Search Results (44)

Background: The methodology of slow-paced breathing (SPB) to optimize cardiorespiratory function requires further refinement. The aim of this study was to identify the methodological ranges of resonance breathing frequencies during SPB in healthy young adults with optimal and suboptimal spirometric indices. Methods: Twenty-eight healthy Indian students living in the Arctic Russian region (age 21–24 years; 20 males, 8 females) underwent spirometry and 2 min HRV recordings at 6 time points: baseline (spontaneous breathing) and SPB periods of 9–13 s with biofeedback. Results: Participants were divided into Group 1 (FEV1 ≥ 80% predicted, n = 13) and Group 2 (FEV1 < 80% predicted, n = 15). At baseline, Group 2 showed reduced overall HRV, lower vagal activity, a higher stress index and lower baroreflex power (by LFmx) vs. Group 1. During SPB, Group 1 exhibited more significant vagal enhancement, peaking at 9–10 s breathing periods. Group 2 showed delayed, wave-like responses with peak effects at 9 s and/or 12–13 s. Conclusions: SPB frequency depends on the level of FEV1: 9–10 s periods in individuals with FEV1 ≥ 80% predicted, and 9 s and/or 12–13 s periods (delayed effect) in those with FEV1 < 80% predicted, which may be due to cardiorespiratory strain under uncomfortable climatic conditions. Full article

Heart rate variability (HRV) is widely used as a non-invasive marker of autonomic regulation and physiological adaptability, with relevance across cardiovascular, metabolic, neuropsychiatric, and stress-related conditions. HRV biofeedback has emerged as a non-pharmacological intervention intended to influence autonomic function through paced breathing, resonance-frequency training, and real-time physiological feedback. Although this approach has shown promise in improving stress regulation, emotional symptoms, autonomic balance, and selected cardiovascular outcomes, its effects are not consistent across individuals or clinical states. The reasons for this variability remain insufficiently conceptualized. In this narrative conceptual review, we propose the concept of autonomic non-responsiveness during HRV biofeedback as a descriptive framework for situations in which expected autonomic engagement is weakened, absent, or fails to translate into meaningful physiological or clinical benefit. We discuss potential contributors to non-response, including reduced autonomic flexibility, impaired baroreflex function, disease burden, fatigue, stress-related overload, dysfunctional breathing, methodological limitations, and cognitive-behavioral constraints. We then consider the clinical implications of recognizing non-response as a potentially informative state rather than a simple negative outcome. Finally, we outline a future research agenda focused on operational definition, candidate biomarkers, temporal characterization, and minimally adaptive closed-loop systems. Full article

This systematic review synthesized the existing evidence on neurofeedback interventions applied to football players, aiming to clarify their effects on cognitive, technical–tactical, physical and psychological performance. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, four databases (PubMed, Web of Science, SCOPUS and SportsDiscus) were searched up to November 2025. Seven studies met the inclusion criteria, involving 133 players across youth, amateur, national and elite levels. Neurofeedback protocols primarily targeted alpha or sensorimotor rhythm (SMR) activity, and some were combined with heart rate variability (HRV) biofeedback. Across studies, neurofeedback may be associated with improvements in several cognitive outcomes, including improvements in working memory, visuospatial memory, task switching, mental rotation and decision-making. Limited evidence suggests potential improvements in technical skills (particularly shooting accuracy) and tactical decision-making. Some studies reported changes in physiological markers and stress-recovery capacity, although their interpretation remains uncertain. However, the evidence base remains constrained by small samples, heterogeneous protocols and limited use of randomized controlled designs. Overall, neurofeedback appears to be a potentially promising but still experimental tool to support cognitive and psychophysiological readiness in football, warranting more rigorous and standardized research to establish efficacy and optimal training parameters. Full article

