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THE EFFECT OF PHONATED BREATHING ON OXYGEN 
UPTAKE DURING AND AFTER SUBMAXIMAL CYCLING
Kaja STANKOVIĆ1, Nejka POTOČNIK1
1Institute of Physiology, Medical Faculty, University of Ljubljana, Slovenia
Corresponding author:
Nejka POTOČNIK
University of Ljubljana, Medical Faculty,  Institute of Physiology,  Zaloška 4, 1000 Ljubljana, 
Slovenia
Phone: +386 1 543 7523 
E-mail: nejka.potocnik@mf.uni-lj.si
ABSTRACT
Purpose: Positive expiratory pressure (PEP) exhalation during exercise is reported 
to improve body adaptation to exercise and enhance the exercise tolerance in patients 
with chronic obstructive pulmonary disease. Wearing mouthguards results in lower 
oxygen consumption and increased performance by increasing PEP in athletes. Airway 
resistance during expiration can be manipulated by phonation. Thus, the aim of our 
study was to examine the effects of phonated breathing on cardiopulmonary adaptation 
to moderate exercise and subsequent recovery. 
Methods: 26 young healthy participants conducted the same moderate stea-
dy cycling protocol using three different breathing patterns: spontaneous breathing 
(BrP1), phonated breathing pronouncing the sound “h” (BrP2) and phonated breathing 
pronouncing the sound “sh” (BrP3). Heart rate, oxygen consumption, CO2 production, 
respiratory rate, tidal volume, respiratory exchange ratio and ventilatory equivalents 
were measured (Cosmed, Italy) before, during and 20 minutes after cycling. Data were 
analyzed using SPSS, with significance level p<0.05. 
Results: The analysis revealed no significant differences related to the breathing 
economy; respiratory rate was increased, and tidal volume decreased with spontaneous 
breathing compared to both phonated breathing patterns during exercise; no effect of 
BrPs on cardiopulmonary parameters was found in recovery.
Conclusion: Our results do not confirm the assumption that PEP breathing improves 
exercise economy probably because of the low exercise intensity applied. Further studies 
should be conducted at higher exercise loads or in patients with pulmonary dysfunction.
Keywords: phonated exhalation, breathing pattern, positive expiratory pressure, 
metabolic efficiency, moderate exercise
Original scientific article                       DOI: https://doi.org/10.35469/ak.2021.329
received: 2022-07-05                UDC: 612.2:796.01
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VPLIV DIHALNEGA VZORCA NA VENTILACIJO IN PRIVZEM 
KISIKA MED IN PO SUBMAKSIMALNI VADBI NA SOBNEM 
KOLESU
IZVLEČEK
Cilj: Izdih s pozitivnim tlakom (PEP) izboljša zmožnost fiziološke prilagoditve na 
napor ter vadbeno toleranco pri bolnikih s kronično obstruktivno pljučno boleznijo. 
Nošenje ustnih varoval, ki prav tako povečale upor v dihalnih poteh, zmanjša porabo 
kisika in poveča zmogljivost športnikov. Upor v dihalnih poteh lahko spreminjamo s fo-
nacijo. Tako je namen naše raziskave ugotoviti, ali fonacija med zmerno telesno vadbo 
vpliva na spremembe srčnih in dihalnih parametrov med in po taki vadbi 
Metode: 26 mladih prostovoljcev je trikrat izvedlo enako zmerno kolesarjenje, vsa-
kič ob uporabili drugačnega dihalnega vzorca (DV): spontano dihanje (DV1) in izdih 
ob izgovarjanju glasu H (DV2) oziroma Š (DV3). Pred, med in 20 minut po vadbi smo 
merili srčno frekvenco, porabo kisika, izločanje ogljikovega dioksida, frekvenco in vo-
lumen dihanja, pljučno ventilacijo, respiratorni količnik in ventilacijske ekvivalente z 
metabometrom Cosmed. Podatke smo obdelali s programom SPSS in postavili mejo 
signifikantnosti pri p<0,05. 
Rezultati: Analiza rezultatov ni pokazala nobenih statistično značilnih sprememb 
metabolnih parametrov, kakor tudi ne srčne frekvence z ozirom na uporabljen DV. Zna-
čilno povečana je bila le frekvenca dihanja in zmanjšan dihalni volumen pri spontanem 
dihanju glede na oba s fonacijo povezana DV med naporom. V okrevanju po naporu ni 
bilo nobenih razlik v merjenih parametrih.
