Heart Rate Variability Podcast

Medical disclaimer: The information shared on this podcast is for educational and informational purposes only. It is not intended as medical advice and should not be used as a substitute for professional guidance from a qualified healthcare provider. If you have questions about your health or a medical condition, please consult a licensed clinician who knows you and your history. This week on This Week in Heart Rate Variability, we open a new themed month by looking at where heart rate variability is headed next. Six studies map the future of the field — from a unifying theory of cardiovascular instability built on Shannon entropy, to the regulatory and technical realities of validating consumer wearables, to a meta-analysis quantifying how far photoplethysmography still is from true electrocardiography-derived HRV, to a virtual reality study, a forest-based multimodal field study, and a deep dive into the asymmetric structure of the heartbeat itself. RESEARCH HIGHLIGHTS THIS WEEK 1. Shannon Entropy in Heart Rate Variability: A Unified Indicator of Electrical and Hemodynamic Cardiovascular Instability PUBLICATION: Medical Research Archives AUTHORS: Orazio Antonio Barra KEY FINDING: This systematic review pooled 22 published studies that applied Shannon entropy of RR intervals to atrial fibrillation and tilt-induced syncope. Entropy declined progressively across both conditions — roughly ten percent at baseline instability, fifteen to twenty percent approaching pre-crisis, and twenty-five to thirty percent as crisis became imminent — with entropy showing better specificity than other HRV indices while holding onto its sensitivity. SIGNIFICANCE: Entropy looks less like a metric tied to one specific condition and more like a general-purpose marker of autonomic complexity loss that shows up consistently whether the underlying instability is electrical or hemodynamic. This is a synthesis of existing studies rather than a new trial, so it should be read as a strong, well-supported hypothesis rather than a validated bedside tool. Read the full study: https://esmed.org/MRA/mra/article/view/7606 2. Validity, Reliability, and Regulatory Considerations for Consumer Devices in Clinical Research Data Collection PUBLICATION: Applied Clinical Trials Online AUTHORS: Lauren Crooks, Greta Marie van Schoor, Anthony Everhart, Bill Byrom, and Thijs Sondag KEY FINDING: This article maps the validity, reliability, and regulatory landscape for consumer wearables used in decentralized clinical trials. Heart rate accuracy can approach ECG-level concordance under favorable conditions, but motion artifacts, device-to-device variation, and demographic performance gaps can cause aggregate agreement statistics to mask large individual-level errors. Only an estimated 11% of devices on the market have been rigorously and publicly validated. SIGNIFICANCE: Regulators are converging on "fit-for-purpose" validation rather than universal accuracy claims — asking whether a specific device is accurate enough for a specific clinical question, not whether it's accurate for everything. That's a useful discipline for anyone using consumer devices outside a formal trial, too. Read the full study: https://www.appliedclinicaltrialsonline.com/view/validity-reliability-regulatory-considerations-consumer-devices-clinical-research-data-collection 3. Accuracy of Photoplethysmography-Derived Pulse Rate Variability Compared with Electrocardiography-Derived Heart Rate Variability: A Systematic R...

In this follow-up episode of the Heart Rate Variability Podcast, Matt Bennett reconnects with Lieven Van Linden to discuss the newly published English version of his book, Fully Charged. Since their last conversation two years ago, Lieven’s work has continued to evolve at the intersection of leadership, nervous system regulation, sustainable performance, and HRV. Lieven shares how his engineering background shaped the framework behind Fully Charged, applying process improvement thinking to human performance. Rather than treating energy, resilience, and leadership as vague concepts, his model looks at the body as a system with inputs, processes, outputs, and measurable feedback. HRV plays a central role as a biomarker for nervous system health, recovery, and available energy. Matt and Lieven also explore what has changed since the book's original publication, including new English-language chapters on artificial intelligence and women's energy levels. Lieven reflects on the slower-than-expected adoption of HRV technology in Europe and the growing conversation around AI health coaches. While AI can support education and insight, Lieven emphasizes that human connection remains essential for lasting behavioral change. The conversation also moves into Lieven’s personal evolution. After years of extreme endurance racing, he has shifted toward freediving, which challenges him in a very different way. Rather than pushing through suffering, freediving requires relaxation, self-regulation, inner awareness, and trust in the body.

Medical disclaimer: The information shared on this podcast is for educational and informational purposes only. It is not intended as medical advice and should not be used as a substitute for professional guidance from a qualified healthcare provider. If you have questions about your health or a medical condition, please consult a licensed clinician who knows you and your history. This week on This Week in Heart Rate Variability, we open our second themed month with a focus on medical health. Six studies map how heart rate variability behaves under real medical strain — from a rigorous methodological look at glucose sensing, to a two-decade cohort tracking cardiovascular mortality, to hidden autonomic signals in normal brain recordings, to the flattening and even reversal of breath-heart coupling in brain-injured intensive care patients, to a call for multi-window autonomic assessment in critically ill cancer patients, and finally to autonomic flexibility as a biomarker for fatigue in multiple sclerosis. A quick reminder that this is the newly curated, theme-based format we kicked off last month, and this week's center of gravity is medical health. RESEARCH HIGHLIGHTS THIS WEEK 1. Re-evaluating heart rate variability biomarkers for glucose sensing: the impact of age normalization and subject-independent validation PUBLICATION: BMC Medical Informatics and Decision Making AUTHORS: Md Basit Azam, Sarangthem Ibotombi Singh KEY FINDING: In a rigorously validated model built on data from forty-three men with type two diabetes, heart rate variability features derived from the electrocardiogram showed a modest but significant association with hemoglobin A1c (R-squared of about zero point two two), while none of the six tested age-normalization methods improved model performance — suggesting age-related decline in heart rate variability was not confounding the signal. SIGNIFICANCE: This study is a piece of methodological conscience in the wearable glucose monitoring space. It shows that heart rate variability carries a real but modest signal for glycemic status, that honest subject-independent validation is essential, and that a fashionable statistical correction is not worth adding until you have checked whether it actually helps. Read the full study: https://pmc.ncbi.nlm.nih.gov/articles/PMC13169770/ 2. Differential associations of resting heart rate and heart rate variability indices with cardiovascular and coronary heart disease mortality risk: the prospective KORA study PUBLICATION: Scientific Reports AUTHORS: Kolade Oluwagbemigun, Dan Ziegler, Alexander Strom, Margit Heier, Gidon J. Bönhof, Michael Roden, Wolfgang Rathmann, Christa Meisinger, Annette Peters, Stefanie M. Hauck, Agnese Petrera, Moritz F. Sinner, Stefan Kääb, Barbara Thorand, Christian Herder KEY FINDING: In a prospective German cohort followed for more than two decades, higher resting heart rate was associated with greater cardiovascular and coronary heart disease mortality across the whole group, while the relationships between heart rate variability indices and mortality differed by glucose status — including an S-shaped, nonlinear association between the root mean square of successive differences and cardiovascular mortality in people with type two diabetes. SIGNIFICANCE: The metabolic context changes the meaning of the measurement. The same heart rate variability index does not convey the same message in a person with normal blood sugar as in a person with diabetes, and greater variability is not always better. Long-cohort work like this reframes heart rate variability as a context-dependent marker rather than a univ...

Medical disclaimer: This podcast is for informational and educational purposes only and does not constitute medical advice. Please consult your healthcare provider before making any changes based on this content. Welcome to This Week in Heart Rate Variability. This is the next installment in our newly curated, theme-based format, and this week's theme is mental health: what the rhythm of the heart can—and cannot—tell us about the mind. Across seven studies, a single thread keeps surfacing: the body's story and the mind's story refuse to line up neatly. Sometimes lower heart rate variability marks distress; sometimes it does not move where we most expect it to; and in at least one striking case, higher variability marks not health but trouble. RESEARCH HIGHLIGHTS THIS WEEK 1. A meta-analysis of heart rate variability and psychopathology: An investigation guided by the hierarchical taxonomy of psychopathology framework PUBLICATION: Journal of Psychopathology and Clinical Science AUTHORS: Tam Pham, Carly J. Johnco, Ana Neves, Wilson P. H. Lim, Gladys J. Heng, Rachel Ygnacio, Miriam K. Forbes KEY FINDING: Pooling 430 studies (732 effect sizes across roughly 62,000 people), lower resting heart rate variability was associated with most of the psychopathology hierarchy — including schizophrenia, bipolar disorder, autism, generalized anxiety disorder, panic disorder, borderline personality disorder, post-traumatic stress disorder, and major depression — but not with obsessive-compulsive disorder, social anxiety disorder, or attention-deficit/hyperactivity disorder. Associations were strongest in psychotic conditions and consistently stronger in more severely symptomatic samples. SIGNIFICANCE: Reduced heart rate variability looks less like a disorder-specific fingerprint and more like a transdiagnostic marker of systemic dysregulation tied to illness severity — a fever, not a rash. It may be most useful for gauging overall strain and tracking change over time rather than sorting people into diagnoses. This is a meta-analysis of largely cross-sectional data, so it shows association, not causation. Read the full study: https://pubmed.ncbi.nlm.nih.gov/42490257/ 2. Heart rate variability and risk of agitation in Alzheimer's disease: the Atherosclerosis Risk in Communities Study PUBLICATION: Brain Communications AUTHORS: Kathy Y. Liu, Eric A. Whitsel, Gerardo Heiss, Priya Palta, Suzanne Reeves, Feng V. Lin, Mara Mather, Jonathan P. Roiser, Robert Howard KEY FINDING: In 120 participants from the Atherosclerosis Risk in Communities study whose dementia was attributed solely to Alzheimer's disease, higher heart rate variability was associated with greater agitation risk, with the strongest signal coming from the change in vagally mediated variability over roughly two decades. The associations were adjusted for cognitive status, resting heart rate, demographics, comorbidities, and medications affecting the autonomic nervous system. SIGNIFICANCE: The meaning of heart rate variability is context-dependent: in a brain undergoing neurodegeneration, an increase in autonomic signal may reflect a loss of regulatory control rather than resilience. This is a candidate marker of propensity for agitation, not yet a clinical tool. Observational design and a small subgroup mean this is association, not causation. Read the full study: https://academic.oup.com/braincomms/article/5/6/fcad269/7311113?login=false 3. Physiological correlates of interoception and the effect of heart rate variability biofeedback ...

In this episode of the Heart Rate Variability Podcast, Matt Bennett speaks with Zuzu Karen Arms about the deep connection between gut health, the autonomic nervous system, and heart rate variability. Zuzu shares her personal journey of reversing epilepsy, scoliosis, and other health challenges through holistic approaches. The conversation explores how the gut microbiome supports nervous system regulation, why GABA production matters, and how gut health may influence conditions like POTS, dysautonomia, and low HRV. Matt and Zuzu also discuss nutrition, fiber, probiotics, prebiotics, acupuncture, biofeedback, and the importance of creating the right internal environment for better autonomic balance. Topics Covered Zuzu’s personal health journey and holistic recovery The relationship between gut health and the autonomic nervous system How the microbiome influences HRV and nervous system regulation GABA production in the gut and why it matters POTS, dysautonomia, and nervous system imbalance Dietary approaches for supporting gut and nervous system health Why processed carbohydrates may negatively affect GABA levels The role of fiber, prebiotics, and probiotics Maintaining healthy gut pH Acupuncture and biofeedback as supportive therapies Rethinking the modern emphasis on protein consumption Key Takeaways Gut health plays a major role in nervous system regulation, and the microbiome may directly influence HRV through mechanisms like GABA production, inflammation, and autonomic signaling. Zuzu emphasizes that supporting the gut is not just about digestion. It can also affect energy, neurological function, emotional regulation, cardiovascular control, and resilience. The discussion also challenges common nutrition assumptions, including the overemphasis on protein intake, while highlighting the importance of plant-based nutrients, fiber, and gut-friendly dietary patterns.

Medical disclaimer: This podcast is for informational and educational purposes only and does not constitute medical advice. Please consult your healthcare provider before making any changes based on this content. Ethical Principles and Practice Standards in Clinical Biofeedback with Dr. Donald Moss — 3 APA CE credits, BCIA-aligned https://www.optimalhrv.com/event-details-registration/master-ethical-principles-practice-standards-in-clinical-biofeedback-aligned-with-bcia This Week in Heart Rate Variability. This is a milestone edition — our 50th episode in the This Week in HRV format, and the start of a more curated approach that organizes episodes around themes rather than publication timing. We begin that new chapter with performance, following the autonomic nervous system across five studies: from whether burnout leaves a measurable mark on the working heart, to the quiet self-talk that sharpens a golfer's focus, to hydrogen-rich water and faster recovery, to syncing breath with heartbeat at the edge of exhaustion, and finally to a blueprint for building biofeedback into how athletes train. RESEARCH HIGHLIGHTS THIS WEEK 1. What Your Heart Reveals About Workplace Burnout PUBLICATION: Frontiers in Physiology AUTHORS: Irina Böckelmann, Jonas Hartung, Sabine Darius, Stefan Sammito, Beatrice Thielmann KEY FINDING: In 202 employees working in interaction-heavy jobs — nursery teachers, bank clerks, and medical assistants — only about 5 percent showed elevated burnout risk. Where heart rate variability differed by burnout risk, the differences showed up in the 24-hour and daytime recordings but not during sleep, and the correlations between HRV and burnout were mostly weak. Age and gender influenced HRV more than burnout status did. SIGNIFICANCE: This is a cross-sectional study, so it can show association but not causation — it cannot tell us that burnout changes HRV or the reverse. Still, the pattern hints that if HRV is going to reflect occupational strain, daytime and on-the-job recordings may be more sensitive than overnight data. For now, HRV looks like a possible complement to validated burnout questionnaires, not a standalone screening tool. Read the full study: https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2026.1908141/full 2. How Self-Talk Quietly Sharpens Focus Under Pressure PUBLICATION: Behavioral Sciences AUTHORS: Emmanouil Tzormpatzakis, Theodoros Proskinitopoulos, Orestis Panoulas, Evangelos Galanis, Evgenia Nikolakopoulou, Nikos Comoutos, Yannis Theodorakis, Antonis Hatzigeorgiadis KEY FINDING: Forty novice golfers were split into a control group and a group trained in strategic self-talk. The self-talk group improved their putting significantly more and outperformed the control group at the final assessment, while showing greater parasympathetic activation (in the root mean square of successive differences), especially toward the later stages of the task. The authors note the HRV pattern did not reach multivariate significance. SIGNIFICANCE: The physiological signal fits an attentional explanation: self-talk may help performers execute with less mental effort, keeping the rest-and-digest system more engaged under pressure. Strategic self-talk is a low-cost, teachable tool that appears to accelerate skill learning. The performance benefit is solid; the HRV mechanism...

