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Slow-paced breathing has been shown to enhance the self-regulation abilities of athletes via its influence on cardiac vagal activity. However, the role of certain respiratory parameters (i.e., inhalation/exhalation ratio and presence of a respiratory pause between respiratory phases) still needs to be clarified. The aim of this experiment was to investigate the influence of these respiratory parameters on the effects of slow-paced breathing on cardiac vagal activity. A total of 64 athletes (27 female; Mage = 22, age range = 18–30 years old) participated in a within-subject experimental design. Participants performed six breathing conditions within one session, with a 5 min washout period between each condition. Each condition lasted 5 min, with 30 respiratory cycles, and each respiratory cycle lasted 10 s (six cycles per minute), with inhalation/exhalation ratios of 0.8, 1.0, 1.2; and with or without respiratory pauses (0.4 s) between respiratory phases. Results indicated that the root mean square of successive differences (RMSSD), a marker of cardiac vagal activity, was higher when exhalation was longer than inhalation. The presence of a brief (0.4 s) post-inhalation and post-exhalation respiratory pause did not further influence RMSSD. Athletes practicing slow-paced breathing are recommended to use an inhalation/exhalation ratio in which the exhalation phase is longer than the inhalation phase.
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Sustainability 2021, 13, 7775. https://doi.org/10.3390/su13147775 www.mdpi.com/journal/sustainability
Article
Slow-Paced Breathing: Influence of Inhalation/Exhalation Ratio
and of Respiratory Pauses on Cardiac Vagal Activity
Sylvain Laborde 1,2,*, Maša Iskra 1, Nina Zammit 1, Uirassu Borges 1,3, Min You 4, Caroline Sevoz-Couche 5
and Fabrice Dosseville 6,7
1 Department of Performance Psychology, Institute of Psychology, German Sport University Cologne,
Cologne 50933, Germany; masa.iskra@gmail.com (M.I.); ninazt27@gmail.com (N.Z.)
2 UFR STAPS, EA 4260 CESAMS, Normandie Université, 14000 Caen, France
3 Department of Health & Social Psychology, Institute of Psychology, German Sport University Cologne,
50933 Cologne, Germany; u.borges@dshs-koeln.de
4 UFR Psychologie, EA3918 CERREV, Normandie Université, 14000 Caen, France; you.min14@gmail.com
5 INSERM, Unité Mixte de Recherche (UMR) S1158 Neurophysiologie Respiratoire Expérimentale et Clinique,
Sorbonne Université, 75000 Paris, France; caroline.sevozcouche@gmail.com
6 UMR-S 1075 COMETE, Normandie Université, 14000 Caen, France
7 INSERM, UMR-S 1075 COMETE, 14000 Caen, France; fabrice.dosseville@unicaen.fr
* Correspondence: s.laborde@dshs-koeln.de, +49-221-49-82-57-01
Abstract: Slow-paced breathing has been shown to enhance the self-regulation abilities of athletes
via its influence on cardiac vagal activity. However, the role of certain respiratory parameters (i.e.,
inhalation/exhalation ratio and presence of a respiratory pause between respiratory phases) still
needs to be clarified. The aim of this experiment was to investigate the influence of these respiratory
parameters on the effects of slow-paced breathing on cardiac vagal activity. A total of 64 athletes
(27 female; Mage = 22, age range = 18–30 years old) participated in a within-subject experimental
design. Participants performed six breathing conditions within one session, with a 5 min washout
period between each condition. Each condition lasted 5 min, with 30 respiratory cycles, and each
respiratory cycle lasted 10 s (six cycles per minute), with inhalation/exhalation ratios of 0.8, 1.0, 1.2;
and with or without respiratory pauses (0.4 s) between respiratory phases. Results indicated that
the root mean square of successive differences (RMSSD), a marker of cardiac vagal activity, was
higher when exhalation was longer than inhalation. The presence of a brief (0.4 s) post-inhalation
and post-exhalation respiratory pause did not further influence RMSSD. Athletes practicing slow-
paced breathing are recommended to use an inhalation/exhalation ratio in which the exhalation
phase is longer than the inhalation phase.
Keywords: cardiac vagal activity; slow-paced breathing; respiratory parameters; RMSSD
1. Introduction
During sport competitions, athletes are required to effectively regulate their emo-
tions [1–3] and cope with stressors [4,5]. Among the strategies addressing athletes’ emo-
tional regulation, slow-paced breathing (SPB), the voluntarily slowing down of breathing
frequency, has been increasingly used (e.g., [6,7–9]). However, the effectiveness of varying
certain parameters of SPB, such as the inhalation/exhalation ratio and the presence of a
respiratory pause (i.e., brief cessation of air flow) between respiratory phases, still needs
to be understood. Consequently, the current study aims to further understand the role of
varying these two parameters on the effectiveness of SPB, as measured by cardiac vagal
activity (CVA), an indicator for self-regulation mechanisms [10–16].
SPB is a technique used to decrease overall activation and trigger relaxation [17]. It
involves timed inhalation and exhalation periods (“paced”), at a rate of around six cycles
per minute (cpm), which is at least half as slow than the spontaneous breathing rate,
Citation: Laborde, S.; Iskra, M.;
Zammit, N.; Borges, U.; You, M.;
Sevoz-Couche, C.; Dosseville, F.
Slow-Paced Breathing: Influence
of Inhalation/Exhalation Ratio
and of Respiratory Pauses
on Cardiac vagal activity.
Sustainability 2021, 13, 7775.
https://doi.org/10.3390/su13147775
Academic Editors: Santos Villafaina,
Juan Pedro Fuentes García and
Daniel Collado-Mateo
Received: 25 May 2021
Accepted: 9 July 2021
Published: 12 July 2021
Publisher’s Note: MDPI stays neu-
tral with regard to jurisdictional
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tional affiliations.
Copyright: © 2021 by the authors. Li-
censee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and con-
ditions of the Creative Commons At-
tribution (CC BY) license (http://crea-
tivecommons.org/licenses/by/4.0/).
Sustainability 2021, 13, 7775 2 of 14
normally ranging between 12 and 20 cpm [18,19]. The exact mechanisms by which SPB
influences emotion regulation are still debated, but they are likely to involve the strength-
ening of the baroreflex, the action on pulmonary afferents, as well as specific oscillations
in brain networks involved in emotion regulation [20–25]. Overall SPB is suggested to
trigger the activation of the vagus nerve [21], the main nerve of the parasympathetic nerv-
ous system which is responsible for rest and digest functions, as well as self-regulation
within the body [11,26,27].
Heart rate variability (HRV), the variation in the time intervals between adjacent
heart beats [10,28,29], is a non-invasive indicator of CVA, as explained by the neurovis-
ceral integration model [11,27]. Among the time domain measures of the HRV parameters
that index CVA, the root mean square of successive differences (RMSSD) is commonly
used. The interpretation of the physiological underpinnings of HRV frequency parame-
ters requires taking into account the respiratory frequency. When breathing frequency is
higher than 9 cpm, CVA is reflected in the high-frequency (HF) band [10,28,29]. However,
when breathing frequency is lower than 9 cpm, CVA is then shifted to low-frequency (LF)
HRV [30]. Given that RMSSD is relatively free from respiratory influences, and more sta-
tistically reliable than frequency-domain indicators [31,32], it is the main outcome of in-
terest in this study.
CVA, whether considering its resting, reactivity, or recovery levels [12], has been
found to be related to different cognitive and physical aspects of sport performance. For
example, morning resting measurements have been used to monitor the effects of training
loads, to adjust training loads, and to predict subsequent performance [33–35]. Addition-
ally, CVA has been linked to executive cognitive performance in athletes [36–40], to their
coping effectiveness with stress and pressure [37,41–46], and to sport performance, such
as shooting [47,48] and dart throwing performance [49]. Consequently, increasing CVA
can be considered an appropriate aim for athletes.
