Heart Rate Variability Podcast

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...

This Week in HRV  In this episode of This Week in HRV, Matt Bennett explores five recent studies that deepen our understanding of heart rate variability across time, technology, cardiovascular health, brain aging, and addiction recovery. Together, these papers highlight both the strengths and limitations of HRV as a window into nervous system regulation. 1. Unveiling the Extremely Low Frequency Component of Heart Rate Variability Authors: Krzysztof, Adam G. Journal: Applied Sciences This study demonstrates that ultra-low-frequency HRV is not a single physiological process, but can be decomposed into two independent components reflecting circadian and ultradian rhythms. The findings expand our understanding of long-term autonomic regulation and biological timing. https://www.mdpi.com/2076-3417/16/1/426 2. Limited Evidence for Heart Rate Variability as a Predictor of Cognitive and Pathophysiological Brain Markers Authors: Sofia, Jaime D., Arie, Balewgizie, Harriëtte, Rozemarijn, Rudi, Ronald, Peter Paul Journal: Journal of Alzheimer’s Disease Using a long-term longitudinal design, this study examined whether midlife HRV predicts later cognitive performance, brain imaging findings, or Alzheimer’s biomarkers. Results suggest HRV alone is not a reliable early predictor of neurodegenerative pathology. https://journals.sagepub.com/doi/10.1177/13872877251409343 3. Beyond Motion Artifacts: Optimizing PPG Preprocessing for Accurate Pulse Rate Variability Estimation Authors: Yuna, Natasha, Aarti, Varun, Matthew S. Conference Proceedings: ACM (UbiComp) This engineering study shows that preprocessing choices—particularly band-pass filtering—strongly influence the accuracy of pulse-rate variability derived from wearable PPG sensors. The authors demonstrate that adaptive preprocessing significantly improves HRV estimation accuracy. https://dl.acm.org/doi/epdf/10.1145/3714394.3756241 4. Association of Diurnal Blood Pressure Patterns with Heart Rate Variability and Retinopathy in Patients with Essential Hypertension Authors: Fengping, Hui, Tianfeng, Chen Journal: Scientific Reports This clinical study links abnormal nighttime blood pressure patterns with reduced HRV and a markedly higher prevalence of hypertensive retinopathy. The findings highlight the relationship between circadian autonomic regulation and microvascular health. https://www.nature.com/articles/s41598-025-29694-9 5. Yoga for Opioid Withdrawal and Autonomic Regulation: A Randomized Clinical Trial Authors: Suddala, Hemant, Bharath, Jayant, Ravindra P., Nishitha, Venkata Lakshmi, Urvakhsh Meherwan, Shivarama, Ganesan, Prabhat, Bangalore Nanjundiah, Kevin P., Matcheri, Pratima Journal: JAMA Psychiatry This randomized clinical trial shows that adding yoga to standard opioid detoxification significantly accelerates withdrawal recovery, improves HRV, reduces anxiety, improves sleep, and decreases pain—demonstrating the role of autonomic regulation in addiction recovery. https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2843424 Sponsor...

In this episode, Matt Bennett is joined by Dr. Inna Khazan and Dr. Mara Mather to discuss Dr. Mather's research on heart rate variability biofeedback. Dr. Mather's work opens exciting new insights to the real and potential power of HRV biofeedback. 