Medical disclaimer: This podcast is for informational and educational purposes only and does not constitute medical advice. Please consult your healthcare provider before making any changes based on this content. Ethical Principles and Practice Standards in Clinical Biofeedback with Dr. Donald Moss — 3 APA CE credits, BCIA-aligned https://www.optimalhrv.com/event-details-registration/master-ethical-principles-practice-standards-in-clinical-biofeedback-aligned-with-bcia This Week in Heart Rate Variability. In this episode, we trace the autonomic nervous system across an entire human lifespan — from a mother's anxiety reaching her baby's heart in the womb, to ADHD and the "vagal brake," to a middle school experiment on weight stigma and peer support, to how your menstrual cycle quietly reshapes your heart rhythm, all the way to AI models learning to forecast your next heartbeat. RESEARCH HIGHLIGHTS THIS WEEK 1. Does Mom's Anxiety Change Baby's Heartbeat? It Depends on Baby's Sex PUBLICATION: Journal of Affective Disorders AUTHORS: Anna M. Zhou, Sarah E. Maylott, Nicolette C. Molina, Dylan Neff, Elisabeth Conradt, Sheila E. Crowell KEY FINDING: In 159 mother-fetus pairs, higher maternal anxiety was linked to elevated fetal heart rate specifically in male fetuses, not female ones. Broader maternal depression and anxiety symptoms were tied to lower fetal heart rate variability regardless of fetal sex. SIGNIFICANCE: This suggests prenatal maternal mental health shapes fetal autonomic development in sex-specific ways, reinforcing why prenatal mental health screening matters for the baby, not just the mother. Read the full  study: https://www.sciencedirect.com/science/article/abs/pii/S0165032726011833 2. What Your Heart Rate Reveals About ADHD (And What It Doesn't) PUBLICATION: Middle East Current Psychiatry AUTHORS: Davoud Amiri, Lamberto Briziarelli, Swetang J. Shah, Sara Amiri, Hadi Rahimi-Danesh KEY FINDING: This clinical review found that reduced heart rate variability in ADHD shows up most consistently under cognitive or emotional stress, not at rest, with wide variation driven by age, medication status, and coexisting anxiety. SIGNIFICANCE: The authors propose a "phenotype-informed" framework linking autonomic profiles to emotional dysregulation and medication tolerability — a promising but still hypothesis-generating direction, not a diagnostic tool. Read the full study: https://link.springer.com/article/10.1186/s43045-026-00658-7 3. The Middle School Study That Shows Why Peer Support Protects the Heart PUBLICATION: Adolescents AUTHORS: Meghan J. Gangel, Daniel Hamill, Alleyne P. R. Broomell KEY FINDING: In 31 middle schoolers, internalized weight stigma alone didn't predict stress reactivity — but among adolescents with low peer acceptance, higher weight stigma triggered a significantly larger sympathetic stress response. High peer acceptance eliminated that effect entirely. SIGNIFICANCE: Peer belonging may physiologically buffer adolescents from the harms of internalized weight stigma, suggesting interventions should target social acceptance, not just body-image beliefs, on thei...

In this episode of the Heart Rate Variability Podcast, Matt Bennett speaks with Dr. Diana Driscoll about her work in autonomic health, POTS, inflammation, and recovery from complex chronic illness. Dr. Driscoll shares her journey from optometrist to patient-researcher after developing POTS following a viral illness. When traditional medical care failed to help her and her family, she began investigating the underlying causes of autonomic dysfunction. She explains why she views POTS not as a single disease, but as a presentation of deeper issues involving inflammation, neurotransmitter disruption, cardiovascular problems, intracranial pressure, and genetic predispositions. The conversation also explores her development of Parasym Plus and her recovery-focused approach to treatment. Matt and Dr. Driscoll discuss how HRV can be used to track autonomic function and recovery over time, as well as the importance of persistence, proactive care, and continuing to search for answers. Topics Discussed Dr. Driscoll’s personal experience with POTS Why POTS may be a presentation, not a disease Inflammation and autonomic dysfunction Parasympathetic nervous system function Parasym Plus and neurotransmitter support HRV as a tool for tracking recovery Why Dr. Driscoll believes many patients can improve significantly Key Takeaway Dr. Driscoll offers a recovery-focused view of POTS and autonomic dysfunction, emphasizing the importance of identifying and treating the underlying causes rather than only managing symptoms.

Medical disclaimer: This podcast is for informational and educational purposes only and does not constitute medical advice. Please consult your healthcare provider before making any changes based on this content. BCIA HRV Biofeedback Training with Dr. Inna Khazan — 16 APA CE credits https://www.optimalhrv.com/event-details-registration/bcia-aligned-hrv-biofeedback-training-led-by-dr-inna-khazan Ethical Principles and Practice Standards in Clinical Biofeedback with Dr. Donald Moss — 3 APA CE credits, BCIA-aligned https://www.optimalhrv.com/event-details-registration/master-ethical-principles-practice-standards-in-clinical-biofeedback-aligned-with-bcia This week Matt covers seven new studies spanning psychiatry, neurology, endocrinology, and sports science — from a systematic review mapping how heart rate variability is used across clinical research, to adolescent depression, suicide risk, music and athletic recovery, seizure disorders, and two studies on diabetes. It's a dense, wide-ranging episode with real implications for clinicians, coaches, and researchers alike. RESEARCH HIGHLIGHTS THIS WEEK 1. Application of heart rate variability in clinical practice and research: A systematic review of recent years PUBLICATION: Autonomic Neuroscience: Basic and Clinical AUTHORS: Camila Maldonado-Veas, Paula León, Claudia Lerma, and Juan C. Echeverría KEY FINDING: This systematic review screened recent heart rate variability literature to catalog how HRV indices are applied for diagnosis, severity staging, and disease tracking across cardiovascular, neurological, and psychiatric conditions. The authors found substantial inconsistency in which indices are reported and how confounding variables are handled across studies. SIGNIFICANCE: The authors propose a standardized roadmap for selecting and interpreting heart rate variability indices in future research, arguing that greater methodological consistency is needed before findings across studies can be meaningfully compared. Read the full study: https://cardiovasculardynamicslab.com/en/aplication-of-heart-rate-variability-in-clinical-practice-an-research-a-systematic-review-of-recent-years/ 2. Divergence of clinical and autonomic recovery in adolescent major depressive disorder: A 10-week prospective heart rate variability study with nocturnal electrocardiogram monitoring PUBLICATION: Journal of Affective Disorders AUTHORS: Haisi Chen, Xiaona Zhang, Shuning Hong, Zhenghe Yu, and Wanlin Chen KEY FINDING: In forty-three adolescent inpatients with major depressive disorder followed for ten weeks of routine treatment, depression and anxiety symptoms improved significantly, but only about seven percent achieved early clinical response. Heart rate variability deficits present at baseline did not normalize, and autonomic function instead shifted further toward sympathetic dominance by the end of the study. SIGNIFICANCE: Clinical symptom improvement and autonomic recovery may follow independent tracks in adolescent depression. Reduced somatic anxiety was associated with less sympathetic deterioration, though this reflects a correlation rather than evidence that...

DISCLAIMER: This podcast and its accompanying show notes are for educational and informational purposes only and are not a substitute for professional medical, psychological, or clinical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare professional with any questions you may have regarding a medical condition. Dr. Inna Khazan's HRV Biofeedback Training (BCIA-aligned, 16 APA CE credits) Registration Link: https://www.optimalhrv.com/event-details-registration/bcia-aligned-hrv-biofeedback-training-led-by-dr-inna-khazan Dr. Donald Moss's Ethical Principles and Practice Standards in Clinical Biofeedback (BCIA-aligned, 3 APA CE credits)  Registration Link: https://www.optimalhrv.com/event-details-registration/master-ethical-principles-practice-standards-in-clinical-biofeedback-aligned-with-bcia This week we cover five studies that stretch heart rate variability into some surprising territory. We start with elite wrestlers and what heart rate variability reveals about training recovery, move into the modern office to look at heart rate variability as an objective marker of musculoskeletal pain risk, and head into neurology for two studies on seizure diagnosis and unexplained neurological symptoms. We close with a study on sound your ears can't consciously hear, but your nervous system apparently can. RESEARCH HIGHLIGHTS THIS WEEK 1. Investigating the Acute Effect of Different Training Protocols on Heart Rate Variability PUBLICATION: Sports AUTHORS: Burhan Demirkıran, Tuba Melekoğlu, Grzegorz Żurek KEY FINDING: In thirteen elite Greco-Roman wrestlers, both high-intensity interval training and prolonged endurance training produced dramatic acute suppression of heart rate variability, with SDNN dropping seventy-three to eighty-two percent immediately after exercise, followed by partial recovery at the twenty-four-hour mark. After correcting for multiple comparisons, there was no statistically significant difference between the two training protocols. SIGNIFICANCE: Coaches often assume that different training modalities carry meaningfully different acute costs to the nervous system, but this study suggests that intense effort of either type may impose a comparable autonomic burden, at least in this population and time frame. That has real implications for how training loads are planned in the days leading up to competition. Read full study: https://www.mdpi.com/2075-4663/14/7/299 2. Heart Rate Variability as an Objective Biomarker for Work-Related Musculoskeletal Disorder Risk: A Cross-Sectional Study of Hong Kong (China) Professionals PUBLICATION: Exploration of Musculoskeletal Diseases AUTHORS: Adrian Low, Benny Lam KEY FINDING: In 105 Hong Kong office professionals, lower heart rate variability coherence was associated with higher musculoskeletal pain intensity and a broader spread of pain across the body, even after accounting for self-reported stress. Forward head posture and thoracic kyphosis helped explain part of the relationship between coherence and neck and shoulder pain, and daily sedentary hours changed the strength of the overall association. SIGNIFICANCE: This cross-sectional study points to heart rate variability coherence a...

Join host Matt Bennett and Dr. Fred Shaffer on the Heart Rate Variability Podcast as they debunk common misconceptions about the low-frequency to high-frequency (LF/HF) ratio. Dr. Shaffer explains how short-term low-frequency power more accurately reflects blood pressure regulation than sympathetic tone, and clarifies that everyday stress is often simply vagal withdrawal rather than a true fight-or-flight sympathetic response. He also recommends more reliable metrics for assessing autonomic balance, such as RMSSD. Finally, the episode introduces Mentor, a custom AI tool rigorously trained on peer-reviewed biofeedback and HRV research, designed to serve as a reliable, 24/7 educational tutor for both practitioners and enthusiasts.

DISCLAIMER: This podcast and its accompanying show notes are for educational and informational purposes only and are not a substitute for professional medical, psychological, or clinical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare professional with any questions you may have regarding a medical condition. This week we're covering eight new studies spanning addiction, psychiatry, neonatal care, occupational health, women's health, and exercise science. You'll hear how alcohol cues and stress pull on heart rate variability in different directions, how short-term heart rate variability tracked suicide risk in hospitalized patients, how much a simple change in posture shifts your numbers, and more. As always, we break down what each study actually found, what it means for your practice, and where the caveats live. RESEARCH HIGHLIGHTS THIS WEEK 1. The link between subjective feelings (arousal and craving) and physiological responses (heart rate variability) in stress- and alcohol cue-reactivity among young adults engaged in hazardous drinking: a counterbalanced study PUBLICATION: Addictive Behaviors AUTHORS: Insan Firdaus, Annet Kleiboer, Anne Marije Kaag, Anja C. Huizink KEY FINDING: In 56 young hazardous drinkers, handling an alcoholic beverage increased both craving and heart rate variability, while a mental arithmetic stress task raised subjective stress without increasing craving at all. When the stress task came first, exposure to the alcohol cue afterward actually lowered perceived stress. SIGNIFICANCE: Craving and stress don't always move together, which means "avoid your triggers" may be an incomplete relapse-prevention strategy. Alcohol cues may function as a short-term emotional reset for some hazardous drinkers, independent of craving itself. Read the full study:  https://www.sciencedirect.com/science/article/pii/S0306460326001875 2. Short-term HRV dynamics track suicide risk changes in depressive inpatients: A retrospective one-week longitudinal study PUBLICATION: Journal of Affective Disorders AUTHORS: Yi Wang, Chaohua Huang, Baoyi Zhong, Yang Lu, Hao Yu, Yujie Liu, Lanyang Gao, Bo Xiang, Tingting Wang, Kezhi Liu KEY FINDING: Across 177 depressive inpatients, those with moderate-to-high suicide risk showed faster heart rate and lower heart rate variability at admission. As suicide risk dropped over one week of treatment, heart rate variability recovered in step, independent of changes in depression, anxiety, or sleep. SIGNIFICANCE: This is an association, not proof of causation, but it's a compelling one: the heart rate variability signal tracked suicide risk specifically, not just general symptom improvement. That raises real potential for an objective, adjunctive signal in inpatient risk monitoring. Read the full study: https://www.sciencedirect.com/science/article/abs/pii/S0165032726010852 3. Postural Impacts Based on HRV in Young Adults – A Statistical Analysis PUBLICATION: Procedia Computer Science AUTHORS: Prashant Kumar, Ashis Kumar Das, Suman Halder KEY FINDING: Testing three postures in young adults, researchers found statistically significant differences across nearly every heart rate variability parameter, with approximate entropy the lone exception. Short-term and long-term variability measures stayed strongly correlated regardless of posture. SIGNIFICANCE:

Disclaimer: This episode is for educational and professional development purposes only and does not constitute medical advice. Please consult the comprehensive published research and use your own clinical judgment before making any changes to practice. This week we're breaking format. Instead of our usual roundup across multiple sources, we're spotlighting seven studies published in a single journal, Applied Psychophysiology and Biofeedback, spanning cardiac rehabilitation, meditation, aviation safety, occupational fatigue, workplace stress, traumatic brain injury recovery, and music-based biofeedback. Host Matt Bennett walks through the methodology, findings, and honest limitations of each one. Whether you're a clinician, researcher, coach, or practitioner, this special episode offers a rare, single-journal snapshot of where HRV research is headed right now. RESEARCH HIGHLIGHTS THIS WEEK 1. When Diet and Biofeedback Team Up for Heart Recovery Publication: Applied Psychophysiology and Biofeedback Authors: Valeria Carola, Valeria Gigli, Filippo Cellucci, Marco Coli, Sofia Nicolais, Caterina Piras, Giovanni Melina, Cristina Ottaviani, Giampaolo Nicolais KEY FINDING: This systematic review found that heart rate variability biofeedback may enhance autonomic regulation, ease psychological distress, and in some cases shorten hospital stays for cardiac patients, while Mediterranean-style dietary patterns rich in omega-3 fatty acids showed potential to reduce inflammation and favorably modulate cardiovascular risk markers. SIGNIFICANCE: Evidence supporting these noninvasive approaches in postoperative rehabilitation and established cardiovascular disease remains limited, with considerable heterogeneity across studies. This review offers a structured map of where the evidence stands and where standardized protocols are still needed. Read the full study: https://link.springer.com/article/10.1007/s10484-025-09742-w 2. Does Biofeedback Make Meditation Apps Better at Building Body Awareness? Publication: Applied Psychophysiology and Biofeedback Authors: Konrad Rudnicki, Luna Schepers, Koen Rummens, Glen Joris, Karolien Poels KEY FINDING: In this randomized controlled trial of 105 meditation-naive participants, interoceptive accuracy improved in both the cardiac biofeedback-assisted meditation group and the standard app-based meditation group, but not in non-meditating controls. The accuracy gain was concentrated among participants who reported a positive user experience with their device. SIGNIFICANCE: The benefit of biofeedback-assisted meditation apps may depend as much on user experience design as on the underlying biofeedback mechanism itself, an important consideration for anyone recommending these tools to clients. Read the full study: https://link.springer.com/article/10.1007/s10484-025-09728-8 3. What Happens to Pilots' Hearts When the Guide Lights Go Dark Publication: Applied Psychophysiology and Biofeedback Authors: Chuang Liu, Chenyang Zhang, Wenbing Zhu, Shuaitao Jiao, Yu Zhang, Rongbing Xu, Yaowei Liang KEY FINDING: In simulated flights with sixteen cadet pilots, the absence of Precision Approach Path Indicator lights significantly increased mental workload, confirmed by both instructor ratings and heart rate variability measures including SDNN, CVNNI, minimum heart rate, and SD2 from Poincaré analysis.

DISCLAIMER: This podcast is for educational and informational purposes only and does not constitute medical advice. Please consult a licensed healthcare provider regarding any health concerns or before making changes to your care or practice. This week we're covering an unusually wide range of ground: body weight and exercise recovery, a workplace sleep intervention, autonomic function in youth with cerebral palsy, a clinical breakthrough in reading consciousness after brain injury, an AI model predicting cardiovascular risk in older adults, a behind-the-scenes look at what it takes to run 24-hour HRV monitoring, and a study of professional footballers in Senegal. Seven studies, seven populations, one shared physiological language.  RESEARCH HIGHLIGHTS THIS WEEK 1. Why Body Weight Changes How Your Heart Bounces Back After Exercise PUBLICATION: CureusAUTHORS: Vishwadeepak Rajput, Vishavdeep Kaur, Ankalayya Bobbara KEY FINDING: Comparing 100 normal-weight and 100 overweight young adults before and after the Harvard Step Test, researchers found that the overweight group had lower resting heart rate variability and continued to show reduced RMSSD, SDNN, and HF power in the early minutes after exercise, along with a lower Physical Fitness Index score. SIGNIFICANCE: The gap wasn't just present at baseline — it also appeared in how each group's autonomic system responded over time, suggesting that body composition shapes not only resting vagal tone but also the speed and quality of post-exercise recovery. RMSSD and SDNN stood out as the most reliable markers of this difference. Read the full study: https://www.cureus.com/articles/499608-autonomic-response-to-the-harvard-step-test-in-normal-bmi-and-overweight-young-adults-a-heart-rate-variability-study 2. Can a Workplace Program Actually Improve Your Sleep? PUBLICATION: Journal of Activity, Sedentary and Sleep BehaviorsAUTHORS: Johanna Edvinsson, Svend Erik Mathiassen, David M. Hallman KEY FINDING: Office workers who took part in an individual course plus a team-based workshop on managing flexible work arrangements gained 36 minutes of sleep per night over a year, while a comparison group lost 23 minutes per night. Daytime activity levels and sleep-time heart rate variability didn't shift significantly in either group. SIGNIFICANCE: Sleep duration may be the first, fastest-moving lever when organizations help teams set shared norms around flexible work — even before autonomic markers catch up. It's a useful, measurable early win for occupational health programs. Read the full study: https://link.springer.com/article/10.1186/s44167-026-00107-0 3. More Active Youth With Cerebral Palsy Show Better Heart Rhythms PUBLICATION: Journal of Developmental and Physical DisabilitiesAUTHORS: Sonny Riquelme, María Isabel Cornejo, Rosemery Arenas, Javier Russell-Guzmán, Alexis Espinoza-Salinas, Rafael Lima Kons, Matías Henríquez KEY FINDING: In 18 ambulatory youth with cerebral palsy, those reporting higher physical activity levels showed better cardiorespiratory endurance and sprint performance, along with a lower LF/HF ratio — a marker suggesting more favorable autonomic balance — compared to their less active peers. SIGNIFICANCE: This is exploratory...

Welcome to the Heart Rate Variability Podcast! In this episode, Matt Bennett interviews Adrian Low about a fascinating paper combining workplace wellbeing with biofeedback and mindfulness techniques. They discuss how these practices contribute to overall health and stress management. Remember, this information is for informational purposes only; please consult your medical provider for personalized advice.

This week's episode spans nine studies — from biofeedback and cognitive performance to chronic parenting stress, leadership in VR, body composition, AI-powered hypertension detection, post-cardiac-procedure monitoring, academic burnout, and the question everyone keeps asking about 5G. Whether you're a practitioner, researcher, or someone tracking your own autonomic health, this episode offers something worth sitting with.RESEARCH HIGHLIGHTS THIS  WEEK 1. Can HRV Biofeedback Sharpen Your Memory? A Systematic Review Weighs InPublication: International Journal of PsychophysiologyAuthors: Fernando Rosendo da Cunha e Silva, Esther P.F. Wöllner, Carlos Eduardo Norte KEY FINDING:Across ten studies, HRV biofeedback consistently increased HRV — but its effects on working memory were mixed. Clinical populations, particularly veterans with PTSD, showed meaningful cognitive improvements. Healthy young adults and older adults showed less consistent gains. Significance:HRV biofeedback reliably shifts autonomic function, but cognitive benefits appear context-dependent. Who you're training matters as much as how you're training. Read full study: https://www.sciencedirect.com/science/article/pii/S0167876026000644 2. Low HRV Predicts Worse Outcomes in Somatic Symptom Disorder — 12 Months Out Publication: Journal of Psychosomatic ResearchAuthors: Paul Hüsing, Wei-Lieh Huang, Kerstin Maehder, Franz Pauls, Yvonne Nestoriuc, Bernd Löwe, Kristina Blankenburg, Sophie Schmitz, Stefanie Hahn, Anne Toussaint KEY FINDING:In 148 patients with Somatic Symptom Disorder, those with a low HRV pattern showed consistently higher somatic symptom severity, depression, and psychological distress — and these differences held stable across a full 12 months with no significant change over time. Significance:HRV pattern classification at baseline may identify which SSD patients are at risk for persistent, long-term symptom burden — offering a physiological lens for a condition that is otherwise difficult to stratify. Read full study: https://www.sciencedirect.com/science/article/pii/S0022399926003855 3. Chronic Parenting Stress Shows Up in HRV — and in the Blood Publication: Stress and HealthAuthors: Marija Ljubičić, Ivana Kolčić KEY FINDING:Parents of children with chronic conditions — particularly autism spectrum disorder — showed reduced HRV and elevated Advanced Glycation End Products (AGEs), a marker of oxidative stress. A child's challenging behaviour and parental stress were the key drivers of these physiological changes. Significance:Chronic caregiving stress doesn't just feel hard — it produces measurable autonomic and oxidative consequences. HRV monitoring in caregiving populations may be an underutilized health tool. Read full study: https://onlinelibrary.wiley.com/doi/10.1002/smi.70185 4. Reading the Room in VR: How Physiological Signals Could Help Leaders Facilitate Better Publication: Frontiers in Computer ScienceAuthors: Chenghao Gu, Jiadong Chen, Tianyuan Y...

This week on This Week in Heart Rate Variability, we explore four studies that collectively challenge us to think more deeply about what autonomic function tells us — and what it doesn't tell us on its own. From addiction treatment to heart failure, adolescent fitness to chronic pain, this episode traces the threads connecting heart rate variability to some of the most pressing questions in clinical and population health. Whether you're a practitioner, researcher, or someone tracking your own autonomic health, there's something in this episode that will change how you think about what your nervous system is doing.RESEARCH HIGHLIGHTS THIS WEEK1. HRV and the Recovery Gap: When Physiology and Mental Health Walk Different Paths Publication: Frontiers in Psychiatry Authors: Wendy Insalaco, Charlotte Clapham, Brett Gelino, Jami Mayo Barney, Brianna Billings, Jennifer D. Ellis, J. Gregory Hobelmann, Andrew S. Huhn, Vadim Zipunnikov, Jill A. RabinowitzKEY FINDING:In fifty-nine individuals undergoing residential substance use disorder treatment, resting heart rate, heart rate variability, and self-reported stress, anxiety, and depression all tended to improve over the first month. However, at the individual level, physiological improvement and mental health improvement did not reliably co-occur — fewer than half of participants with improving physiological metrics showed concurrent improvements across all mental health domains. Significance:This finding challenges the assumption that wearable physiological metrics and subjective mental health assessments are capturing the same recovery signal. For clinicians and treatment providers, it suggests that both dimensions of recovery must be monitored independently, and that physiological improvement should not be interpreted as a proxy for psychological wellbeing in early recovery.→ Read full study: https://doi.org/10.3389/fpsyt.2026.1755153 2. The Clock is Broken: Circadian HRV Disruption in Heart FailurePublication: BiomedicinesAuthors:Natalia Buitrago-Ricaurte, Andre J. Riveros, Rafael González Niño, Liliana Otero, Juan David Meléndez, Alain Riveros-RiveraKey Finding:In eighty-six patients with cardiac remodeling compared to eighty-six controls, twenty-four-hour autonomic monitoring with Cosinor modeling revealed not only reduced overall heart rate variability but blunted circadian amplitude and phase shifts in autonomic modulation — a loss of the normal day-night rhythm of sympathovagal balance. Significance:This study highlights that the timing and rhythm of autonomic dysfunction may matter as much as its average level. Circadian HRV profiling may provide diagnostic and prognostic information in heart failure patients beyond what short-term or snapshot measurements offer, and opens therapeutic avenues targeting circadian autonomic restoration.→ Read full study: https://doi.org/10.3390/biomedicines14051054 3. Moving More Matters Most When It's Hardest: Physical Activity and HRV in Young MenPublication: Physical Activity and HealthAuthors: Jaakko Tornberg, Tiina Ikäheimo, Kaisu Kaikkonen, Riitta Pyky, Marjukka Nurkkala, Arto Hautala, Timo Jämsä, Raija Korpelainen Key Finding:Across three thousand three hundred and eighty-nine adolescent men, higher physical activity was significantly associated with higher RMSSD across all body mass...

In this episode, Matt Bennett talks to Cameron Allen about his work in heart rate variability biofeedback and the benefits of biofeedback in virtual reality. 

This week's episode covers five studies spanning sleep medicine, transportation safety, signal complexity methodology, cardiac mortality prediction, and autonomic neuroscience in a rare genetic condition. Together, they reveal how much untapped information lives in the heart rate variability signal — and how rapidly the field is developing tools to access it. RESEARCH HIGHLIGHTS THIS WEEK 1. Can an AI Stage Your Sleep From Your Heartbeat Alone? Publication: The National Medical Journal of India Authors: Suvradeep Chakraborty, Manish Goyal, Paritosh Goyal, Priyadarshini Mishra KEY FINDING: A random forest classifier trained on time-domain, frequency-domain, and nonlinear heart rate variability features — with ectopic beat correction and epoch index as a temporal marker — achieved 78.9% accuracy, a Cohen's kappa of 0.70, and a macro F1 score of 0.789 on external validation for five-stage sleep classification using electrocardiogram data alone. SIGNIFICANCE: Heart rate variability-based automated sleep staging is approaching clinical viability as a population-level research and screening tool, though it is not yet a replacement for polysomnography. The study demonstrates that preprocessing quality and temporal context are as important as model architecture — findings with direct implications for any wearable-based sleep monitoring application. Read the full study: https://nmji.in/artificial-intelligence-based-automated-sleep-staging-using-heart-rate-variability-assessment-of-performance-and-clinical-prospects/ 2. A 30-Second Heartbeat Test Before You Drive Publication: IAES International Journal of Artificial Intelligence Authors: Tia Haryanti, Eri Prasetyo Wibowo, Wahyu Kusuma Raharja, Rossi Septy Wahyuni, Ilmiyati Sari KEY FINDING: A subject-independent logistic regression model trained on short-term heart rate variability features from 30-second electrocardiogram recordings achieved an ROC-AUC of 0.687 and 100% sensitivity for detecting pre-driving fatigue (Karolinska Sleepiness Scale score of 7 or above) at the chosen operating threshold, with a proposed three-tier triage scheme to manage the high false positive rate. SIGNIFICANCE: This feasibility study demonstrates that brief, wearable-compatible heart rate variability recordings carry discriminable signal about fatigue state under subject-independent validation — the appropriate test for real-world deployment. Specificity remains very low at the sensitivity-optimized threshold, and replication in larger samples is needed before operational translation. Read the full study: https://ijai.iaescore.com/index.php/IJAI/article/view/30466/15254 3. Bubble Entropy Earns Its Place in the HRV Toolkit Publication: Entropy Authors: Dimitrios Platakis, Roberto Sassi, George Manis KEY FINDING: Bubble entropy consistently outperformed sample entropy, approximate entropy, and permutation entropy in classifying RR interval time series from healthy individuals versus cardiac patients across four machine learning classifiers and multiple feature-importance ranking methods. SIGNIFICANCE: Bubble entropy's freedom from the tolerance parameter that limits cross-study comparability of sample entropy is a genuine methodological advantage. This head-to-head benchmark strengthens the cas...