This review examines what constitutes heart rate variability (HRV), the relationship between HRV and the autonomic nervous system, and the physiology driving HRV. HRV is correlated with vagal nerve activity and parasympathetic nervous activation. Higher HRV is correlated with youth, active lifestyle, adaptive capacity, and good health. Next, the review examines the medical significance of HRV, especially the correlation between lower HRV and the presence of medical and psychological disorders. In general, HRV serves as a biomarker for health and disease, an index of autonomic nervous system dysregulation, an index of prefrontal cortical functionality, and a marker for psychopathology across diagnoses. Higher HRV is associated with several characteristics associated with successful psychotherapy and hypnotherapy: social engagement, compassion, emotional regulation, and cognitive flexibility. Given this association, somatic regulation should be regarded as integral to treatment alongside psychotherapy and hypnosis. Understanding HRV can enable the psychotherapist and hypnotherapist to optimize treatment. In effect, the therapist can harness the power of the brain and nervous system to better prepare the patient for therapy and to enhance the process of therapy. This review encourages therapists to utilize several strategies and interventions to increase patients’ HRV levels prior to and during therapy. The review will be most applicable for those hypnotherapists who integrate hypnosis into counseling and psychotherapy. The review describes the process by which HRV biofeedback training guides the individual to voluntarily increase HRV. It also identifies a number of lifestyle parameters and self-care practices (including self-hypnosis) that increase HRV. Encouraging lifestyle and self-care practices to increase HRV can support a greater response to hypnotherapy and psychotherapy. With additional training, hypnotherapists can integrate HRV biofeedback into a hypnosis practice. Further, several simple interventions already within the scope of most hypnosis practitioners can be utilized to enhance HRV at the beginning of a hypnotherapy process, and again during the process of therapy. Full article

Post-stroke rehabilitation integrates technological feedback systems to enhance motor relearning and autonomic regulation. Among these, physiological biofeedback—based on electromyography (EMG), heart rate variability (HRV) and electrocardiography (ECG)—represents a multimodal approach for restoring neuromotor control and autonomic balance. EMG biofeedback enables patients to visualize and voluntarily modulate muscle activation, supporting cortical reorganization and improving movement precision through real-time feedback. Recent meta-analyses confirm that EMG biofeedback significantly improves upper- and lower-limb function in stroke survivors, particularly when combined with task-oriented physiotherapy. EMG biofeedback demonstrates improvements in swallowing function, motor control, and patient motivation. Beyond the motor domain, HRV biofeedback has shown substantial benefits lately, especially in regulating the autonomic nervous system (ANS) activity, improving vagal tone, and reducing sympathetic overdrive: a major contributor to fatigue and cardiovascular instability post-stroke. By targeting the sympathetic–parasympathetic balance, HRV biofeedback not only enhances autonomic flexibility but also supports emotional and cognitive recovery. Together, these modalities integrate neuromuscular and autonomic rehabilitation, offering a path toward individualized, feedback-driven recovery protocols. This narrative review synthesizes recent evidence on the mechanisms, the clinical outcomes, and translational potential of EMG- and HRV-based biofeedback in stroke rehabilitation, highlighting their role in advancing physiotherapy toward an adaptive, data-driven, and neuroplastic paradigm, as from now on, the emerging directions will include integrating physiological biofeedback with immersive or AI-driven platforms for enhanced personalization and motivation. Full article

Heart Rate Variability (HRV) biofeedback could be considered as a tool to help athletes to optimize their performance. This study aimed to examine the effects of a one-week HRV biofeedback (HRV-BFB) program on physiological indices, sensorimotor functions, and kata performance in Eastern martial arts athletes. Forty high-level martial arts athletes (karate, wushu, taekwondo, kyokushinkai) aged 17–27 years were divided into two groups: a control group (n = 20) and a biofeedback group (BFB, n = 20). Athletes from both groups underwent assessment of sensorimotor functions and the technical quality of their kata routines. The primary outcome was the expert-rated kata performance score. All routines were video-recorded and independently rated by three certified judges. The BFB group completed a hybrid HRV-BFB program consisting of supervised resonance-frequency breathing sessions in the laboratory and one week of home-based practice. During supervised sessions, athletes performed slow abdominal-paced breathing (6 breaths/min). At home, they practiced the same breathing pattern twice daily for one week (5 min per session, smartphone-guided). Nonparametric tests were used because several variables deviated from normality, and the sample size per group was limited (n = 20). After completing the HRV-BFB training, movement oscillation frequency improved significantly, reflected by lower movement oscillation frequency (p = 0.0009, r = 0.79), faster choice reaction time at a tendency level (p = 0.0793, r = 0.39), and an increase in blood volume pulse (BVP) (p = 0.037, r = 0.48) in BFB group compared to control group. Following BFB training, the judges’ scores did not change in the control group, while a significant increase was observed in the BFB group (p = 0.038, r = 0.44), indicating a positive effect of BFB training on kata performance. Regular HRV-BFB training emphasizing slow-paced abdominal breathing may enhance autonomic regulation, fine motor control, and improve the technical execution of kata routines in athletes. Full article

