This Week in Heart Rate Variability: Metabolic Syndrome, Nerve Blocks, EDS & Autonomic Health In this episode of The Heart Rate Variability Podcast – This Week in HRV, we explore how the autonomic nervous system function connects metabolic disease, genetic disorders, targeted neural interventions, and the future of biofeedback science. Episode Highlights How Metabolic Syndrome drives chronic sympathetic overactivation and reduced HRV Experimental evidence showing how the stellate ganglion block directly alters HRV and sympathetic tone New data validating dysautonomia in Ehlers–Danlos Syndrome using HRV and autonomic testing Why HRV is emerging as a critical clinical and research biomarker A preview of the 2026 AAPB Annual Scientific Meeting and why it matters for clinicians and researchers Featured Studies & Resources Cureus (2025) — Autonomic Nervous System Dysregulation in Metabolic Syndrome https://www.cureus.com/articles/431819-autonomic-nervous-system-dysregulation-in-metabolic-syndrome-an-association-with-hypertension-and-cardiovascular-risk#!/ Autonomic Neuroscience (2025) — Selective Sympathetic Action on HRV After Stellate Ganglion Block https://www.sciencedirect.com/science/article/abs/pii/S1566070225001298 Cureus (2025) — Heart Rate Variability and Intrinsic Autonomic Coupling in Ehlers–Danlos Syndrome https://www.cureus.com/articles/429326-heart-rate-variability-and-intrinsic-autonomic-coupling-in-ehlers-danlos-syndrome?score_article=true#!/ Association for Applied Psychophysiology and Biofeedback (AAPB) About AAPB: https://aapb.org/about 2026 Annual Conference: https://aapb.starchapter.com/meetinginfo.php?id=43&ts=1763415344 Key Takeaway Heart rate variability is a universal marker of resilience, translating metabolic stress, genetic vulnerability, and neural interventions into measurable physiological signals. HRV is no longer just a wellness metric—it's a clinical and scientific lens into autonomic health. Sponsor This episode is sponsored by Optimal HRV, providing evidence-based tools for measuring and training heart rate variability for individuals, clinicians, and organizations. Now offering e-gift cards for HRV training, app access, and professional dashboards. Learn more at www.optimalhrv.com

Episode 15 – This Week in Heart Rate Variability Welcome to this week's exploration of the latest HRV science. In Episode 15, we discuss nine newly published studies that expand our understanding of HRV in mental health, physiology, chronic illness, and digital health innovation. This episode highlights remote biofeedback, pediatric heart dynamics, pregnancy and thyroid status, elite performance, cardiac rehabilitation, personalized training prediction, global research trends, autoimmune flare detection, and neurostimulation safety. Featured Studies: Remote HRV Biofeedback and Mental Health “Efficacy and Methodology of Remote Heart Rate Variability Biofeedback Interventions for Mental Health: A Systematic Review and Meta-Analysis” Vann-Adibe et al., Applied Psychophysiology and Biofeedback (2025) https://link.springer.com/article/10.1007/s10484-025-09750-w Pediatric HRV and Cardiac Complexity “Age-dependent patterns of cardiac complexity unveiled by topological data analysis of pediatric heart rate variability” Domínguez-Monterroza et al., PLOS ONE (2025) https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0337620 Subclinical Hypothyroidism in Pregnancy and HRV “Comparative Evaluation of Thyroid Profiles and Heart Rate Variability in Newly Diagnosed Subclinical Hypothyroid and Euthyroid Pregnant Women” Singh et al., Cureus (2025) https://www.cureus.com/articles/427419-comparative-evaluation-of-thyroid-profiles-and-heart-rate-variability-in-newly-diagnosed-subclinical-hypothyroid-and-euthyroid-pregnant-women?score_article=true#!/ Performance Optimization in Firefighters “Mental imagery and breathing exercises integrated into a standardized warm-up routine enhance sympathetic activation and optimize muscular performance in firefighters” Biéchy et al., PLOS ONE (2025) https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0337431 Innovative Respiratory-Synchronized Pacemaker University of Auckland research feature: “Pacemaker could help the heart heal” Paton, Ben-Tal, Nogaret, and Stiles https://www.auckland.ac.nz/en/news/2025/12/02/pacemaker-could-help-heart-heal.html HRV and Personalized Fitness Modeling “Advancing training effectiveness prediction in mass sport through longitudinal data: A mathematical model approach based on the Fitness-Fatigue Model” Wang et al., PLOS ONE (2025) https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0337824 Global Trends in HRV Research “A Two-Decade Bibliometric Analysis of Heart Rate Variability Research (2005–2024)” Sharma et al., Psychiatry Research (2025)

