{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,15]],"date-time":"2026-04-15T07:11:25Z","timestamp":1776237085367,"version":"3.50.1"},"reference-count":62,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2021,8,13]],"date-time":"2021-08-13T00:00:00Z","timestamp":1628812800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Many studies have shown that slow breathing training is beneficial for human health. However, several factors might discourage beginners from continuing their training. For example, a long training period is generally required for benefit realization, and there is no real-time feedback to trainees to adjust their breathing control strategy. To raise the user\u2019s interest in breathing exercise training, a virtual reality system with multimodal biofeedback is proposed in this work. In our system, a realistic human model of the trainee is provided in virtual reality (VR). At the same time, abdominal movements are sensed, and the breathing rate can be visualized. Being aware of the breathing rate, the trainee can regulate his or her breathing to achieve a slower breathing rate. An additional source of tactile feedback is combined with visual feedback to provide a more immersive experience for the trainees. Finally, the user\u2019s satisfaction with the proposed system is reported through questionnaires. Most of the users find it enjoyable to use such a system for mediation training.<\/jats:p>","DOI":"10.3390\/s21165462","type":"journal-article","created":{"date-parts":[[2021,8,13]],"date-time":"2021-08-13T09:22:38Z","timestamp":1628846558000},"page":"5462","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":25,"title":["Slow Breathing Exercise with Multimodal Virtual Reality: A Feasibility Study"],"prefix":"10.3390","volume":"21","author":[{"given":"Kun-Chan","family":"Lan","sequence":"first","affiliation":[{"name":"Department of Computer Science and Information Engineering, National Cheng Kung University, Tainan 701, Taiwan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Che-Wei","family":"Li","sequence":"additional","affiliation":[{"name":"EBeam Operation Division, Taiwan Semiconductor Manufacturing Company, Hsinchu 300, Taiwan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yushing","family":"Cheung","sequence":"additional","affiliation":[{"name":"Smart Microsystems Technology Center, Industrial Technology Research Institute, Tainan 709, Taiwan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,8,13]]},"reference":[{"key":"ref_1","first-page":"154","article-title":"Acute effects of deep breathing for a short duration (2\u201310 minutes) on pulmonary functions in healthy young volunteers","volume":"55","author":"Sivakumar","year":"2012","journal-title":"Indian J. Physiol. Pharmacol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"566","DOI":"10.1016\/j.mehy.2006.02.042","article-title":"Physiology of long pranayamic breathing: Neural respiratory elements may provide a mechanism that explains how slow deep breathing shifts the autonomic nervous system","volume":"67","author":"Jerath","year":"2006","journal-title":"Med. Hypotheses"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"189","DOI":"10.1089\/acm.2005.11.189","article-title":"Sudarshan Kriya Yogic Breathing in the Treatment of Stress, Anxiety, and Depression: Part I\u2014Neurophysiologic Model","volume":"11","author":"Brown","year":"2005","journal-title":"J. Altern. Complement. Med."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"714","DOI":"10.1161\/01.HYP.0000179581.68566.7d","article-title":"Slow Breathing Improves Arterial Baroreflex Sensitivity and Decreases Blood Pressure in Essential Hypertension","volume":"46","author":"Joseph","year":"2005","journal-title":"Hypertension"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"12","DOI":"10.1016\/j.pain.2009.10.001","article-title":"The effects of slow breathing on affective responses to pain stimuli: An experimental study","volume":"149","author":"Zautra","year":"2010","journal-title":"Pain"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"743504","DOI":"10.1155\/2013\/743504","article-title":"Cardiovascular and Respiratory Effect of Yogic Slow Breathing in the Yoga Beginner: What Is the Best Approach?","volume":"2013","author":"Mason","year":"2013","journal-title":"Evid. Based Complement. Altern. Med."},{"key":"ref_7","first-page":"115","article-title":"Effect of short-term practice of breathing exercises on autonomic functions in normal human volunteers","volume":"120","author":"Pal","year":"2004","journal-title":"Indian J. Med. Res."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1361","DOI":"10.1097\/01.hjh.0000125446.28861.51","article-title":"Effects of slow, controlled breathing on baroreceptor control of heart rate and blood pressure in healthy men","volume":"22","author":"Radaelli","year":"2004","journal-title":"J. Hypertens."