=Paper= {{Paper |id=Vol-2903/IUI21WS-HEALTHI-7 |storemode=property |title=A Playful Smartphone-based Self-regulation Training for the Prevention and Treatment of Child and Adolescent Obesity: Technical Feasibility and Perceptions of Young Patients |pdfUrl=https://ceur-ws.org/Vol-2903/IUI21WS-HEALTHI-7.pdf |volume=Vol-2903 |authors=Tobias Kowatsch,Chen-Hsuan (Iris) Shih,Yanick X. Lukic,Olivia C. Keller,Katrin Heldt,Dominique Durrer,Aikaterini Stasinaki,Dirk Büchter,Björn Brogle,Nathalie Farpour-Lambert,Dagmar l’Allemand-Jander |dblpUrl=https://dblp.org/rec/conf/iui/KowatschSLKHDSB21 }} ==A Playful Smartphone-based Self-regulation Training for the Prevention and Treatment of Child and Adolescent Obesity: Technical Feasibility and Perceptions of Young Patients== https://ceur-ws.org/Vol-2903/IUI21WS-HEALTHI-7.pdf
A Playful Smartphone-based Self-regulation Training for
the Prevention and Treatment of Child and Adolescent
Obesity: Technical Feasibility and Perceptions of Young
Patients
Tobias Kowatscha,b,c , Chen-Hsuan (Iris) Shiha , Yanick X. Lukica , Olivia C. Kellera ,
Katrin Heldtd , Dominique Durrere , Aikaterini Stasinakid,g , Dirk Büchterd , Björn Brogled ,
Nathalie Farpour-Lambertf and Dagmar l’Allemand-Janderd,g
a
  Centre for Digital Health Interventions, Department of Management, Technology and Economics, ETH Zurich, Zurich, Switzerland
b
  Centre for Digital Health Interventions, Institute of Technology Management, University of St.Gallen, St.Gallen, Switzerland
c
  Saw Swee Hock School of Public Health, National University of Singapore, Singapore
d
  Adolescent Medicine, Children’s Hospital of Eastern Switzerland, St.Gallen, Switzerland
e
  Child and Youth School Health Service, Department of Education and Youth, Vevey, Switzerland
f
  Service of Endocrinology, Diabetology, Nutrition and Therapeutic Patient Education, Department of Medicine, University Hospitals of Geneva,
Geneva, Switzerland
g
  Pediatric Endocrinology, Children’s Hospital of Eastern Switzerland, St.Gallen, Switzerland


                                             Abstract
                                             Effective interventions for the prevention and treatment of child and adolescent obesity play an important role in reducing
                                             the global health and economic burden of non-communicable diseases. Although multi-component interventions targeting
                                             various health behaviors are deemed promising, evidence for their effectiveness is still limited. Self-regulation seems to be a
                                             relevant working mechanism in this regard. Therefore, we propose a playful, smartphone-based self-regulation training that
                                             also utilizes the health benefits of a slow-paced breathing exercise. The mobile app uses the microphone of the smartphone to
                                             detect breathing sounds (e.g. inhalation, exhalation) and translates these sounds into a visual biofeedback on the smartphone
                                             screen. The design and evaluation of a very first prototype is described in this interdisciplinary work of obesity experts,
                                             clinical psychologists, young patients, and computer scientists. The apps’ breathing detection module uses a random forest
                                             tree for quasi real-time classification of the incoming audio samples and biofeedback generation. A study with 11 children and
                                             adolescents with obesity was conducted to assess the prototype. Results indicate overall positive evaluations and suggestions
                                             for improvement. Implications and limitations are discussed, and an outlook on future work is provided.