In this episode, Matt Bennett talks with Dr. Richard Harris about his article: Single-case report: dynamic changes in cardiac function during shamanic journeying and Qigong meditation Read the full article here: https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2025.1608442/full

In this episode, we dive deep into the latest research from late 2025 and explore the exploding field of Psychophysiology. We look at how Heart Rate Variability (HRV) is becoming the "master key" for detecting everything from complex emotions to psychosis. We also break down a massive new study on how antidepressants shift your physical metabolism, the effectiveness of "light-guided" breathing for office stress, and how VR gaming affects your autonomic nervous system. Links & Resources Mentioned: Clinical Psychiatry & Pharmacology Article: Which Antidepressants Shift Physiology? (Conexiant) Takeaway: A look at how different antidepressant classes impact weight, blood pressure, and heart rate. Paper: Reducing Artifact Preprocessing in HRV-Based Personalized Psychosis Prediction (World Scientific) Takeaway: Using AI to predict psychosis directly from wearable data. Breathing & Interventions Paper: Light-guided resonant breathing enhances psychophysiological stress recovery in a simulated office environment (Nature Scientific Reports) Paper: Resonant breathing in hospitalised psychiatric patients with persistent somatic symptoms (General Psychiatry / BMJ) The Science of Stress & Emotion (HRV) Paper: Measures of the psychophysiological response to recurrent anticipatory stress - the influence of neuroticism (Nature Scientific Reports) Paper: Heart rate variability reveals graded task difficulty effects and sensitization dynamics (Springer / J. Physiol. Anthropol.) Paper: HRV-Based Recognition of Complex Emotions: Feature Identification (MDPI Healthcare) Physiology in Action (VR & Exercise) Paper: Impact of Stereoscopic Technologies on Heart Rate Variability in Extreme VR Gaming Conditions (MDPI Technologies) Paper: A controlled comparative study on the effect of arterial occlusion pressure on immediate sympathetic responses (Nature Scientific Reports)

This Week’s Studies: Cardiac-vagal rhythm echoes on the heartbeat's mechanosensory imprint in the brain Candia-Rivera & Chavez — Communications Biology https://www.nature.com/articles/s42003-025-08969-x Box breathing or six breaths per minute: Which strategy improves athletes' post-HIIT cardiovascular recovery? Kasap & Aydin — PLOS ONE https://doi.org/10.1371/journal.pone.0336615 The tolerance-related psychology and dynamic activity in the peripheral nervous system of Internet Gaming Disorder Chi & Hsiao — BioMedical Engineering Online https://biomedical-engineering-online.biomedcentral.com/articles/10.1186/s12938-025-01471-9 Heart rate variability biofeedback in adults with chronic spinal cord injury: a randomised feasibility study Schoffl et al. — BMC Neurology https://bmcneurol.biomedcentral.com/articles/10.1186/s12883-025-04423-x

Video link: https://youtu.be/3vn_TF-ezTE   In this episode of The Heart Rate Variability Podcast, host Matt Bennett sits down once again with Stephanie White, HRV coach and educator known affectionately as “the HRV Guru.” Together, they dive deep into advanced heart rate variability concepts—especially heart rate fragmentation (HRF), very high frequency (VHF) activity, and new HRV metrics that can reveal hidden issues in autonomic health. Stephanie shares insights from her work with clinicians, coaches, and patients—explaining why sometimes clients can’t reach the “Optimal Zone” in the Optimal HRV app and what physiological patterns might be behind it. She also outlines the importance of minerals, CO₂ balance, and careful data interpretation when working with HRV readings. Key Topics Covered Stephanie’s Background – Her recovery journey from chronic illness using HRV biofeedback and her work with VCU’s Comprehensive Autonomic Center. Why HRV Data Sometimes “Doesn’t Make Sense” – How heart rate fragmentation can hijack HRV signals and confuse traditional measures like RMSSD. RMSSD vs. SDNN – Why SDNN may better capture resonance frequency breathing and coherent sine wave patterns. Understanding Heart Rate Fragmentation (HRF) – How alternating or sawtooth heart rhythms create misleading HRV statistics and mask underlying autonomic issues. Introducing “Very High Frequency (VHF)” – What happens when HRF shifts heart power above 0.4 Hz, and why current HRV software often misses it. The Role of CVNN and PSS – New or underused HRV metrics that can quantify fatigue, allostatic load, and fragmentation. Practical Clinical Applications – How coaches and clinicians can identify HRF, interpret data accurately, and help clients avoid “false high” HRV readings. Mineral Balance and HRV Health – Why calcium, sodium, potassium, and magnesium are crucial for healthy cardiac rhythm and recovery. Building an HRV Coaching Certification Pathway – Stephanie’s vision for “HRV Behavioral Health Coaches” and measurable, data-driven client progress.