Zaključek: Rezultati naše študije niso potrdili domneve, da dihanje s PEP, ki ga 
povzročimo s fonacijo, poveča učinkovitost telesne vadbe, zmanjša porabo kisika in iz-
boljša telesno zmogljivost vendar ocenjujemo, da je bila intenziteta vadbe v naši študiji 
premajhna, da bi se tovrstne razlike izkazale. Zato bi bilo treba opraviti še nadaljnje 
raziskave in sicer z večjo obremenitvijo pri zdravih preiskovancih ali pa na bolnikih z 
respiratorno motnjo.
Ključne besede: fonacija, dihalni vzorec, pozitivni tlak v dihalnih poteh med izdi-
hom, metabolna učinkovitost, zmerna vadba
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INTRODUCTION
Breathing patterns (BrP) differ according to breathing frequency, breathing depth, 
inhalation/exhalation time relationship, and maneuvers applied during expiration (Dal-
lam & Kies, 2020). Expiratory maneuvers are particularly important since changing the 
resistance of the airways upon expiration can help maintain a positive pressure until 
the end of exhalation, thus keeping the alveoli and airways open (Francis & Brasher, 
1991) longer during the exhalation period. Phonation requires sustained/controlled ex-
halation. During speech and singing, breath duration and flow rates are controlled to 
support sound generation by the larynx (Lewis et al., 2021). Regulation of the glottic 
aperture by laryngeal muscle activity also helps to control ventilation (Lewis et al., 
2021). Therefore, the larynx could be considered a key modulator of expiratory flow 
upon phonation. Pronunciation of different voices can be used to change the resistance 
in the airways during exhalation (Hoffmann, Torregrosa, & Bardy, 2012). Grunting has 
been shown to improve force production during exercise (O'Connell et al., 2016).
In elite sports, there is a continuous search for strategies to improve performance 
(Harbour, Stöggl, Schwameder, & Finkenzeller, 2022). On the other hand, in patients 
with compromised breathing, strategies to minimize breathing effort during exercise 
would be appreciated to allow these patients to minimize the exercise associated dis-
comfort (Fagevik Olsén, Lannefors, & Westerdahl, 2015). The way we breathe strongly 
affects not only the respiratory system itself but also other systems in our body: car-
diovascular, nervous, endocrine, lymphatic, immune, digestive (Saoji, Raghavendra, 
Madle, & Manjunath, 2018).
To manipulate exhalation, pursed lip breathing (Tiep, Burns, Kao, Madison, & Her-
rera, 1986), specially designed mouthguards (Lässing et al., 2021) or simply phonati-
on of some particular voices could be applied during exercise to increase the airways 
resistance during exhalation. By breathing out against increased resistance, positive 
expiratory pressure (PEP) is achieved and it is commonly believed that PEP improves 
ventilation, at least in patients with pulmonary diseases (Fagevik Olsén & Westerdahl, 
2009; Fagevik Olsén , Lannefors, & Westerdahl, 2015), and potentially during exercise 
(Phimphasak, Ubolsakka-Jones, & Jones, 2018).
There are only a few studies about the effects of BrP on the physiological respon-
se to exercise (Green, Benson, & Martin, 2018; Lässing et al., 2021). Our recent 
study (Klanjšček, 2018) found that BrPs with increased expiratory resistance had a 
significant favorable effect on the economy of short-lasting trunk stabilization exer-
cise. Expiratory resistance was manipulated by pronouncing different sounds during 
exercise (Klanjšček, 2018) ‒ sound “sh” (as in push to increase resistance, and “h” 
(as in host) to decrease it ‒ and compared to spontaneous breathing. Oxygen con-
sumption and carbon dioxide production decreased during short-lasting trunk stabi-
lization exercise in the “sh” breathing pattern compared to the “h” breathing pattern 
and spontaneous breathing. Additionally, the respiratory quotient, ventilation, and 
heart rate during exercise decreased while ventilatory equivalents increased in the 
“sh” pattern compared to the “h” pattern and spontaneous breathing. The participants 
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perceived the “sh” pattern to be significantly easier compared to the other two BrPs 
(Klanjšček, 2018). 