Among the methods used to increase CVA [50–52], SPB has been found to be effective
in athletes, either combined with biofeedback [53,54] or without biofeedback (e.g., [6,7–
9]). Biofeedback includes displaying physiological variables of interest (e.g., heart rate,
heart rate variability, respiratory frequency) to the person being monitored, through real-
time measures realized with a dedicated device, smartphone, or a computer [55]. The use
of biofeedback may contribute to additional motivation through providing positive rein-
forcement to the client [25,55–57]. Additionally, biofeedback can assist in identifying the
breathing pattern that leads to the highest CVA increase [24,25,58,59]. Nonetheless, so far,
no clear evidence has emerged of the physiological benefits of adding biofeedback to SPB
[60]. Consequently, the current study focuses on SPB without biofeedback, given that from
an applied perspective, it requires athletes to use less technology.
SPB without biofeedback has been associated with positive cognitive and physiolog-
ical outcomes in athletes [8,9,61–63]. More specifically, positive effects were found on ex-
ecutive functions such as inhibition in resting conditions [61,62], working memory, and
cognitive flexibility [62], and after physical exertion on inhibition [9]. A robust increase in
CVA during SPB has systematically been found, even if the effects tend to cease immedi-
ately upon stopping SPB [8,62]. Importantly, long-term SPB interventions (15 min per day
for 30 days) seem to trigger increases in resting CVA [63].
Regarding the characteristics of SPB, it is usually performed with a longer exhalation
than inhalation phase [24,25]. Adapting a longer exhalation phase is suggested to create a
larger increase in CVA, as can be explained through the properties of respiratory sinus
arrhythmia (RSA) [64,65]. RSA reflects the influence of respiration on heart rate—more
specifically, the fact that heart rate increases with inhalation, and decreases with exhala-
tion [66,67]. Inhalation is driven by sympathetic nervous activity, and exhalation by par-
asympathetic nervous activity. Theoretically, a longer exhalation would activate the par-
asympathetic nervous system more strongly. This has been confirmed experimentally in
previous research [64,65], where a longer exhalation phase in comparison to inhalation
was found to provoke larger increases in RSA, as calculated by the difference between
Sustainability 2021, 13, 7775 3 of 14
maximum and minimum cardiac interbeat intervals per breath. Although this way of cal-
culating RSA is suggested to reflect CVA, it does not belong to the classic HRV parameters
recommended to index CVA [10,28,29]. In addition, Strauss-Blasche, Moser, Voica,
McLeod, Klammer and Marktl [65] did not focus on SPB (10 cpm), SPB being characterized
by breathing frequencies lower than 10 cpm [22]. Additionally, the sample sizes used in
those previous studies were rather small, with N = 12 [65] and N = 23 [64]. The inhala-
tion/exhalation ratio was also investigated by Lin, et al. [68]. Contradictory to previous
studies, they concluded that an equal inhalation/exhalation ratio was the most beneficial
regarding HRV. However, this experiment presents several drawbacks: RMSSD was not
reported, and among the variables reported, only LF may have indexed CVA. However,
the findings are difficult to interpret, due to the use of a between-subject design involving
N = 11 or N = 12 in each of the four respiratory patterns (6 cpm 5:5; 6 cpm 4:6; 5.5 cpm 5:5;
and 5.5 cpm 4:6). Finally, Edmonds, Kennedy, Hughes and Calzada [58] investigated the
influence of different breathing patterns around 6 cpm: 1:1 breathing ratio with post-in-
halation and post-exhalation respiratory pauses, 1:1 ratio with no respiratory pauses, 1:2
breathing ratio with no respiratory pauses, 1:2 with post-inhalation and post-exhalation
respiratory pauses, and finally, a condition requiring the participants to breathe in sync
with their heart rate. The focus was not on between-subject analysis, but on within-subject
analysis, and the authors found that for each participant, a specific breathing pattern pro-
duced the highest increase in LF. Moreover, all breathing patterns were found to produce
a descriptive increase in LF; however, no inferential statistics were run at the group level
to investigate differences between breathing patterns. To sum up, given the large interin-
dividual variability of HRV frequency-domain variables [10,69] and the lower reliability
of frequency parameters when breathing characteristics are modified [31,32], we wanted
to address in this study the shortcomings of previous experiments by using a larger sam-
ple size, measuring RMSSD as a robust indicator of CVA, which is relatively free from
respiratory influences, and by using a within-subject design.
The second parameter of interest in this study is the presence of a post-inhalation and
post-exhalation respiratory pause during SPB, an aspect that has received very little at-
tention so far (for an exception, see [70]). In [70], the authors tested the influence of a post-
exhalation respiratory pause on HRV (4 s). In comparison to a condition without post-
exhalation respiratory pause, a post-exhalation respiratory pause showed a higher HF-
HRV, while no differences were found regarding RMSSD and LF-HRV. The authors con-
cluded that a post-exhalation respiratory pause improves CVA and hence self-regulatory
control. However, this interpretation of the results is likely inaccurate, given that HF-HRV
does not reflect CVA when breathing frequency is lower than 9 cpm [10,28,29]. The pattern
of results based on the increase in both RMSSD and LF from baseline in both conditions,
with and without post-exhalation respiratory pause, suggests that they both trigger an
increase in CVA. Finally, the authors did not provide a physiological rationale for having
a post-exhalation respiratory pause besides triggering a higher HF-HRV. Other authors
suggested that a post-inhalation respiratory pause may trigger bradycardia via a rapid
activation of vagal activity, based on the effects of breath-holding [71]. It may be specu-
lated that SPB provokes a certain strain on respiratory muscles due to the forced and pro-
longed inhalation and exhalation phases, and would potentially also result in hyperven-
tilation with increased tidal volume [70]. Consequently, the current study aimed to test
the influence of a brief post-inhalation and post-exhalation respiratory pause on CVA.
To sum up, research points to positive effects of SPB without biofeedback on CVA
[8,9,62,63]. However, the influence of certain characteristics of SPB still needs to be clari-
fied, such as the influence of the inhalation/exhalation ratio, as well as the presence of a
respiratory pause between the respiratory phases. The current study therefore aims to
address these issues. Regarding the inhalation/exhalation ratio, we hypothesize that a
longer exhalation phase in comparison to inhalation would trigger larger increases in
CVA [64,65]. Regarding the respiratory pause, we hypothesized that a brief post-inhala-
tion and post-exhalation respiratory pause may potentially produce a bradycardia and
Sustainability 2021, 13, 7775 4 of 14
reduce the demands on respiratory muscles, therefore resulting in a greater increase in
CVA [70,71].
2. Materials and Methods
2.1. Participants
Regarding sample size, previous research on this topic using a within-subject design
had a rather low sample size, N = 12 for Strauss-Blasche, Moser, Voica, McLeod, Klammer
and Marktl [65], and N = 23 for Van Diest, Verstappen, Aubert, Widjaja, Vansteenwegen
and Vlemincx [64]. Following recommendations for HRV research [10,69], we recruited 66
athletes to take part in this research project. Athletes were here defined as individuals
regularly engaging in sport training. Recruiting a homogenous athletic sample helps to
limit inter-individual differences in HRV that can be found in the general population, en-
abling a better interpretation of the findings [69]. Exclusion criteria were self-reported car-
diovascular diseases and other chronic diseases that might influence breathing or HRV
patterns, such as asthma, diabetes, psychiatric, and neurological diseases [10]. Due to tech-
nical issues, the data of 2 participants had to be excluded, and the final sample comprised
64 athletes (27 female; MAge = 22, age range = 18–30 years old; BMI: M = 23.10, SD = 2.16;
waist-to-hips ratio: M = 0.80, SD = 0.08; number of sport hours per week: M = 7.5 h; SD =
3.2). The experimental protocol was approved by the Ethics Committee of the local uni-
versity (Project Identification Code 06/11/2014).