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1039","DOI":"10.1089\/acm.2009.0577","article-title":"Effect of Slow Abdominal Breathing Combined with Biofeedback on Blood Pressure and Heart Rate Variability in Prehypertension","volume":"16","author":"Wang","year":"2010","journal-title":"J. Altern. Complement. Med."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"874","DOI":"10.3389\/fpsyg.2017.00874","article-title":"The Effect of Diaphragmatic Breathing on Attention, Negative Affect and Stress in Healthy Adults","volume":"8","author":"Ma","year":"2017","journal-title":"Front. Psychol."},{"key":"ref_11","first-page":"85","article-title":"Biofeedback in medicine: Who, when, why and how?","volume":"7","author":"Frank","year":"2010","journal-title":"Ment. Health Fam. Med."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2172","DOI":"10.3389\/fpsyg.2019.02172","article-title":"Heart Rate Variability Biofeedback Based on Slow-Paced Breathing With Immersive Virtual Reality Nature Scenery","volume":"10","author":"Blum","year":"2019","journal-title":"Front. Psychol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"539","DOI":"10.1007\/s10055-020-00471-5","article-title":"A mobile VR-based respiratory biofeedback game to foster diaphragmatic breathing","volume":"25","author":"Rockstroh","year":"2021","journal-title":"Virtual Real."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"272","DOI":"10.1080\/15213269.2015.1015740","article-title":"How immersive is enough? A meta-analysis of the effect of immersive technology on user presence","volume":"19","author":"Cummings","year":"2016","journal-title":"Med. Psychol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"332","DOI":"10.1038\/nrn1651","article-title":"From presence to consciousness through virtual reality","volume":"6","author":"Slater","year":"2005","journal-title":"Nat. Rev. Neurosci."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1016\/0272-4944(95)90001-2","article-title":"The restorative benefits of nature: Toward an integrative framework","volume":"15","author":"Kaplan","year":"1995","journal-title":"J. Environ. Psychol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"731579","DOI":"10.1155\/2015\/731579","article-title":"The Influence of Buddhist Meditation Traditions on the Autonomic System and Attention","volume":"2015","author":"Amihai","year":"2015","journal-title":"BioMed. Res. Int."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"199","DOI":"10.1016\/j.ijpsycho.2004.07.004","article-title":"Changes in EEG and autonomic nervous activity during meditation and their association with personality traits","volume":"55","author":"Takahashi","year":"2005","journal-title":"Int. J. Psychophysiol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"189","DOI":"10.1159\/000079113","article-title":"Individual Trait Anxiety Levels Characterizing the Properties of Zen Meditation","volume":"50","author":"Murata","year":"2004","journal-title":"Neuropsychobiology"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"147","DOI":"10.1023\/A:1011343307783","article-title":"The Physiological Correlates of Kundalini Yoga Meditation: A Study of a Yoga Master","volume":"26","author":"Arambula","year":"2001","journal-title":"Appl. Psychophysiol. Biofeedback"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1027","DOI":"10.2466\/pms.2000.90.3.1027","article-title":"Decrease in Serum Cortisol during Yoga Exercise is Correlated with Alpha Wave Activation","volume":"90","author":"Kamei","year":"2000","journal-title":"Percept. Mot. Ski."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"662","DOI":"10.1378\/chest.90.5.662","article-title":"Resistive Breathing Training in Patients with Chronic Obstructive Pulmonary Disease","volume":"90","author":"Belman","year":"1986","journal-title":"Chest"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"298","DOI":"10.1183\/20734735.009817","article-title":"The physiological effects of slow breathing in the healthy human","volume":"13","author":"Russo","year":"2017","journal-title":"Breathe"},{"key":"ref_24","first-page":"584","article-title":"Effects of abdominal and thoracic breathing on breathing pattern components in normal Trainees and in patients with chronic obstructive pulmonary disease","volume":"130","author":"Sackner","year":"1984","journal-title":"Am. Rev. Respir. Dis."