Background: Emerging evidence indicates that some individuals recovering from COVID-19 develop persistent symptoms, including fatigue, pain, cognitive difficulties, and psychological distress, commonly known as Long COVID. These symptoms often overlap with those seen in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME), underscoring the need for integrative, non-pharmacological interventions. This Phase II controlled trial aimed to evaluate the feasibility and preliminary efficacy of Heart Rate Variability Biofeedback (HRV-BF) in individuals with Long COVID who meet the diagnostic criteria for CFS/ME. Specific objectives included assessing feasibility indicators (drop-out rates, side effects, participant satisfaction) and changes in fatigue, depression, anxiety, pain, and health-related quality of life. Methods: Participants were assigned alternately and consecutively to the HRV-BF intervention or Treatment-as-usual (TAU), in a predefined 1:1 sequence (quasirandom assignment). The intervention consisted of 10 HRV-BF sessions, held twice weekly over 5 weeks, with each session including a 10 min respiratory preparation and 40 min of active training. Results: The overall drop-out rate was low (5.56%), and participants reported a generally high level of satisfaction. Regarding side effects, the mean total Simulator Sickness Questionnaire score was 24.31 (SD = 35.42), decreasing to 12.82 (SD = 15.24) after excluding an outlier. A significantly greater improvement in severe fatigue was observed in the experimental group (H = 4.083, p = 0.043). When considering all outcomes collectively, a tendency toward improvement was detected in the experimental group (binomial test, p < 0.0001). Conclusions: HRV-BF appears feasible and well tolerated. Findings support the need for Phase III trials to confirm its potential in mitigating fatigue in Long COVID. Full article

Traditional relaxation techniques such as meditation and slow breathing often rely on subjective self-assessment, making it difficult to objectively monitor physiological changes. Electrocardiograms (ECG), which are commonly used by clinicians, provide one-dimensional signals to interpret cardiovascular activity. In this study, we introduce a visual interpretation framework that transforms heart rate variability (HRV) time series into fuzzy recurrence plots (FRPs). Unlike ECGs’ linear traces, FRPs are two-dimensional images that reveal distinctive textural patterns corresponding to autonomic changes. These visually rich patterns make it easier for even non-experts with minimal training to track changes in relaxation states. To enable automated detection, we propose a multi-domain feature fusion framework suitable for wearable systems. HRV data were collected from 60 participants during spontaneous and slow-paced breathing sessions. Features were extracted from five domains: time, frequency, non-linear, geometric, and image-based. Feature selection was performed using the Fisher discriminant ratio, correlation filtering, and greedy search. Among six evaluated classifiers, support vector machine (SVM) achieved the highest performance, with 96.6% accuracy and 100% specificity using only three selected features. Our approach offers both human-interpretable visual feedback through FRP and accurate automated detection, making it highly promising for objectively monitoring real-time stress and developing biofeedback systems in wearable devices. Full article

(1) Background: Biofeedback and neurofeedback are gaining attention as non-invasive rehabilitation strategies in Parkinson’s disease (PD) treatment, aiming to modulate motor and non-motor symptoms through the self-regulation of physiological signals. (2) Objective: This review explores the application of biofeedback techniques, electromyographic (EMG) biofeedback, heart rate variability (HRV) biofeedback, and electroencephalographic (EEG) neurofeedback in PD rehabilitation, analyzing their impacts on motor control, autonomic function, and cognitive performance. (3) Methods: This review critically examined 15 studies investigating the efficacy of electromyographic (EMG), heart rate variability (HRV), and electroencephalographic (EEG) feedback interventions in PD. Studies were selected through a systematic search of peer-reviewed literature and analyzed in terms of design, sample characteristics, feedback modality, outcomes, and clinical feasibility. (4) Results: EMG biofeedback demonstrated improvements in muscle activation, gait, postural stability, and dysphagia management. HRV biofeedback showed positive effects on autonomic regulation, emotional control, and cardiovascular stability. EEG neurofeedback targeted abnormal cortical oscillations, such as beta-band overactivity and reduced frontal theta, and was associated with improvements in motor initiation, executive functioning, and cognitive flexibility. However, the reviewed studies were heterogeneous in design and outcome measures, limiting generalizability. Subgroup trends suggested modality-specific benefits across motor, autonomic, and cognitive domains. (5) Conclusions: While EMG and HRV systems are more accessible for clinical or home-based use, EEG neurofeedback remains technically demanding. Standardization of protocols and further randomized controlled trials are needed. Future directions include AI-driven personalization, wearable technologies, and multimodal integration to enhance accessibility and long-term adherence. Biofeedback presents a promising adjunct to conventional PD therapies, supporting personalized, patient-centered rehabilitation models. Full article