Studies & Resources Discussed Insomnia and HRV in Medical Students Publication: Cureus Title: “Insomnia and Its Impact on Psychomotor Reactivity, Autonomic Function, and Psychological Well-Being Among Medical Students: A Cross-Sectional Analytical Study” Authors: Dhanusri, Rajalakshmi, Prakash, Bharadwaj, and Harichandrakumar Key Finding: The severity of insomnia among medical students was associated with slower reaction times and higher psychological distress, while short-term resting HRV remained largely unchanged. Early cognitive and mood changes appear before resting HRV declines, underscoring that subjective fatigue and attention lapses can be earlier indicators than RMSSD or SDNN. Link: https://www.cureus.com/articles/427559-insomnia-and-its-impact-on-psychomotor-reactivity-autonomic-function-and-psychological-well-being-among-medical-students-a-cross-sectional-analytical-study#!/ Meta-Analysis: HRV in Insomnia Disorder Publication: Sleep and Breathing Title: “Heart rate variability in patients with insomnia disorder: a systematic review and meta-analysis” Authors: Zhao and Jiang Key Finding: Across 17 studies and 921 participants, insomnia showed only mild, non-significant reductions in HRV measures such as SDNN and HF-norm. The review emphasizes methodological variability and suggests that chronic insomnia’s autonomic signature is subtle and context-dependent. Link: https://link.springer.com/article/10.1007/s11325-022-02720-0 Sleep Deprivation and HRV Publication: Frontiers in Neurology Title: “Effects of Sleep Deprivation on Heart Rate Variability: A Systematic Review and Meta-Analysis” Authors: Zhang, Niu, Ma, Wei, Zhang, and Du Key Finding: Eleven trials revealed consistent sympathetic dominance after sleep deprivation, as evidenced by decreased RMSSD, increased LF and LF/HF, and stable SDNN. These findings reinforce that RMSSD is the most sensitive marker of HRV for acute sleep loss and stress load. Link: https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2025.1556784/full COMISA: Insomnia and Sleep Apnea Combined Publication: Scientific Reports Title: “Heart Rate Variability Analysis in Comorbid Insomnia and Sleep Apnea (COMISA)” Authors: Martín-Montero, Vaquerizo-Villar, García-Vicente, Gutiérrez-Tobal, Penzel, and Hornero Key Finding: Using over 5,000 overnight ECGs, COMISA patients showed reduced parasympathetic tone while awake and increased sympathetic drive during sleep. This dual imbalance likely explains elevated cardiovascular risk when both disorders coexist. Link: https://www.nature.com/articles/s41598-025-02541-7 Depression and HRV in Students Publication: Kompasiana Title: “Diagnosis of Depressio...

Studies & Resources Discussed   HRV Biofeedback for PTSD & Chronic Pain Publication: Journal of Affective Disorders Title: "Heart rate variability biofeedback improves co-occurring posttraumatic stress disorder and chronic pain symptoms: A randomised waitlist controlled trial" Key Finding: This is the first RCT for this co-occurring population. Just six weeks of HRV biofeedback (HRVBF) led to a 24.3% decrease in PTSD symptoms and a 24.9% reduction in pain interference. Biofeedback in Pediatric Care Publication: Cleveland Clinic ConsultQD Title: "Biofeedback Interventions With Psychotherapy in Pediatric Care: The Present and the Future" Key Finding: A clinical guide and call to action for integrating biofeedback (like HRV) with psychotherapy to make self-regulation a concrete, measurable skill for children (e.g., pairing HRV biofeedback with exposure therapy for phobias). Slow-Paced Contraction (SPC) Publication: Biosourcesoftware.com Title: "Add Slow-Paced Contraction to Your Practice" Key Finding: This article details the "how-to" for Slow-Paced Contraction, a vital alternative to slow-paced breathing for patients with contraindications (like severe COPD, kidney disease, or metabolic acidosis). Tai Chi & HRV Publication: Medicine Title: "Effects of a Tai Chi dance intervention on the autonomic nervous system in university students" Key Finding: A 16-week Tai Chi intervention was shown to be an effective method to prevent excessive declines in resting HRV in university students, building autonomic resilience. HRV & Non-Suicidal Self-Injury (NSSI) Publication: Taylor & Francis Online Title: "Association between heart rate variability and emotion dysregulation in adolescents with non-suicidal self-injury" Key Finding: This review frames reduced HRV as a key physiological marker of the Emotion Dysregulation and autonomic imbalance that underlies the distress leading to NSSI in adolescents. HRV in IPV Offenders Publication: Journal of Criminal...