2.2. Material and Measures
2.2.1. Heart Rate Variability
HRV was measured with an ECG device (Faros 180°, Bittium, Kuopio, Finland) at a
sampling rate of 500 Hz. Two disposable ECG pre-gelled electrodes (Ambu L-00-S/25,
Ambu GmbH, Bad Nauheim, Germany) were used. The negative electrode was placed in
the right infraclavicular fossa (just below the right clavicle) while the positive electrode
was placed on the left side of the chest, below the pectoral muscle in the left anterior axil-
lary line. From ECG recordings, we extracted RMSSD with Kubios (University of Eastern
Finland, Kuopio, Finland). The ECG signal was visually inspected for artefacts and these
were corrected manually in the cases required (<0.001% of the heartbeats), as recom-
mended by Laborde, Mosley and Thayer [10]. In order to provide an overview of the dif-
ferent HRV parameters, following Laborde, Mosley and Thayer [10], we also extracted the
R-R interval, the heart rate, the standard deviation of the NN interval (SDNN) for the
time-domain and the frequency domain with Fast Fourier Transform LF (0.04 to 0.15 Hz),
HF (0.15 to 0.40 Hz), and the LF/HF ratio. Respiratory frequency was computed via the
ECG-derived respiration algorithm of Kubios [72].
2.2.2. Slow-Paced Breathing
Similar to previous research (e.g., [8,73]), SPB was conducted with a video showing
a ball moving up and down at the rate of 6 cpm, based on the EZ-Air software (Thought
Technology Ltd., Montreal, Canada). Participants were instructed to inhale continuously
through the nose while the ball was going up, and exhale continuously with pursed lips
when the ball was going down. The video displayed a 5 min SPB exercise, with six condi-
tions, varying in the inhalation/exhalation ratio (inhalation = exhalation; inhalation > ex-
halation; inhalation < exhalation) and the presence/absence of a respiratory pause (0.4 s)
after both inhalation and exhalation phases (see Figure 1). The inhalation/exhalation ratio
was 4.5 s/5.5 s and 5.5 s/4.5 s, based on Allen and Friedman [74]. The six conditions were
the following: 4.6 s/0.4 s/4.6 s/0.4 s (inhalation/exhalation ratio = 1.0); 4.1 s/0.4 s/5.1 s/0.4 s
(inhalation/exhalation ratio = 0.8); 5.1 s/0.4 s/4.1 s/0.4 s (inhalation/exhalation ratio = 1.2);
5 s/5 s (inhalation/exhalation ratio = 1); 4.5 s/5.5 s (inhalation/exhalation ratio = 0.8); 5.5
s/4.5 s (inhalation/exhalation ratio = 1.2).
Sustainability 2021, 13, 7775 5 of 14
.
Figure 1. The six breathing conditions, realized in a randomized order during the experiment. Note: ascending arrows
depict the inhalation phase and descending arrows depict the exhalation phase; I: inhalation, E: exhalation; time indicated
in seconds.
2.2.3. Procedure
Participants were recruited via flyers on the campus of the local university and via
posts on social network groups linked to the local university. In line with recommenda-
tions for psychophysiological experiments involving HRV measurements [10], partici-
pants were instructed to follow their usual sleep routine the night prior to the experiment,
not to consume alcohol or engage in strenuous physical activity in the previous 24 h, nor
drink or eat 2 h before taking part in the experiment. All participants gave written in-
formed consent before participation, and were informed that they could withdraw from
the study at any time without explanation and without any consequences. The partici-
pants attended the lab once in accordance with the within-subject design. The whole ses-
sion lasted 90 min (the protocol is described in Figure 2). After being welcomed to the lab,
they were asked to fill out an informed consent form and a demographic questionnaire
regarding variables potentially influencing HRV [10,51,52]. The ECG device was attached,
and participants watched a 15 min familiarization video to get acquainted with SPB. The
participants started with a 5 min rest period (baseline), where they were breathing spon-
taneously, with open eyes. After the 5 min rest period, they performed the six breathing
conditions in a randomized order, with a 5 min washout period between each respiratory
condition, similarly to Russell, Scott, Boggero and Carlson [70]. The washout period char-
acteristics were similar to those of the baseline. At the end of the experiment, the ECG
device was detached, and participants were thanked and debriefed.
Sustainability 2021, 13, 7775 6 of 14
Figure 2. Experimental protocol.
2.3. Data Analysis
HRV variables were exported from the Kubios output. Data were checked for nor-
mality and outliers. Regarding outliers, 0.002% of the cases were found to be univariate
outliers (>2 SD, z-scores higher than 2.58; none were found being >3 SD, with z-scores
higher than 3.29). Running the analyses without them did not change the pattern of re-
sults; therefore, they were kept in the analysis. As the RMSSD data were non-normally
distributed, a log-transformation was applied, as is usually recommended for HRV re-
search [10].
As a manipulation check, we first checked whether the participants were breathing
at 6 cpm during the different conditions, and whether the breathing frequencies differed
among conditions, by conducting a repeated-measures ANOVA. Further, we conducted
a series of t-tests (two-tailed) to show whether the breathing conditions differed from
baseline, with log RMSSD as the dependent variable, with Bonferroni correction (0.05/6 =
0.008). We conducted a repeated-measures ANOVA, with inhalation/exhalation ratio (in-
halation = exhalation; inhalation > exhalation; inhalation < exhalation) and respiratory
pause (with/without) as independent variables, and log RMSSD as the dependent varia-
ble.
3. Results
Descriptive statistics are presented in Table 1 for all study variables. The first manip-
ulation check revealed that participants followed the 6 cpm breathing frequency, ranging
Sustainability 2021, 13, 7775 7 of 14
from 6.48 (SD = 0.20) to 6.55 (SD = 0.26). A repeated-measures ANOVA with the Green-
house–Geisser correction was conducted, and showed no significant effect of condition on
breathing frequency, with F (4.401, 277.232) = 0.696, p = 0.608, and partial η2 = 0.01.
The first analysis showed that log RMSSD was significantly higher in all the breath-
ing conditions than in the baseline, for inhalation > exhalation (respiratory pause) with t
(63) = 8.693, p < 0.001, Cohen’s d = 1.09; for inhalation < exhalation (respiratory pause) with
t (63) = 10.853, p < 0.001, Cohen’s d = 1.36; for inhalation = exhalation (respiratory pause)
with t (63) = 9.925, p < 0.001, Cohen’s d = 1.24; for inhalation > exhalation (no respiratory
pause) with t (63) = 8.393, p < 0.001, Cohen’s d = 1.05; for inhalation > exhalation (no res-
piratory pause) with t (63) = 9.428, p < 0.001, Cohen’s d = 1.05; and for inhalation > exhala-
tion (no respiratory pause) with t (63) = 8.944, p < 0.001, Cohen’s d = 1.12.
A repeated-measures ANOVA with the Greenhouse–Geisser correction was con-
ducted and showed a significant main effect of inhalation/exhalation ratio, with F (1.996,
125.753) = 8.778, p < 0.001, and partial η2 = 0.12; no main effect of respiratory pause, with F
(1, 63) = 2.495, p = 0.119, and partial η2 = 0.04; and no interaction effect between inhala-
tion/exhalation ratio and respiratory pause, with F (1.676, 105.567) = 0.141, p = 0.832, and
partial η2 = 0. Regarding the main effect of inhalation/exhalation ratio, further post-hoc t-
tests were conducted, applying Bonferroni’s correction with the alpha level adjusted to p
= 0.016 (0.05/3). Log RMSSD was found to be significantly higher in the condition with
inhalation < exhalation in comparison to inhalation > exhalation, with t (63) = 4.059, Co-
hen’s d = 0.51, and p < 0.001; and in comparison to inhalation = exhalation, with t (63) =
2.928, Cohen’s d = 0.37, and p = 0.012. No differences were found between the condition
inhalation > exhalation and inhalation = exhalation, with t (63) = 1.155, Cohen’s d = 0.14,
and p = 0.758. The results of this analysis are presented in Figure 3.
Sustainability 2021, 13, 7775 8 of 14
Table 1. Descriptive statistics.