                                             Keywords
                                             human-computer interaction, self-regulation, digital health intervention, biofeedback, breathing training, breathing detection



1. Introduction                                                                                                     nutrition, physical inactivity and resulting metabolic risk
                                                                                                                    factors, for example, obesity [5]. The earlier in life ef-
Non-communicable diseases (NCDs), such as cardiovas-                                                                fective interventions are delivered, the lower the future
cular diseases or mental disorders, are the leading cause                                                           financial burden of NCDs and the more likely the uptake
of death worldwide, contributing to 73% of deaths [1].                                                              of health-promoting behaviors is due to heightened neu-
NCDs also lead to a significant financial burden [2, 3],                                                            roplasticity and cognitive flexibility in children and ado-
for example, up to 90% of all health care spending in the                                                           lescents [6, 7]. These efforts are especially important as
U.S. [4].                                                                                                           child and adolescent obesity has increased substantially
   To address this important problem, health interven-                                                              worldwide [8], while recent systematic reviews found
tions must target adverse health behaviors such as mal-                                                             only low to moderate evidence for effective interventions
                                                                                                                    [9, 10].
Joint Proceedings of the ACM IUI 2021 Workshops, April 13–17, 2021,
College Station, USA                                                                                                   Although evidence suggests multi-component inter-
Envelope-Open tkowatsch@ethz.ch (T. Kowatsch);                                                                      ventions that target, for example, physical activity and
dagmar.lallemand@kispisg.ch (D. l’Allemand-Jander)                                                                  diet, underlying mechanisms for why and for whom they
GLOBE https://www.c4dhi.org/ (T. Kowatsch)                                                                          work are still under investigation [10]. Self-regulation
Orcid 0000-0001-5939-4145 (T. Kowatsch); 0000-0002-2576-6569                                                        has been proposed as an important mechanism in child
(Y. X. Lukic); 0000-0001-8761-8214 (O. C. Keller);
0000-0001-6478-7269 (N. Farpour-Lambert); 0000-0003-3144-3907                                                       health [11] as it refers to the ”cognitive and behavioral
(D. l’Allemand-Jander)                                                                                              processes through which an individual maintains levels
                                       © 2021 Copyright © 2021 for this paper by its authors. Use permitted under
                                       Creative Commons License Attribution 4.0 International (CC BY 4.0).          of emotional, motivational, and cognitive arousal that
    CEUR
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    Proceedings
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                  ISSN 1613-0073
                                       CEUR Workshop Proceedings (CEUR-WS.org)
are conducive to positive adjustment and adaptation, as
                                                                                                      Smartphone
reflected in positive social relationships, productivity,
                                                                   adaptation of breathing based
achievement, and a positive sense of self.” [12, p. 900] For                                             Playful
                                                                   on biofeedback visualization
instance, obese children, require self-regulation skills to                                           Biofeedback
resist the urge to eat unhealthy food. In this context, it                                            Visualization
was demonstrated that children who have experienced
loss of control eating report a higher use of maladaptive                          Goal
                                                                                 Improving
strategies for the regulation of emotions than children         User           self-regulation
                                                                                                        Breathing
without a history of loss of control eating [13]. Similarly,                        skills              Detection
                                                                                                     (inhalation, exhalation,
another study identifies emotional regulation as the mod-                                               silence, and noise)
erator for the relationship between perceived stress and
emotional eating [14].
   Furthermore, a systematic review indicates that self-                                               Microphone
                                                                   Slow-paced breathing
regulation skills are among the best predictors of out-
comes in obesity interventions in adults [15]. Another
study with a representative sample of U.S. children not        Figure 1: Concept of the self-regulation training
only found a link between self-regulation and the risk of
obesity, but further identified that this link is stronger
between boys and girls [16]. Moreover, a recent system-
                                                              acceptance.
atic review found that interventions with self-regulation
                                                                 Empirical results of another related work by Shih et
interventions can be effective in children and adoles-
                                                              al. [27] were more promising. They implemented a
cents, with possible health benefits [17]. All in all, self-
                                                              similar self-regulation training and found positive ef-
regulation skills represent a relevant target in multi-
                                                              fects on physiological outcomes and technology accep-
component interventions for the prevention and treat-
                                                              tance. However, the authors tested their prototype with
ment of child and adolescent obesity.
