Heart rate variability biofeedback using different breathing rates: a randomized study

ISRCTN	ISRCTN17808563
DOI	https://doi.org/10.1186/ISRCTN17808563
Sponsors	Central Institute for Labour Protection, Ministry of Science and Higher Education
Funder	Centralny Instytut Ochrony Pracy - Państwowy Instytut Badawczy

Submission date: 31/12/2025
Registration date: 20/01/2026
Last edited: 20/01/2026

Recruitment status: No longer recruiting
Overall study status: Completed
Condition category: Mental and Behavioural Disorders

Prospectively registered

Protocol

Statistical analysis plan

Results

Individual participant data

Record updated in last year

Plain English summary of protocol

Not provided at time of registration

Contact information

Ms Sylwia Sumińska
Public, Scientific, Principal investigator

Central Institute for Labour Protection - National Research Institute
Czerniakowska 16
Warsaw
00-701
Poland

ORCID ID	0000-0003-1335-3385
Phone	+48 (0)22 623 32 06
Email	sysum@ciop.pl

Study information

Primary study design	Interventional
Allocation	Randomized controlled trial
Masking	Open (masking not used)
Control	Uncontrolled
Assignment	Parallel
Purpose	Basic science
Scientific title	Effects of heart rate variability biofeedback using individualized resonance frequency versus fixed-rate breathing on psychological outcomes, resting heart rate variability, and physiological stress responses in adults with elevated stress: a randomized controlled trial
Study objectives	1. To evaluate whether heart rate variability biofeedback (HRV-B) training with individually determined resonance frequency (RF) leads to greater improvements in self-reported psychological outcomes (perceived stress, anxiety, and depressive symptoms) and resting heart rate variability compared with HRV-B performed at a fixed breathing rate of 0.1 Hz. 2. To examine the effects of HRV-B training on affective and autonomic responses to an experimentally induced mental stressor, including stress reactivity and post-stress recovery, in comparison with a waitlist control group. 3. To assess whether repeated HRV-B training and daily home practice influence the subjective affective experience of slow-paced breathing at 0.1 Hz, making the task more relaxing over time.
Ethics approval(s)	Approved 15/11/2021, Ethics Committee for Research with Human Participations of Warsaw University of Life Sciences in Poland (Instytut Nauk o Żywieniu Człowieka, Szkoła Główna Gospodarstwa Wiejskiego w Warszawie, Nowoursynowska 159c, Warsaw, 02-776, Poland; +48 (0)22 59 37 010; inzc@sggw.edu.pl), ref: 48/2021
Health condition(s) or problem(s) studied	Prevention of psychological difficulties in healthy individuals with elevated stress levels
Intervention	Participants were randomly assigned to one of three study groups: 1. HRV biofeedback with individually determined resonance frequency (RF Group), 2. HRV biofeedback at a fixed breathing rate of 0.1 Hz (0.1 Hz Group), 3. A waitlist control group (Control Group). Randomization was performed using a computer-generated simple randomization sequence with a 1:1:1 allocation ratio. Group assignment was concealed from participants until completion of baseline assessments. Participants in both intervention groups received heart rate variability biofeedback (HRV-B) training over a 4-week period. The intervention consisted of weekly individual laboratory sessions and daily home practice. Laboratory sessions were conducted once per week, lasted approximately 40 minutes, and were delivered individually. During the sessions, participants were instructed in slow-paced breathing techniques, including diaphragmatic breathing, relaxation breathing, and prolonged exhalation, with explicit guidance to avoid hyperventilation. Participants practiced slow-paced breathing while receiving real-time visual feedback of heart rate (cardiotachogram) and respiration. HRV-B training was delivered using Biograph Infiniti software and standard training protocols provided by the biofeedback equipment manufacturer (Thought Technology Ltd., Montreal, Canada). Participants were instructed to practice slow-paced breathing at home for 20 minutes using a provided visual breathing pacer. The two HRV-B groups differed only in the breathing frequency applied: 1. RF Group: The breathing rate was individually determined based on each participant’s resonance frequency, assessed during a standardized RF evaluation procedure. This breathing rate was used during both laboratory sessions and home practice. 2. 0.1 Hz Group: The breathing rate was fixed at 0.1 Hz (6 breaths per minute) for both laboratory sessions and home practice, regardless of the individual RF assessment. For both intervention groups, the inhalation-to-exhalation ratio was set at 4:6 during laboratory sessions and home practice. Participants assigned to the Control Group received no intervention during the 4-week study period (waitlist control). They completed the same pre- and post-intervention assessments as the intervention groups. After completion of the final assessment, participants in the Control Group were offered the opportunity to take part in the HRV-B training. No follow-up assessments were conducted after the post-intervention measurement.
Intervention type	Behavioural
Primary outcome measure(s)	Stress, symptoms of anxiety and depression measured using Depression Anxiety and Stress Scale (DASS-21) at immediately after completion of the intervention Resing heart rate variability measured using electrocardiography (ECG) at immediately after completion of the intervention Affect measured using the Swedish Core Affect Scale (SCAS) at during intervention and immediately after completion of the intervention Physiological reaction to laboratory-induced mental stress measured using electrocardiography (ECG), surface electromyography (sEMG), electrodermal activity (EDA), blood volume pulse (BVP), respiratory rate, and skin temperature of the hand at immediately after completion of the intervention
Key secondary outcome measure(s)
Completion date	30/11/2022

Eligibility

Participant type(s)
Age group	Adult
Lower age limit	25 Years
Upper age limit	40 Years
Sex	All
Target sample size at registration	88
Total final enrolment	88
Key inclusion criteria	1. Age between 25 and 40 years 2. All sexes 3. High self-reported stress levels
Key exclusion criteria	1. Chronic diseases (e.g., diabetes) 2. Psychiatric disorders (e.g., depressive disorders, anxiety disorders) 3. Neurological disorders (e.g., epilepsy) 4. Cardiovascular diseases (e.g., hypertension, heart failure, myocardial infarction, arrhythmias) 5. Respiratory diseases (e.g., asthma) 6. Substance use disorders or addiction to psychoactive substances (e.g., alcohol, nicotine) 7. Use of medications affecting the central nervous system or cardiovascular system (e.g., hypnotics, antidepressants, anxiolytic medications, cardiovascular medications) 8. Current participation in psychotherapy 9. Regular practice of breathing-based techniques (e.g., yoga, meditation, breathing exercises) 10. Pregnancy
Date of first enrolment	01/02/2022
Date of final enrolment	31/10/2022

Locations

Countries of recruitment

Poland

Study participating centres

Results and Publications

Individual participant data (IPD) Intention to share	Yes
IPD sharing plan summary	Stored in publicly available repository
IPD sharing plan	The datasets generated during and/or analysed during the current study will be stored in a publicly available repository (the Zenodo repository, doi: 10.5281/zenodo.17733890). All shared data will be fully anonymized to protect participant confidentiality. Data will include de-identified questionnaire responses, resting HRV measurements, and physiological parameters recorded during laboratory procedures. The datasets will be accessible upon publication of the study results and will remain available indefinitely. Access to the data will be unrestricted for researchers, who may use it for secondary analyses or meta-analyses. There are no additional ethical or legal restrictions beyond the protection of participant privacy.

Editorial Notes

02/01/2026: Study's existence confirmed by the Ethics Committee for Research with Human Participations of Warsaw University of Life Sciences in Poland.