Conditions HR SDNN RMSSD Log RMSSD LF HF LF/HF Breathing Frequency
M SD M SD M SD M M SD SD M SD M SD M SD
Baseline 67.18 7.97
92.22 37.37 57.14 33.17 1.70 4.09 3.91 0.22 3735.74 6586.00 1266.25 1450.35 11.45 2.03
I > E RP 68.23 6.68
138.11 54.94 85.29 38.95 1.89 17.52 14.53 0.20 14,031.93 10,768.08 1427.02 1473.48 6.55 0.26
I < E RP 68.23 6.53
133.89 45.04 90.27 41.38 1.91 14.30 12.38 0.20 14,587.38 11,754.30 1954.86 1918.53 6.49 0.30
I = E RP 68.37 6.57
132.06 42.74 86.82 39.35 1.89 16.52 12.95 0.21 14,352.57 11,242.16 1664.05 1702.17 6.51 0.22
I > E no RP 68.91 7.06
127.94 39.02 82.44 38.09 1.87 16.92 12.22 0.20 12,761.97 9874.21 1415.16 1621.83 6.52 0.23
I < E no RP 68.59 6.86
161.10 42.80 89.93 41.39 1.91 16.13 13.15 0.20 14,580.16 11,277.36 1602.47 1403.40 6.54 0.32
I = E no RP 68.78 6.30
128.27 38.72 82.94 34.54 1.88 15.91 11.81 0.18 13597.23 9134.12 1465.51 1506.67 6.48 0.20
Note: I: inhalation; E: exhalation; Rest: with post-inhalation and post-exhalation respiratory pauses; SDNN = standard deviation of all RR intervals; RMSSD: root mean square of the
successive differences; LF = low-frequency; HF = high-frequency; RP: respiratory pause.
Sustainability 2021, 13, 7775 9 of 14
Figure 3. Root mean square of successive differences (RMSSD) and inhalation/exhalation ratio.
Note: We display here the raw RMSSD values given that they are more informative for the reader,
as opposed to the log transformed values on which the analyses were based. The main effect of the
inhalation/exhalation ratio is shown here, meaning that the conditions with respiratory pauses and
without respiratory pauses are pooled for each ratio. I: inhalation; E: exhalation.
4. Discussion
The aim of this study was to investigate the influence of the inhalation/exhalation
ratio and of a respiratory pause on CVA during SPB. Regarding the inhalation/exhalation
ratio, findings showed that CVA is higher when the exhalation phase lasts longer than the
inhalation phase, confirming our hypothesis. Regarding the presence of a respiratory
pause, contrary to our hypothesis, there was no evidence for CVA to be influenced by the
presence of a respiratory pause after the inhalation or exhalation phase.
Findings concerning the inhalation/exhalation ratio are in line with previous research
[64,65], with the exception of Lin, Tai and Fan [68]; however, their study suffered from a
number of methodological issues, regarding sample size, design, and HRV variables re-
ported, as noted in the introduction section. Based on the characteristics of RSA [66,67],
heart rate increases with inhalation and decreases with exhalation. Inhalation is driven by
sympathetic nervous activity and inhibits parasympathetic nervous activity, while exha-
lation reactivates parasympathetic nervous activity. Consequently, we can assume that a
longer exhalation provokes a longer activation of the parasympathetic nervous system,
which is reflected in CVA. It is expected that at slow breathing frequencies, more acetyl-
choline is released during exhalation, due to its longer duration [75]. Due to the time con-
stants of acetylcholine hydrolysis around 1.5 s to 2.0 s [76,77], longer exhalation is sug-
gested to provoke a summation of sinoatrial responses, and hence maximally inhibit sino-
atrial node firing. This longer exhalation in comparison to inhalation was also found to
trigger more benefits, for example in terms of pain perception [78]. However, we have to
note that the inhalation/exhalation ratio range was reduced in this study (0.8–1.2) in com-
parison to other studies, such as 0.5–1 [58]; 0.4–2.3 [64], or 1–3.4 [65]. Our rationale was to
investigate whether slight variations in the ratio would already have an effect on CVA,
but larger ranges may reveal different physiological effects.
With regard to the respiratory pause during SPB, the findings did not show any
changes in CVA with the presence or absence of a respiratory pause. As we mentioned in
the introduction, Russell, Scott, Boggero and Carlson [70] concluded inaccurately that a
0
20
40
60
80
100
120
140
Baseline I > E I < E I = E
RMSSD
*
*
*
*
*
*
Sustainability 2021, 13, 7775 10 of 14
post-exhalation respiratory pause (4 s) increased CVA, drawing conclusions on HF-HRV
during SPB, which in this case does not reflect CVA [30]. Based on previous research
[70,71], we argued that a post-inhalation and post-exhalation respiratory pause may be
less demanding for the participant, by not requiring such a prolonged inhalation and ex-
halation, and that it would additionally trigger a bradycardia. Given that no changes were
observed in CVA, it may be that the respiratory pause we chose in this design (0.4 s) may
have been too short to elicit these effects. Other research used a respiratory pause of 4 s
but had an exhalation phase of 2 s [70], which we deemed too short given that the inhala-
tion phase lasted 4 s, and regarding previous research, a longer exhalation triggers higher
increases in CVA [64,65].
Our study had several strengths, such as a larger sample size than previous inhala-
tion/exhalation ratio-related research [64,65] and the investigation of RMSSD to index
CVA, as it is suggested to be relatively free of respiratory influences [31]. Limitations in-
clude first the sample chosen, comprising only athletes. This limits the generalization of
our findings, given that athletes have higher resting HRV than the general population
[79], and a ceiling effect may appear with SPB. Future research must investigate this re-
search question in different samples. Additionally, demographics related to the sport
practiced were collected. Second, the 5 min washout period between the conditions might
not have been sufficiently long to cancel the effects of previous breathing techniques.
Third, our equipment did not allow us to control precisely the exact duration of the inha-
lation, exhalation, and respiratory pauses, so it is not possible for us to evaluate how ac-
curately the participants performed the breathing techniques. Still, we were able to control
for respiratory frequency, to assure that our participants followed the 6 cpm rhythm, by
using the respiration algorithm of Kubios [72]. Additionally, the experimenter paid close
attention that the participants were following the breathing pacer. Finally, we also
checked the visual display of R-R values with Kubios, given that during slow-paced
breathing, oscillations matching the respiratory frequency can be observed [24]. Nonethe-
less, future research should use a respiratory belt to offer an online measurement of res-
piratory frequency. The fourth limitation is the design of the respiratory pause—future
research should endeavor to disentangle the effects of a post-inhalation and post-exhala-
tion respiratory pauses by investigating them separately, and should also consider respir-
atory pauses of different durations. We originally chose a 0.4 s respiratory pause duration
to enable our participants to avoid switching abruptly from inhalation to exhalation, and
from exhalation to inhalation. However, we acknowledge that this duration is much
shorter than those used in previous studies, such as 4 s in Russell, Scott, Boggero and
Carlson [70], and consequently, future research should investigate whether longer respir-
atory pauses trigger different physiological effects. Additionally, the inhalation/exhala-
tion ratio range was reduced (0.8–1.2), and future research should consider investigating
larger ranges [58,64,65].
Furthermore, the investigation of a respiratory pause should also include gas ex-
change measurement and consider, in particular, end-tidal CO2 values for enhanced un-
derstanding of its consequences on CVA, as well as consider its impact on tidal volume,
given the effects of respiratory pauses on RSA [67,70,71]. Additionally, other variables
related to HRV may be considered, such as the RSA, calculated as the difference between
the maximum and minimum cardiac interbeat interval per breath. The RSA has also been
suggested to index CVA [80–82] and has been used in previous research investigating a
similar research question [64]. Finally, future research should also consider investigating
the inhalation/exhalation ratio at different breathing frequencies [64,68,83] and take into
account the effects on other cardiovascular parameters, such as baroreflex sensitivity [84]
and blood pressure [85]. Authors should discuss the results and how they can be inter-
preted from the perspective of previous studies and of the working hypotheses. The find-
ings and their implications should be discussed in the broadest context possible. Future
research directions may also be highlighted.