Thus, we aimed to test whether the BrP where exhalation is manipulated by prono-
uncing different sounds during exercise affects the physiological response to aerobic 
exercise. To this purpose, the heart rate, oxygen consumption, CO2 production, and 
ventilation were measured before, during and after moderate cycling at constant load 
using the three different BrPs: the pronunciation of “sh” or “h” during exhalation, and 
spontaneous breathing. Crossover design was used to avoid differences between parti-
cipants. 
METHODS
The study was performed in the Exercise Physiology Laboratory of the Institute of 
Physiology, Medical Faculty, University of Ljubljana. Ethical approval of the study 
was obtained from the National Ethics Committee (No. 0102-326 / 2018/5). 
Subjects
26 healthy participants with comparable levels of physical activity were recruited by 
public invitation to participate voluntarily in this crossover study. Their physical exami-
nation and histories revealed no autonomic dysfunction, chronic diseases, medication 
usage or smoking. Their ECG and arterial blood pressure values were normal. Written 
informed consent was obtained before participation. The trial included 18 women and 8 
men, 20.85 ± 0.2 years old, with body mass index (BMI) 22.97 ± 0.59 kg/m2.
Experimental procedure
The study was carried out in a climate controlled laboratory room between 9 and 12 
am. The participants refrained from physical exertion for at least 1 day before the first 
exercise test and were asked not to perform additional physical activities during the 
experiment period. They were not allowed to consume any alcohol, caffeine or tobacco 
for at least 2 hours before the beginning of each exercise test and were asked to eat a 
light meal 1 hour before coming to the laboratory. Each participant visited the labo-
ratory 3 times in February and March with at least one relaxing day between the two 
consecutive visits. During the three visits, participants performed the same submaximal 
aerobic cycling with different BrPs during exercise. The BrP applied during a particular 
visit was chosen randomly and marked BrP1 for spontaneous breathing and BrP2/BrP3 
for exhaling upon pronouncing “h”/“sh”, respectively.
Each session started with blood pressure measurement at sitting rest and an expla-
nation of the breathing technique for the selected BrP. A silicone breathing mask was 
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placed upon the mouth and nose (Quark, Cosmed, Italy) to measure oxygen consump-
tion, CO2 production, and ventilation; ECG electrodes and a finger cuff for continuous 
blood pressure tracing were attached (Finapres 2300, Ohmeda, USA). The measure-
ment consisted of 5 minutes sitting at rest on a cycloergometer Ergoselect 100 (Ergo-
line, Germany) (baseline), 5 minutes of cycling at 100 W (women) and 140 W (men), 
respectively, at a cadence of 60 rpm and followed by 10 minutes of passive recovery. 
During cycling, a randomly selected BrP was applied.
Data acquisition and statistical analysis
Signals were captured simultaneously breath by breath using Quark CPET hard-
ware and software (Cosmed, Italy); arterial blood pressure and ECG were recorded 
by DATAQ system (DATAQ instruments Inc., DI-720 series, Ohio, USA). For analy-
sis, three separate intervals were determined: the last three minutes of sitting rest 
(baseline), the last three minutes of cycling (exercise), and the last three minutes of 
recovery (recovery). Oxygen consumption per body mass (VO2/kg), CO2 production 
per kg (VCO2/kg), respiratory exchange ratio (RER), ventilator equivalents (Veq for 
O2 and CO2), respiratory rate (RR), tidal volume (VT), and heart rate (HR) were 
determined. The data are presented on graphs as mean values ± standard deviation 
(SD). Additionally, enhanced post-exercise oxygen consumption (O2 debt) and oxy-
gen deficit (O2 deficit) at the onset of exercise were determined using Quark CPET 
analyzing software (Cosmed, Italy) based on the work of Hughson and Morrissey 
(Hughson and Morrissey 1983).
Statistical analysis was completed using IBM SPSS Statistics, version 27 (IBM, 
New York, USA). Data were tested for normality and a p<0.05 level of confidence was 
selected. We compared mean differences in measured parameters over time (before 
and during exercise + recovery) for all three BrPs with a one-way repeated measures 
ANOVA (rANOVA). The assumption of sphericity was checked using Mauchly's test; 
Greenhouse-Geisser or Huynh-Feldt corrections were applied when sphericity assump-
tion was violated as published elsewhere (Hopkins, Marshall, Batterham, & Hanin, 
2009). When detecting a significant time effect, corresponding contrast tests were used 
to identify differences between means according to BrP and time interval. For post hoc 
comparisons a least significant difference test was applied and the Bonferroni correc-
tion was used to eliminate type I error in multiple comparisons (Hopkins et al. 2009). 