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Zhang, Z., Wu, H., Wang, W., and Wang, B. (2010, January 16\u201318). A smartphone based respiratory biofeedback system. Proceedings of the 2010 3rd International Conference on Biomedical Engineering and Informatics, Yantai, China.","DOI":"10.1109\/BMEI.2010.5640072"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1007\/s10484-007-9048-4","article-title":"The Influence of Respiration on Biofeedback Techniques","volume":"33","author":"Pastor","year":"2008","journal-title":"Appl. Psychophysiol. Biofeedback"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1053\/seiz.2000.0478","article-title":"Biofeedback treatment in patients with refractory epilepsy: Changes in depression and control orientation","volume":"10","author":"Uhlmann","year":"2001","journal-title":"Seizure"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1007\/s10484-018-9421-5","article-title":"Respiratory Biofeedback Does Not Facilitate Lowering Arousal in Meditation through Virtual Reality","volume":"44","author":"Tinga","year":"2019","journal-title":"Appl. Psychophysiol. Biofeedback"},{"key":"ref_29","unstructured":"MCQE (2019, June 01). Astronomy VR. Available online: https:\/\/store.steampowered.com\/app\/1062690\/Astronomy_VR\/."},{"key":"ref_30","unstructured":"PaleBlue XYZ (2019, June 01). Number Hunt. Available online: https:\/\/store.steampowered.com\/app\/851770\/Number_Hunt\/."},{"key":"ref_31","unstructured":"STRIVR (2019, June 01). 30 Percentage Point Increase in Recall of Topics After Using STRIVR. Available online: https:\/\/www.strivr.com\/30-percent-increase-in-recall\/."},{"key":"ref_32","unstructured":"EON Reality (2019, June 01). EON Sports VR Project OPS with Jason Giambi. Available online: https:\/\/www.youtube.com\/watch?v=KTOrNNqtTTE."},{"key":"ref_33","unstructured":"Balfour Beatty (2019, June 01). Virtual Reality Is Shaping the Future of Construction. Available online: https:\/\/www.youtube.com\/watch?v=R4gWpXuPAXo."},{"key":"ref_34","unstructured":"Ford Motor Company (2019, June 01). Virtual Reality at Ford Motor Company. Available online: https:\/\/www.youtube.com\/watch?v=zmeR-u-DioE."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"561","DOI":"10.1016\/j.janxdis.2007.04.006","article-title":"Virtual reality exposure therapy for anxiety disorders: A meta-analysis","volume":"22","author":"Powers","year":"2008","journal-title":"J. Anxiety Disord."},{"key":"ref_36","unstructured":"Cho, B.H., Lee, J.M., Ku, J.H., Jang, D.P., Kim, J.S., Kim, I.Y., Lee, J.H., and Kim, S.I. (2002, January 24\u201328). Attention Enhancement System using virtual reality and EEG biofeedback. Proceedings of the IEEE Virtual Reality 2002, Orlando, FL, USA."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Wake, N., Sano, Y., Oya, R., Sumitani, M., Kumagaya, S.-I., and Kuniyoshi, Y. (2015, January 22\u201324). Multimodal virtual reality platform for the rehabilitation of phantom limb pain. Proceedings of the 2015 7th International IEEE\/EMBS Conference on Neural Engineering (NER), Montpellier, France.","DOI":"10.1109\/NER.2015.7146741"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"68","DOI":"10.1080\/00140130303534","article-title":"Multimodal feedback: An assessment of performance and mental workload","volume":"46","author":"Vitense","year":"2003","journal-title":"Ergonomics"},{"key":"ref_39","unstructured":"Haas, J.K. (2014). A History of the Unity Game Engine, Worcester Polytechnic Institute."},{"key":"ref_40","unstructured":"(2019, June 01). Available online: https:\/\/www.youtube.com\/watch?v=tRVq8Tmf8KY."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"585","DOI":"10.1089\/acm.2008.0416","article-title":"Zen Meditation: An Integration of Current Evidence","volume":"15","author":"Chiesa","year":"2009","journal-title":"J. Altern. Complement. Med."},{"key":"ref_42","unstructured":"(2019, June 01). Available online: https:\/\/store.neurosky.com\/."},{"key":"ref_43","unstructured":"(2019, June 01). FSR 406 Data Sheet. Available online: https:\/\/cdn.sparkfun.com\/assets\/c\/4\/6\/8\/b\/2010-10-26-DataSheet-FSR406-Layout2.pdf."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"11342401","DOI":"10.1016\/S0029-6465(22)02528-2","article-title":"Meditation, yoga, and guided imagery","volume":"36","author":"Pettinati","year":"2001","journal-title":"Nurs. Clin. N. Am."},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Kozhevnikov, M., Elliott, J., Shephard, J., and Gramann, K. (2013). Neurocognitive and Somatic Components of Temperature Increases during g-Tummo Meditation: Legend and Reality. PLoS ONE, 8.","DOI":"10.1371\/journal.pone.0058244"},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Elgendi, M., Norton, I., Brearley, M., Abbott, D., and Schuurmans, D. (2013). Systolic Peak Detection in Acceleration Photoplethysmograms Measured from Emergency Responders in Tropical Conditions. PLoS ONE, 8.","DOI":"10.1371\/journal.pone.0076585"},{"key":"ref_47","unstructured":"TAFI AVATARS (2019, June 01). MCS Male. Available online: https:\/\/assetstore.unity.com\/packages\/3d\/characters\/humanoids\/mcs-male-45805."