Sustainability 2021, 13, 7775 11 of 14
5. Conclusions
In conclusion, the aim of this study was to investigate the role of two characteristics
of SPB on CVA, namely the inhalation/exhalation ratio and the presence of a respiratory
pause. Findings showed that adopting a respiratory pattern with a longer exhalation
phase triggered higher CVA in comparison to respiratory patterns with longer inhalation
than exhalation, or with equal duration of both phases. No changes in CVA were pro-
voked by a respiratory pause, but methodological limitations in our design guarantee fur-
ther scrutiny of this parameter in the future.
Manipulating the autonomic nervous system is often the target of sport psychological
techniques [86,87], with either activating or relaxing purposes, through methods such as
power posing [88] and hypnosis [13]. Within the autonomic nervous system, CVA is a
particularly desirable target for athletes, given its role in self-regulation [10–12,14–16]. In
contrast to other methods that exist to stimulate the vagus nerve, such as transcutaneous
vagus nerve stimulation [89–91], SPB without biofeedback does not require external de-
vices besides a respiratory pacer, and can be easily implemented as an acute [8,9,61,62] or
long-term intervention [63] in athletes. SPB with respiratory patterns involving a longer
exhalation phase compared to inhalation may therefore show potential as a performance
habit [92] in order to trigger the highest possible changes in CVA.
Author Contributions: Conceptualization, S.L. and F.D.; methodology, S.L. and F.D.; formal analy-
sis, S.L. and M.Y.; investigation, S.L. and M.Y.; resources, S.L.; data curation, S.L.; writing—original
draft preparation, S.L., M.I., N.Z., U.B., M.Y., C.S.-C., F.D.; writing—review and editing, S.L., M.I.,
N.Z., U.B., M.Y., C.S.-C., F.D.; visualization, M.I. and N.Z.; supervision, S.L. and F.D.; project ad-
ministration, S.L. and F.D. All authors have read and agreed to the published version of the manu-
script.
Funding: This research received no external funding.
Institutional Review Board Statement: The experimental protocol was approved by the Ethics
Committee of the German University Cologne (Project Identification Code 06/11/2014).
Informed Consent Statement: Informed consent was obtained from all subjects involved in the
study.
Data Availability Statement: Data can be shared by the corresponding author upon reasonable re-
quest.
Conflicts of Interest: The authors declare no conflict of interest.
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... Apart from slowing the breath, volitional breathing includes changes in the relative duration of inspiration to expiration (e.g., low i/e breathing) (Van Diest et al., 2014). Low i/e breathing is believed to increase VmHRV partly by respiration-induced influences on cardiac oscillations (Laborde et al., 2021;Noble & Hochman, 2019;Sevoz-Couche & Laborde, 2022). Medullary rhythm generator neurons inhibit vagal efferent outflow during inspiration hence increasing the heart rate, while during expiration the inhibition is released to reduce the heart rate (this change is in phase with respiration, though there is a time lag between respiration and these cardiac oscillations). ...
... The resulting heart rate oscillations have a 180-degree phase relationship to arterial pressure changes but are in phase with respiration (Noble & Hochman, 2019;Sevoz-Couche & Laborde, 2022). Hence in spontaneous breathing with normal breath frequencies, cardiac oscillations termed Respiratory Sinus Arrhythmia (RSA) are induced by two influences: direct (through central medullary neurons) and indirect (associated with changes in arterial pressure), without coherence between them (Laborde et al., 2021;Noble & Hochman, 2019;Sevoz-Couche & Laborde, 2022). These cardiac oscillations with respiration can be modified with changes in specific breath characteristics including the relative durations of inspiration and expiration (Laborde et al., 2021;Noble & Hochman, 2019;Sevoz-Couche & Laborde, 2022). ...
... Hence in spontaneous breathing with normal breath frequencies, cardiac oscillations termed Respiratory Sinus Arrhythmia (RSA) are induced by two influences: direct (through central medullary neurons) and indirect (associated with changes in arterial pressure), without coherence between them (Laborde et al., 2021;Noble & Hochman, 2019;Sevoz-Couche & Laborde, 2022). These cardiac oscillations with respiration can be modified with changes in specific breath characteristics including the relative durations of inspiration and expiration (Laborde et al., 2021;Noble & Hochman, 2019;Sevoz-Couche & Laborde, 2022). During low i/e breathing healthy individuals showed (i) increased HF-HRV (Bae et al., 2021;Strauss-Blasche et al., 2000;Van Diest et al., 2014) and (ii) increased RMSSD (Bae et al., 2021;De Couck et al., 2019;Laborde et al., 2021) suggesting that low i/e breathing increases VmHRV. ...
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Reduced vagally mediated heart rate variability (VmHRV) has been reported in patients with chronic pain. In healthy persons, breathing with longer expiration relative to inspiration increases VmHRV at 12 breaths per minute. The present study aimed to determine the immediate effect of breathing with longer expiration relative to inspiration on VmHRV and mood states in patients with chronic pain. Fifty patients with chronic pain aged between 20 and 67 years were prospectively randomized as two groups with an allocation ratio of 1:1. The interventional group practiced breathing with metronome based visual cues, maintaining an inspiration to expiration ratio of 28:72 (i/e ratio, 0.38) at a breath rate of 12 breaths per minute. The average i/e ratio they attained based on strain gauge respiration recording was 0.685 (SD 0.48). The control group, which looked at the metronome without conscious breath modification had an average i/e ratio of 0.745 (SD 0.69). The VmHRV, respiration and self-reported mood states (using the Brief Mood Introspection Scale (BMIS)) were assessed. There was a significant increase in HF-HRV and RMSSD during low i/e breathing (repeated measures ANCOVA, Bonferroni adjusted post-hoc test, p < 0.05; in all cases). Self-reported mood states changed as follows: (i) following low i/e breathing positive-mood states increased while the aroused mood state decreased whereas (ii) following the control intervention the aroused mood state increased (repeated measure ANOVA, p < 0.05; in all cases). Hence breathing with prolonged expiration is possibly useful to increase VmHRV and improve self- reported mood states in patients with chronic pain.
... Indeed, gold standard manuals for HRV biofeedback teach clients to slow their respiration rate to the RF range, which is between 4.5 Zachary M. Meehan meehanz@udel.edu effects of breathing at various IE ratios (Bae et al., 2021;Cappo & Holmes, 1984;Edmonds et al., 2009;Klintworth et al., 2012;Laborde et al., 2021;Lin et al., 2014;Paprika et al., 2014;Strauss-Blasche et al., 2000;Van Diest et al., 2014). However, these studies present methodological challenges that may have influenced the findings. ...
... One study reported an advantage for equal inhalations and exhalations (Lin et al., 2014), and another reported an advantage for longer inhalation periods (Paprika et al., 2014). Four studies observed an advantage for longer exhalations than inhalations (Bae et al., 2021;Laborde et al., 2021;Strauss-Blasche et al., 2000;Van Diest et al., 2014). Because only Laborde and colleagues (2021) confirmed that their participants breathed at 6 bpm, this was the only study that evaluated the effect of IE ratio on HRV during RF-range breathing. ...
... Specifically, four studies neglected to randomize their participants and/or counterbalance the conditions (Bae et al., 2021;Klintworth et al., 2012;Strauss-Blasche et al., 2000;Van Diest et al., 2014). Additionally, eight studies did not confirm that the participants breathed at their assigned RR or IE ratios (Bae et al., 2021;Cappo & Holmes, 1984;Edmonds et al., 2009;Klintworth et al., 2012;Laborde et al., 2021;Lin et al., 2014;Strauss-Blasche et al., 2000;Van Diest et al., 2014). Finally, three studies reported only significant findings for a select group of the metrics evaluated (Bae et al., 2021;Cappo & Holmes, 1984;Paprika et al., 2014), thereby increasing the possibility of inflated Type I error rates (Kepes et al., 2014). ...