Episode Show Notes: This Week in HRV – January 2026 Welcome to the first episode of 2026! Today, host Matt Bennett explores ten groundbreaking studies that bridge the gap between autonomic health, mental well-being, and physical performance. From the cardiac strain of early psychosis to the "neuroimmune triad" in diabetes, we dive deep into the latest science of Heart Rate Variability. Detailed Study Summaries 1. Myocardial deformation and pro-arrhythmic indices in first-episode patients with psychosis before and one year after the initiation of antipsychotic treatment Authors: Marios Plakoutsis, Aris Bechlioulis, Aidonis Rammos, Spyridon Sioros, Andreas Karampas, Georgios Georgiou, Lampros K. Michalis, Katerina K. Naka, and Petros Petrikis. This study highlights that a first psychotic episode is a full-body stressor causing immediate autonomic imbalance. Even without prior heart disease, patients showed abnormal HRV and subtle weakening of heart muscle contraction. While treatment rebalances the autonomic system, it requires vigilant monitoring due to medication-induced QT interval prolongation. 2. Perception of effort decreases with motor sequence learning Authors: Bahram Ghafari Goushe, Thomas Mangin, Benjamin Pageaux, and Jason L. Neva. Learning a new skill isn't just a brain-based phenomenon. This experiment shows that as a task becomes automated, the body stays calmer (higher RMSSD) and the subjective perception of effort drops, reducing the physiological "price" of performance. 3. Serum cytokine levels and heart rate variability in the frequency domain in patients with chronic Chagas heart disease Authors: Reinaldo B. Bestetti Sr., Renata Dellalibera-Joviliano, Milton Faria Junior, Rosemary A. Furlan Daniel, and Cláudia C. Domingos. Focusing on the inflammatory reflex, researchers found that Interleukin-23 (IL-23) specifically correlates with reduced vagal tone in Chagas heart disease, suggesting this cytokine interferes with the nervous system's ability to regulate the heart. 4. Research on changes in psychological, physical fatigue and emotional states in the National Youth Orienteering Preparation Camp Authors: Haiyan Li. Comparing athletes at an intensive camp to those training at home, this study proves that structured recovery (fixed hydration, rest, and mental skills training) leads to significantly better HRV adaptations and lower cortisol, preventing burnout despite high training loads. 5. Autonomic-inflammatory crosstalk in diabetic atherogenesis: a neuroimmune triad (HRV-LMR-hsCRP) predicts carotid plaque risk in type 2 diabetes Authors: Xinrui Zhou, Xiaowei Bai, Li Ding, Shuai Zhang, and Ya Li. This paper introduces a practical "neuroimmune triad"—combining HRV with immune markers (LMR and hsCRP)—to accurately predict the risk of carotid plaques in diabetic patients, identifying those at highest risk for stroke. 6. Effect of Tai Chi and Qigong on Heart Rate Variability: A Systematic Review and Meta-Analysis Examining Baseline Autonomic Function and Intervention Complexity as Moderators in Adults Authors: Yasmine A. Gunawan, Mein-Woei Suen, Hanifa M. Denny, Ishita Chauhan, Milcha Fakhria, Siswi Jayanti, and Earl F.I. Mallari. A meta-analysis of 15 studies confirms that mind-body exercises improve HRV regardless of routine complexity. However, gains are largest for those who enter the practice with a relatively healthy baseline autonomic state. 7. Sympathovagal imbalance in drug-naïve chronic obstructive pulmonary disease patients: a physiological mechanism to cope with the severity of airway obstruction in an observational study Authors: Durgesh K. Gupta, Shibu S. Awasthi, Suman Gupta, and Himani H. More. In COPD, the body reflexively boosts sympathetic drive t...