In case of significant differences, Cohen’s d was determined to represent the effect 
size (ES) (Hopkins et al., 2009).
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RESULTS
RR increased during exercise in all three BrPs (Figure 1, Table 1), most in BrP1, 
where the mean value was 22.56 ± 1.1 min-1. RR in BrP1 was significantly higher than 
in BrP2 (p < 0.001) and BrP3 (p = 0.007). There were no statistical differences between 
BrP2 and BrP3 (p = 0.103). After exercise, RR dropped as expected, but in the last 3 
minutes of recovery it was still higher than the baseline values in all BrPs, but signifi-
cantly higher only in BrP1 (p = 0.001) (Table 1).
Table 1: Effect sizes presented as Cohen’s d values for all significant differences.
RR VT VE RER VO2/kg
VCO2/
kg
Veq 
for O2
Veq 
for 
CO2
BrP1base/ex 1.59 3.53 6.46 1.34 6.94 6.48 1.50 4.03
BrP1base/rec 0.67 - 1.26 0.80 - - 0.99 0.60
BrP1ex/rec 1.227 3.42 6.27 0.81 6.71 6.58 2,19 3.23
BrP2base/ex 0.41 3.46 4.00 1.18 6.54 6.59 1.81 2.38
BrP2base/rec - - 0.68 - - - 0.82 6.82
BrP2ex/rec 0.22 3.54 5.01 1.43 6.69 6.89 2.44 6.89
BrP3base/ex 0.41 3.24 4.42 1.50 7.49 6.76 1.41 2.40
BrP3base/rec - 0.46 1.10 0.76 - 0.63 1.14 0.63
BrP3ex/rec 0.47 3.23 4.36 0.88 6.55 6.07 1.96 6.37
BrP1ex/BrP2ex 0.72 1.05 - - - - - -
BrP1ex/BrP3ex 0.14 0.35 - - - - - -
BrP2ex/BrP3ex - 0.72 - - - - - -
BrP1 – breathing pattern 1, BrP2 - breathing pattern 2, BrP3 – breathing pattern 3, base – base-
line, ex – exercise, rec – recovery, RR – respiratory rate, VT – tidal volume, VE – ventilation, RER 
– respiratory exchange ratio, VO2 /kg – oxygen consumption per body mass, VCO2 /kg – carbon 
dioxide production per body mass, Veq for O2 – ventilatory equivalent for oxygen, Veq for CO2 - 
ventilatory equivalent for carbon dioxide. 
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Figure 1: Changes in RR during rest, exercise and recovery in different BrPs. Values 
are presented as the mean ± SD. * - significant difference between BrP1 and BrP2, 
# - significant difference between BrP1 and BrP3, § - significant difference in all BrPs 
between rest and exercise, Ω - significant difference in all BrPs between exercise and 
recovery, ∞ - significant difference in all BrPs between rest and recovery.
Figure 2: Changes in tidal volume during rest, exercise and recovery in different BrPs. 
Values are presented as the mean ± SD. * - significant difference between BrP1 and 
BrP2, # - significant difference between BrP1 and BrP3, ‡ significant difference be-
tween BrP2 and BrP3, § - significant difference in all BrPs between rest and exercise, 
Ω - significant difference in all BrPs between exercise and recovery, ∞ - significant 
difference in all BrPs between rest and recovery.
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Figure 2 shows the changes in VT, related effect sizes are presented in Table 1. The 
value increased the most in the group with BrP2, which had the lowest RR during exer-
cise. We found significant differences between all three BrP; the statistical difference 
between BrP1 and BrP2 was p < 0.001, between BrP1 and BrP3 p = 0.016 and between 
BrP2 and BrP3 p = 0.002. As can be seen from Figure 2, the values returned to baseline 
values at recovery; only in BrP3 did we find a significant difference between baseline 
and recovery (p = 0.008).
During exercise ventilation increased (Figure 3, Table 1), but no significant diffe-
rences were found between the groups. During the recovery, the values dropped but not 
to baseline values. Ventilation in recovery was significantly higher compared to baseli-
ne (p <0.001 for BrP1 and BrP3, and p = 0.003 for BrP2, respectively).