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Aris, S.A.M., Lias, S., and Taib, M.N. (2010, January 8\u20139). The relationship of alpha waves and theta waves in EEG during relaxation and IQ test. Proceedings of the 2010 2nd International Congress on Engineering Education, Kuala Lumpur, Malaysia.","DOI":"10.1109\/ICEED.2010.5940766"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"393","DOI":"10.1016\/j.ctim.2012.07.008","article-title":"Clinical utility of paced breathing as a concentration meditation practice","volume":"20","author":"Park","year":"2012","journal-title":"Complement. Ther. Med."},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"Nargundkar, S., Manage, P., and Desai, V. (2020, January 8\u201310). A Survey on Effects of Various Meditation Interventions on Overall Performance of College Students. Proceedings of the 2020 IEEE Bangalore Humanitarian Technology Conference (B-HTC), Vijiyapur, India.","DOI":"10.1109\/B-HTC50970.2020.9297859"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"982","DOI":"10.1080\/00140130701817062","article-title":"Blinks and saccades as indicators of fatigue in sleepiness warnings: Looking tired?","volume":"51","author":"Schleicher","year":"2008","journal-title":"Ergonomics"},{"key":"ref_52","first-page":"319","article-title":"Experimental evaluation of eye-blink parameters as a drowsiness measure","volume":"89","author":"Caffier","year":"2003","journal-title":"Graefe\u2019s Arch. Clin. Exp. Ophthalmol."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1016\/j.cmpb.2015.10.011","article-title":"Detection of eye blink artifacts from single prefrontal channel electroencephalogram","volume":"124","author":"Chang","year":"2016","journal-title":"Comput. Methods Programs Biomed."},{"key":"ref_54","unstructured":"Rani, M.S.B.A., and Mansor, W.B. (2009, January 23\u201326). Detection of eye blinks from EEG signals for home lighting system activation. Proceedings of the 2009 6th International Symposium on Mechatronics and Its Applications, Sharjah, United Arab Emirates."},{"key":"ref_55","doi-asserted-by":"crossref","unstructured":"Toi, V., Toan, N., Dang Khoa, T., and Lien Phuong, T. (2013). A Mean Threshold Algorithm for Human Eye Blinking Detection Using EEG. 4th International Conference on Biomedical Engineering in Vietnam, Springer. IFMBE Proceedings.","DOI":"10.1007\/978-3-642-32183-2"},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"265","DOI":"10.1089\/109493101300117947","article-title":"Presence and Reflection in Training: Support for Learning to Improve Quality Decision-Making Skills under Time Limitations","volume":"4","author":"Romano","year":"2001","journal-title":"CyberPsychol. Behav."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"2284","DOI":"10.3233\/WOR-2012-0452-2284","article-title":"Skill training in Multimodal virtual environments","volume":"41","author":"Gopher","year":"2012","journal-title":"Work"},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"167","DOI":"10.30773\/pi.2018.12.25.1","article-title":"Visuo-Haptic-Based Multimodal Feedback Virtual Reality Solution to Improve Anxiety Symptoms: A Proof-of-Concept Study","volume":"16","author":"Kim","year":"2019","journal-title":"Psychiatry Investig."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"225","DOI":"10.5334\/tohm.192","article-title":"Virtual Reality Feedback Cues for Improvement of Gait in Patients with Parkinson\u2019s Disease","volume":"4","author":"Badarny","year":"2014","journal-title":"Tremor Other Hyperkinet. Mov."},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"991","DOI":"10.1007\/s00415-010-5866-z","article-title":"The effect of real and virtual visual cues on walking in Parkinson\u2019s disease","volume":"258","author":"Griffin","year":"2011","journal-title":"J. Neurol."},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"10","DOI":"10.3389\/frobt.2020.00010","article-title":"Synchronized Tactile Stimulation on Upper Limbs Using a Wearable Robot for Gait Assistance in Patients With Parkinson\u2019s Disease","volume":"7","author":"Kishi","year":"2020","journal-title":"Front. Robot. AI."},{"key":"ref_62","doi-asserted-by":"crossref","unstructured":"van Rooij, M., Lobel, A., Harris, O., Smit, N., and Granic, I. (2016, January 7\u201312). DEEP: A biofeedback virtual reality game for children at-risk for anxiety. Proceedings of the 2016 CHI Conference Extended Abstracts on Human Factors in Computing Systems, San Jose, CA, USA.","DOI":"10.1145\/2851581.2892452"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/16\/5462\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:45:25Z","timestamp":1760165125000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/16\/5462"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,8,13]]},"references-count":62,"journal-issue":{"issue":"16","published-online":{"date-parts":[[2021,8]]}},"alternative-id":["s21165462"],"URL":"https:\/\/doi.org\/10.3390\/s21165462","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,8,13]]}}}