Background: A commonly observed phenomenon is that although the players in a baseball team have received the same training content and volume, their batting performance is quite different. As no optimal solution exists for this problem at present, this study attempted to explore the potential of heart rate variability biofeedback (HRVB) to reduce anxiety and improve batting performance in university baseball players. Materials and Methods: A total of 18 college baseball players were randomly divided into an experimental group and a control group. Both groups answered questionnaires and had their physiological signals and batting performance measured on the first and last days of the experiment (i.e., days 0 and 10, respectively). Only the experimental group received HRVB training between the first and last days (10 days in total). Results: The results showed that before training, no significant differences were found in physiological, psychological, or performance parameters between the two groups. Compared to the control group, following HRVB training, the experimental group showed a notable decrease in cognitive anxiety (before HRVB: 23.56 ± 4.07; after HRVB: 20.11 ± 4.78; p < 0.05) and their batting performance improved significantly (batting score increased from 9.8 ± 11.7 to 19.8 ± 12.0 after HRVB; p < 0.05). Conclusions: This study validated that the use of HRVB can help to improve batting performance and reduce anxiety in college baseball players. Therefore, HRVB can be applied before competition matches, helping the players to perform better. Full article

Cardiovascular diseases pose a significant threat to global health, and cardiac rehabilitation (CR) has become a critical component of patient care. Heart Rate Variability Biofeedback (HRVB) is a non-invasive approach that helps modulate the Autonomic Nervous System (ANS) through Resonance Frequency (RF) breathing, supporting CR for cardiovascular patients. However, traditional HRVB techniques rely heavily on manual RF selection and face-to-face guidance, limiting their widespread application, particularly in home-based CR. To address these limitations, we propose a remote human-computer collaborative HRVB system, “FreeResp”, which features autonomous RF adjustment through a simplified cognitive computational model, eliminating the reliance on therapists. Furthermore, the system integrates wearable technology and the Internet of Things (IoT) to support remote monitoring and personalized interventions. By incorporating tactile guidance technology with an airbag, the system assists patients in performing diaphragmatic breathing more effectively. FreeResp demonstrated high consistency with conventional HRVB methods in determining RF values (22/24) from 24 valid training samples. Moreover, a one-month home-based RF breathing training using FreeResp showed significant improvements in Heart Rate Variability (HRV) (p < 0.05). These findings suggest that FreeResp is a promising solution for home-based CR, offering timely and precise interventions and providing a new approach to long-term cardiovascular health management. Full article

Background/Objectives: For the rapid, objective characterization of the physiological stress response, there is currently no generally recognized standard. The stress measurement methods used in practice (e.g., for psychological measures of stress) are often subjective, or in the case of biological markers (e.g., cortisol, amylase), they usually require a blood test. For this reason, the use of heart rate variability (HRV) to characterize stress has recently come to the fore. HRV is the variability in the length of heartbeat intervals, which indicates the ability of the heart to respond to various physiological and environmental stimuli. However, the conventional HRV metrics are not corrected for heart rate dependence; hence, they fail to fully account for the complex physiology of stress and relaxation. In order to remedy this problem, here we introduce a novel HRV parameter, the normalized variability derived from an RMSSD “Master Curve”, and we compare it with the conventional metrics. Methods: In Study 1, the relaxation state was induced either by heart rate variability biofeedback training (N = 21) or by habitual relaxation (N = 21), while in Study 2 (N = 9), the Socially Evaluated Cold Pressor Test and the Socially Evaluated Stroop Test were used to induce stress in the subject. For a statistical evaluation of the data, the Kolmogorov–Smirnov test was used to compare the distributions of mean HR, log(RMSSD), log(SDNN), and normalized variability before, during, and after relaxation and stress. Results: The results of this study indicate that while log(RMSSD) and log(SDNN) did not change significantly, the normalized variability did undergo a significant change both in relaxation states and in stress states induced by the Socially Evaluated Cold Pressor Test. Conclusions: Overall, we suggest this novel type of normalized variability ought to be used as a sensitive stress indicator, and in general, for the characterization of the complex processes of the vegetative nervous system. Full article