This week's episode covers four peer-reviewed studies spanning machine learning feature selection, clinical epidemiology, wearable device validation, and real-world mobile health observation. Whether you are a clinician, researcher, coach, or practitioner, this episode has direct relevance for how you think about measuring and applying HRV in your work. RESEARCH HIGHLIGHTS THIS WEEK Adaptive Genetic Selection of Heart Rate Variability and Electrocardiographic Morphology Features for Cognitive Stress Detection Using Multi-Classifier Evaluation PUBLICATION: Eng AUTHORS: Salvador Ortiz-Santos, Georgina Mota-Valtierra, Jesús-Norberto Guerrero-Tavares, Xóchitl Siordia-Vásquez, Miguel Rojas-Hernández, Juvenal Rodríguez-Reséndiz KEY FINDING: A binary genetic algorithm with a dimensionality penalty selected eleven features from a pool of over three hundred HRV and electrocardiographic morphology descriptors across twelve leads, achieving a mean area under the receiver operating characteristic curve of 0.830 for cognitive stress classification. This outperformed both the full feature set and principal component analysis when paired with a radial basis function support vector machine classifier. SIGNIFICANCE: Supervised, discriminative feature selection outperforms unsupervised variance-based reduction for cognitive stress detection from multichannel electrocardiogram data. The finding that 11 compact features can achieve meaningful classification performance supports the feasibility of wearable-compatible stress-monitoring systems, though validation in more diverse and clinically representative populations is needed before this approach can inform practice. Read the full study: https://doi.org/10.3390/eng7060273 Association of Severe Obesity, Hypertension, and Physical Activity with 24-h Heart Rate Variability in Adults PUBLICATION: Journal of Cardiovascular Development and Disease AUTHORS: Débora Andrea Castiglioni Alves, Pamela Carvalho da Rosa, Andréa Castiglioni Alves Teixeira e Silva, Joceli Fernandes Alencastro Bettini de Albuquerque Lins, Gisela Arsa, Lucieli Teresa Cambri KEY FINDING: In a retrospective cross-sectional study of 1,048 adults undergoing bariatric surgery evaluation, severe obesity was associated with lower 24-hour HRV and higher odds of hypertension (odds ratio 2.04) and antihypertensive medication use (odds ratio 1.98). Hypertension was associated with lower HRV and higher odds of diabetes (odds ratio 4.20) and dyslipidemia (odds ratio 2.85). Meeting physical activity criteria was associated with higher HRV and lower odds of hypertension (odds ratio 0.64). SIGNIFICANCE: This large cross-sectional study documents the co-occurrence of lower 24-hour HRV with severe obesity, hypertension, and physical inactivity in a bariatric surgery evaluation population. Note that cross-sectional designs identify associations, not causes. The findings reinforce the clinical value of 24-hour HRV assessment for characterizing autonomic impairment in high cardiometabolic risk profiles and highlight physical activity as a meaningful modifier of autonomic health, even in this population. Read the full study: https://doi.org/10.3390/jcdd13060242 Validation of photoplethysmography-derived short-term heart rate variability using a wearable device PUBLICATION: Scientific Reports AUTHORS: Christine S. Zuern, Maximilian Felkel, Florian Tilquin, Yann Le Guillou, Emmanuel Dervie...

In this episode, Dr. Andrew Seely joins Matt Bennett to discuss his work with HRV in the ICU and health care. 

From the reliability of the tools we use to measure it, to a mathematical algorithm built in its image, to machine learning models that read stress from its patterns, to a clinical trial showing it shifts in response to music — this week's four studies reveal HRV science at its most wide-ranging. Whether you're a clinician, researcher, coach, or curious practitioner, this episode offers something worth sitting with. Study 1: A Reproducible Benchmark of QRS Detection Algorithms Across Diverse ECG Datasets and Noise Conditions Publication: Scientific Reports Authors: Simon Maximilian Wolf, Tim Rahlmeier, Stefan Lustfeld, Detlef Schoder KEY FINDING: Seventeen R-peak detection algorithms were benchmarked across five ECG databases in a unified, reproducible framework. Under strict cross-dataset generalization conditions, traditional signal processing methods outperformed machine learning and deep learning approaches in consistency across diverse signal environments. SIGNIFICANCE: The algorithm used to detect R-peaks in an ECG signal is not a neutral technical detail — it directly shapes the accuracy of every HRV metric derived from that signal. Researchers and practitioners selecting HRV tools should ask how the underlying detection algorithm has been validated across diverse populations and noise conditions. Read the full study: https://www.nature.com/articles/s41598-026-53724-9 Study 2: Heart Rate Optimizer: A Novel Bio-Inspired Metaheuristic Algorithm Publication: Scientific Reports Authors: Mosa E. Hosney, Marwa M. Emam, Mohammed R. Saad, Nagwan Abdel Samee, Essam H. Houssein KEY FINDING: A novel bio-inspired optimization algorithm called the Heart Rate Optimizer — modeled on HRV dynamics and autonomic nervous system regulation — outperformed nine competing state-of-the-art algorithms on standard mathematical benchmarking suites and real-world engineering design problems. SIGNIFICANCE: The success of an algorithm explicitly built around HRV dynamics offers an independent, cross-disciplinary argument for why high HRV matters: the adaptive, flexible balance between sympathetic and parasympathetic regulation that high HRV reflects is computationally rich enough to serve as a blueprint for solving complex, high-dimensional problems. Low HRV, by analogy, corresponds to a system locked out of that adaptive range. Read the full study: https://www.nature.com/articles/s41598-026-44516-2 Study 3: Mental Stress Recognition Using Interpretable Machine Learning Models with Heart Rate Variability Among Chinese University Students Publication: World Journal of Psychiatry Authors: Yan-Ge Wei, Lu-Han Yang, Shi-Sen Qin, Yuan-Le Chen, Jin-Nan Yan, Rong-Xun Liu, Yi-Meng Ma, Chao Wang, Zhen-Jie Song, Fei Wang, Guang-Jun Ji KEY FINDING: In a cross-sectional study of 207 Chinese university students, eleven resting-state HRV parameters showed significant differences between stressed and non-stressed groups. A random forest classifier achieved an AUC of 0.733 (95% CI: 0.655–0.811) and 68.9% accuracy. SHAP analysis identified the Diastolic/Systolic Pressure-Time Index (DPTI/SPTI) as the most important classification feature. SIGNIFICANCE: This observational study found that resting HRV parameters are associated with self-reported stress status — it does not establish that stress caused the observed differences. The findings represent a well-structured proof of concept for HRV-based stress monitori...

This week's lineup takes HRV science somewhere it doesn't always go — into genetics labs, operating theaters, and the physiology of breath control. Five new peer-reviewed studies examine HRV biofeedback combined with mindfulness for long-term workplace stress, a genetic polymorphism that shapes athlete burnout risk, yoga's measurable impact on autonomic function, a novel method for detecting high-intensity thresholds directly from an electrocardiogram signal, and whether a simple preoperative HRV reading can predict dangerous hemodynamic instability in diabetic surgical patients. Each study opens a different window on what HRV can tell us — and what it still can't. Research Highlights This Week 1. Exploring the Long-Term Effects of HRV Biofeedback Interventions Combined with Mindfulness Practices in Alleviating Workplace Stress Among Asian Professionals Publication: International Journal of Innovative Research and Scientific Studies Authors: Adrian Low, Benny Lam KEY FINDING: In a two-group, 8-week trial of 100 Hong Kong professionals, participants who combined HRV biofeedback with structured mindfulness practice showed significantly greater improvements in SDNN, RMSSD, coherence, and perceived stress than those who received biofeedback alone — and crucially, those gains continued to grow at a 6-month follow-up, while the biofeedback-only group showed attrition of benefits. SIGNIFICANCE: The durability gap between the two groups is the central finding here: mindfulness appears to provide a psychological scaffold that sustains the autonomic improvements initiated by biofeedback, even after formal programming ends. Qualitative data also revealed that emotional suppression is a culturally embedded barrier among Asian professionals, and that mindfulness framed around cognitive clarity rather than emotional processing proved more culturally acceptable and sustainable. Read the full study →: https://www.ijirss.com/index.php/ijirss/article/view/11655/2772 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 2. The Influence of the COMT Val158Met Polymorphism on Heart Rate Variability Parameters, Psychoemotional Status, and Sports Burnout in Athletes Publication: Research Journal of Pharmacy and Technology Authors: Mavlyanova Z.F., Kim O., Doniyorov B.B., Ibragimova M.S., Khudoykulova F.V., Khalimova F.T. KEY FINDING: Among 100 male athletes, those carrying the AA (Met/Met) genotype of the catechol-O-methyltransferase Val158Met polymorphism showed resting heart rates 9.6% higher and RMSSD values 32.5% lower than GG (Val/Val) athletes, along with 17% higher anxiety scores and significantly greater risk of emotional exhaustion on the Athlete Burnout Questionnaire. The AG heterozygous group fell between both extremes on all measures. SIGNIFICANCE: This observational study suggests that a meaningful portion of the individual variation in athletes' HRV and susceptibility to burnout may be constitutionally determined by catecholamine clearance rate—an enzyme variant that modulates ambient norepinephrine and dopamine levels throughout the autonomic system. For practitioners interpreting chronically suppressed HRV in athletes who appear otherwise well recovered, genotypic baseline differences are a plausible contributor to consider. Read the full study →: https://www.rjptonline.org/HTML_Papers/Research%20Journal%20of%20Pharmacy%20and%20Technology__PID__2026-19-3-25.html ━━━━━━━━━━━━━━...

The LF/HF ratio has been a fixture in heart rate variability research for decades. In this episode, we take a close look at why it persists, what the evidence actually says it measures, and why it so often appears to be the metric that moves most dramatically—in studies and in consumer apps alike. The 1996 Task Force paper, which helped establish LF/HF as a field standard, was more cautious than its legacy suggests. It described sympathovagal balance as a perspective held by some investigators, not an established fact. That restraint has largely been lost in translation. We examine Billman's 2013 review, The LF/HF Ratio Does Not Accurately Measure Cardiac Sympatho-Vagal Balance, which systematically dismantles the assumptions underlying the ratio—including the finding that LF/HF can rise even when both sympathetic and parasympathetic control decrease. Supporting work from Hopf and colleagues, Goldstein and colleagues, Rahman and colleagues, Martelli and colleagues, Reyes del Paso and colleagues, Thomas and colleagues, and Hayano and Yuda builds a consistent picture: LF/HF does not constitute a clean or reliable sympathetic marker. We also address why the ratio is so mathematically lively—how posture, respiration, mean heart rate, vagal withdrawal, and ratio mechanics can all make LF/HF move without that movement carrying clear physiological meaning. The second half of the episode addresses the consumer side directly. When LF/HF is framed as a readout of sympathetic activation or autonomic balance in an app dashboard, a contested interpretation becomes practical misinformation—not through deception, but by presenting uncertainty as settled science. People use these outputs to decide whether to train, rest, push, or worry. That stakes that framing. The episode closes with a direct call to researchers, clinicians, and app developers: retire LF/HF from primary mechanistic claims, demand transparency about the metrics underlying consumer products, and frame what is genuinely unknown as unknown. Key topics covered Why LF/HF persists despite longstanding methodological criticism What the 1996 Task Force paper actually said—and what got dropped Billman (2013): the core argument against LF/HF as a sympathetic marker Why LF/HF is mathematically sensitive but physiologically non-specific The role of respiration, posture, and mean heart rate in ratio movement Normalized versus absolute spectral values and what gets hidden How contested research interpretations migrate into app dashboards and health decisions Standards being called for: researchers, clinicians, and app developers References Amekran, Y., Damoun, N., & El Hangouche, A. J. (2024). Analysis of frequency-domain heart rate variability using absolute versus normalized values: Implications and practical concerns. Frontiers in Physiology, 15, Article 1470684. https://doi.org/10.3389/fphys.2024.1470684 Berntson, G. G., Bigger, J. T., Jr., Eckberg, D. L., Grossman, P., Kaufmann, P. G., Malik, M., Nagaraja, H. N., Porges, S. W., Saul, J. P., Stone, P. H., & van der Molen, M. W. (1997). Heart rate variability: Origins, methods, and interpretive caveats. Psychophysiology, 34(6), 623–648. https://doi.org/10.1111/j.1469-8986.1997.tb02140.x Billman, G. E. (2013). The LF/HF ratio does not accurately measure cardiac sympatho-vagal balance. Frontiers in Physiology, 4, Article 26. https://doi.org/10.3389/fphys.2013.00026 DeBeck, L. D., Petersen, S. R., Jones, K. E., & Stickland, M. K. (2010). Heart rate variability and muscle sympathetic nerve activity response to acute stress:...

