of the six-letter cancellation test (SLCT).
The F values, Huynh-Feldt epsilon, df, and P values for (i) BMIS, (ii) TGV and TGA, (iii) STAI-s, and (iv) SLCT are presented in Table 2.
Table 2.
Analyses of variances table with F values, Huynh-Feldt epsilon, degree of freedom, and adjusted P values for (i) Brief Mood Introspection Scale, (ii) Global Vigor and Affect Scale, (iii) Spielberger's State Anxiety-State, and (iv) six-letter cancellation test
| Measures | Variables | Factors | F | df | Huynh-Feldt | P | αadj |
|---|---|---|---|---|---|---|---|
| Brief Mood Introspection Scale | P-U | Sessions | 0.829 | 3.00, 117.00 | 0.923 | 0.480 | 0.05 |
| States | 16.961 | 1.00, 39.00 | 1 | <0.001 | 0.017 | ||
| Session×states | 2.708 | 3, 117.00 | 0.967 | 0.048 | 0.025 | ||
| A-C | Sessions | 2.283 | 3.00, 117.00 | 1 | 0.083 | 0.025 | |
| States | 6.359 | 1.00, 39.00 | 1 | 0.016 | 0.017 | ||
| Sessions×states | 1.498 | 3.00, 117.00 | 1 | 0.219 | 0.05 | ||
| P-T | Sessions | 0.139 | 2.52, 98.18 | 0.839 | 0.911 | 0.05 | |
| States | 8.884 | 1.00, 39.00 | 1 | 0.005 | 0.017 | ||
| Sessions×states | 1.716 | 3.00, 117.00 | 0.955 | 0.167 | 0.025 | ||
| N-R | Sessions | 2.409 | 3.00, 117.00 | 1 | 0.071 | 0.025 | |
| States | 23.215 | 1.00, 39.00 | 1 | <0.001 | 0.017 | ||
| Sessions×states | 1.858 | 3.00, 117.00 | 1 | 0.141 | 0.05 | ||
| GVAS | Global vigor | Sessions | 0.239 | 3.00, 117.00 | 0.686 | 0.869 | 0.05 |
| States | 19.05 | 1.00, 39.00 | 1 | <0.001 | 0.017 | ||
| Sessions×states | 0.437 | 3.00, 117.00 | 1 | 0.727 | 0.025 | ||
| Global affect | Sessions | 1.103 | 3.00, 117.00 | 0.985 | 0.351 | 0.05 | |
| States | 28.944 | 1.00, 39.00 | 1 | <0.001 | 0.017 | ||
| Sessions×states | 2.044 | 3.00, 117.00 | 0.987 | 0.112 | 0.025 | ||
| Spielberger's State-Trait Anxiety Inventory | Sessions | 1.303 | 3.00, 117.00 | 0.818 | 0.277 | 0.025 | |
| States | 20.027 | 1.00, 39.00 | 1 | <0.001 | 0.017 | ||
| Sessions×states | 0.522 | 3.00, 117.00 | 0.965 | 0.668 | 0.05 | ||
| SLCT | TA | Sessions | 1.089 | 2.85, 111.13 | 0.95 | 0.355 | 0.025 |
| States | 7.244 | 1.00, 39.00 | 1 | 0.010 | 0.017 | ||
| Sessions×states | 0.611 | 2.43, 94.80 | 0.81 | 0.576 | 0.05 | ||
| Wrongly attempted | Sessions | 0.367 | 2.57, 100.18 | 0.856 | 0.745 | 0.05 | |
| States | 1.908 | 1.00, 39.00 | 1 | 0.175 | 0.017 | ||
| Sessions×states | 1.199 | 2.62, 102.01 | 0.872 | 0.312 | 0.025 | ||
| Net attempted | Sessions | 1.1 | 88.97, 80.87 | 0.938 | 0.350 | 0.025 | |
| States | 6.067 | 227.80, 37.55 | 1 | 0.018 | 0.017 | ||
| Sessions×states | 0.684 | 36.47, 53.31 | 0.8 | 0.533 | 0.05 |
Significant adjusted P values for sessions×states, sessions or states are underlined. GVAS: Global Vigor and Affect Scale, SLCT: Six-letter cancellation test, P-U: Pleasant-unpleasant, A-C: Arousal-calm, P-T: Positive-tired, N-R: Negative-relaxed, TA: Total attempted
Post hoc analysis
The low i/e session significantly increased (P < 0.05; in all cases) (i) P-U (ii) P-T, (iii) TGV, and (iv) TGA and decreased (i) N-R and (ii) STAI-s. The equal i/e session increased (i) P-U, (ii) TGV, and (iii) TGA and decreased (i) N-R (ii) STAI-s, and (iii) TA scores of the SLCT. The high i/e session increased TGV and decreased STAI-s. The control session increased (i) TGV and (ii) TGA and decreased (i) N-R and (ii) STAI-s.
