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This study investigates whether the psychophysiological benefits of breathing exercises are driven by a specific physiological rhythm (6 breaths per minute) or by the general psychological experience of performing a structured, mindful activity. Researchers aim to determine if "coherent breathing", which is hypothesized to synchronize heart and respiratory rhythms, offers unique physiological protection against stress compared to breathing at a natural pace or simple resting. The main questions it aims to answer are:
Researchers will compare three groups to see if the specific rhythm of "coherent breathing" offers unique benefits:
Participants will:
This three-arm randomized controlled trial is designed to investigate whether the therapeutic benefits of slow-paced breathing stem from specific physiological mechanisms (cardiorespiratory resonance) or non-specific psychological factors, such as attention, expectancy, and structured relaxation.
The study directly compares resonant-frequency breathing against a structurally identical sham intervention and a passive control group.
Experimental Protocol:
The study utilizes the Maastricht Acute Stress Test (MAST) as a highly structured and validated laboratory stressor to capture the dynamic psychophysiological response to acute distress.
The protocol consists of the following phases:
Baseline Phase (BASE): A 5-minute measurement of baseline physiological (HRV - Heart Rate Variability) and psychological (STAI-S - State-Trait Anxiety Inventory-State, VAMS - Visual Analogue Mood Scales) parameters.
First Intervention (10 min): Participants perform their assigned breathing technique or sit quietly to assess the preventive "buffering" effect of the intervention.
Acute Stress Induction (MAST): A 15-minute structured stressor combining periods of hand immersion in cold water and mental arithmetic under social-evaluative pressure. The water temperature is strictly maintained within the range of 4.5 - 5.5 °C using a TECO chiller to ensure consistent stress induction across all participants.
Post-Stress Recovery (POST): Immediate 5-minute measurement following the conclusion of the MAST protocol.
Second Intervention (10 min): A repeat of the breathing/control protocol to evaluate its impact on psychophysiological recovery.
Final Assessments (END & FOLLOW): Measurements are taken immediately after the second intervention and following a 15-minute recovery phase to capture the peak glucocorticoid (cortisol) response.
Data Collection and Analysis:
Adherence Check: Participant adherence to the paced breathing protocols is verified using the Kubios RESP (respiratory rate estimation) algorithm. This software-based solution extracts respiratory frequency from the RR interval data to confirm that participants maintained the target rates of 6 bpm (breaths per minute) or 15 bpm.
Research Arms:
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Coherent Breathing (6 bpm) | Experimental | Participants perform 10 minutes of guided nasal diaphragmatic breathing at a rate of 6 breaths per minute (~0.1 Hz). The practice involves a 5.5-second inhalation and 5.5-second exhalation phase, guided by rhythmic audio bell cues (low tone for inhale, high tone for exhale). Participants focus on abdominal movement and sensations of air flow. This intervention is performed twice: once before the acute stressor (MAST) and once during the recovery phase. |
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| Sham Breathing (15 bpm) | Sham Comparator | Participants perform 10 minutes of guided nasal diaphragmatic breathing at a rate of 15 breaths per minute, which matches a natural spontaneous breathing pace. The practice involves a 2.0-second inhalation and 2.0-second exhalation phase, guided by identical rhythmic audio bell cues as the experimental arm. This arm mimics the structural and attentional components of the active intervention without inducing cardiorespiratory resonance. Performed twice: before and after the MAST protocol. |
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| Spontaneous Breathing (Control) | No Intervention | Participants in this passive control group sit quietly with their eyes closed for 10 minutes. They receive initial brief relaxation instructions (two deep breaths with a sigh, body muscles relaxation) but do not receive any specific rhythmic guidance, audio cues, or instructions to modulate their breathing pattern. This arm serves as a baseline to control for the natural course of the stress response and the passage of time. |
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Coherent Breathing (6 bpm) | Behavioral | A 10-minute session of guided nasal diaphragmatic, coherent breathing. Participants follow rhythmic audio bell cues: a low tone for a 5.5-second inhalation and a high tone for a 5.5-second exhalation. Instructions emphasize silent, gentle nasal breathing and abdominal (diaphragmatic) expansion without lifting the shoulders. Participants are asked to focus their attention on the sensations of air flow or abdominal movement throughout the session. The intervention is performed twice: before and after the stress protocol |
| Measure | Description | Time Frame |
|---|---|---|