HRV, Stress, Spirituality, and the Body's Hidden Autonomic Life: 4 Studies Worth Your Time Heart rate variability research doesn't always stay neatly inside the cardiovascular system — and this week's episode is proof. From the psychological interior of hypertensive patients, to the anatomy of the vagus nerve in a clinical encounter with postprandial dysfunction, to the cutting edge of wearable biosensor engineering, to a theoretical physics framework for understanding catastrophic neurological collapse, Episode 38 covers four studies that each push our understanding of autonomic physiology into new territory. Whether you're a clinician, researcher, coach, or practitioner, there's something in this episode that will change how you think about what HRV is actually measuring. Research Highlights This Week 1. Your Inner Life Shows Up in Your Heart Rate Publication: Healthcare Authors: Funda Eldemir, İsa Ardahanlı KEY FINDING: In a sample of hypertensive patients, higher perceived stress was significantly associated with reduced heart rate variability indices reflecting parasympathetic activity, while higher spiritual orientation was associated with more favorable autonomic profiles. Critically, spiritual orientation appeared to buffer the adverse autonomic effects of perceived stress — patients with high stress but high spiritual orientation maintained better heart rate variability than those with high stress and low spiritual orientation. SIGNIFICANCE: This observational study adds to growing evidence that the psychological and existential dimensions of a patient's life are not separate from their cardiovascular physiology — they are reflected in it. For clinicians and practitioners using heart rate variability monitoring, baseline readings carry information about perceived stress burden and sense of meaning and purpose, not just fitness and sleep. The electrocardiographic repolarization findings add a further layer: spiritual orientation and perceived stress were both associated with indices of ventricular repolarization stability, with potential implications for arrhythmia risk in hypertensive populations. → Read the full study: https://www.mdpi.com/2227-9032/14/10/1316 2. When Eating Disrupts the Heart: A Case for the Vagus Nerve Publication: Cureus Authors: Harbi Shehadeh KEY FINDING: This case report describes a patient experiencing postprandial cardiovascular symptoms consistent with disrupted autonomic regulation, treated with osteopathic manipulative techniques targeting the cervical and thoracic spine, diaphragm, and mesenteric attachments. Following treatment, the patient reported substantial symptom improvement, and heart rate variability measurements showed changes consistent with improved parasympathetic tone and reduced sympathovagal imbalance in the postprandial recording window. SIGNIFICANCE: As a single-patient case report, this paper cannot establish efficacy or prove causation, but it presents a mechanistically coherent hypothesis: that fascial and structural dysfunction along the anatomical course of the vagus nerve can contribute to postprandial autonomic dysregulation, and that osteopathic intervention targeting those structures may normalize autonomic function in some patients. For practitioners working with unexplained postprandial cardiovascular symptoms, the case is a reminder that the vagus nerve is a physical structure embedded in tissue — and its mechanical environment matters. → Read the full study:

This week on This Week in Heart Rate Variability, Matt Bennett covers five peer-reviewed studies that span the full breadth of HRV science — from a controlled laboratory experiment on fast-paced breathing to a neurointensive care unit monitoring study, with stops along the way at the gut microbiome, a drowsy driver detection system, and a case report on osteopathic treatment for postprandial dizziness. These are the papers shaping how researchers and practitioners understand autonomic function right now. RESEARCH HIGHLIGHTS THIS WEEK 1. When Fast Breathing Meets the Heart: Not All Frequencies Are Equal Publication: Psychophysiology Authors: Maša Iskra, Sylvain Laborde, Tasha Poppa, Caterina Salvotti, Elisa Weinand, Markus Raab, Laura Voigt KEY FINDING: In 38 physically active adults completing breathing conditions at 6, 15, 35, and 55 cycles per minute, fast-paced breathing at 55 cycles per minute produced a reciprocally coupled autonomic response — simultaneously reduced HRV (via RMSSD) and increased cardiac contractility (via shorter pre-ejection period) — while 35 cycles per minute reduced HRV without significantly elevating cardiac contractility. The full sympatho-vagal activation pattern is frequency-dependent and only reliably emerges at the higher frequency tested. SIGNIFICANCE: Practitioners using fast-paced breathing as a pre-performance activation tool cannot assume that any frequency above the spontaneous range produces the same physiological effect. This study provides the first rigorous dual-measure characterization of autonomic cardiac responses across a range of fast-paced breathing frequencies, and the frequency threshold finding has direct implications for protocol design. The independence of HRV and cardiac contractility at the individual level also underscores the value of simultaneously measuring both branches of the autonomic nervous system. → Read the full study: https://doi.org/10.1111/psyp.70305 2. Your Gut, Your Vagus Nerve, and Your Immune System: A Three-Way Conversation in Infectious Disease Publication: Cureus Authors: Shruti Tiwari, Uprinder Kaur, Narinder Kaur, Waqas Alauddin, Sayali Khairnar, Rosy Bala, Vipasha Kaushal, Mohit Mishra KEY FINDING: This PRISMA-guided systematic review of eleven studies found consistent evidence that gut microbiota dysbiosis increases intestinal permeability and drives systemic elevation of pro-inflammatory cytokines, including interleukin-6, tumor necrosis factor-alpha, and interferon-gamma. The autonomic nervous system — particularly via vagal signaling and the cholinergic anti-inflammatory pathway — functions as a critical intermediary between gut microbial state and immune regulation. When dysbiosis disrupts bidirectional gut-brain communication, the result is autonomic imbalance and impaired immune control, worsening infectious disease severity and mortality. SIGNIFICANCE: For HRV researchers and clinicians, this review provides a mechanistic account of why vagal tone and HRV decline during infection and why that decline carries prognostic weight. The vagus nerve sits at the convergence of microbial, immune, and autonomic regulation, and its functional state — indexed by HRV — reflects the integrity of the entire network. The overall evidence quality was rated low to moderate, and the authors call for longitudinal interventional studies with standardized methods before therapeutic conclusions can be drawn. → Read the full study: https://www.cureus.com/articles/484173-the-gut-brain-im...

This week on This Week in Heart Rate Variability, we cover seven studies that push the boundaries of where HRV science is being applied — from predicting cardiovascular events in asymptomatic adults to detecting anger using a wrist sensor, from modeling how blood pressure cascades through the brain to understanding what happens to a mother's nervous system when her baby is born too soon. We also close with a genuinely surprising study using wearable jewelry as an HRV-measurable intervention for depression. Whether you're a clinician, a researcher, or simply someone fascinated by the science of the nervous system, this episode has something for you. Research Highlights This Week 1. When Trauma Becomes Growth: HRV in Brain Tumor Patients and Caregivers Publication: Cancer Medicine Authors: Tenggang Shen, Ting Shu, Zijun Yuan, Detian Liu, Linxin Xie, Hongzhen Xie KEY FINDING: In a study of 55 brain tumor patient-caregiver dyads, caregivers showed significantly higher total, high-frequency, and low-frequency power than patients. Across both groups, individuals who showed posttraumatic growth had significantly higher SDNN and RMSSD than those who did not. SIGNIFICANCE: HRV may serve as an objective physiological correlate of posttraumatic growth — suggesting that greater parasympathetic capacity is associated with the kind of psychological processing that enables growth after trauma. This opens a potential pathway for using HRV as a biomarker to identify individuals who may benefit from growth-oriented psychosocial interventions. → Read full study 2. Your Resting HRV Today, Your Heart Health Tomorrow Publication: Journal of Health, Wellness and Community Research Authors: Mohammad Asad Shaheen Baloch, Ayesha Ashraf, Shanza Ahmad, Abdullah Saeed, Turfa Asghar, Muhammad Rahman, Muhammad Rizwan KEY FINDING: In a 12-month prospective cohort of 300 asymptomatic adults with cardiovascular risk factors, cardiovascular event rates were 23.5% in the low HRV group, 13.3% in the intermediate group, and 6.0% in the high HRV group. After adjusting for age, hypertension, obesity, diabetes, and smoking, low HRV remained an independent predictor of events with an adjusted hazard ratio of 3.12. SIGNIFICANCE: A simple five-minute resting HRV measurement predicts who will experience a cardiovascular event over the next year, independently of conventional risk markers. This supports HRV as a practical, inexpensive addition to cardiovascular risk stratification in clinical settings — particularly in populations with multiple cardiometabolic risk factors. → Read full study 3. Can Your Heartbeat Reveal Your Anger? Publication: Iranian Journal of Psychiatry and Behavioral Sciences Authors: Zahra Dehghanizadeh, Behrooz Dolatshahi, Masoud Nosratabadi, Hadi Moradi KEY FINDING: Using a blood volume pulse sensor and biofeedback device, the RR interval — the time between successive heartbeats — distinguished high-anger from low-anger adults with an area under the curve of 0.71, outperforming frequency-domain measures. The optimal cut-off RR value was 690.66 milliseconds. SIGNIFICANCE: Even a simple time-domain HRV measure derived from a consumer-grade sensor carries meaningful signals about a person's anger profile. While not a stand-alone clinical tool, this finding supports the inclusion of RR interval data in wearable emotion recognition systems and opens pathways for physiological monitoring in anger-related mental health contexts....

In this episode, Stephanie White joins Matt Bennett to discuss fascinating science related to heart health and HRV at the cellular level.

This episode of This Week in Heart Rate Variability takes four very different windows into the autonomic nervous system and finds a single coherent message: your HRV is tracking the full texture of your life, not just your sleep or your workouts. We look at which psychosocial job demands most damage parasympathetic tone, how COPD reshapes autonomic regulation over time, whether walking through nature at night changes how your heart recovers, and what your facial micro-movements might reveal about your heart during pain. Pull up a chair — this one goes deep. Research Highlights This Week 1. The Stressors That Actually Suppress Your Vagus Nerve Publication: Journal of Occupational Health Authors: Kati Karhula, Maria Hirvonen, Hanna Jantunen, Maria Sihvola, Jarno Turunen, Piia Seppälä KEY FINDING: In a study of 163 municipal employees wearing ECG monitors over four consecutive nights, dominance analysis revealed that, after age, the psychosocial job demands most strongly associated with reduced parasympathetic HRV were encountering bullying, facing violence or threats at work, experiencing ethically challenging situations, and effort-reward imbalance — not workload or time pressure. SIGNIFICANCE: The interpersonal and moral dimensions of work may carry more autonomic weight than its sheer volume or pace. This reframes how workplace wellbeing initiatives should prioritize their efforts — and raises the possibility that chronic HRV suppression in workers may reflect relational and ethical harm, not just busyness. Read full study: https://doi.org/10.1093/joccuh/uiag025 2. How Long You've Had COPD May Matter More Than How Severe It Is Publication: Cureus Journal of Medical Science Authors: Dinakaran Umashankar, Karthikeyan Ramaraju, Anupama Murthy, Nagashree R KEY FINDING: Among 47 patients with stable chronic obstructive pulmonary disease, HRV parameters did not significantly correlate with spirometric severity, BODE index, or ABCD phenotype classification. However, longer disease duration was significantly negatively correlated with both RMSSD (r = −0.324, p = 0.026) and pNN50 (r = −0.332, p = 0.027), and greater quality-of-life impact correlated negatively with SDNN (r = −0.294, p = 0.043). SIGNIFICANCE: Autonomic dysregulation in COPD tracks time-in-disease and quality-of-life burden more than it tracks standard lung function metrics. HRV may capture aspects of COPD's systemic toll that spirometry misses, suggesting a potential role as a complementary biomarker in clinical monitoring. Read full study: https://doi.org/10.7759/cureus.107493 2. Walk in the Woods, Recover at Night Publication: npj Urban Sustainability Authors: Karl Samuelsson, Matteo Giusti, David M. Hallman, Sarah Koch, Elena Farahbakhsh Touli, Joren Buekers, Matilda van den Bosch, Anna Bornioli, Payam Dadvand, Stephan Barthel KEY FINDING: Across ten months of GPS and heart rate data from 45 individuals in Sweden, within-person analysis showed that active movement in nature — but not passive time in nature or active movement in non-natural settings — was associated with lower-than-usual resting heart rate and higher-than-usual HRV the following night. Effects were significant in the full sample and in female participants specifically. SIGNIFICANCE: The combination of physical activity and natural environment appears to be the operative factor for nighttime cardiac regulation benefit — neither element alone produces the same effect. This is real-world, l...

In this episode, Stephan Streuber joins Matt Bennett to discuss the role heart rate variability played in his recent research and article Remote collaboration in virtual reality induces physiological synchrony comparable to face-to-face interaction. Dr. Stephan Streuber holds a Diploma in Media Informatics from Harz University of Applied Sciences and a PhD in Neural and Behavioral Sciences from the Max Planck Institute for Biological Cybernetics in Tübingen, Germany (2013), supported by a Research Fellowship from the Max Planck Society. He later held research positions at the Max Planck Institute for Intelligent Systems and the Brain Mind Institute at EPFL in Lausanne, Switzerland. In 2018, he joined the University of Konstanz as an Assistant Professor for Virtual Reality and Collective Behavior, a role he held until 2021. Since then, he has been a Full Professor of Usability Engineering and Interaction Design in Visual Computing at Coburg University of Applied Sciences and Arts, where he leads the Virtual Environments and Social Interaction Lab (socialVRlab.com). His main research aim is to understand the mechanisms behind social interactions. To do this, he creates immersive multi-user virtual environments with realistic avatars and AI-powered agents, facilitating the study of group coordination, synchronization, and emotion contagion. His work also investigates body perception and representation, with clinical applications in eating disorders, stroke rehabilitation, and XR-based mental health research and treatment.

Heart rate variability science is moving in several directions at once this week — deeper into neural mechanisms, broader across clinical populations, and more precise in its analytical tools. Episode 34 covers six studies ranging from a new graph-theory method for detecting sex differences in resting autonomic activity to the neural pathway behind a side effect affecting millions of patients on GLP-1 medications to what HRV can and cannot tell us about cardiovascular fitness in high-risk individuals. Whether you're a clinician, researcher, or practitioner, this episode has something to sharpen your thinking. 1. When the Average Hides the Signal: Graph Theory and Sex Differences in HRV Publication: Biology of Sex Differences Authors: Lin Sørensen, Elisabet Kvadsheim, Julian Koenig, Julian F Thayer, DeWayne P Williams, Hayley Jessica MacDonald, Ryan Douglas McCardle, Daniel Wollschlaeger, Ole Bernt Fasmer, Berge Osnes KEY FINDING: In 269 healthy young adults, a similarity graph theory algorithm detected significant sex differences in nonlinear inter-beat interval variability — males showing higher graph metric values, indicating lower dynamic IBI fluctuations — while standard measures lnRMSSD and lnHF-HRV failed to distinguish sexes when used alone. The odds ratio for the graph metric predicting sex was 2.78 (95% CI: 1.32–5.86). SIGNIFICANCE: Conventional averaged HRV metrics may systematically underdetect sex-based autonomic differences that exist in the rapid, nonlinear structure of beat-to-beat activity. Nonlinear graph-theoretic approaches offer a complementary analytical lens that could refine how sex is accounted for in autonomic research and in clinical HRV norms. → Read full study: https://www.researchgate.net/publication/403769793_Capturing_sex_differences_in_spontaneous_autonomic_fluctuations_of_resting_heart_rate_using_a_similarity_graph_theory_approach 2. Why Your GLP-1 Medication Raises Your Heart Rate: A Neural Explanation Publication: Hypertension Research Authors: Yui Koyanagi, Kamon Iigaya, Keiko Ikeda, Hiroshi Onimaru, Masahiko Izumizaki KEY FINDING: Exendin-4, a major GLP-1 receptor agonist, increased sympathetic nerve activity and produced membrane depolarization in preganglionic neurons of the spinal cord and neurons in the rostral ventrolateral medulla in vitro. The effect was blocked by a GLP-1 receptor antagonist, confirming receptor-mediated sympathetic excitation at both spinal and brainstem levels. SIGNIFICANCE: This study provides the clearest mechanistic evidence to date that GLP-1 receptor agonists can directly excite sympathetic neurons — offering a plausible neural explanation for the heart rate increases commonly observed in patients on this medication class. For practitioners monitoring autonomic function in patients on GLP-1 therapies, this finding provides important physiological context. → Read full study: https://www.nature.com/articles/s41440-026-02633-5 3. Two Systems Failing Together: HRV and Nerve Conduction in Early Diabetes Publication: Cureus Authors: Anwar H. Siddiqui, Md S. Alam, Ahmad Faraz, Nazia Tauheed, Hamid Ashraf, SAA Rizvi KEY FINDING: In 100 patients with type 2 diabetes of less than 5 years' duration, compared with 100 matched controls, parasympathetic HRV indices and peripheral nerve amplitudes were both significantly reduced in the diabetes group, with the strongest single correlation between high-frequency HRV power and sural SNAP amplitude (r = 0.62). Multiv...