                                                              19 healthy university students and thus, these findings
   To this end, we propose a playful self-regulation train-
                                                              may not translate to children and adolescents. Another
ing for children and adolescents. The training is delivered
                                                              limitation of this study is that the authors employed a
via a mobile app and focuses on a breathing exercise. The
                                                              breathing detection model based on an attention-based
app uses the microphone of a smartphone to detect in-
                                                              long short-term memory model in conjunction with a
halation, exhalation, silence and noisy sounds to then
                                                              preceding convolutional neural network which may not
visually guide the user to perform a slow-paced breath-
                                                              run on older smartphones with limited computational
ing training. With the help of the visual biofeedback,
                                                              power.
breathing can be adjusted with the overall goal to im-
                                                                 Another study by Hunter et al. [28] investigated whether
prove self-regulation skills. A conceptual overview of
                                                              a slow-paced breathing training with a mobile app that
the training is depicted in Fig. 1.
                                                              features heart rate variability biofeedback affects the re-
   After a brief overview of related work in the next sec-
                                                              covery from an artificial stressor. They found that the
tion, we describe the design of a very first prototype and
                                                              app had a significant effect on salivary alpha amylase re-
the evaluation procedure targeting obese children and
                                                              covery while not showing a significant effect on cortisol
adolescents. We then present and discuss the results and
                                                              recovery or self-reported stress recovery. Technically, the
conclude with a summary and outlook on future work.
                                                              app does not detect breathing but the heartbeat from the
                                                              smartphone’s rear camera in conjunction with the flash-
2. Related Work                                               light. Thus, the app can present the breathing exercise’s
                                                              impact on the user’s heart rate variability. However, the
Slow-paced breathing was chosen in this investigation heart rate variability is not consciously controlled and its
because it is not only a common self-regulation tool [e.g., measurement is time-delayed. Consequently, the breath-
18, 19, 20, 21, 22] but also shows positive ”side” effects on ing training does not allow responsive user interaction.
cardiac functioning and mental well-being [23, 24, 25].
   The work of Carlier et al. [26] is similar to our training
as they implemented a mobile game that uses the micro- 3. Methods
phone of a smartphone to detect an ”ommm”-sound to
                                                              The design and evaluation of the smartphone-based self-
then visually guide children through a breathing exercise.
                                                              regulation training was collaboratively carried out by
They tested their prototype with three children suffer-
                                                              an interdisciplinary team of computer scientists, obese
ing from autism spectrum disorder. However, results
                                                              children and adolescents as well as several obesity ex-
indicated no effects on stress reduction or technology
                                                              perts including physicians, psychotherapists, and diet
and sport experts from a children’s hospital. The project
described in this work was also approved by the local
ethics board. The specifics of the design and evaluation
phases are outlined in the following sections.

3.1. Design of the Mobile App
3.1.1. User Interface
A focus group discussion with 11 young patients, moder-
ated by obesity experts, was conducted as a first step to
gather design requirements for the self-regulation train-
ing. In response to that discussion, a first conceptual
draft of the user interface was developed. The overall
goal of the self-regulation training was to ”move” a boat
sailing on an ocean towards an isle, far far away, with
the help of slow-paced breathing. Specifically, exhalation
should imitate wind that blows the boat forward while in-
halation should imitate the collection of wind energy for
the next breathing cycle. A draft of this idea is depicted
in Fig. 2 which also shows a distance-to-destination indi-
cator on the bottom and speech bubbles with additional
breathing instructions.
   Based on feedback from the obesity experts and young
patients, several elements were dropped and revised to
further streamline the user interface. For example, the
distance indicator at the bottom and the wind energy in-
dicator on the right-hand side were removed so that users
could better focus better on the sailboat and its move-
ments toward the destination isle. Further, the speech
bubbles were replaced by a digital coach at the top of
the screen who had the role to ”guide” users through         Figure 2: Draft of the App’s User Interface
the training. Moreover, moving clouds were introduced
to support the boat movements towards the destination
isle and to provide also a visual feedback for inhalation    To match the style of the user interface of the app, the
sounds. In the latter ”inhalation” case, clouds gathered     video clip employs a comic-like character and elements
together at the center of the screen while they moved        of the mobile user interface (e.g. ocean, sailboat and
apart when inhaling. The high-level biofeedback logic        clouds). The resulting instructional video clip was shown
was also defined collaboratively among young patients,       to four young patients who were then asked to perform
obesity experts and computer scientists. It is outlined in   the communicated slow-paced breathing. The breathing
Algorithm 1. A prototype of the graphical user interface     technique was assessed by the obesity experts according
was then implemented for the Android operating system.       to the guidelines communicated through the video clip
Fig. 3 shows a screenshot of that interface.                 and deemed appropriate.