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Slow-paced breathing at an individual’s resonance frequency (RF) is a common element of heart rate variability (HRV) biofeedback training (Laborde et al. in Psychophysiology 59:e13952, 2022). Although there is strong empirical support for teaching clients to slow their respiration rate (RR) to the adult RF range between 4.5 and 6.5 bpm (Lehrer & Gevirtz, 2014), there have been no definitive findings regarding the best inhalation-to-exhalation (IE) ratio to increase HRV when breathing within this range. Three methodological challenges have frustrated previous studies: ensuring participants breathed at the target RR, IE ratio, and the same RR during each IE ratio. The reviewed studies disagreed regarding the effect of IE ratios. Three studies found no IE ratio effect (Cappo & Holmes in J Psychosom Res 28:265-273, 1984; Edmonds et al. in Biofeedback 37:141-146, 2009; Klintworth et al. in Physiol Meas 33:1717-1731, 2012). One reported an advantage for equal inhalations and exhalations (Lin et al. in Int J Psychophysiol 91:206?211, 2014). Four studies observed an advantage for longer exhalations than inhalations (Bae et al. in Psychophysiology 58:e13905, 2021; Laborde et al. in Sustainability 13:7775, 2021; Strauss-Blasche et al. in Clin Exp Pharmacol Physiol 27:601?60, 2000; Van Diest et al. in Appl Psychophysiol Biofeedback 39:171?180, 2014). One study reported an advantage for longer inhalations than exhalations (Paprika et al. in Acta Physiol Hung 101:273?281, 2014). We conducted original (N = 26) and replication (N = 16) studies to determine whether a 1:2 IE ratio produces different HRV time-domain, frequency-domain, or nonlinear metrics than a 1:1 ratio when breathing at 6 bpm. Our original study found that IE ratio did not affect HRV time- and frequency-domain metrics. The replication study confirmed these results and found no effect on HRV nonlinear measurements.
... Different paced breathing techniques were shown to modulate both the parasympathetic and sympathetic nervous systems (sympathovagal balance) (Bernardi et al., 2001;Zaccaro et al., 2018) with several studies successfully exploring the effectiveness of slow-breathing exercises in promoting parasympathetic stimulation (Bae et al., 2021;Komori, 2018;Laborde et al., 2022;Laborde, Lentes, et al., 2019;Laborde et al., 2021;Magnon et al., 2021;You et al., 2021You et al., , 2022. However, it is still not yet completely understood to which extent the features of the paced breathing, other than respiratory rate, contribute to its effectiveness. ...
... Therefore, controlling the relative timing of inspiration and expiration in breathing exercises (i/e ratio) seems to be an effective way to modulate the sympathovagal balance. A recent study showed that a deep and slow breathing pattern with a prolonged exhalation phase (low i/e ratio) stimulates the PNS for a higher period, which evidenced positive cognitive and physiological outcomes (Hoffmann et al., 2019;Laborde et al., 2022;Laborde, Lentes, et al., 2019;Laborde et al., 2021). ...
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Paced breathing exercises with prolonged exhalation have been commonly used to reduce stress and anxiety by stimulating parasympathetic activity. However, increasing sympathetic activity may also provide benefits such as increased alertness and energy levels. In this work, we investigate the physiological impact of an 80-second breathing exercise with a prolonged inspiratory period of 6 seconds followed by 2 seconds of exhalation on the sympathetic system. We collected raw two-channel prefrontal electroencephalography and photoplethysmography signals of 19 subjects using EMOTAI’s headband while performing the proposed exercise every workday for 2 weeks straight. Physiological metrics such as heart rate, heart rate variability, and absolute power of the brain waves were extracted before and during the exercise to measure its effectiveness. A marked increase in beta wave power was observed, along with a significant increase in both heart rate and heart rate variability. The cardiovascular results indicate that the proposed exercise effectively raised sympathetic activity. Simultaneously, the observed neural activity is consistent with that seen during focused attention and heightened mental processing.
... These might be the basis of the in uence of abdominal breathing on mental health. As for the breathing method with altered inhalation and exhalation duration, participants in a study reported increased relaxation, stress reduction, mindfulness, and positive energy when breathing with a low I/E ratio compared to a high I/E ratio [18][19][20][21]. The processes of inhalation and exhalation have distinct effects on the autonomic nervous system. ...
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Background Breathing exercises, particularly those involving altered inhalation/exhalation duration ratios (I/E ratios) and increased abdominal movement, have demonstrated the potential for alleviating symptoms of mental health issues. However, it remains unclear which approach is more effective. This study aims to examine how resting respiratory patterns (e.g., I/E ratios and abdominal movement) relate to mental health, potentially guiding psychologists in recommending tailored breathing exercises. Methods A total of 240 university students (120 male and 120 female) were recruited by systematic sampling. The I/E ratio and the contribution of abdominal movement to the sum of abdominal and thoracic movements AM/(AM + TM) were recorded by respiration belts, while depression, anxiety, and stress levels were assessed with the DASS-21. Data were analyzed for each gender; each gender being categorized into either a low or high level symptom category. Results Women with high stress symptoms exhibited significantly lower I/E ratios (a lower I/E ratio indicates breathing with relatively shorter inhalation and longer exhalation) compared to those with lower stress symptoms (n = 117, F = 4.198, p = 0.043, ηp² = 0.035). A negative correlation was observed between I/E ratios and depression in women (n = 117, r = -0.211, p = 0.023). For students with high anxiety symptoms, I/E ratios were negatively correlated with anxiety scores in both men (n = 61, r = -0.292, p = 0.022) and women (n = 70, r = -0.392, p < 0.001). There were no substantial correlations between abdominal movement and mental health. Conclusions In general, university students who exhibit relatively shorter inhalations and longer exhalations tend to have poorer mental health, especially among women; This respiratory pattern may represent an autonomic compensatory strategy for coping with psychological distress. More attention could be devoted to breathing exercises involving altered I/E ratios as part of mental health management programs.
... In a study of athletes using slow-paced breathing self-Non-Contact Monitoring of Inhalation-Exhalation (I:E) Ratio in Non-Ventilated Subjects regulation to influence cardiac vagal activity, it was observed that vagal activity increased as the exhalation phase grew resulting in a lower I:E ratio [10]. This is in agreement with findings in healthy volunteers where increased relaxation and stress reduction were observed at lower I:E ratios [11]. ...
Article
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Objective: The inhalation-exhalation (I:E) ratio, known to be an indicator of respiratory disease, is the ratio between the inhalation phase and exhalation phase of each breath. Here, we report on results from a non-contact monitoring method for the determination of the I:E ratio. This employs a depth sensing camera system that requires no sensors to be physically attached to the patient. Methods: A range of I:E ratios from 0.3 to 1.0 over a range of respiratory rates from 4 to 40 breaths/min were generated by healthy volunteers, producing a total of 3,882 separate breaths for analysis. Depth information was acquired using an Intel D415 RealSense™ camera placed at 1.1 m from the subjects’ torso. This data was processed in real-time to extract depth changes within the subjects’ torso region corresponding to respiratory activity. This was further converted into a respiratory signal from which the I:E ratio was determined (I:E depth ). I:E depth was compared to spirometer data (I:E spiro ). Results: A Bland Altman analysis produced a mean bias of –0.004, with limits of agreement [–0.234, 0.227]. A linear regression analysis produced a line of best fit given by I:E depth = 1.004 × I:E spiro – 0.006, with 95% confidence intervals for the slope [0.988, 1.019] and intercept [–0.017, 0.004]. Conclusion: We have demonstrated the viability of a non-contact monitoring method for determining the I:E ratio on healthy subjects breathing without mechanical support. This measure may be useful in monitoring the deterioration in respiratory status and/or response to therapy within the patient population.
... Preliminary results suggest that breathing patterns may interact with RR and influence HRV indices and subjective feelings of anxiety or relaxation (Lin et al., 2014;Van Diest et al., 2014). A recent study on athletes investigated the relationship between I/E ratio and vmHRV during 5min breathing sessions at 0.1 Hz (Laborde et al., 2021). In this withinsubject experiment, several I/E ratios were compared, and the results indicated that longer exhalation was related to higher vmHRV levels. ...