Needles, Treadmills, Wearables, and Operating Rooms: Four Ways the Autonomic Nervous System Shows Up Where You Least Expect It This week's episode covers four studies across four completely different clinical domains — acupuncture, exercise physiology, sleep medicine, and urology — and finds the same thread running through them all: HRV as a window into autonomic regulation. Whether the stimulus is a needle, a treadmill, an overnight wearable patch, or a surgical instrument, the nervous system responds in ways HRV can detect. Episode 33 explores what that means for practice, research, and the expanding frontier of autonomic science. Research Highlights This Week Mapping Ancient Points onto Modern Mechanisms: The Case for a Biomedical Acupuncture Framework Publication: Cureus Authors: Yiangos Karavis, Miltiades Karavis KEY FINDING: A structured narrative review of 71 studies found convergent mechanistic evidence for a candidate cluster of acupuncture points — including ST36, PC6, LI4, SP6, LR3, and GV20 — across autonomic modulation, neuroimmune signaling, and HRV outcomes. ST36 and PC6 were repeatedly associated with vagal pathway activation and increased high-frequency HRV, while multiple points suppressed pro-inflammatory cytokines and modulated nuclear factor kappa B and NOD-like receptor thermal protein domain-associated protein 3 inflammasome signaling. SIGNIFICANCE: This review offers one of the most systematic attempts to translate traditional acupuncture point designations into a biomedically grounded teaching framework. While prospective validation is still required, the mechanistic convergence across independent studies suggests that peripheral stimulation at specific anatomical sites can engage autonomic and neuroimmune circuits in measurable ways — with real implications for integrative practice, pain medicine, and HRV research. Read full study: https://doi.org/10.7759/cureus.106511 Six Weeks on the Treadmill: Autonomic Recovery in Sedentary Obese Young Adults Publication: Journal of Datta Meghe Institute of Medical Sciences University Authors: Subha Shankar Sahoo, Shivani Patil, M. Premkumar KEY FINDING: Forty-one sedentary obese adults aged 17–25 completed a 6-week moderate-intensity treadmill program. By 45 days, all measured HRV parameters — the standard deviation of normal-to-normal intervals, the standard deviation of normal-to-normal intervals index, high-frequency power, low-frequency power, and very low-frequency power — improved significantly (p < 0.001). Resting and minimum heart rates decreased, systolic blood pressure dropped, and peak exercise heart rate increased, suggesting improved chronotropic competence alongside enhanced vagal tone. SIGNIFICANCE: This study provides time-resolved evidence that a practical, moderate-intensity exercise program can produce measurable autonomic improvements in a population with common dysregulation. The gains in high-frequency HRV point specifically toward enhanced vagal tone. While the pre–post design without a control group limits causal conclusions, the direction and magnitude of effects are clinically encouraging for practitioners using exercise as an autonomic rehabilitation tool. Read full study: https://doi.org/10.4103/jdmimsu.jdmimsu_731_25 From Snoring to Signal: Using a Wearable HRV Patch and Artificial Intelligence to Screen for Sleep Apnea Publication:

In this week’s episode of The Heart Rate Variability Podcast, we step away from our usual multi-paper review to focus on a singular, defining debate in the field: the current controversy surrounding Polyvagal Theory. Polyvagal Theory has profoundly shaped how clinicians, trauma survivors, and the HRV community understand the relationship between the nervous system, safety, and social engagement. However, as the theory has moved from academic psychophysiology into the cultural mainstream, it has faced increasing scrutiny from the scientific community. Today, we break down the history of the theory, the core of the scientific disagreement, and what this means for the future of HRV interpretation. The Evolution of a Theory Polyvagal Theory did not appear overnight. It evolved through decades of work by Dr. Stephen Porges, moving from specific observations about cardiac regulation to a broad "science of safety." 1980s–Early 1990s: Porges focuses on Respiratory Sinus Arrhythmia (RSA) as a window into the vagal regulation of the heart. 1995: Formal introduction of Polyvagal Theory, arguing that the vagus system consists of different pathways with distinct functional roles. 2001: The framework expands to include the "Social Nervous System," highlighting the phylogenetic shift in mammals toward social engagement as a regulatory strategy. 2011–Present: The theory becomes a cornerstone of trauma-informed care, introducing concepts like neuroception and the vagal brake. The Core of the Controversy: Two Perspectives The debate reached a fever pitch in 2026 following a major critical evaluation by Paul Grossman and 38 coauthors, followed by a direct rebuttal from Porges. The disagreement spans three primary domains: 1. The Interpretation of RSA and HRV The Critique: Critics argue that RSA is not a "pure" measure of cardiac vagal tone. Factors like breathing rate, depth, age, and baroreflex dynamics make it impossible to treat RSA as a direct readout of the "ventral vagus." The Defense: Porges argues the theory doesn't claim RSA is a global measure of total vagal tone, but a context-sensitive index of a specific, functional cardioinhibitory pathway. 2. The Dorsal vs. Ventral Vagus Distinction The Critique: Anatomists argue that the "ladder" of autonomic states is oversimplified. They suggest the Dorsal Motor Nucleus does not play the primary role in human "shutdown" or "fainting" states, as the theory suggests. The Defense: Porges maintains that the theory describes functional reorganization and state-dependent recruitment, rather than a rigid anatomical switch. 3. The Evolutionary Timeline The Critique: Evolutionary biologists point out that many "mammalian" traits (complex sociality, myelinated vagal fibers) are also found in reptiles, challenging the theory’s phylogenetic claims. The Defense: Porges clarifies that the claim is about the integration of these systems—specifically, how mammals coordinated the vagus with cranial nerves to support co-regulation. Key Takeaways for the HRV Community Interpretation requires humility: A single HRV or RSA value cannot be used as a definitive "safety meter." Context is everything: Respiration and activity significantly influence the signal. Clinical utility vs. Mechanistic accuracy: A theory can be a powerful tool for healing even while its underlying biological mechanisms are being refined. References Doody, J. S., Burghardt, G. M., & Dinets, V. (2023)...

This week's edition of This Week in HRV examines nine new studies that push the boundaries of what heart rate variability can tell us — from the psychology lab to the emergency department, the running trail to the pediatric pain clinic. We explore whether HRV biofeedback's benefits are real or a placebo, what chaos theory reveals about your heartbeat during cognitive work, whether a cleared concussion athlete's nervous system has truly recovered, and how listening to music can objectively shift the autonomic nervous system in patients with chronic pain. 1. Real or Placebo? Putting HRV Biofeedback to the Test Minjoz and colleagues published a randomized controlled trial in Biological Psychology comparing genuine HRV biofeedback against a convincing sham condition in 47 healthy adults. Key Findings: HRV biofeedback improved positive affectivity and reduced depression significantly more than the sham condition. However, no significant differences in HRV itself were detected between groups, and higher HRV during practice did not reliably predict greater psychological benefit. Significance: The psychological benefits of HRV biofeedback are real and exceed those of a placebo, but the mechanism may not be HRV changes themselves. This challenges practitioners to be more precise about how and why they recommend this intervention. Study Link: View Article 2. Your Thinking Brain Has Its Own HRV Signature Mao, Okutomi, and Umeno published a study in Scientific Reports comparing time-domain, frequency-domain, and chaos and complexity HRV indices during both physical and mental tasks. Key Findings: During mental tasks, conventional HRV metrics — RMSSD, LF, HF — showed no significant changes. But chaos and complexity indices increased significantly, marking cognitive engagement with a unique nonlinear fingerprint. Significance: The brain-heart connection during cognitive work speaks a language that standard HRV metrics cannot hear. Researchers and practitioners relying solely on RMSSD or LF/HF during mental tasks may be measuring the wrong dimension of the signal entirely. Study Link: View Article 3. Concussion Cleared — But Is the Nervous System? Delling-Brett, Jakobsmeyer, Coenen, and Reinsberger published an exploratory study in Scientific Reports examining nocturnal autonomic activity in athletes with regular versus prolonged return to sport after concussion. Key Findings: No autonomic differences were found between groups during active recovery. But post-clearance, athletes with prolonged recovery showed significantly lower nocturnal RMSSD and fewer phasic electrodermal activity events during sleep — even after symptoms had fully resolved. Significance: Clinical symptom clearance and autonomic recovery may be running on different timelines. Nocturnal HRV could capture a layer of incomplete recovery that symptom checklists cannot see. Study Link: View Article 4. After a Heart Attack, Which Way Is Your HRV Heading? Marković, Petrović, Babić, Bojić, and Milovanović published a retrospective-prospective study in Diagnostics tracking short-term HRV in 230 heart attack patients at day one and day twenty-one post-infarction. Key Findings: Patients who died during follow-up showed lower HRV at day 21 and more pronounced declines across the three-week window. Decreased delta LF and shorter RR intervals independently predicted overall mortality in multivariable analysis. Significanc...

This week’s edition of This Week in HRV dives into ten fresh studies that illustrate how heart rate variability is being used to decode everything from the heat of the climate to the heat of a high-stakes police encounter. We explore how HRV acts as a mediator for pain, a predictor of cognitive decline in extreme temperatures, and even a marker for the "acute effects" of professional gaming. 1. The Gateway of Fear: HRV, Pain, and Perception A study in the Journal of Clinical Medicine by Venezia et al. explored the psychological architecture of pain. Researchers investigated whether our physiological "braking system" (HRV) explains why people who fear pain actually feel it more intensely. Key Findings: The study found that HRV significantly mediates the relationship between a person’s "Fear of Pain" and their actual "Pain Perception." Essentially, a more flexible autonomic nervous system can buffer the impact of fear on the physical experience of pain. Significance: This suggests that improving autonomic regulation isn't just about heart health; it’s a viable strategy for chronic pain management and desensitization. Study Link: View Article 2. Impulsivity and the Bottle: Alcohol Cue-Induced HRV Published in Addictive Behaviors Reports, Taniajura and colleagues looked at "cue-reactivity"—how the body responds to the sight or smell of alcohol—and how impulsivity plays a role in drinking behavior. Key Findings: The research identified a specific link between alcohol-cue-induced HRV changes and subsequent drinking, particularly in individuals with high impulsivity. Significance: HRV may serve as a real-time "relapse warning system," identifying moments when an individual’s self-regulation is compromised by environmental triggers. Study Link: View Article 3. Cognitive Performance in the Heat: 150 Minutes of Stress As global temperatures rise, understanding heat-induced cognitive fatigue is critical. Zhu et al. published a study in Energy and Buildings focusing on human attentional performance during sustained heat exposure. Key Findings: Using HRV indices, researchers predicted shifts in human attention and performance after 150 minutes of heat exposure. Significance: This provides a blueprint for "smart buildings" and occupational safety protocols that use wearable HRV data to prevent heat-related errors in industrial settings. Study Link: View Article 4. Protecting the Frontline: HRV in Agricultural Workers In a parallel vein to the study above, Lung et al. (published in Nature) utilized lightweight personal sensors to track agricultural workers in the field. Key Findings: The study validated an "innovative method" for evaluating the immediate impact of environmental heat on the autonomic nervous system of outdoor laborers. Significance: This moves HRV research out of the lab and into the "real world," proving that mobile sensors can effectively monitor the health of vulnerable populations in extreme climates. Study Link: View Article 5. Inside the Heart: HRV in the Operating Room A study in Frontiers in Physiology by Skoczyński et al. took HRV into the most acu...

In this episode, Matt Bennett talks to Stephanie White about her work to create an HRV database to guide future research and HRV interventions. As always, Stephanie brings her expertise and passion to the show!

This Week in HRV Edition explores five newly published studies that push the boundaries of how we measure, modulate, and apply heart rate variability. These papers cover a diverse range of topics, including novel non-linear metrics, the efficacy of mindfulness, the future of digital psychiatry, light-based vagal stimulation, and the management of performance anxiety in musicians. A central theme connects these findings: HRV is evolving from a static "snapshot" of health into a dynamic, high-resolution map of human resilience and regulation. 1. Heart Rate Fragmentation: A New Window into Allostatic Load A study published in Applied Psychophysiology and Biofeedback by Jennifer F. Chan, Judith Andersen, and colleagues introduced a novel non-linear HRV metric called Heart Rate Fragmentation (HRF). Unlike traditional metrics that look at the magnitude of variability, HRF tracks the frequency of "directional changes" in heart rate (accelerations vs. decelerations), which can signal a breakdown in autonomic control. Key Findings: Analyzing 156 healthy adults, researchers found that while traditional HRV indices didn't always distinguish between healthy and "probable mental health" (pMH) groups, HRF reactivity was significantly higher in healthy individuals ($p < 0.001$). Significance: HRF may serve as a more sensitive biomarker for allostatic load (the "wear and tear" on the body), capturing subtle autonomic dysregulation that standard time-domain metrics might miss. Study link: https://link.springer.com/article/10.1007/s10484-025-09721-1 2. The Power of Brief Mindfulness Meditation A systematic review published in Applied Psychophysiology and Biofeedback investigated whether "Brief Mindfulness Meditation" (BMM) is sufficient to induce measurable changes in cardiac autonomic tone. The research team synthesized data from across four major databases to clarify the "dose-response" relationship between mindfulness and HRV. Key Findings: The review highlights that even single-session or short-term mindfulness interventions can significantly influence HRV, particularly increasing parasympathetic markers. Significance: This provides robust evidence for the clinical use of "micro-interventions," suggesting that patients and athletes don't necessarily need years of practice to begin re-regulating their autonomic "baseline." Study link: https://link.springer.com/article/10.1007/s10484-025-09724-y 3. Setting Digital Psychiatry in Motion A perspective published in NPP—Digital Psychiatry and Neuroscience (Nature Portfolio) by Axel Constant, Emre Koksal, and Lena Palaniyappan argues for a shift toward Dynamic Digital Markers (DDMs). The authors critique "static" entropy measures, which summarize data over long periods, potentially losing the "motion" of psychiatric symptoms. The Proposal: By using smartphones and wearables to track moment-to-moment temporal dependencies, clinicians can capture the dynamic regulatory mechanisms of psychopathology. Significance: This approach moves HRV and digital phenotyping from a diagnostic "label" to a "weather map" that can predict shifting, unstable mental states in real time. Study link: https://www.nature.com/articles/s44277-026-00059-y 4. Photobiomodulation: Light Therapy for the Vagus...