3.1.2. Instructional Video Clip                              3.1.3. Breathing Detection
To ensure consistent and evidence-based instructions on      The overall goal of the breathing detection module of
how to perform a slow-paced breathing training, an in-       the self-regulation training is to process audio signals
structional video clip was produced with the help of the     in quasi real time to distinguish between inhalation, ex-
involved obesity experts. This video clip would be pre-      halation, silence, and noise captured by a smartphone’s
sented to the user before she or he would perform the        microphone.
self-regulation training with the app for the very first        In a first step, we aimed at assessing the technical fea-
time. The clip explains in ca. 30s how a deep abdominal      sibility of this approach and built a database of audio
breathing is conducted and instructs the audience to in-     samples. Due to limited access to young patients and to
hale through the nose and to exhale through the mouth        reduce the burden of them as patients, as well as due to
while performing circa six breath cycles per minute [25].    the feasibility character of this investigation, we decided
                                                               Algorithm 1: Biofeedback Logic
    You are doing great.                    digital coach
                                              messages          Input: detection = {inhalation, exhalation, silence,
    Keep it up!                                                        noise}
                     124s                                       Output: biofeedback = {clouds, sailboat, and
                                                                         digital coach message}
                                             destination      1 while destination not reached do
                                                              2    switch detection do
                                                              3        case inhalation do
                                                              4            clouds gather together
                                                              5        case exhalation do
                                                              6            clouds expand
                                                              7            sailboat moves towards destination
                                                              8            digital coach provides positive
                                                                            feedback
                                                              9        case silence do
                                                  clouds     10            digital coach motivates user to inhale
                                                             11        case noise do
                                                sailboat     12            digital coach recommends to reduce
                                                                            surrounding noise
                                                             13    end
                                                             14 end

                                            sailing route

                                                             were supplemented with four descriptive statistical mea-
Figure 3: Annotated Screenshot of the App                    sures. From the time-domain we used the mean, variance,
                                                             and maximum of the raw audio amplitude and from the
                                                             frequency-domain the peak frequency amplitude.
                                                                Third, and consistent with prior work that was suc-
to collect audio samples from four doctoral students (2      cessful in detecting breathing patterns [30], a Random
females; all between 25 and 27 years old). We asked the      Forest model was used with 100 trees, which was empiri-
doctoral students to sit comfortably in a chair in their     cally found to result in the best prediction performance
office and perform a slow-paced breathing exercise for       for our data set.
three minutes according to the instructions of the video        Since our audio database was relatively small com-
clip described in Section 3.1.2. The audio was recorded      pared to related work [e.g., 27] and to prevent our model
with a Samsung Galaxy S6 Edge through a customized           from over-fitting, we applied k-fold cross-validation for
app that uses the Android AudioRecord API (PCM, 16bit,       training and validation. We trained the random forest
44.1 kHz). The distance to the smartphone for these          model using the WEKA library. First, we applied a 80/20
recordings was about 20cm, a distance we found optimal       training to test split over all four participants. Second,
for the breathing exercise, too. One co-author listened to   we conducted 10-fold cross-validation on the training
the resulting recordings and manually cut them into sep-     data. Third, we tested the best model on the test set. The
arate audio files labeling them as inhalation, exhalation,   performance of the model on the test set is reported in
or silence. To collect additional samples for silence and    Table 1. The results indicate that the trained model is able
noise, the same smartphone was used to record sounds         to appropriately differentiate between the four classes
in an office. This resulted in audio samples of passing      for the breathing of known individuals.