Find the article here: https://jamanetwork.com/journals/jamapsychiatry/article-abstract/2839605 Episode Summary In this insightful episode of The Heart Rate Variability Podcast, host Matt Bennett sits down with Dr. David Eddie, a clinical psychologist and researcher at Massachusetts General Hospital and Assistant Professor at Harvard Medical School. Together, they explore how Heart Rate Variability (HRV) is transforming the landscape of addiction recovery, psychotherapy, and digital mental health. Dr. Eddie shares how HRV can serve as both a biomarker for relapse risk and a tool for emotional regulation, shedding light on how AI, wearable technology, and stress-detection algorithms could revolutionize real-time intervention in substance use treatment. Listeners will gain a deeper understanding of how HRV biofeedback, digital monitoring, and personalized algorithms can support clients in recovery, enhance self-awareness, and inform clinicians’ decision-making in psychotherapy. Key Topics Covered How Dr. David Eddie began his HRV journey during graduate research at Rutgers and the Recovery Research Institute. HRV as a biomarker for pathology and relapse risk in substance use disorder and mental health conditions. Developing stress-detection algorithms that leverage real-time HRV data through wearables and AI. Challenges of variability and individual differences in HRV data across populations. Integrating ecological momentary assessment (EMA) and ambulatory psychophysiological monitoring for clinical insights. How HRV biofeedback supports recovery and emotional regulation in psychotherapy and addiction treatment. Ethical and practical issues around proprietary algorithms, data transparency, and commercial wearables. The future of HRV research, AI integration, and passive monitoring in clinical psychology. Key Takeaways HRV is both a symptom and contributor to addiction and mental health challenges, offering potential for early detection of relapse risk. Wearables and AI can help clinicians intervene in real time — possibly preventing relapse or emotional crises before they occur. Personalized baselines and individual calibration are essential to improve algorithm accuracy for diverse populations. HRV biofeedback provides an accessible, evidence-based method to help clients build resilience, reduce craving, and regulate their nervous system. Future advances will make passive, scalable HRV monitoring a core element of digital mental health and recovery care. About the Guest Dr. David Eddie is a clinical psychologist and researcher at Massachusetts General Hospital’s Recovery Research Institute and the Center for Digital Mental Health, as well as an Assistant Professor of Psychiatry at Harvard Medical School. His work focuses on addiction recovery, psychophysiology, and integrating HRV into digital and clinical interventions. Follow his work at Recovery Research Institute or through Harvard Medical School publications.

Show Notes Resource 1: Title: Associations between mental health disorder symptoms and cardiac function among Royal Canadian Mounted police cadets during the Cadet training program Authors: R.N. Carleton, T.A. Teckchandani, J.P. Neary, J.E. Samayoa, J.M.B. Khoury, K.Q. Maguire, G.P. Krätzig, & G.J.G. Asmundson Publication: Journal of Psychiatric Research Link: https://www.sciencedirect.com/science/article/pii/S0022395625006521 Resource 2: Title: Transgenerational effects of violence in adolescents exposed to grandmaternal intimate partner violence during pregnancy: Heart rate variability and DNA methylation Authors: Nayara Cristina dos Santos Oliveira, Aline Furtado Bastos, Fernanda Serpeloni, & Simone Gonçalves de Assis Publication: Behavioural Brain Research Link: https://www.sciencedirect.com/science/article/abs/pii/S0166432825004735 Resource 3: Title: The role of separation anxiety and autonomic dysregulation in pediatric vasovagal syncope. A cross-sectional study Authors: Gaia Cuzzocrea, Andrea Fontana, Cristiana Alessia Guido, Marta Mascanzoni, Alberto Spalice, Camilla Guccione, Angelos Halaris, Stephen Porges, Lucia Sideli, & Vincenzo Caretti Publication: Journal of Psychiatric Research Link: https://www.sciencedirect.com/science/article/abs/pii/S0022395625006351 Resource 4: Title: Acute cardiovascular and cerebral blood flow responses to high-frequency, low-amplitude vibration on the neck Authors: Viet Q Dinh, Malinda Hansen, K Austin Davis, Lindsey Peralez, & Caroline A Rickards Publication: Journal of Applied Physiology (via PMC) Link: https://pmc.ncbi.nlm.nih.gov/articles/PMC12551627/ Resource 5: Title: Autonomic Flexibility and Early Treatment Success: Heart Rate Variability Predicts Remission in First-Episode Psychosis Authors: Judith Rohde, Samantha Weber, Mateo de Bardeci, Aygün Ertuğrul, Grammato Amexi, Eva Schultz, & Sebastian Olbrich Publication: Schizophrenia Bulletin Link: https://academic.oup.com/schizophreniabulletin/advance-article/doi/10.1093/schbul/sbaf191/8305265?login=false Resource 6: Title: Interplay between ke...