This Week in HRV Edition explores four newly published studies that highlight the remarkable breadth of heart rate variability research. These papers span nutritional neuroscience, digital phenotyping in social virtual reality, neonatal intensive care, and ophthalmic hemodynamics. Across all four studies, one theme emerges clearly: HRV reflects the structure of physiological adaptability. The nervous system is constantly adjusting to nutritional status, social environments, developmental maturity, and systemic vascular health. HRV captures those adjustments as patterns of variability, complexity, and stability. 1. Nutritional Modulation of the Vagal Brake A systematic review and meta-analysis published in the World Journal of Clinical Pediatrics investigated how Omega-3 fatty acid supplementation influences cardiac autonomic regulation. Researchers Hoda Atef Abdelsattar Ibrahim, Kamal Gouda Kamal, Mohamed Khaled Ali Mohamed Ali Zid, Albraa Ashraf Hamad, Ayesha Kuraishi, and Marwa Taha analyzed data from multiple randomized controlled trials. The results showed that Omega-3 supplementation was associated with a significant increase in time-domain HRV indices, including RMSSD and SDNN. This suggests that essential fatty acids may enhance the sinoatrial node's sensitivity to parasympathetic input, thereby stabilizing the heart's electrical threshold. Study link: https://www.wjgnet.com/2219-2808/full/v15/i1/116331.htm 2. Social Anxiety and Autonomic Expression in VR A study published in the Journal of Medical Internet Research explored the automated inference of social anxiety using behavioral data captured in virtual reality. Authors Gayoung Son and Marius Rubo used eye trackers and microphones to monitor 128 participants during a 30-minute social interaction. Higher levels of social anxiety were significantly linked to: Reduced high-frequency HRV (HF-HRV) Reduced gaze toward the partner’s eyes while speaking Quieter speech volume: The study found a strong correlation (r = 0.94) between these behaviors and broader psychopathology, suggesting that our "autonomic basement" displays consistent safety behaviors across digital and physical environments. Study link: https://www.jmir.org/2026/1/e79147 3. HRV as a Sentinel for Neonatal Morbidity A study published in Pediatric Research by Karen D. Fairchild examined the predictive value of depressed HRV in the neonatal intensive care unit. The study utilized advanced signal processing to monitor cardioregulatory patterns in both preterm and term infants. Lower HRV indices were robustly linked to: Intraventricular hemorrhage (IVH) Necrotizing enterocolitis (NEC) Chronic lung disease: While depressed HRV serves as a "canary in the coal mine," the author emphasizes that predictive power varies by gestational age and postnatal development, requiring context-aware clinical interpretation. Study link: https://www.nature.com/articles/s41390-026-04897-6 4. Ocular Hemodynamics and Systemic Autonomic Health A study published in PLOS ONE investigated the relationship between heart rate variability and retinal vein occlusion (RVO) in glaucoma patients. Researchers Ji Hye Lee and Young-Hoon Park compared 29 patients who developed RVO with 34 con...

In this episode, Matt Bennett interviews Ana Miranda about her research on HRV, allostatic load, and the stress response. 

In this week’s episode of The Heart Rate Variability Podcast: This Week in HRV Edition, we explore seven newly published studies that highlight the remarkable breadth of heart rate variability research. These papers span wearable digital biomarkers, sleep medicine, machine learning and mental health, critical care pharmacology, virtual environments, stroke recovery, and intermittent hypoxia. Across all seven studies, one theme emerges clearly: HRV reflects the structure of physiological adaptability. The nervous system is constantly adjusting to behavioral habits, environmental stressors, emotional meaning, and disease processes. HRV captures those adjustments as patterns of variability, complexity, and stability. 1. HRV Stability as a Digital Biomarker of Behavior A large study published in the American Journal of Physiology – Heart and Circulatory Physiology examined the stability of HRV measurements across multiple nights of wearable recordings. Researchers analyzed nearly 2 million nocturnal HRV measurements from over 21,000 individuals. Instead of focusing on single HRV readings, the study measured the coefficient of variation of HRV (HRV-CV) — essentially how much HRV fluctuates from night to night. The results revealed that five nights of data are required to reliably estimate a person’s baseline HRV stability. Higher HRV variability was associated with: Greater alcohol consumption Lower physical activity Shorter sleep duration Irregular sleep timing This suggests that autonomic stability may function as a digital biomarker of behavioral consistency. Study link: https://journals.physiology.org/doi/10.1152/ajpheart.00738.2025 2. Sleep Interventions and the “Autonomic Lag” A systematic review and meta-analysis published in the European Heart Journal Open examined how behavioral sleep interventions influence cardiovascular physiology. Researchers evaluated randomized controlled trials studying treatments such as Cognitive Behavioral Therapy for Insomnia (CBT-I). Sleep interventions significantly improved: Systolic blood pressure Diastolic blood pressure However, HRV parameters did not significantly change. The researchers propose what may be described as an “autonomic lag.” While sleep improvements quickly influence vascular physiology, deeper remodeling of the autonomic nervous system may take months of consistent behavioral change. Study link: https://pmc.ncbi.nlm.nih.gov/articles/PMC12915584/ 3. Machine Learning and HRV-Based Depression Detection A study published in Frontiers in Digital Health explored whether HRV signals can be used to classify depression using machine learning algorithms. Researchers addressed a common challenge in biomedical AI: imbalanced datasets, where healt...

In this week’s episode, host Matt Bennett explores the expanding frontier of heart rate variability as a bridge between subjective stress, neural adaptability, physiological arousal, and early cognitive decline detection. Rather than treating HRV as a static “stress number,” this episode highlights its role as a dynamic biomarker of regulatory flexibility across psychological, neurological, and cognitive domains. From perceived stress in healthy adults to social brain plasticity, from acute cold exposure to wearable-driven dementia detection, this episode emphasizes HRV as a real-time window into autonomic adaptability and system resilience. HRV is increasingly understood as a measure of regulatory range — the nervous system’s capacity to flex, adapt, and recalibrate. Across the studies reviewed this week, HRV emerges not merely as a marker of stress, but as a functional reflection of how the brain and body coordinate in response to internal and external demands. Studies Reviewed in This Episode Perceived Stress and Autonomic Regulation in Healthy Adults Study: The Relationship Between Perceived Stress Scale and Heart Rate Variability in Healthy Adults Authors: Alper Perçin, Ramazan Cihad Yılmaz, Dilan Demirtaş Karaoba, and Büsra Candiri Link: https://www.researchgate.net/publication/401048214_The_Relationship_Between_Perceived_Stress_Scale_and_Heart_Rate_Variability_in_Healthy_Adults Key Insight: Higher perceived stress scores were significantly associated with lower vagally mediated HRV indices, including RMSSD and high-frequency power. Even in healthy adults without psychiatric diagnoses, subjective stress perception meaningfully aligned with reduced parasympathetic flexibility. Clinical Relevance: HRV and psychological stress scales measure overlapping but distinct domains. When both subjective stress and HRV suppression are present, vulnerability may increase. Divergence between the two may provide additional diagnostic insight into resilience or under-recognized physiological load. Neural Mechanisms of Social Homeostasis and Dynamic Range Plasticity Study: Neural Mechanisms of Social Homeostasis: Dynamic Range Plasticity Authors: Jianna Cressy, Caroline Jia, Jonathan Salk, and Kay M. Tye Link: https://www.jneurosci.org/content/46/8/e0224252025 Key Insight: The study demonstrates that neural systems responsible for social regulation exhibit dynamic plasticity, adjusting their functional range in response to environmental demands. This adaptive range mirrors principles found in neurovisceral integration models, where flexibility in central networks is reflected in peripheral autonomic flexibility. Clinical Relevance: HRV may serve as a peripheral marker of central regulatory capacity. Interventions that enhance autonomic flexibility — including biofeedback and resonance breathing — may indirectly support neural adaptability involved in emotional and social regulation. Acute Cold Exposure and Cognitive Performance Study: The Immediate Effect of Cold Spinal Spray and Cold Spinal Bath on Cognition Among Young Adults: A Three-Armed Randomized Controlled Trial Authors: Avishee Sinha and Sujatha KJ Link: 

In this episode, Matt Bennett interviews Dr. Inna Khazan about how people can use different options to maximize their biofeedback practice. 

In this week’s episode, host Matt Bennett moves beyond environmental stressors to explore the biological architecture that governs our autonomic responses. From the inflammatory milieu of coronary arteries to the 24-hour coordination of the circadian axis, we analyze how Heart Rate Variability (HRV) serves as a blueprint for physiological integrity and a non-invasive window into the developing brain. Thematic Overview: HRV as a Blueprint While HRV is often used as a reactive "stress score," the latest research indicates it functions as a predictor of structural stability. This episode highlights HRV as a transdiagnostic marker of autonomic flexibility, shifting the clinical focus from mere observation to the identification of causal pathways of chronic disease and neurodevelopmental risk. Studies Reviewed in This Episode 1. Coronary Plaque Vulnerability and AI-Driven Imaging Study: Heart rate variability, unstable coronary plaques, and cardiovascular outcomes Authors: Yue Yu, Weifeng Guo, Ziwei Shen, Han Chen, Changyi Zhou, Cheng Yan, Yanli Song, Chenguang Li, Mengsu Zeng, Li Shen, Dijia Wu, Jiasheng Yin, and Junbo Ge Key Finding: Lower HRV (specifically SDNN) is independently associated with higher Fat Attenuation Index (FAI) values—a high-fidelity biomarker for inflammation in the perivascular adipose tissue surrounding the heart. Each 1-SD decrease in SDNN was associated with a 2.05-fold increase in the risk of major adverse cardiovascular events. 2. Schizophrenia and Cognitive Endophenotypes Study:(https://www.cureus.com/articles/447595-heart-rate-variability-and-cognitive-function-as-potential-endophenotypes-in-schizophrenia-a-cross-sectional-observational-study-using-first-degree-relatives#!/) Authors: Priyadarsini Samanta, Barsha B. Parida, Jigyansa I. Pattnaik, Rama Chandra Das, Rashmi Kumari, Vedaant Parekh, Jayanti Mishra, Jyotiranjan Sahoo, and Laxman Kumar Senapati Key Finding: Patients with schizophrenia exhibit a significantly higher LF/HF ratio compared to healthy relatives (1.57 vs. 0.79), indicating chronic sympathovagal imbalance. This autonomic profile showed a strong positive correlation with cognitive performance on the Wechsler Abbreviated Scale of Intelligence. 3. Exercise Physiology and the Fractal Heart ($DFA \alpha 1$) Study: Agreement between heart rate variability-derived and lactate/ventilatory thresholds during a 4-min stepwise incremental cycling test in male adults Authors: Anton Olieslagers, Yoram Müller-Jabusch, Margot Vancoillie, Emma Delen, and Toon de Beukelaar Key Finding: The non-linear metric DFA \alpha 1 at a value of 0.50 (HRVT2) is a highly accurate surrogate for the anaerobic threshold. However, the lower aerobic threshold (HRVT1 at 0.75) demonstrated poor agreement with gold-standard metabolic markers, suggesting it is not yet reliable for setting low-intensity zones. 4. Neonatal Maturation and Neurodevelopmental Risk Study:(https:/...

In this week’s episode of The Heart Rate Variability Podcast: This Week in HRV Edition, we explore five new studies that highlight the remarkable breadth of heart rate variability research — from the emotional intensity of football matches to adolescent development, from neurofeedback training to fasting physiology, and from cardiometabolic health to organ dysfunction in critical care. Across all five papers, one theme emerges clearly: HRV reflects adaptability. Whether we are celebrating a goal, training the brain, fasting, recovering from illness, or navigating adolescence, autonomic flexibility shapes outcomes. ⚽ Football Fever: HRV During Competitive Match Viewing A new study published in Scientific Reports (Nature Portfolio) investigates real-time cardiovascular and autonomic responses during high-stakes football matches. Researchers monitored spectators’ heart rates and HRV during key match events—goals, penalties, near misses, and final outcomes. Moments of uncertainty and threat to the favored team produced: Significant reductions in vagally mediated HRV Rapid increases in heart rate Sustained sympathetic activation in some individuals Recovery patterns differed based on match outcomes, with prolonged vagal withdrawal observed following unexpected losses. This research provides mechanistic insight into why major sporting events have been associated with spikes in cardiovascular incidents at the population level. Study link: https://www.nature.com/articles/s41598-026-36182-1 Neurofeedback and Autonomic Regulation Published through Scientific Research Publishing, this study examined whether structured neurofeedback training influences heart rate variability and cognitive performance. Participants completed multiple neurofeedback sessions targeting EEG regulation associated with attention and emotional control. Findings included: Increases in parasympathetic HRV markers Improved cognitive task performance Reductions in anxiety-related symptoms The results support a bidirectional neurocardiac integration model — suggesting that improving cortical regulation may enhance vagal tone. For clinicians, this raises compelling questions about combining neurofeedback and HRV biofeedback for synergistic regulatory effects. Study link: https://www.scirp.org/journal/paperinformation?paperid=149580 ⏳ Fasting, Cardiometabolic Health, and Autonomic Balance In a paper published in Arteriosclerosis, Thrombosis, and Vascular Biology (American Heart Association), researchers examined the cardiovascular effects of structured fasting interventions. Key findings included: Improvements in triglyceride levels Enhanced insulin sensitivity Variable autonomic responses depending on metabolic status Early fasting phases were associated with increased sympathetic activity in some participants, while longer-term adaptation appeared to stabilize or improve HRV in metabolically resilient individuals. This highlights an important clinical principle: Fasting is a physiological stressor. Whether it becomes adaptive depends on individual autonomic resilience. Study link: https://www.ahajournals.org/doi/10.1161/ATVBAHA.125.323355 HRV as a Predictor of Organ Dysfunction Published in the Journal of Clinical Monitoring and Computing, this study explored heart rate variability as a biomarker of organ dysfunct...