cars and streetcars or the speech of office workers, which      Finally, the trained random forest model was inte-
were manually marked as noise. Silent audio samples          grated into the mobile app using the WEKA Android
were manually labeled as silence. The data collection        API. The feature extraction in the app was reproduced
resulted in around 28,000 audio samples of 80ms length.      using Java in conjunction with the audio processing li-
This length was chosen as it represented the minimum         brary OpenIMAJ 1.3.9. The resulting predictions of the
buffer size that could be acquired through the Android       incoming data would then trigger the animations of the
audio engine at the time of implementation.                  user interface outlined in Algorithm 1.
   In a second step, we calculated for each sample the
first 13 Mel-frequency cepstral coefficients [29] with a
window size of 25ms and a 50% overlap. The coefficients
                           Table 1
                           Offline Performance of the Random-Forest Breathing Detection Algorithm

                             Class              TPR       FPR        PRE      F1-Score       AUC-ROC
                             Inhalation        0.942      0.012     0.955       0.949           0.990
                             Exhalation        0.940      0.007     0.977       0.948           0.992
                             Silence           0.963      0.023     0.931       0.947           0.994
                             Noise             0.980      0.021     0.954       0.967           0.996
                             All 4 classes     0.954      0.016     0.954       0.955           0.994
                             Note: true positive rate (TPR), false positive rate (FPR), precision (PRE),
                             area under the curve receiver operating characteristic (AUC-ROC)



3.2. Evaluation Procedure                                            4. Results
A study with obese children and adolescents was con-                 Overall, 8 female and 3 male young 9-16 year-old (M
ducted in the children’s hospital of the participating obe-          = 12.6, SD = 2.4) children and adolescents with obesity
sity experts to assess the technical feasibility and percep-         participated in the study. All patients were able to reach
tions of the self-regulation training. The procedure was             the goal set by the training app in 40 to 120 seconds.
as follows.                                                          However, obesity experts observed that due to the playful
   First, patients were instructed to watch the educational          character of the app, three subjects started to perform
breathing video clip and to perform the breathing exer-              an adverse breathing pattern (e.g. hyperventilation or
cise without the app. Obesity experts provided feedback              extensive and long exhalation), motivated by the goal to
on their breathing to assure a correct technique.                    bring the sailboat as quickly as possible to its destination,
   In a second step, obesity experts handed over the An-             despite being instructed otherwise.
droid smartphone, the same model used for data collec-                  The descriptive statistics of the patients’ self-reported
tion (i.e. the Samsung S6 Edge), with the self-regulation            perceptions of the participating patients are listed in Ta-
training app to the patients. The experts then explained             ble 2 and corresponding boxplots with raw responses are
the purpose of the app and its visual feedback logic.                shown in Fig. 4. The high average mean values for all
   Finally, obesity experts asked the patients to perform            constructs indicate that the patients found the training
the app’s slow-paced breathing exercise. The patients’               app easy to use and conducive to relaxation at home. Ad-
goal was to ”sail” the sailboat to the destination. Dur-             ditionally, the patients reported enjoying its actual usage
ing the exercise and for safety purposes, obesity experts            and indicated that they could even imagine using the
observed the patients and intervened in case of any ad-              app-based training every day. Finally, patients shared
verse breathing activity. Moreover, they noted down                  that they were able to relax using the app. One-sample
whether the goal was achieved and the sailboat reached               sign tests confirmed these results as the self-reported
the destination, and how long it took the patients to get            scores all lie significantly above the neutral scale value
there.                                                               of zero.