Show Notes Resource 1: Title: Top 50 scariest movies of 2025 (and Fright Night Physiology) Publication: WISN.com / Science of Scare Project Link: https://www.wisn.com/article/top-50-scariest-movies-2025/69140286 Resource 2: Title: Heart Rate Variability as a Key to Regulation and Stress Author: D. N. Solomon Publication: Psychology Today Link: https://www.psychologytoday.com/us/blog/the-narrative-nurse-practitioner/202412/heart-rate-variability-as-a-key-to-regulation-and Resource 3: Title: Haunted House, Healthy Heart Publication: Business Health Trust Link: https://businesshealthtrust.com/news_insights/haunted-house-healthy-heart/ Resource 4: Title: Why Do We Love Being Scared? The Science Behind Horror Movies Author: A. Bennett Publication: Promega Connections Link: https://www.promegaconnections.com/the-science-behind-horror-movies/ Resource 5: Title: Playing With Fear: A Field Study in Recreational Horror Authors: M. M. Andersen, A. Coltan, et al. Publication: PMC (via Emotion) Link: httpss://pmc.ncbi.nlm.nih.gov/articles/PMC7734554/ Resource 6: Title: Scared together: Heart rate synchrony and social closeness in a high-intensity horror setting Authors: M. M. Andersen, et al. Publication: PubMed (via Psychological Science) Link: https://pubmed.ncbi.nlm.nih.gov/40720311/ Resource 7: Title: I tracked my heart rate through the 10 haunted houses of Halloween Horror Nights... Author: K. Weekman Publication: Yahoo.com Link: https://www.yahoo.com/entertainment/article/i-tr...

Show Notes Resource 1: Title: Pleasant odors specifically promote a soothing autonomic response and brain–body coupling through respiratory modulation Authors: Valentin Ghibaudo, Matthias Turrel, Jules Granget, Maëlys Souilhol, Samuel Garcia, Jane Plailly & Nathalie Buonviso Publication: Scientific Reports Link: https://www.nature.com/articles/s41598-025-20422-x Resource 2: Title: Improved non-invasive detection of sleep stages when combining skin sympathetic nerve activity and heart rate variability analysis with AI Authors: Md. Aktaruzzaman & Thomas H. Everett IV Publication: Scientific Reports Link: https://www.nature.com/articles/s41598-025-20282-5 Resource 3: Title: Increased sleep apnea-specific hypoxic burden is independently associated with cardiovascular autonomic dysfunction in obstructive sleep apnea: A large-scale study Authors: Chenyang Li, Zhenger Zhou, Xiaozhen Zhang, Enhui Zhou, Tianjiao Zhou, Jingyu Zhang, Xinyi Li, Jianyin Zou, Huajun Xu, Jian Guan, Yupu Liu, Suru Liu, Xiaoyue Zhu, Weijun Huang, Hongliang Yi, Shankai Yin Publication: Sleep Medicine Link: https://www.sciencedirect.com/science/article/abs/pii/S1389945725005386 Resource 4: Title: Strengthening the heart by means of a gratitude intervention? Authors: Andreas R. Schwerdtfeger, Claudia Traunmüller, Bernhard Weber & Christian Rominger Publication: The Journal of Positive Psychology Link: https://www.tandfonline.com/doi/full/10.1080/17439760.2025.2574048?af=R#abstract Resource 5: Title: Child and marital stress are associated with a psychophysiological index of self-regulatory capacities among parents of preschool children Authors: Sasha MacNeil, Chelsea da Estrela, Warren Caldwell, Jean-Philippe Gouin Publication: International Journal of Psychophysiology Link: https://www.sciencedirect.com/science/article/pii/S0167876025007470?via%3Dihub Resource 6: Title: Factors influencing heart rate variability in nurses following night shifts: a prospective observational clinical study Authors:

Resonance Frequency Breathing Explained In this solo episode of the Heart Rate Variability Podcast, Matt Bennett explores the science and practicality of resonance frequency breathing, a term he notices is often misused. He introduces his AI counterpart, AI Matt, to present the research on resonance frequency breathing, which involves finding a natural rhythm for breathing that aligns with the body's optimal pace. Matt aims to delve into the correct usage of this term, discuss its scientific basis, and share practical applications in the episode. Resonance Frequency Breathing Techniques Matt discussed resonance frequency breathing, explaining that while 6 breaths per minute is often cited, the actual rate can vary based on factors like height. He noted that trained biofeedback practitioners have observed rates as low as 3.5 breaths per minute in special operators and professional athletes. Matt emphasized the importance of synchronization between the heart, breath, and nervous system, as well as the impact on brain functioning. Resonance Frequency Breathing Assessment Matt discussed the concept of resonance frequency breathing, noting that while research suggests an average of 6 breaths per minute, individual rates can vary widely. He explained that resonance frequency assessments involve gradually reducing breathing rate from 7 to 3.5 breaths per minute to find the rate that maximizes HRV. Matt emphasized that while height may influence resonance frequency, factors like fitness and body mass could also affect it, particularly for former athletes. He recommended practicing paced breathing before taking the assessment and suggested that repeated testing might show small changes in breathing rate over time. Breathing Patterns and Resonance Frequency Matt discussed the importance of regularly reassessing one's resonance frequency breathing to ensure accuracy, especially if consistent readings are obtained over several months without significant lifestyle changes. He shared his personal experience with adjusting his breathing patterns, including experimenting with a 4.5 to 3.5 breaths per minute rate and a 2:1 inhale-to-exhale ratio, inspired by recent research suggesting extended exhales can improve low-frequency heart rate variability. Matt emphasized the significance of personalized assessments using tools like the OptimalHRV app to determine optimal breathing patterns and encouraged others to explore different breathing techniques for maximum impact. Residence Frequency Breathing Assessment Matt discussed the importance of practicing residence frequency breathing assessment and emphasized the value of this technique in maximizing breathwork practices. He noted that while the concept is gaining recognition among fitness influencers and in peer-reviewed research, the full impact of the science is often overlooked in blog posts. Matt planned to include relevant research in the show notes and promised to cover this topic further in the next episode.

Show Notes Resource 1: Title: The relationship between heart rate variability and affective disorders: associations with symptomatic improvement and therapeutic alliance Authors: Alexandra F. Gonçalves, Eugénia Ribeiro, Adriana Sampaio, Natividade S. Couto-Pereira, Pedro Moreira & Joana F. Coutinho Publication: BMC Psychology Link: https://bmcpsychology.biomedcentral.com/articles/10.1186/s40359-025-02960-1 Resource 2: Title: Development and validation of the socio-evaluative N-back task to investigate the impact of acute social stress on working memory Authors: Matthias Haucke, Sabrina Golde & Stephan Heinzel Publication: Scientific Reports Link: https://www.nature.com/articles/s41598-025-22611-0 Resource 3: Title: Panic Attack Prediction for Patients With Panic Disorder via Machine Learning and Wearable Electrocardiography Monitoring: Model Development and Validation Study Authors: Hayoung Oh, Hunmin Do, Chaehyun Maeng, Jinsuk Park, Taejun Yoon, Jihwan Kim, Hyeran Hwang, Seoin Choi, & Piao Huilin Publication: Journal of Medical Internet Research Link: https://www.jmir.org/2025/1/e69045 Resource 4: Title: Non-invasive cardiovascular risk stratification in type 2 diabetes: a pulse wave and pulse rate variability analysis with machine learning Authors: Saurav Kumar, Apakrita Tayade, Amber Shrivastava, & Ravi Bhallamudi Publication: Biomedical Signal Processing and Control (via Science Direct) Link: https://www.sciencedirect.com/science/article/abs/pii/S1746809425014491 Resource 5: Title: How Tracking Your Health Metrics Can Help You Live Longer Author: Alice Park (Interview with Zahi Fayad) Publication: TIME Link: https://time.com/7324741/health-metrics-tracking-live-longer/ Resource 6: Title: Stressed at Work? Your Heart Disease Risk Just Jumped 50%. Here’s the One Number That Shows How to Fight Back Author: Julien Raby Publication: BoxLife Magazine Link: https://boxlifemagazine.com/boost-heart-resilience-by-tracking-hrv/ Resource 7: Title: “Resonance Breathing” Is The Anti-Stress Hack You Can Do Anywhere Author: Carolyn Steber Publication:...