In this episode, Matt Bennett interviews chiropractor Dr. Tommy Rhee about his utilization of heart rate variability in his innovative approach to regenerative health, recovery, and performance.

In Episode 24 of the Heart Rate Variability Podcast, we explore five recent studies that span trauma recovery, personality theory, migraine prediction, heart failure monitoring, and fundamental vagal sensory mechanisms. Together, these papers deepen our understanding of HRV not as a static metric, but as a dynamic signal shaped by interoception, context, and time. This episode emphasizes HRV as a marker of felt safety, autonomic integration, and physiological sensing, highlighting how vagal activity reflects not only brain-mediated regulation but also incoming sensory information from the body. Implications are discussed for clinicians, researchers, and individuals seeking a more nuanced and compassionate understanding of nervous system function. Medical Disclaimer This podcast is for educational and informational purposes only and does not constitute medical advice. The information presented is not intended to diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare professional before making changes to medical care, mental health treatment, or lifestyle practices. STUDIES DISCUSSED IN THIS EPISODE Felt Safety and Body-Oriented Trauma Intervention Full Title:From Somatic Experiencing to felt safety: Assessing the effects of a body-oriented intervention in adults with various degrees of child maltreatment Authors:Jörgen LehmivaaraBilly JanssonJens BernhardssonMarylène CloitreMonique C. Pfaltz Journal:European Journal of Psychotraumatology Publication Year:2026 Key Points:• A brief Somatic Experiencing–based intervention significantly increased psychological safety• Participants showed improvements in affect and social connectedness• Heart rate decreased, and HRV increased during the intervention• Reductions in disrupted body boundaries and increased interoceptive awareness were observed• Findings support felt safety as an embodied, physiologically measurable state Article Link:https://doi.org/10.1080/20008066.2026.2613544 Autonomic Integration and the Triangle Therapy Hypothesis Full Title:Integrating autonomic and affective pathways in borderline personality disorder: The triangle therapy hypothesis Author:Daniel Juraszek Journal:Frontiers in Psychology Publication Year:2026 Key Points:• Proposes a somatic pre-phase intervention targeting autonomic regulation• Centers on exposure to silence, sound, and isolation as ancestral affective conditions• Frames BPD as a disorder of autonomic-affective integration rather than cognition alone• Suggests HRV as a physiological marker of treatment readiness and integration• Emphasizes bottom-up tolerance before top-down therapeutic work Article Link:https://www.frontiersin.org/articles/10.3389/fpsyg.2026.1686068/full Sleep-Time HRV and Migraine Prediction Full Title:Heart rate variability as a predictor of migraine: Sleep-time data analysis of pre-migraine nights Authors:Rūta JankevičiūtėViroslava KapustynskaVytautas Abromavičius Journal:Technology and Health Care Publication Year:2026 Key Points:• Sleep-time HRV patterns differed on nights preceding migraine attacks• Significant inter-individual variability was observed...

EPISODE 23 – THIS WEEK IN HEART RATE VARIABILITY Episode Title:HRV Across Cardiovascular Disease, Stress, Cognition, Development, and Social Connection Episode Summary:In Episode 23 of the Heart Rate Variability Podcast, we take an in-depth look at six recent peer-reviewed studies that collectively illustrate how heart rate variability (HRV) is being used across medicine, neuroscience, psychology, and emerging technologies. From cardiovascular disease prognosis to chronic stress burden, from Alzheimer’s-related fall risk to virtual reality–based physiological synchrony, this episode highlights HRV as a transdiagnostic marker of autonomic flexibility, resilience, and vulnerability. Rather than treating HRV as a single “good or bad” number, this episode emphasizes context, interpretation, and clinical nuance. HRV is explored as a window into nervous system regulation across the lifespan and across settings, with implications for clinicians, researchers, and individuals alike. Medical Disclaimer:This podcast is for educational and informational purposes only and does not constitute medical advice. The information presented is not intended to diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare professional before making changes to medical care, mental health treatment, or lifestyle practices. STUDIES DISCUSSED IN THIS EPISODE Cardiovascular Disease and HRV (Review Article) Full Title:Heart rate variability in cardiovascular disease diagnosis, prognosis, and management Authors:Brian Xiangzhi Wang, MDElla Brennand, MDPierre Le Page, MDAndrew R. J. Mitchell, MD, PhD Affiliations:Department of Medicine, Jersey General Hospital, St. Helier, JerseyDepartment of Medicine, John Radcliffe Hospital, Oxford University Hospitals, Oxford, United Kingdom Journal:Frontiers in Cardiovascular MedicineSection: Cardiac RhythmologyPublication Date: January 26, 2026 Key Points:• Reduced HRV is associated with arrhythmias, heart failure, ischemic heart disease, and post–myocardial infarction outcomes• HRV may reveal early autonomic dysfunction before overt clinical symptoms• Prognostic value of HRV remains debated due to mixed findings and methodological variability• HRV shows promise for tracking recovery and monitoring comorbid conditions such as depression• Wearable devices and machine learning may expand HRV’s clinical utility• Major challenges include a lack of standardization and limited incremental predictive value over established risk factors Article Link:https://doi.org/10.3389/fcvm.2025.1680783 Allostatic Load, HRV, and Brain Networks Full Title:Linking allostatic load, heart rate variability and brain functional networks and structures in healthy men Authors:Juan M. Solano-AtehortuaGabriel CastrillónJazmin X. Suarez-ReveloJuan D. Sánchez-LópezDaniel A. Vargas-TejadaValentina Hawkins-CaicedoJuan C. CalderónJaime Gallo-VillegasYedselt V. Ospina-SerranoJuan D. Caicedo-JaramilloAna L. Miranda-Angulo Journal:PsychoneuroendocrinologyPublication Year: 2026 Key Points:• Higher allostatic load is associated with lower HRV in healthy men• A seven-biomarker allostatic load index (ALI-7) was positively associated with the LF/HF ratio• Findings suggest increased sympathetic dominance with gr...

In this episode, Matt Bennett interviews Dr. Jennifer S. Addleman and Nicholas S. Lackey about their recent article Heart Rate Variability Applications in Medical Specialties: A Narrative Review. You can find the article here: https://link.springer.com/article/10.1007/s10484-025-09708-y. Dr. Jennifer S. Addleman, DO, CSCS, is a resident physician and certified strength and conditioning specialist (CSCS). She is currently completing her intern year in the Sutter Roseville Transitional Year Residency Program, followed by advanced training in Physiatry at the Stanford Physical Medicine and Rehabilitation Residency Program. Dr. Addleman is active in research involving gait analysis, wearable technology, and heart rate variability. She is passionate about exploring the applications of HRV across medicine and strength and conditioning. Nicholas Lackey, PhD, BCB, is a Psychology Postdoctoral Resident with the Kaiser Permanente Mental Health Training Program in Northern California. He earned his PhD from Alliant International University in San Diego, during which he also completed the requisite experience for his Board Certification in Biofeedback. He explored research on meta-analyses and then on the implementation of Biofeedback. His dissertation explored the efficacy of a scale in examining types of chronic pain and Central Sensitization. Dr. Lackey aims to continue his career in Health Psychology and to examine the intersection of Psychology and Medicine through multidisciplinary collaboration and practice. Here is their previous article on strength and conditioning training and heart rate variability mentioned in the episode: https://pubmed.ncbi.nlm.nih.gov/38921629/

This Week in HRV - Episode 22 In this episode of "This Week in HRV", Matt Bennett explores four recent studies that broaden our perspective on autonomic regulation across diverse physiological contexts. This week’s collection highlights the nuances of female reproductive physiology as captured by wearables, the specific cardiovascular mechanics of volitional sighing, the superior recovery potential of yoga practice, and the intricate neural coupling between the heart and brain during complex motor tasks. Together, these papers underscore the nervous system's adaptability to hormonal, behavioral, and cognitive demands. 1. Wearable-Derived Heart Rate Variability Across the Menstrual Cycle, Hormonal Contraceptive Use, and Reproductive Life Stages in Females: A Living Systematic Review Authors: Eline de Jager, Brian Caulfield, Evgenia Angelidi, Brian MacNamee & Sinead Holden Journal: Sports MedicineShutterstock This systematic review aggregates data from wearable technology to map HRV trends across the female reproductive lifespan. The authors examine how natural menstrual cycle phases, hormonal contraceptives, and different reproductive stages influence autonomic metrics. The findings emphasize the importance of context when interpreting wearable data in females, as hormonal fluctuations drive distinct shifts in autonomic balance that must be distinguished from training load or stress. https://link.springer.com/article/10.1007/s40279-025-02388-y 2. Dissecting Cardiovascular Responses to a Fixed-Interval Volitional Sighing Protocol Using a Mixed Modeling Approach Authors: Neel Muzumdar, Kelly Sun, Samuel Zhang, Kelsey Piersol, Anthony P. Pawlak, Marsha E. Bates & Jennifer F. Buckman Journal: Psychophysiology Investigating the mechanics of breathwork, this study utilized a mixed modeling approach to analyze cardiovascular responses to a specific protocol of volitional sighing. The research dissects how fixed-interval sighing alters heart rate dynamics, providing granular insight into how this specific respiratory behavior—often used for acute stress relief—modulates autonomic output and cardiovascular stability. https://onlinelibrary.wiley.com/doi/10.1111/psyp.70235 3. Autonomic recovery following submaximal exercise in yoga practitioners versus aerobic and strength-trained individuals Authors: Sreenath N., Pallavi L. C., Baskaran Chandrasekaran, Lavya Shetty, Lavina M. Manu & Shivaprakash Gangachannaiah Journal: Annals of Physical and Rehabilitation Medicine This comparative study assessed autonomic recovery speeds following submaximal exercise across three distinct groups: yoga practitioners, aerobic athletes, and strength-trained individuals. The results suggest that long-term yoga practice may confer a unique advantage in parasympathetic reactivation and in the speed of autonomic recovery post-exertion compared to traditional aerobic or resistance training backgrounds. https://www.tandfonline.com/doi/full/10.1080/07853890.2026.2615509 4. The interplay between cardiac and brain activities within a balancing skill-challenge context during goal-directed motor control Authors: Heng Gu, Qunli Yao, Chao Yang, Zhaohuan Ding, Xiaoli Li & He Chen Journal: Cerebral CortexGetty Images Focusing on the brain-heart axis, this study explores the synchronization between cardiac rhythms and cortical activity during goal-directed motor control tasks requiring balance. The researchers id...

This Week in HRV - Episode 21 In this episode of This Week in HRV, Matt Bennett explores five recent studies that deepen our understanding of heart rate variability as a marker of autonomic regulation across endocrine health, sleep physiology, theoretical neuroscience, extreme environmental exposure, and performance nutrition. Together, these studies illustrate how HRV reflects the nervous system’s capacity to integrate hormonal, behavioral, environmental, and recovery-related demands. 1. Comparative Analysis of Heart Rate Variability in Women with and Without Polycystic Ovary Syndrome (PCOS) Authors: Sivaranjani; Prabhavathi; Keerthi; Bhavisha Sreenivasan; Thamarai Selvi; Saravanan; Panneerselvam Journal: Journal of Pharmacy and Bioallied Sciences This study examined resting heart rate variability in women with and without PCOS. Women with PCOS showed reduced HRV, reflecting diminished parasympathetic modulation and altered autonomic balance. The findings suggest that autonomic dysregulation may be present early in PCOS, even before overt cardiovascular disease develops. https://journals.lww.com/jpbs/fulltext/2025/10000/comparative_analysis_of_heart_rate_variability_in.9.aspx 2. Autonomic Characteristics of Periodic Limb Movements: Comparison of Whole-Night and Stage N2 Linear and Non-Linear Heart Rate Variability Authors: Elif Simin; Selahattin; Elif Göksu Journal: Clinical Autonomic Research Using overnight polysomnography, this study analyzed how periodic limb movements during sleep affect autonomic regulation. HRV analysis revealed transient sympathetic activation during limb movement events and reduced autonomic complexity across the night. https://link.springer.com/article/10.1007/s10286-025-01184-y 3. Biofeedback from the Free Energy Principle Perspective: Some Psychoeducational and Clinical Implications Author: Yossi Journal: Biofeedback This theoretical paper applies the Free Energy Principle to biofeedback practice, framing HRV biofeedback as a process of reducing physiological uncertainty and improving adaptive regulation. https://biofeedback.kglmeridian.com/view/journals/biof/53/3/article-p47.xml 4. Autonomic Regulation across Sleep and Wake during an Antarctic Overwintering Authors: C. Tortello; A. Folgueira; B. Cauda; L. E. González; E. Sala Lozano; N. Pattyn; G. Simonelli; S. A. Plano; D. E. Vigo Journal: Scientific Reports This study tracked heart rate variability across months in individuals overwintering in Antarctica, showing reduced parasympathetic activity, weakened circadian organization, and diminished sleep–wake autonomic differentiation during prolonged isolation. https://www.nature.com/articles/s41598-025-31009-x 5. The Effects of an Acute Dose of Cannabidiol on Health and Two-Mile Time Trial Performance—A Pilot Study Authors: Elyssa R., Brandon, Seth M., and Laura K. Journal: Nutrients This pilot study examined the effects of an acute cannabidiol dose on endurance performance and physiological markers. While performance did not improve, changes in autonomic recovery markers suggest CBD...