   Afterwards, the patients received a questionnaire that               The qualitative feedback indicated that the digital coach
allowed them to assess the app. Constructs of inter-                 moderating the self-regulation exercise should be cus-
est were adopted from technology acceptance research                 tomizable, for example, regarding their outfit. Moreover,
[31, 32] and included perceived ease of use, perceived en-           the training session was perceived as too short and thus,
joyment, expected usefulness at home, intention to use               it was suggested to extend the journey with the sailboat.
and perceived relaxation after use. Consistent with prior            It was also suggested to add further elements to the ocean
work [33, 34], a single item per construct was used to               scene, for example, additional milestones such as smaller
reduce the burden of the young patients. All items were              isles or surface marker buoys as sub-ordinate targets that
anchored on 7-point Likert scales ranging from strongly              would trigger points when passing by with the sailboat.
disagree (-3) to strongly agree (3). All constructs and              Interestingly, there were some enquiries into whether
item wordings are listed in Table 2. Finally, patients were          the training app was available on Apple’s iOS platform,
asked to write down any suggestions they may have to                 which indicated further interest in the training app.
improve the app.                                                        Overall, the qualitative feedback confirmed the posi-
                                                                     tive quantitative results presented above.
Table 2
Perceptions of 11 Young Children and Adolescents with Obesity

 Construct                                   Scale item wording                                           Mean      SD      95% CI        p-value
 Perceived ease of use                       I found it easy to blow the sailboat to the next island.      2.64    0.67    [2.21 3.00]   < 0.001***
 Perceived enjoyment                         I enjoyed the breathing exercise.                             2.73    0.65    [3.00 3.00]   < 0.001***
 Expected usefulness at home                 I could imagine the exercise helping me relax at home.        1.55    1.04    [1.00 3.00]    0.002**
 Intention to use                            I can imagine doing this exercise every day.                  2.27    1.27    [2.00 3.00]    0.006**
 Perceived relaxation                        With this exercise I could relax well just now.               1.45    1.29    [0.00 3.00]    0.008**
 Note: confidence interval (CI); p < .001 = *** and p < .01 = ** for one-sample sign tests with 0 as test value and alternative
 hypothesis being greater as 0; 7-point Likert scales were anchored from strongly disagree (-3) to strongly agree (3)


   strongly
     agree
          3
                                                                               self-regulation training might be smartphone addiction
                                                                               [35, 36]. Limiting the number of exercises per day could
          2
                                                                               be a solution in this regard. Finally, adding additional
          1                                                                    playful elements as suggested by the young patients
                                                                               raises the question to which degree the experiential effect
   neither 0
                                                                               of the app can potentially cancel out the development of
         −1
                                                                               self-regulation skills and other health benefits of slow-
                                                                               paced breathing such as calming down or strengthening
         −2                                                                    the cardiac system. Related work provides first evidence
         −3                                                                    that both experiential and instrumental effects can coex-
    strongly
   disagree                                                                    ist [27, 37].
                Perceived    Perceived    Expected    Intention   Perceived
               ease of use   enjoyment   usefulness     to use    relaxation      This work has also several limitations. First, the of-
                                          at home     everyday
                                                                               fline performance of the detection model is based on
                                                                               a small sample of only four doctoral students and not
Figure 4: Boxplots and Answers of Self-reported Perceptions                    on breathing data from the target population. Both as-
of 11 Young Children and Adolescents with Obesity                              pects, the small sample size resulting in low variance of
                                                                               breathing sounds and the mismatch of model develop-
                                                                               ment with population A and assessment by population
5. Discussion                                                                  B, limit the generalizability of the findings. Second, the
                                                                               training and test sets were collected in the same context,
The current work presented a playful, smartphone-based                         i.e. the same recording environment and smartphone
self-regulation training that was collaboratively devel-                       model, and contain breathing sounds from the same in-
oped by an interdisciplinary team of obesity experts, clin-                    dividuals. Consequently, the detection performance for
ical psychologists, children and adolescents with obesity,                     unknown individuals, other devices, or different envi-
as well as computer scientists. The evaluation of the train-                   ronments remains unknown. Third, the data collection
ing with 11 young obesity patients showed the technical                        with respect to noisy environments was limited to only
feasibility, as all patients were able to bring the sailboat                   one specific environment (the office). Fourth, only one
to its destination. Moreover, self-reports of the partici-                     specific biofeedback theme was evaluated, i.e. the ”ocean-
pating patients resulted in overall positive technology                        and-sailboat” theme, and thus, it is open to which degree
assessments and various suggestions for improvement                            visual elements may have an impact on the effects of
were provided.                                                                 the self-regulation training. Third, the cross-sectional
   However, the evaluation also resulted in relevant in-                       study setting in the children’s hospital does not allow to
sights regarding potential side effects. First, the playful                    draw any conclusions on long-term engagement with the
biofeedback visualization motivated patients to adopt                          app. Finally, the evaluation procedure did not contain
a breathing technique that could lead to dizziness due                         any validated instrument to assess self-regulation and
to hyperventilation or prolonged periods of exhalation.                        thus, no conclusions can be drawn in this regard, too.