Article
The primary aim was to investigate how respiration rate and inhalation/exhalation ratio influence self‐reported state anxiety during a single slow diaphragmatic breathing exercise session. Eight hundred and twenty‐eight participants completed the study at two separate geographical locations (Poland and Spain). Participants performed a 10‐min online guided breathing exercise. Respiration rates were sampled from a continuous uniform distribution (ranging from 6 to 12 breaths/min). Similarly, inhalation/exhalation ratios were treated as continuous variables and sampled from a uniform distribution for each participant. An application programed for this experiment displayed visual and auditory cues adjusted for each participant. Before and after the breathing exercise, each participant filled in the Current Anxiety Level Measure questionnaire. Self‐trait anxiety was measured with the Clinically Useful Anxiety Outcome Scale. A linear regression model showed that respiration rate, trait anxiety, pre‐test anxiety, and nationality (Polish/Spanish) were positively related to post‐test anxiety levels. Adding quadratic terms of respiration rate and inhalation/exhalation ratio did not improve model fit. Polish participants exhibited higher post‐test anxiety levels compared with the Spanish subsample. Age was negatively associated with post‐test anxiety. No significant relationships between inhalation/exhalation ratio and post‐test anxiety level were found. Slower respiration rates during a single‐session breathing exercise are linearly associated with lower post‐test anxiety levels in a large and varied sample. This study is the largest to date and may offer further guidance for predicting expected effect sizes for the relationships between anxiety and respiratory dynamics.
... For example, 2:2 may be an appropriate ratio for moderate and high-intensity running but may lead to hyperventilation at lower relative intensities. Highly unequal ratios (e.g., 3:6) may be useful for cueing long exhales, while the reverse (6:3) is undesirable for its excessively short exhale phase47 . ...
... This has a positive impact on the vagal tone and a negative impact on sympathetic discharge. Recordings from the cardiac autonomic nerves show that neuronal activity rises in the sympathetic during inspiration and vagal fibres during expiration (Adhana et al. 2013;Gerritsen & Band 2018;Koeppen 2009;Laborde et al. 2021). ...
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ABSTRAK Senaman adalah bahagian penting dalam rawatan bukan farmakologi bagi individu dengan prahipertensi, hipertensi atau mereka yang menerima rawatan antihipertensi. Untuk kesihatan optimum, orang dewasa yang lebih tua harus melakukan 150-300 minit aktiviti aerobik ringan hingga sederhana atau 75-150 minit aktiviti aerobik berat setiap minggu mengikut saranan semasa. Kajian kawalan rawak selama 14 minggu telah dijalankan dengan 87 peserta yang berusia lebih daripada 30 tahun, mengalami hipertensi, indeks jisim badan (BMI) 18.5-24.99 kg/m 2 , dan tidak aktif secara fizikal. Peserta telah dibahagikan kepada empat kumpulan; kawalan (n:24), latihan pernafasan (BE) (n:21), latihan interval berintensiti tinggi (HIIT) (n:20), dan Campuran (n:22). Kumpulan BE melakukan latihan pernafasan perlahan mengikut protokol 8 set selama 10 minit. Kumpulan HIIT mengikuti protokol senaman selama 40 minit. Kumpulan campuran melakukan kedua-duanya manakala kumpulan kawalan mengekalkan aktiviti harian. Penilaian awal dilakukan pada Minggu 0,
Article
Objective Slow-paced breathing (SPB) with prolonged exhalation is assumed to stimulate vagal reflexes, which is represented by increased heart rate variability (HRV) values. However, most trials were conducted in healthy participants. We sought to evaluate the feasibility of SPB in hospitalized patients with confirmed bilateral COVID-19 pneumonia with major respiratory impairment and to investigate if SPB shows acute increasing effects on HRV measures in these severely ill patients with distinctly reduced vagal tone. Methods This single-center randomized controlled clinical trial enrolled 23 patients in the intervention (4-second inhalation, 6-second exhalation for 20 minutes 3× daily) and 23 patients in the control group (IG/CG). The effects of SPB on HRV were calculated using post-hoc likelihood ratio tests. Baseline HRV measures between the groups over time were compared using multilevel mixed-effect linear regression models with random slope including the covariates relevant comorbidities, COVID-19 medication, and age. Results HRV values at baseline were significantly decreased in all patients. During SPB, HRV parameters increased significantly (ln(SDNN), ln(LF), ln(TP); all p < .001). Higher breathing rate at baseline correlated with lower LF during SPB ( p < .045). IL-6 morning levels were associated with lower HRV measures ( p < .001). Resting HRV measures as well as subjective health increased over hospitalization time with no differences between IG and CG (comparing random slope with random slope interaction models: all LR χ ² (5) < 4.5; p > .48). Conclusion SPB is feasible and safe in patients with bilateral COVID-19 pneumonia and appears to be an effective self-performed intervention to acutely increase HRV measures. This observation was independent of comorbidities and comedication. Further trials should corroborate these findings and extend it to other severely ill populations. Registration German Clinical Trials Register under ID DRKS00023971 (https://drks.de/search/en/trial/DRKS00023971), with a Universal Trial Number (UTN) U1111-1263-8658
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The aim of this experiment was to test the immediate effects of slow-paced breathing on executive function. Slow-paced breathing is suggested to increase cardiac vagal activity, and the neurovisceral integration model predicts that higher cardiac vagal activity leads to better executive functioning. In total, 78 participants (41 men, 37 women; M age = 23.22 years) took part in two counterbalanced experimental conditions: a 3 × 5 min slow-paced breathing condition and a television viewing control condition. After each condition, heart rate variability was measured and participants performed three executive function tasks: the color-word match Stroop (inhibition), the automated operation span task (working memory), and the modified card sorting task (cognitive flexibility). Results showed that performance on executive function tasks was better after slow-paced breathing compared to control, with higher scores observed for Stroop interference accuracy, automated operation span score, and perseverative errors, but not Stroop interference reaction times. This difference in executive function between experimental conditions was not mediated by cardiac vagal activity. Therefore, findings only partially align with predictions of the neurovisceral integration model. Slow-paced breathing appears a promising technique to improve immediate executive function performance. Further studies are recommended that address possible alternative underlying mechanisms and long-term effects.
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Introduction Slow-paced breathing (SPB) is a well-known relaxation technique in athletes, which has also the potential to help optimize addiction treatments based on its effects on the autonomic nervous system. Specifically, these effects directly impact cardiac vagal activity (CVA), the activity of the vagus nerve regulating cardiac functioning. The effects of long-term SPB interventions on CVA have already received some attention; however, the effects of a single SPB session on CVA still require further investigation. Consequently, the aim of this study was to investigate the effects of SPB on CVA during, immediately after, and 60 min after a single SPB session. Methodology Twenty-four athletes were involved in a within-subject design, with two conditions: slow-paced breathing (at 6 cycles per minute) and a control condition watching an emotionally neutral TV documentary while breathing at a spontaneous breathing rate. CVA was derived from heart rate variability measurement and indexed via the root mean square of successive differences, RMSSD. Results Results showed that RMSSD measured during SPB was significantly higher than when measured before SPB, right after SPB, and 60 min after SPB. No changes were observed in the control condition. Discussion Findings regarding concomitant effects of SPB on CVA are in line with previous literature. The return to baseline observed immediately after SPB and 60 min after SPB suggests that the effects on CVA are only transitory. Practical Implications Given higher CVA has been linked to decreased cravings in addictions, future research should investigate to which extent SPB may be an effective technique to help coping with craving attacks on an acute basis.