| Change in Root Mean Square of Successive (RMSSD) | The Root Mean Square of Successive Differences (RMSSD) measured in milliseconds (ms). This is a time-domain HRV parameter used to assess parasympathetic nervous system activity. An increase indicates higher parasympathetic activity, while a decrease indicates a stress response. | Measured at 5 time points: at Baseline (0 minutes), and approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| Change in PNS Index | This outcome measure is reported as a single composite score (standardized Z-score) representing the aggregated modulation of vagal activity. The final value is automatically calculated by Kubios HRV Scientific software from the mathematical combination of three specific assessments: mean RR interval, RMSSD, and the non-linear SD1 parameter, normalized against a reference database. Only the final aggregated Z-score will be reported as the endpoints for these measures. A value of 0 represents the population average; positive values indicate enhanced parasympathetic tone and recovery capacity. | Measured at 5 time points: at Baseline (0 minutes), and approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| Change in Salivary Cortisol Concentration | Concentration Measured via enzyme-linked immunosorbent assay (ELISA) in nmol/L. This neuroendocrine marker assesses the activation of the hypothalamic-pituitary-adrenal (HPA) axis. It is used to quantify the objective impact of the breathing intervention on the peak hormonal stress response (typically reaching maximum concentration 15-30 minutes after the stressor). | Measured at 5 time points: at Baseline (0 minutes), and approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| Change in STAI-State score | A validated self-report questionnaire used to measure the current intensity of anxiety, tension, and nervousness. Scores range from 20 to 80, with higher scores indicating greater subjective psychological distress. |
| Measure | Description | Time Frame |
|---|---|---|
| Change in SNS Index | This outcome measure is reported as a single composite score (standardized Z-score) representing the aggregated physiological arousal and sympathetic activity. The final value is automatically calculated by Kubios HRV Scientific software from the mathematical combination of three specific assessments: mean heart rate (HR), Baevsky's Stress Index, and the non-linear SD2 parameter, normalized against a reference database. Only the final aggregated Z-score will be reported as the endpoints for these measures. Positive values indicate sympathetic dominance and physiological arousal, providing a quantitative measure of the "cost" of the stressor and the effectiveness of the intervention in reducing sympathetic overdrive. |
| Measure | Description | Time Frame |
|---|---|---|
| Depression Anxiety Stress Scales (DASS-21) | A 21-item self-report instrument used to characterize the participants' baseline psychological distress over the past week. Subscales for Depression, Anxiety, and Stress (scores 0-21 each) will serve as covariates to analyze the interaction between baseline state and intervention results. | At Baseline only (at the start of the Preparation Phase on Day 1). |
Inclusion Criteria:
Exclusion Criteria:
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Adam Siebieszuk, Master | Contact | +48 85 748 55 85 | adam.siebieszuk@sd.umb.edu.pl |
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Medical University of Bialystok. Department of Physiology. | Recruiting | Bialystok | Podlaskie Voivodeship | 15-222 | Poland |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 24746049 | Background | Dick TE, Hsieh YH, Dhingra RR, Baekey DM, Galan RF, Wehrwein E, Morris KF. Cardiorespiratory coupling: common rhythms in cardiac, sympathetic, and respiratory activities. Prog Brain Res. 2014;209:191-205. doi: 10.1016/B978-0-444-63274-6.00010-2. | |
| 35167847 | Background | Sevoz-Couche C, Laborde S. Heart rate variability and slow-paced breathing:when coherence meets resonance. Neurosci Biobehav Rev. 2022 Apr;135:104576. doi: 10.1016/j.neubiorev.2022.104576. Epub 2022 Feb 12. |
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Anonymized individual participant data that underlie the results reported in the published article (including HRV parameters, cortisol levels, and psychological scale scores) will be made available from the corresponding author upon reasonable request. Raw physiological signal files will not be shared to protect participant privacy. Data will be provided in a standardized tabular format (e.g., Excel or CSV).
Beginning 6 months and ending 36 months following article publication.
Data will be shared with qualified researchers who provide a methodologically sound proposal. Requests should be directed to the corresponding author (adam.siebieszuk@sd.umb.edu.pl). To gain access, data requestors will need to sign a data access agreement.
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| Type | Includes Protocol | Includes SAP | Includes ICF | Document Label | Document Date | Document Uploaded Date | Document File Name |
|---|---|---|---|---|---|---|---|
| Prot_SAP_ICF | Yes | Yes | Yes | Study Protocol, Statistical Analysis Plan, and Informed Consent Form | Feb 1, 2026 |
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This is a three-arm, single-blinded, randomized sham-controlled trial using a parallel assignment model. Participants are randomly assigned to one of three arms: the active intervention (coherent breathing at 6 breaths per minute), a sham-placebo control (paced breathing at 15 breaths per minute), or a passive control (spontaneous breathing). The study design is specifically intended to isolate the psychophysiological mechanisms of the 6 bpm rhythm from non-specific psychological factors, such as attention and participant expectancy.