The 2024 Year in Review — Research That Shaped 2025 The Heart Rate Variability Podcast In this special "Year in Review with a Twist," we shift our focus from the weekly news cycle to the big picture. We examine the most influential, highly cited research of 2024 to understand how these findings are revolutionizing clinical thinking and personal wellness in 2025. HRV is no longer just a metric on a wearable; it has become the definitive framework for understanding resilience, adaptation, and human regulation. Episode Highlights The Anxiety Biomarker: Why 2024 research confirms HRV as a "top-down" signal of how the brain calms itself and its potential for identifying anxiety subtypes. Combatting "Inflammaging": Exploring the link between vagal tone and chronic low-grade inflammation in aging populations. The Autonomic Conditioning of Exercise: How physical activity trains the nervous system, not just the heart muscle. Context is King: A deep dive into the 2024 "Sensitivity Review" highlighting how noise, heat, and even genetics must be accounted for in accurate readings. Biofeedback Frontiers: From COPD and Spinal Cord Injury to classroom attention, we look at how HRV training is breaking new ground in rehabilitation and education. Key Research Reviewed Psychophysiology & Mental Health (2024): A landmark review synthesizing decades of data to establish HRV as a marker of prefrontal cortex regulation over the amygdala in anxiety disorders. Gerontology & Immunology (2024): Research into "Inflammaging," positioning HRV as a non-invasive biomarker for biological age rather than just chronological age. Sports Science & Performance (2024): A systematic review on HRV-guided training, emphasizing individual baselines over population norms for sustainable athletic performance. Clinical Biofeedback Trials (2024): Notable studies involving COPD patients and those with chronic spinal cord injuries, proving the feasibility of HRV training even in complex physiological cases. Neurodevelopmental Interventions (2024): Exploratory research into using HRV biofeedback for anxiety in Autism Spectrum Disorder and attention-building in school-aged children. The 2025 Takeaway "The question is no longer whether HRV is relevant, but how we apply it thoughtfully and responsibly. Autonomic flexibility is the foundation of emotional resilience, physical health, and cognitive performance." Sponsor This episode is brought to you by Optimal HRV. Bridge the gap between data and action with evidence-based tools designed for individuals, clinicians, and organizations. Explore our professional dashboards and HRV training e-gift cards today. Learn more at www.optimalhrv.com Disclaimer: The information shared in this podcast is for educational purposes only and is not intended as medical advice. Always consult a qualified healthcare professional before changing your health or wellness routines.

In this episode, Stephanie White joins Matt Bennet to explore the nature and uses of Very High Frequency Heart Rate Variability.

This Week in Heart Rate Variability: Air Pollution, Spiritual Wellbeing, Consciousness & Clinical Prediction In this episode of The Heart Rate Variability Podcast – This Week in HRV, we expand the horizons of autonomic science. From the hidden impact of environmental pollutants to the neuro-spiritual connection of the "heart-brain axis," we examine how HRV serves as a vital bridge between our environment, our consciousness, and our clinical outcomes. Episode Highlights Environmental Stressors: New research into how air pollution and lead exposure synergistically drive autonomic dysfunction. The Spirituality-HRV Link: Exploring Bayesian modeling of Heartbeat Evoked Potentials (HEP) as a biomarker for mental and spiritual wellbeing. HRV as a Clinical Life-Line: A deep dive into a major meta-analysis confirming HRV’s power to predict mortality in heart failure patients. Mapping Consciousness: How 24-hour HRV monitoring is helping clinicians differentiate between unresponsive wakefulness and recovery in patients with disorders of consciousness. Precision and Reliability: Critical insights into the reliability of short-term HRV measurements across different body positions and environments. Featured Studies & Resources Environmental Research (2025) — Air Pollution & Chronic Lead Exposure: The synergistic impact of environmental toxins on cardiac autonomic function. Link to Study Cogent Psychology (2025) — Bayesian Modeling of HEP and HRV: An exploratory study on using HRV and heart-brain communication as biomarkers for spiritual health. Link to ResearchGate Scientific Reports (2025) — The Multidimensional Perspective of HRV: A comprehensive look at the brain-heart axis (BHA) and its role in predicting multi-system disease. Link to Nature Cureus (2025) — HRV as a Predictor of Mortality in Heart Failure: A systematic review and meta-analysis on the prognostic value of HRV in cardiovascular care. Link to Cureus Scientific Reports (2025) — Clinical Reliability of Short-Term HRV Insights into the consistency of HRV measurements in dual-environment and dual-position settings. Link to Nature Acta Neurologica Belgica (2025) — HRV in Disorders of Consciousness Using 24-hour HRV metrics to identify emergence from minimally conscious states (PMID: 41389121). Link to PubMed Psicothema (2025) — Autonomic Modulation & Psychological States Examining the latest protocols for integrating HRV into psychological and behavioral health assessments. Link to ScienceDirect Key Takeaway The "Heart-Brain Axis" is more than a concept—it is a measurable r...

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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