Background: The role of autonomic nervous system (ANS) modulation in chronic neck pain remains elusive. Transcutaneous vagus nerve stimulation (t-VNS) provides a novel, non-invasive means of potentially mitigating chronic neck pain. This study aimed to assess the effects of ANS modulation on heart rate variability (HRV), pain perception, and neck disability. Methods: In this double-blind randomized clinical trial, 102 participants with chronic neck pain were randomly allocated to one of three groups: t-VNS plus standard-care physiotherapy (SC-PT), heart rate variability biofeedback (HRV-BF) with SC-PT, or SC-PT alone. Interventions were administered three times weekly for 6 weeks. The following outcome measures were assessed at baseline and after 6 weeks: HRV, the visual analog scale (VAS), the pressure pain threshold (PPT), and the neck disability index (NDI). Results: The t-VNS group exhibited significant improvements compared to the HRV-BF and SC-PT groups. Specifically, t-VNS increased the RR interval (mean difference [MD] = 35.0 ms; p = 0.037) and decreased the average heart rate (MD = −5.4 bpm; p = 0.039). Additionally, t-VNS reduced the VAS scores (versus HRV-BF: MD = −0.8 cm, p = 0.044; SC-PT: MD = −0.9 cm, p = 0.018), increased the PPT (versus HRV-BF: MD = 94.4 kPa, p < 0.001; SC-PT (MD = 56.2 kPa, p = 0.001)), and lowered the NDI scores (versus HRV-BF: MD = −4.0, p = 0.015; SC-PT: MD = −5.9, p < 0.001). Conclusions: t-VNS demonstrated superior effectiveness compared to HRV-BF and SC-PT in regulating HRV, alleviating pain, and enhancing functional capabilities in individuals with chronic neck pain. Full article

Heart rate variability biofeedback (HRV BF) training aids adaptation to new climatic, geographical, and social environments. Neurophysiological changes during the HRV BF in individuals from tropical regions studying in the Arctic are not well understood. The aim of this study was to research electroencephalographic (EEG) changes during a single short-term HRV BF session in Indian and Russian students studying in the Russian Arctic. The Indian (n = 40) and Russian (n = 40) healthy students (age 19–21 years) at a medical university in Arkhangelsk (64°33′ N 40°32′ E) were studied. HRV and EEG parameters were measured at baseline (5 min) and during a short-term HRV BF session (5 min) to increase the total power (TP, ms²) of the HRV spectrum. The baseline heart rate and stress index levels were significantly higher in the Indian students. During the HRV BF sessions, the sympathetic activity decreased more significantly in Russian students, while the alpha EEG activity significantly increased across all brain regions in both groups. In Indian students, there was a notable increase in theta and beta1 EEG spectral power in the frontal, central, and temporal regions. HRV BF training in Indian students was associated with a more pronounced activation of brain systems compared with Russian students. Full article

Background/Objectives: Chronic low back pain (CLBP) is highly prevalent and relevant in all medical fields. This study evaluated the safety and effectiveness of interdisciplinary fascia therapy (IFT) for CLBP, focusing on its potential to reduce pain intensity, disability, and regulate autonomic nervous system (ANS) activity. Methods: Nine participants with CLBP each underwent nine sessions of IFT, twice weekly. The intervention involved a 12-grip manual sequence targeting deep paravertebral myofascial structures, complemented by heart rate variability (HRV) biofeedback training twice daily for 15 min. Pain and quality-of-life measures were assessed using the Brief Pain Inventory (BPI) questionnaire at baseline, mid-treatment (4th session), and post-treatment (9th session). HRV metrics were monitored with a 24 h ECG Holter device before and after the treatment period. Statistical analyses included paired t-tests, Wilcoxon signed-rank tests, and Cohen’s d for effect size. Results: Significant reductions in pain levels were observed across all subjective BPI measures, including momentary, strongest, minimal, and average pain scores (p < 0.001), with 83% and 87% reductions in pain intensity and disability, respectively. Quality-of-life indicators such as mood, sleep, and enjoyment of life showed significant improvements (p < 0.001). While only one HRV metric (rMSSD) achieved statistical significance, other HRV measures indicated medium to large effect sizes, suggesting favorable trends in ANS regulation. Conclusions: IFT demonstrated significant effects on subjective BPI pain reduction and quality of life, alongside potential regulatory impacts on ANS activity in individuals with CLBP. These results support the use of IFT as an effective intervention for pain management in CLBP and ANS regulation, meriting further exploration. Full article