Below are the links to the studies and articles discussed in this episode: Personalized Respiratory Guidance for HRV: Lin, Z., Kong, W., Qiu, S., Luo, M., Wei, J., Guo, X., ... & Dan, G. (2025). High-precision personalized respiratory guidance model for enhanced breathing training: effects on heart rate variability. Biomedical Signal Processing and Control, 100, 108720. https://www.sciencedirect.com/science/article/abs/pii/S1746809425012315 Therapy with Local Anesthetics and HRV: Weinschenk, S., Topbas-Selcuki, N. F., Benrath, J., Strowitzki, T., & Feisst, M. (2025). Effects of therapy with local anesthetics (TLA) on heart rate variability (HRV) over 24 hours. Chronobiology International. https://www.tandfonline.com/doi/full/10.1080/07420528.2025.2560963?src=exp-la Veterans, Service Dogs, and HRV: Krause-Parello, C. A., Friedmann, E., Taber, D., Zhu, H., Quintero, A., & Yount, R. (2025). Veterans Training Service Dogs for Other Veterans: An Animal-Assisted Intervention for Post-Traumatic Stress Disorder. Behavioral Sciences, 15(9), 1180. https://www.mdpi.com/2076-328X/15/9/1180 Circadian Rhythm of HRV in Pregnancy: Rasouli, M., Feli, M., Azimi, I., Haghayegh, S., Sarhaddi, F., Niela-Vilen, H., ... & Rahmani, A. M. (2025). Circadian rhythm of heart rate and heart rate variability in pregnancy. npj Women's Health, 3(1), 57. https://www.nature.com/articles/s44294-025-00107-6 Wearable Tech in Tennis Players: Wang, Z. (2025). Integration of wearable technologies in monitoring physical performance and psychological stress in tennis players. Acta Psychologica, 260, 105706. https://www.sciencedirect.com/science/article/pii/S0001691825010194 Acoustic Features of Chants: Dolan, E. W. (2025, October 6). Chants across cultures share features that promote relaxation. PsyPost

In this episode of the Heart Rate Variability Podcast, host Matt Bennett sits down once again with Dr. Inna Khazan, a leading expert in HRV biofeedback and applied psychophysiology. Together, they unpack one of the most fascinating and misunderstood aspects of heart rate variability — low-frequency HRV — and its connection to self-regulation, stress resilience, and overall wellness. Understanding Frequency Domains in HRV Dr. Khazan begins by breaking down the concept of frequency domains in HRV. Just as white light contains multiple colors, the heart rate signal is composed of several distinct frequency components. Using tools like the Fast Fourier Transform, researchers can separate heart signals into high-frequency, low-frequency, and very-low-frequency ranges — each linked to specific physiological processes and parts of the autonomic nervous system. Low Frequency HRV and the Baroreflex The conversation dives deep into low-frequency power, which represents the interplay between the baroreflex (the body’s blood pressure regulation system) and the vagus nerve. Dr. Khazan explains how resonance-frequency breathing—typically practiced for 20 minutes a day—acts like strength training for these systems. Over time, this practice enhances emotional regulation, stress recovery, and overall heart-brain coherence. Why Breathing Rate and Context Matter Listeners learn that breathing too long in a low-frequency state can actually suppress other important HRV components, such as high-frequency and very-low-frequency power. Instead, Dr. Khazan recommends brief, consistent training sessions to balance all aspects of the nervous system. She also clarifies common misconceptions, including the outdated idea that low-frequency HRV measures sympathetic activity, emphasizing instead its parasympathetic and baroreflex origins. Making Sense of HRV Metrics in Optimal HRV Matt and Dr. Khazan discuss Optimal HRV’s “Optimal Zone” scale, which tracks the percentage of time users spend in low-frequency dominance during a session. They also unpack metrics like Max-Min and total low-frequency power, explaining how they interact and what each reveals about training efficiency and day-to-day readiness. Practical Takeaways Practice resonance-frequency breathing for 20 minutes a day to enhance self-regulation. Avoid over-training in the low-frequency zone — balance is key. Understand that low-frequency HRV is not a measure of stress or sympathetic activity, but rather a reflection of vagal and baroreflex strength. Leverage your Optimal HRV app metrics to track progress, focus, and nervous-system adaptability. Listen & Learn More Explore more insights from Dr. Khazan and Matt Bennett on heart rate variability, stress regulation, and biofeedback science. Visit OptimalHRV.com for resources, show notes, and upcoming episodes, including the "This Week in HRV" series, which highlights the latest HRV research and applications.

Welcome to the show notes for this week’s episode – This Week in HRV Edition. Below, you’ll find direct links to all the studies and articles discussed in this episode. These sources represent the latest research connecting HRV to mental health, resilience, environmental design, and leadership. Research Studies: Multisensory environmental effects on HRV and psychological restoration – Scientific Reports Walking through green and grey: Exploring sequential exposure and multisensory environmental effects on psychological restoration – Building and Environment The Impact of Vipassana Meditation on Health and Well-being: A Systematic Review of Current Evidence – Cureus Cardiac timing effects on response speed are modulated by blood pressure, but not by heart rate variability, in healthy young adults – Physiological Reports Heart-brain interaction in emotional regulation – Scientific Reports Environmental stress and HRV in agricultural settings – Agricultural and Forest Meteorology HRV and emotion regulation in depression risk – JAMA Psychiatry HRV modulation through breathing and neural coherence – Frontiers in Human Neuroscience News and Features: Professor honored for pioneering heart–brain research – UC Irvine News Solo practitioner uses HRV tech to improve patient care – Healthcare IT News What is heart rate variability and how can it guide smarter leadership decisions – Manila Bulletin HRV: The new secret weapon for heart resilience – Men’s Health Each of these studies and stories offers a unique perspective on how HRV connects the hear...