The group mean values ± SD for (i) BMIS, (ii) TGV and TGA, (iii) STAI-s scores, and (iv) SLCT are given in Table 3, respectively.
Table 3.
Group mean values±standard deviation for (i) Brief Mood Introspection Scale, (ii) Global Vigor and Affect Scale, (iii) Spielberger's State-Trait Anxiety Inventory-State scores, and (iv) performance in six-letter cancellation test
| Measures | Variables | Sessions |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| Low i/e |
Equal i/e |
High i/e |
Gazing at metronome |
||||||
| Pre | Post | Pre | Post | Pre | Post | Pre | Post | ||
| BMIS | P-U | 53.85±7.41 | 58.43±6.27*** | 55.28±8.56 | 57.93±6.61* | 56.50±6.41 | 58.15±5.37 | 55.35±7.85 | 57.10±5.63 |
| A-C | 29.88±3.63 | 28.88±2.42 | 30.03±3.89 | 28.88±2.99 | 28.40±2.68 | 28.65±2.27 | 29.63±3.18 | 28.83±3.00 | |
| P-T | 23.30±3.70 | 24.83±3.07*** | 24.00±3.23 | 24.63±3.10 | 23.85±3.27 | 24.68±2.54 | 23.93±3.24 | 24.38±2.73 | |
| N-R | 9.98±3.29 | 7.85±2.80*** | 9.50±4.38 | 7.85±3.18** | 8.25±2.62 | 7.65±2.37 | 9.33±3.70 | 8.15±2.58* | |
| Global vigor and affect instrument | TGV | 68.39±23.25 | 78.14±17.1** | 70.63±19.79 | 76.59±18.94* | 70.99±19.6 | 78.11±17.58* | 71.39±16.94 | 78.22±16.8** |
| TGA | 76.18±18.49 | 87.4±14.45*** | 73.16±16.14 | 86.45±16.74*** | 80.65±16.12 | 86.15±14.83 | 80.12±14.29 | 86.03±13.53* | |
| Spielberger's State-Trait Anxiety Inventory | 32.05±11.34 | 26.33±7.7*** | 29.88±10.09 | 25.75±7.59** | 30.43±9.1 | 25.08±5.69** | 29.93±8.97 | 25.13±4.64*** | |
| SLCT | TA | 31.13±14.39 | 29.05±9.31 | 29.48±12.27 | 26.25±7.96* | 30.28±8.63 | 28.65±7.86 | 28.53±9.19 | 28.08±9.42 |
| Wrongly attempted | 0.33±0.62 | 0.45±0.90 | 0.53±1.34 | 0.35±0.83 | 0.70±1.22 | 0.33±0.69 | 0.48±1.01 | 0.28±0.64 | |
| Net attempted | 30.80±14.23 | 28.60±9.52 | 28.95±12.05 | 25.90±7.99 | 29.58±8.85 | 28.33±7.85 | 28.05±8.98 | 27.80±9.44 | |
*P<0.05, **P<0.01, ***P<0.001. RM-ANOVA with Bonferroni adjustment when prevalues were compared with postvalues of the respective session. ANOVA: Analyses of variances, RM-ANOVA: Repeated measures ANOVA, i/e: Inspiration to expiration ratio, BMIS: Brief Mood Introspection Scale, GVAS: Global Vigor and Affect Scale, SLCT: Six-letter cancellation test, TGA: Total global affect, TGV: Total global vigor, P-U: Pleasant-unpleasant, A-C: Arousal-calm, P-T: Positive-tired, N-R: Negative-relaxed, TA: Total attempted
Discussion
Participants self-reported > 80% accuracy in volitional modification of inspiration to expiration i/e. Breathing with both low i/e and equal i/e increased pleasant feelings. Low i/e alone increased positive feelings, whereas equal i/e decreased cancellation test scores. All three (i.e. low, equal, or high i/e) and the control decreased state anxiety and increased vigor. High i/e alone did not reduce negative feelings.
