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DISCUSSION However, we have not evaluated psychophysiological
This study evaluated children’s learning ability of a variables to support the improvement of cognitive aspect in
simple breathing technique in order to determine whether our sample.
respiratory exercises can be considered appropriate tools in Based on our study, there was an increase in the
promoting psychophysiological self-regulation in children synchronicity between the sympathetic and parasympathetic
aged 5 to 6 years old. branches of the ANS during RSA after slow breathing
In this sense, we investigated the effects of slow breathing exercise training in preschool children. Regarding the
exercise training on heart rate dynamics and cardiorespiratory nonlinear HRV analysis, the results indicate gain of
coherence in preschool children. As main findings, we complexity, lower linearity and higher fractal behavior.
reported that (1) slow breathing training reduced the In this line, some studies evaluating HRV in different
parasympathetic heart rate control during RSA; (2) which meditation practices revealed interesting aspects of the
was related to improvements in cardiorespiratory coherence relationship between breathing and heart rhythms. Studies
and in the complexity of the heart rate dynamics in preschool evaluating slow breathing techniques reported the same
children during RSA; (3) there was no adverse effects of this heart rate pattern, represented in the frequency spectrum as
intervention. The absence of difference between control and a peak in LF band, around 0.1 Hz, characteristic of the state
intervention protocol reinforced our main data. Our results of cardiorespiratory coherence. Moreover, the literature
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suggest that RSA is not always associated with increase in the have already showed a reduction in vagal tone through
vagal tone. decrease in the HF power, which was attributed to the effects
Our data indicated progressive improvements in of slow breathing on the heart. It is interesting to note that
cardiorespiratory coherence, the best performance was techniques involving spontaneous breathing did not present
recorded in the last data collection, which occurred at the vagal reduction and the characteristic LF peak. 24-27
end of the training. This means that throughout the eight It was previously proposed14 that breathing at a
weeks of training, the children improved their ability to frequency of around 6 breaths / min (the central frequency of
modulate heart rate through the self-application of a the low-frequency band: 0.5 to 0.15 Hz) induce high and low
breathing technique. frequency of heart rate dynamics to synchronize and merge,
The evidence that children in this age group were able to increasing in amplitude and giving rise to the peak in LF in
induce an increase in cardiorespiratory coherence in themselves the power spectrum. The authors proposed that this is due to
has important implications for education. There is evidence a resonant frequency effect.
that the coherence state benefits the superior cognitive Activation in the LF band in the power spectrum is still
functions required in the academic environment, such as erroneously associated with a predominance of sympathetic
attention, memory, reasoning, and task performance. tone on heart rate. According to Billman, there is strong
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Furthermore, the coherence state is associated with a better evidence that the LF band expresses sympathetic and
psychosocial functioning, with reduced perceptions of parasympathetic modulation of heart rate and other unknown
emotional stress and a greater experience of positive emotions. variables. It is also indicated that most of the activation in the
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Techniques that generate the state of coherence have LF band may be explained by the parasympathetic component.
been used as intervention strategies in the promotion of In this way, it is proposed that the peak in LF verified in the
psychophysiological self-regulation. In educational settings, state of cardiorespiratory coherence represents a
the use of coherence-enhancing techniques has been synchronization between the action of the vagus nerve and
associated with improvements in emotional disposition, the sympathetic nerves on the heart. 29
classroom behavior, anxiety management in tests, learning, There are many studies in the literature indicating that
and academic performance. 2,22 slow breathing increases the parasympathetic tone 5,30,31 and
Self-regulation skills are also considered important for others indicating that it decreases vagal tone. 23,24,27,32
appropriate cognitive and psychosocial development in Nevertheless, the aforementioned studies suggest that slow
childhood. A previous study showed that self-regulation breathing promotes cardiorespiratory coherence or
2
skills in preschool children significantly increased the synchronization, characterized by the peak in LF around 0.1
development of children in various aspects, including Hz, which represents a synchronization between sympathetic
cognitive, social / emotional, language and physical aspect, and parasympathetic branches. 29
compared to the children who were not submitted to slow One more important point observed in our study is that
breathing exercise training. 2 resting HRV after the protocol training decreased significantly
In this context, the evidence that children are able to in the experimental group, suggesting that the slow breathing
perform self-regulation techniques through breathing, protocol training would have worsened baseline conditions,
generating a higher level of cardiorespiratory coherence, which seems a paradox. In fact, the conventional variables
associated to the benefic state of coherence, in favor of were much smaller, however, entropy and coherence were
cognitive and psychosocial functioning, make breathing an better in the intervention group (it was more complex and
interesting strategy and promising in promoting more coherent). Therefore, we hypothesized that the children
self-regulation in educational settings. from the experimental group had abnormally increased HRV

20 ALTERNATIVE THERAPIES, JUL/AUG 2020 VOL. 26 NO. 4 Zuanazzi Cruz—Slow Breathing Exercise on Heart Rate