Figure 3: Changes in ventilation during rest, exercise and recovery in different BrPs. 
Values are presented as the mean ± SD. § - significant difference in all BrPs between 
rest and exercise, Ω - significant difference in all BrPs between exercise and recovery, 
∞ - significant difference in all BrPs between rest and recovery.
Figure 4 shows the changes in RER. No significant differences were found betwe-
en BrPs; related effect sizes are reported in Table 1. In recovery, the RER remained 
elevated above the resting value. It was significantly higher in the groups with BrP1 
(p < 0.001) and BrP3 (p = 0.001); in the group with BrP2 we did not find a difference 
(p = 0.333).
As expected, VO2/kg increased during exercise and remained increased at the end of 
the measurement (Fig. 5, Table 1). As can be seen from Figure 5, no significant differen-
ces were observed with regard to BrPs, neither at rest nor during exercise or recovery.
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Figure 4: Changes in respiratory exchange ratio during rest, exercise and recovery in 
different BrPs. Values are presented as the mean ±SD. § - significant difference in all 
BrPs between rest and exercise, Ω - significant difference in all BrPs between exercise 
and recovery, ∞ - significant difference in all BrPs between rest and recovery.
Figure 5: Changes in oxygen consumption during rest, exercise and recovery in differ-
ent BrPs. Values are presented as the mean ±SD. § - significant difference in all BrPs 
between rest and exercise, Ω - significant difference in all BrPs between exercise and 
recovery.
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Regarding VCO2/kg, there were no significant differences between groups during 
rest and exercise, we did, however, find a significant difference between baseline and 
recovery in BrP3 (P < 0.001) (Fig. 6, Table 1).
Figure 6: Changes in production of carbon dioxide during rest, exercise and recovery 
in different BrPs. Values are presented as the mean ± SD. § - significant difference in all 
BrPs between rest and exercise, Ω - significant difference in all BrPs between exercise 
and recovery, ∞ - significant difference in a particular BrP between rest and recovery.
Figure 7 presents the change in VEq for O2. No statistical differences were found 
between the groups in any of the phases, but a higher value was observed in the BrP2 
and BrP3 groups at rest and lower during exercise compared to BrP1. We found a sta-
tistical difference between baseline and exercise as well as between rest and exercise 
with respect to recovery, which was p < 0.001 in all BrPs (Table 1).
No significant differences between groups were observed during exercise and reco-
very in Veq for VCO2 (Figure 8). Statistical differences were observed between baseline 
and recovery. In the group with BrP1 the difference was p = 0.009; in the group with 
BrP2 p = 0.007; and in the group with BrP3 p = 0.002. Veq for CO2 was significantly 
increased during exercise compared to rest or recovery (p < 0.001) (Table 1).
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Figure 7: Changes in ventilatory equivalent of oxygen during rest, exercise and recov-
ery in different BrPs. Values are presented as the mean ± SD. § - significant difference 
in all BrPs between rest and exercise, Ω - significant difference in all BrPs between 
exercise and recovery, ∞ - significant difference in all BrPs between rest and recovery.
Figure 8: Changes in ventilatory equivalent of carbon dioxide during rest, exercise 
and recovery in different BrPs. Values are presented as the mean ± SD. § - significant 
difference in all BrPs between rest and exercise, Ω - significant difference in all BrPs 
between exercise and recovery, ∞ - significant difference in all BrPs between rest and 
recovery.
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Figure 9 shows O2 deficit and O2 debt throughout the three BrPs. O2 deficit (but 
not O2 debt) in spontaneous breathing was significantly higher compared to other BrPs 
(ES = 0.42 for BrP1 compared to BrP2 and 0.36 for BrP1 compared to BrP3, respecti-
vely). O2 debt was significantly lower compared to O2 deficit in all BrPs (ES = 0.87 for 
BrP1, 0.20 for BrP2 and 0.15 for BrP3, respectively).
Figure 9: Changes in oxygen deficit (O2 deficit) and oxygen debt (O2 debt) throughout 
all breathing patterns: spontaneous breathing (BrP1), pronouncing “h” (BrP2) and 
pronouncing “sh” (BrP3), respectively. * - significant with respect to BrPs. # - deficit 
versus debt.
DISCUSSION
Our first main finding was that phonation during moderate exercise has a minimal 
effect on the respiratory response to exercise and recovery in young, healthy partici-
pants. 