Breathing with low i/e and equal i/e increased pleasant feelings (e.g. feeling lively, happy, caring, content, peppy, calm, loving, and active) which may be explained by changes in vagal nerve activity,[16] with reduced vagal activity during inspiration and increased activity during expiration.[17,18] Both direct vagal nerve stimulation and indirect modulation by volitional breathing have relaxation-related therapeutic benefits.[19] Previously, prolonged expiration was associated with feelings of stress reduction, relaxation, greater mindfulness, and positive energy,[2] considered to be related to increased parasympathetic activity. Here, the increase in pleasant and positive feelings with low i/e breathing may be related to increased parasympathetic activity; however, since there were no concurrent physiological assessments, this cannot be decisively concluded.
The increase in pleasant feelings with equal i/e breathing may also be attributed to increased parasympathetic activity, based on previous reports of an increase in cardiac vagal activity with equal i/e.[19,20] Alternatively, equal i/e could be closer to the spontaneous breath pattern and hence easier to follow leading to relaxed and pleasant feelings.[20] The present results are comparable to previously reported feelings of relaxation following both low and equal i/e ratios.[20]
However, in the present study, despite the pleasant feelings reported, breathing with equal i/e lowered the cancellation test scores for sustained attention. The association between positive mood states and cognition is complex since a positive mood reduced attention test performance when individuals were more susceptible to being distracted by irrelevant information.[21,22] Similar reasons may explain the present reduced cancellation test scores following equal i/e. Furthermore, equal i/e alone did not increase feelings of alertness on the Global Vigor and Affect Scale, supporting the reduced cancellation test scores.
All four practices (three regulated breathing ratios and the control intervention which did not have conscious breath modification) reduced state anxiety and increased vigor. In the control session, participants were asked to avoid consciously regulating their breath based on the metronome cues; nonetheless, the metronome was set at a breath frequency of 12 breaths/min with equal i/e, considered to be close to normal average breathing. The changes in the control session were not identical to the equal i/e sessions, suggesting that participants did not completely follow the metronome during the control session. The changes during the control session are comparable to an earlier study, where breath regulation increased subjective feelings of relaxation more than the baseline.[20] Hence, regulating breathing, either consciously or inadvertently, appears to reduce state anxiety, which may also explain decreased negative feelings following breathing with low and equal i/e and in the control session. High i/e alone did not decrease negative feelings, possibly due to the sympathetic stimulating effect associated with inspiration.[17]
Limitations
Understanding the mechanisms underlying the present findings is limited by no concurrent physiological assessment.
Conclusions
Healthy participants breathing with low or equal i/e increased pleasant feelings. High i/e breathing alone did not decrease negative feelings. Varying breath phase ratios did not appear to influence participants' reported anxiety or vigor. The results suggest that breathing with prolonged exhale, effortlessly practiced as Brahmari pranayama, can be considered an effortless way to increase pleasant feelings in healthy persons.
Financial support and sponsorship
The authors gratefully acknowledge Patanjali Research Foundation for funding the study.
Conflicts of interest
There are no conflicts of interest.
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