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Heart rate variability (HRV) represents fluctuations in the time intervals between successive heartbeats, which are termed interbeat intervals. HRV is an emergent property of complex cardiac-brain interactions and non-linear autonomic nervous system (ANS) processes. A healthy heart is not a metronome because it exhibits complex non-linear oscillations characterized by mathematical chaos. HRV biofeedback displays both heart rate and frequently, respiration, to individuals who can then adjust their physiology to improve affective, cognitive, and cardiovascular functioning. The central premise of the HRV biofeedback resonance frequency model is that the adult cardiorespiratory system has a fixed resonance frequency. Stimulation at rates near the resonance frequency produces large-amplitude blood pressure oscillations that can increase baroreflex sensitivity over time. The authors explain the rationale for the resonance frequency model and provide detailed instructions on how to monitor and assess the resonance frequency. They caution that patterns of physiological change must be compared across several breathing rates to evaluate candidate resonance frequencies. They describe how to fine-tune the resonance frequency following an initial assessment. Furthermore, the authors critically assess the minimum epochs required to measure key HRV indices, resonance frequency test-retest reliability, and whether rhythmic skeletal muscle tension can replace slow paced breathing in resonance frequency assessment.
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This systematic review was conducted to evaluate the effect of heart rate variability biofeedback (HRV BFB) on performance of athletes. Six electronic databases (Springerlink, SportDiscus, Web of Science, PROQUEST Academic Research Library, Google Scholar, and ScienceDirect) and article references were searched. Eligibility criteria were: 1. experimental studies involving athletes randomly allocated among groups (randomized control trial); 2. availability of HRV BFB as a treatment compared to a control condition (CON) that involves regular sport/dance training, a placebo (PLA) or other methods of BFB; 3. performance-related variables such as a dependent index; and, 4. peer-reviewed articles written in English. Out of 660 articles, six studies were included in the systematic review which involved 187 athletes (females: n = 89; males n = 98). Six studies compared HRV BFB with a CON, three studies compared HRV BFB with a PLA, and two studies differentiated HRV BFB with other methods of BFB. Findings support HRV BFB as a potential intervention to improve fine and gross motor function in athletes.
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Background Individuals are able to perform goal-directed behaviors thanks to executive functions. According to the neurovisceral integration model, executive functions are upregulated by brain areas such as the prefrontal and cingulate cortices, which are also crucially involved in controlling cardiac vagal activity. An array of neuroimaging studies already showed that these same brain areas are activated by transcutaneous vagus nerve stimulation (tVNS). Despite evidence toward effects of tVNS on specific executive functions such as inhibitory control, there have been no studies investigating what type of inhibition is improved by tVNS by systematically addressing them within the same experiment. Furthermore, the effect of tVNS on another core executive function, cognitive flexibility, has not yet been investigated. Objective We investigated the effects of tVNS on core executive functions such as inhibitory control and cognitive flexibility. Methods Thirty-two participants (nine women, Mage = 23.17) took part in this study. Vagally mediated heart rate variability parameters (root mean square of successive differences, RMSSD, and high frequency, HF) were measured while participants performed four different cognitive tasks that mainly rely on different aspects of both the aforementioned executive functions. Results Despite clear conflict effects in the four tasks, only performance on the task used to measure set-shifting paradigm was improved by tVNS, with switch costs being lower during tVNS than during sham stimulation. Furthermore, HF increased during each of the cognitive flexibility tasks, although HF during tVNS did not differ from HF during sham stimulation. Conclusion The results indicate for the first time (a) that tVNS can increase cognitive flexibility in a set-shifting paradigm, and (b) that tVNS may exert a stronger effect on cognitive flexibility than inhibition. The present study provides only partial evidence for the neurovisceral integration model. Future studies should address further paradigms that demand cognitive flexibility, thus investigating this new hypothesis on the specificity of the tVNS effects on cognitive flexibility.
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We performed a systematic and meta analytic review of heart rate variability biofeedback (HRVB) for various symptoms and human functioning. We analyzed all problems addressed by HRVB and all outcome measures in all studies, whether or not relevant to the studied population, among randomly controlled studies. Targets included various biological and psychological problems and issues with athletic, cognitive, and artistic performance. Our initial review yielded 1868 papers, from which 58 met inclusion criteria. A significant small to moderate effect size was found favoring HRVB, which does not differ from that of other effective treatments. With a small number of studies for each, HRVB has the largest effect sizes for anxiety, depression, anger and athletic/artistic performance and the smallest effect sizes on PTSD, sleep and quality of life. We found no significant differences for number of treatment sessions or weeks between pretest and post-test, whether the outcome measure was targeted to the population, or year of publication. Effect sizes are larger in comparison to inactive than active control conditions although significant for both. HRVB improves symptoms and functioning in many areas, both in the normal and pathological ranges. It appears useful as a complementary treatment. Further research is needed to confirm its efficacy for particular applications.
Article
Efforts in optimizing transcutaneous vagus nerve stimulation (tVNS) are crucial to further develop its potential in improving cognitive and autonomic regulation. The present study focused on this topic. The aim was to compare for the first time the main stimulation areas of the ear currently used in studies with tVNS, taking cognitive as well as neurophysiological effects into account. The main areas to be compared with one another were tragus, cymba conchae, and earlobe (sham) stimulation. Post-error slowing, which has already been shown to be influenced by tVNS, was used to investigate the cognitive effects of tVNS when applied on the different auricular areas. On the neurophysiological level, we measured pupillary responses as an index of norepinephrine activity during post-error slowing, and cardiac vagal activity to investigate the activation of neural pathways involved in post-error slowing. Stimulation of different auricular areas led to no differences in post-error slowing and in pupillary responses. However, the neurological processes involved in post-error slowing could be observed, since norepinephrine activity increased after committing an error. Further, there was an increase in cardiac vagal activity over the test period that was independent of the stimulation areas. The results suggest that tVNS targeting the ear might have a non-specific effect on the processing of error commission, on pupillary responses, and on cardiac vagal activity. We conclude that it is necessary to consider alternatives for sham conditions other than electrical earlobe stimulation.
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Slow deep breathing (SDB) is commonly employed in the management of pain, but the underlying mechanisms remain equivocal. This study sought to investigate effects of instructed breathing patterns on experimental heat pain and to explore possible mechanisms of action. In a within-subject experimental design, healthy volunteers (n = 48) performed four breathing patterns: 1) unpaced breathing (UB), 2) paced breathing at the participant's spontaneous breathing frequency (PB), 3) SDB at six breaths per minute with a high inspiration/expiration ratio (SDB-H), and 4) SDB at six breaths per minute with a low inspiration/expiration ratio (SDB-L). During presentation of each breathing pattern, participants received painful heat stimuli of three different temperatures and rated each stimulus on pain intensity. Respiration, heart rate, and blood pressure were recorded. Compared to UB, participants reported less intense pain during each of the three instructed breathing patterns. Among the instructed breathing patterns, pain did not differ between PB and SDB-H, and SDB-L attenuated pain more than the PB and SDB-H patterns. The latter effect was paralleled by greater blood pressure variability and baroreflex effectiveness index during SDB-L. Cardiovascular changes did not mediate the observed effects of breathing patterns on pain. Perspective: SDB is more efficacious to attenuate pain when breathing is paced at a slow rhythm with an expiration that is long relative to inspiration, but the underlying mechanisms remain to be elucidated.
Article
Detecting errors is crucial for adapting one's own actions. Moreover, behavior is often optimized by adapting to maladaptive actions, i.e. errors. In this regard, recent studies and models of error monitoring point to an involvement of emotional states in error monitoring. A psychophysiological correlate of the latter is the error negativity or error-related negativity (Ne/ERN), reflecting partly the functional implementation of anterior cingulate cortex functions. In the present study, we aimed to test whether neurophysiological aspects of error monitoring can be altered by a relaxation technique, i.e. slow-paced breathing. Slow-paced breathing has been shown to increase cardiac vagal activity. According to the neurovisceral integration model, cardiac vagal activity is thought to be a marker of the effectiveness of executive functions. We tested the effect of slow-paced breathing on error monitoring, i.e. the Ne/ERN and behavioral adaptation in a modified flanker task, a cognitive task during which performance depends on executive control. The Ne was increased following slow-paced breathing compared to a passive control condition. Furthermore, behavioral results indicate that response variability decreased in the slow-paced breathing condition whereas overall performance remained constant. We conclude that slow-paced breathing improves the ability to focus on the task at hand. Thus, the error monitoring system is being supported in keeping the pace, i.e. tracking responses.