A biofeedback visualization that offers time-restricted
inhalation and exhalation windows may overcome this
problem. That is, the sailboat could only be moved for- 6. Summary and Future Work
ward during a pre-defined time window that promotes
a ”healthy” slow-paced breathing [27]. Another poten- We highlighted the relevance of self-regulation mech-
tial side effect promoted by the playful nature of the anisms in interventions targeting the prevention and
                                                             treatment of obesity in children and adolescents. We
proposed, implemented and evaluated a breathing-based                       http://apps.who.int/iris/bitstream/handle/10665/
self-regulation training with young patients affected by                    94384/9789241506236_eng.pdf.
obesity.                                                                [6] F. Y. Ismail, A. Fatemi, M. V. Johnston, Cerebral plas-
   However, the current work also points towards oppor-                     ticity: Windows of opportunity in the developing
tunities for upcoming research. First and foremost, future                  brain, European Journal of Paediatric Neurology
work may focus on environment-agnostic breathing de-                        21 (2017) 23–48. doi:1 0 . 1 0 1 6 / j . e j p n . 2 0 1 6 . 0 7 . 0 0 7 .
tection that generalizes among individuals, smartphones,                [7] F. Buttelmann, J. Karbach, Development and plas-
headsets, and various ”distracting” soundscapes. Second,                    ticity of cognitive flexibility in early and middle
micro-randomized trials may be conducted to assess an                       childhood, Frontiers in Psychology 8 (2017). doi:1 0 .
optimal balance of experiential vs instrumental interface                   3389/fpsyg.2017.01040.
designs. Third, guided-biofeedback interfaces may limit                 [8] T. Lobstein, R. Jackson-Leach, M. L. Moodie, K. D.
cheating in breathing, which, in turn, could reduce any                     Hall, S. L. Gortmaker, B. A. Swinburn, W. P. T. James,
adverse breathing patterns. And finally, the impact of                      Y. Wang, K. McPherson, Child and adolescent obe-
self-regulation training on self-regulation skills and rele-                sity: part of a bigger picture, Lancet 385 (2015)
vant lifestyle behavior should be assessed in longitudinal                  2510–20. doi:1 0 . 1 0 1 6 / s 0 1 4 0 - 6 7 3 6 ( 1 4 ) 6 1 7 4 6 - 3 .
field studies that target the prevention and treatment of               [9] T. Brown, T. H. Moore, L. Hooper, Y. Gao, A. Za-
child and adolescents obesity.                                              yegh, S. Ijaz, M. Elwenspoek, S. C. Foxen, L. Magee,
                                                                            C. O’Malley, E. Waters, C. D. Summerbell, Interven-
                                                                            tions for preventing obesity in children, Cochrane
Acknowledgments                                                             Database Syst Rev 7 (2019) Cd001871. doi:1 0 . 1 0 0 2 /
                                                                            14651858.CD001871.pub4.
We would like to thank the CSS Insurance and the Swiss
                                                                       [10] L. J. Ells, K. Rees, T. Brown, E. Mead, L. Al-Khudairy,
National Science Foundation for their support through
                                                                            L. Azevedo, G. J. McGeechan, L. Baur, E. Love-
grants 159289 and 162724.
                                                                            man, H. Clements, P. Rayco-Solon, N. Farpour-
                                                                            Lambert, A. Demaio, Interventions for treating
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