Our second main finding was that phonated breathing during moderate exerci-
se provoked an increased rate of perceived exertion compared to spontaneous bre-
athing. And our third main finding was that oxygen deficit at the onset of moderate 
exercise is significantly higher in spontaneous compared to phonated breathing. On 
the other hand, EPOC was not affected by BrP, indicating that in a steady state 
during moderate exercise excessive oxygen deficit was successfully eliminated by 
aerobic metabolism. 
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Although not significantly different, evidently lower RER during steady state exer-
cise in BrP3 compared to other BrPs suggested that restricted air flow during expira-
tion may cause CO2 retention. This assumption was supported by the increased CO2 
exhalation in the recovery phase after exercise (Fig.6) in BrP3. Additionally, during 
steady state exercise, RR in BrP3 was higher compared to that in BrP2, presumably 
because of the stimulation of the inspiratory center by increased arterial CO2 partial 
pressure. RR during spontaneous breathing was significantly increased compared to 
those in both BrP2 and BrP3 because of phonation excluding prolonged exhalation. 
Breathing against increased airway expiratory resistance (pronunciation of “sh”) versus 
open airway expiration (pronunciation of “h”) does not appear to alter airway diameter 
sufficiently to augment the minute ventilation response during moderate exercise. Even 
upon spontaneous breathing, minute ventilation was not changed compared to phonated 
breathing patterns.
The similar minute ventilation across all BrPs at steady state moderate exercise 
corresponding to an oxygen uptake of 23.5 mL/kg/min suggests that all BrPs applied 
can accommodate a moderate level of exercise intensity in young healthy participants 
(Plowman and Smith n.d.). 
In our study, VO2 did not differ during moderate physical activity at different BrPs. 
This finding is not in compliance with our previous study, where the reduced VO2 
in the low-intensity trunk stabilization exercise with hand-oscillation was confirmed 
upon phonated exhalation while pronouncing “sh” (Klanjšček, 2018). One possible 
explanation for this could be that the participants breathed in respiratory coupling with 
locomotion in the previous study. The entrainment could be responsible for better bre-
athing economy (Sporer, Foster, Sheel, & McKenzie, 2007). Further, VO2 was measu-
red at the onset of trunk stabilization exercise in our previous study and not during the 
steady state, and thus was accompanied by anaerobic metabolism. When substituting 
anaerobic metabolism with aerobic in the continuation of trunk stabilization exercise, 
the differences in VO2 between different BrPs decreased. This could imply that as the 
exercise is aerobic, the beneficial effects of PEP exhalation are decreased.
The association between anaerobic metabolism and breathing economy in connec-
tion to the use of a mouthguard was established (Schulze, Kwast, & Busse, 2019). 
The results of the studies examining the effect of different mouthguards on athletes’ 
performance concluded that the economy of breathing is improved by wearing mouth-
guards at high but not moderate exercise intensities (Lässing et al., 2021; Schulze et 
al., 2019). The mechanism proposed is altered exhalation, potentially against higher 
resistance produced by mouthguards (Schulze et al., 2019). The impact of breathing 
using mouthguards is being researched in connection with sports that due to their 
nature need this type of protection (such as rugby and hockey) (Phimphasak et al., 
2018; Schulze et al., 2019). Studies including young healthy athletes have found that 
altered exhalation due to wearing this equipment reduces the proportion of anaerobic 
metabolism at high-intensity exertion, compared to unmodified exhalation when not 
wearing it (Lässing et al., 2021). Francis and colleagues (Francis & Brasher, 1991) de-
scribed reduced VO2 and VEq for O2 upon mouthguard usage at high-intensity exercise 
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but not at low-intensity exercise. Since we did not confirm the beneficial effect of BrP3 
in our study, we may speculate again that the beneficial effect of phonated expiration 
is limited to predominantly anaerobic or high-intensity load. Additional investigations 
should be conducted to test this assumption.