In this episode, we review seven new studies published between September 19 and September 25, 2025. Together, they highlight the many ways HRV intersects with brain activity, breathing practices, cardiac recovery, exercise environments, emergency medicine, environmental stressors, and new multimodal measurement approaches. We’ll explore: How brain networks and cognitive load shape HRV readings. Why slow breathing alone is powerful, and what feedback really adds. The Benefits of Yoga Nidra for Patients Recovering from Coronary Artery Bypass Surgery. How walking in natural environments provides a stronger autonomic boost than indoor or urban exercise. Real-world HRV findings in emergency medicine and why lab results don’t always translate. How pollution, heat, and noise suppress vagal tone. New frontiers in dynamic and multimodal HRV metrics. As always, I’ll connect the research to practical, client-ready strategies you can use right away. This podcast is sponsored by Optimal HRV. Learn more at optimalhrv.com. References  Behavioural Brain Research – Neural and cognitive influences on autonomic function. https://doi.org/10.1016/j.bbr.2025.115811 Psychophysiology – Comparing HRV biofeedback and slow-paced breathing. https://doi.org/10.1111/psyp.70156 Cureus – Impact of Yoga Nidra on heart rate variability in coronary artery disease patients undergoing coronary artery bypass grafting. https://www.cureus.com/articles/402202-impact-of-yoga-nidra-on-heart-rate-variability-in-coronary-artery-disease-patients-undergoing-coronary-artery-bypass-grafting-a-comparative-study Psychology of Sport and Exercise – Green exercise randomized controlled trial. https://doi.org/10.1016/j....

Refrences: Ferreira S, Rodrigues M A, Mateus C, Rodrigues P P, Rocha N B. Interventions Based on Biofeedback Systems to Improve Workers’ Psychological Well-Being, Mental Health, and Safety: Systematic Literature Review. Journal of Medical Internet Research (2025). DOI: 10.2196/70134. JMIR+2JMIR+2 Lässing J, Wegener F, Höpker N, Hottenrott K, Gronwald T, Falz R. Heart rate variability response of intensity-matched strength training dependent on body position in females: a pilot randomized crossover study. Scientific Reports (2025). DOI: 10.1038/s41598-025-19817-7. Nature+1 Książek K, Masarczyk W, Głomb P, Romaszewski M, Buza K, Sekuła P, Cholewa M, Kołodziej K, Gorczyca P, Piegza M. Deep learning approach for automatic assessment of schizophrenia and bipolar disorder in patients using R-R intervals. PLoS Computational Biology (2025). DOI: 10.1371/journal.pcbi.1012983. PLOS+1 Zilcha-Mano S, Tchizick A, Nof A, Malka M, Oded Y. Clinical breakthroughs or research oversights? The imperative of integrating modalities to differentiate signal from noise. The British Journal of Psychiatry (First View, 2025). DOI: 10.1192/bjp.2025.10321. Cambridge University Press & Assessment Dear Media. “7 Lab Tests Every Woman in Her 30s Should Know, According to Dr. Sara Szal.” By Jane LaCroix. September 16, 2025. Dear Media

In this episode, Matt Bennett explores how to apply the research on HRV training through muscle contraction into personal practice.   References for this episode.  Fred Shaffer's work: https://youtu.be/ajwgwzn2ZUo Sources for this summary: Vaschillo/Lehrer et al., laboratory demonstration that 0.1-Hz rhythmic skeletal muscle tension increases 0.1-Hz power in heart rate, systolic pressure, and pulse transit time and strengthens HR–BP coupling, consistent with baroreflex resonance; includes with- and without-leg-crossing conditions (N≈37). ResearchGate Shaffer, Moss, & Meehan (2022) randomized study showing that one and six contractions per minute increased multiple HRV metrics versus twelve per minute, with a ~0.10-Hz peak at six per minute. SpringerLink Meehan & Shaffer (2023) within-subjects study showing greater HR, HR max–min, and low-frequency power when adding core contraction and leg-crossing versus wrist-ankle alone at six contractions per minute. SpringerLink Frontiers in Neuroscience review describing the resonance-frequency model and noting that rhythmic skeletal muscle tension, like slow breathing, can stimulate the baroreflex at ~0.1 Hz.