Phonated exhalation can be compared to breathing with pursed lips. There are some 
articles about the effects of pursed lip breathing on the breathing load, but only resear-
ched in patients with impaired pulmonary function (Sakhaei, Sadagheyani, Zinalpoor, 
Markani, & Motaarefi, 2018). Sakhaei and colleagues (Sakhaei et al., 2018) found that 
in patients with COPD, oxygenation and CO2 excretion improve – as respiratory work 
is reduced - upon PEP provoked by pursed lips, while De Araujo (Pereira De Araujo, 
Karloh, Martins Dos Reis, Palú, & Fleig Mayer, 2015) and colleagues found that this 
type of breathing reduces dynamic hyperinflation, improving tolerance for exercise and 
O2 saturation in the blood during exercise in COPB. Breslin (Breslin, 1992) found 
that spontaneous rhythmic breathing through pursed lips can affect the coordination of 
respiratory muscle recruitment and provides patients with a sense of control over venti-
lation, which results in less anxiety, panic, and consequently reduces dyspnea. Exercise 
in healthy participants can be seen as a model of impaired pulmonary function, as it 
increases the load on the respiratory system due to increased need for O2 and produces 
more CO2. Based on our results we can conclude that the intensity of moderate exercise 
applied in our study was not high enough to reveal the advantages of PEP breathing du-
ring exercise in young healthy adults. The physiological effects of phonated breathing 
in COPB patients should be examined to determine the potential benefits of phonated 
exhalation (decrease exercise respiratory load and perceived exertion) during exercise 
in such patients.
We found a significantly increased O2 deficiency at the onset of moderate exercise 
upon spontaneous breathing compared to both phonated breathing patterns, indicating 
that spontaneous respiration was the least economical at the onset of exertion. On the 
contrary, the EPOC did not differ with regard to BrP. This finding supports our specula-
tion that beneficial effects of breathing against increased airway expiratory resistance, 
as in the pronunciation of “sh”, are manifested only when exercise metabolism is pre-
ferentially anaerobic. EPOC is decreased compared to O2 deficit at spontaneous bre-
athing, presumably because the products of anaerobic metabolism were removed and 
aerobically metabolized during steady state exercise due to its low intensity. O2 deficit 
and EPOC did not differ with respect to the sound pronounced. Further studies should 
be directed to explain this finding.
Bonsignore and colleagues (Bonsignore, Morici, Abate, Romano, & Bonsignore, 
1998) chose the VEq for O2 and CO2 as the main measure of respiratory efficiency. In 
our study, we found that both VEq for O2 and CO2 decreased during physical exertion 
compared to baseline, indicating that moderate exercise made the respiration more effi-
cient (Plowman & Smith, n.d., 2013); and there were no significant differences between 
individual BrPs. Differences were indicated, yet not significant: both VEq upon BrP2 
and BrP3 during exercise were lower than during spontaneous respiration. These ob-
servations can be linked to a study by Francis and Brasher (Francis & Brasher, 1991) 
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who found a lower Veq for O2 in subjects wearing mouthguards, indicating improved 
alveolar ventilation and oxygenation that allows an individual to maintain a certain 
level of exercise with less loss to the metabolic system; and to a study by Delaney and 
Montgomery (Delaney & Montgomery, 2005), who found that mouthguards obstruct 
airflow and thus affect VO2 and ventilation during strenuous exercise. Again, both stu-
dies have demonstrated greater breathing efficiency in subjects using mouth protective 
devices only at maximum load. 
There are some limitations to this research: in all participants the same load (140 W 
for males and 100 W for females) was applied as moderate exercise, neglecting indi-
vidual differences, and the correctness of breathing pattern implementation was not 
controlled as the participant’s mouth was covered by a breathing mask.    
In conclusion, we found no physiological benefits of phonation applied upon mode-
rate exercise that could advocate its use for economizing breathing at higher metabolic 
demand. However, decreased oxygen deficit at the onset of moderate exercise upon 
phonated compared to spontaneous breathing confirmed its positive effects on the ana-
erobic phase at the onset of exercise. This finding may potentially provide benefits for 
patients with compromised respiratory function owing to an enhanced proportion of 
anaerobic metabolism even at moderate exercise loads, however, further studies need 
to be conducted to test this assumption. On the other hand, “sh” pronouncing breathing 
may provoke CO2 retention at higher exercise intensities. Because phonated breathing 
during exercise is an atypical breathing pattern, it is subjectively rated as uncomfor-
table compared to spontaneous breathing, yet the latter does not differ from phonated 
breathing with regard to breathing efficiency. It is therefore probable that in athletes 
exercising at higher loads phonated breathing may potentially provide benefits in terms 
of attenuating oxygen deficit.
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