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To ensure effective blinding, participants in the two breathing groups receive identical instructions focused on nasal diaphragmatic (abdominal) breathing and mindful attention to breath sensations. Both groups are guided by 10-minute audio tracks using rhythmic bell cues (low tone for inhalation, high tone for exhalation). The only difference between these groups is the interval between the bells (5.5 s for the 6 bpm group and 2.0 s for the 15 bpm group). Participants are not informed of the specific breathing rates or the names of the techniques to maintain cognitive blinding. To ensure protocol adherence and familiarity with the rhythmic cues, all participants perform a single 10-minute practice session at home using preparatory audio track (3 s interval) 1 day before the lab intervention. The spontaneous breathing (control group) remains open-label as it involves no rhythmic guidance; they receive only initial relaxation instructions and are asked to sit quietly & relax for 10 min
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| Sham Breathing (15 bpm) | Behavioral | A 10-minute session of guided nasal diaphragmatic breathing at a rate of 15 breaths per minute (matching a natural spontaneous pace). Participants follow identical rhythmic audio bell cues as the experimental group: a low tone for a 2.0-second inhalation and a high tone for a 2.0-second exhalation. All other instructions regarding nasal breathing, abdominal mechanics, and mindful attention are identical to the experimental group to ensure structural blinding. The intervention is performed twice: before and after the stress protocol |
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| Measured at 5 time points: at Baseline (0 minutes), and approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| Change in Mean HR | Mean heart rate measured in beats per minute (bpm). This serves as a fundamental indicator of physiological arousal and autonomic nervous system activity. | Measured at 5 time points: at Baseline (0 minutes), and approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| Measured at 5 time points: at Baseline (0 minutes), and approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| Change in Diastolic Blood Pressure (DBP) | Measured in millimeters of mercury (mmHg) using an automated sphygmomanometer. This metric serves as functional hemodynamic endpoint to verify the hypothesis that coherent breathing enhances baroreflex sensitivity and stabilizes blood pressure. | Measured at 5 time points: at Baseline (0 minutes), and approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| Change in Subjective Stress (VAMS) | A specific assessment of subjective stress intensity. Participants mark their current feeling on a 100 mm visual analogue scale (0-100), where 0 indicates "no stress" and 100 indicates "maximum stress" . Only this individual scale value is reported as the endpoint for this measure. | Measured at 5 time points: at Baseline (0 minutes), and approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| Mean Heart Rate (Mean HR) during Experimental Blocks | Continuous monitoring of mean heart rate (bpm) during active interventions and stress induction to evaluate real-time physiological reactivity and recovery dynamics. | Average heart rate measured during three 10-minute periods starting at approximately 10 minutes (First Intervention), 35 minutes (Stress Induction), and 55 minutes after Baseline during the single experimental Day 3. |
| SNS Index during Stress Induction | This outcome measure is reported as a single composite score (standardized Z-score) representing the aggregated physiological arousal and sympathetic activity. The final value is automatically calculated by Kubios HRV Scientific software from the mathematical combination of three specific assessments: mean heart rate (HR), Baevsky's Stress Index, and the non-linear SD2 parameter, normalized against a reference database. Only the final aggregated Z-score will be reported as the endpoint for this measure. | Average score measured during one 10-minute period starting at approximately 35 minutes (Stress Induction) after Baseline during the single experimental Day 3. |
| Change in Standard Deviation of NN intervals (SDNN) | A time-domain metric reflecting the total variability of heart rate rhythm, measured in milliseconds (ms). It represents the overall capacity of the autonomic nervous system to adapt to internal and external stimuli. | Measured at 5 time points: at Baseline (0 minutes), and approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| SNS index during Intervention Blocks | This outcome measure is reported as a single composite score (standardized Z-score) representing the aggregated physiological arousal and sympathetic activity. The final value is automatically calculated by Kubios HRV Scientific software from the mathematical combination of three specific assessments: mean heart rate (HR), Baevsky's Stress Index, and the non-linear SD2 parameter, normalized against a reference database. Only the final aggregated Z-score will be reported as the endpoint for these measures. | Average score measured during two 10-minute periods starting at approximately 10 minutes (First Intervention) and 55 minutes (Second Intervention) after Baseline during the single experimental Day 3. |
| Change in LF power log (ln LF) | The natural logarithm of the HRV absolute power in the low-frequency band (0.04 - 0.15 Hz). | Measured at 5 time points: at Baseline (0 minutes), and approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| Change in Log-transformed High-Frequency HRV Power (ln HF) | The natural logarithm of the HRV absolute power in the high-frequency band (0.15 - 0.40 Hz). | Measured at 5 time points: at Baseline (0 minutes), and approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| PNS Index during Stress Induction | This outcome measure is reported as a single composite score (standardized Z-score) representing the aggregated modulation of vagal activity. The final value is automatically calculated by Kubios HRV Scientific software from the mathematical combination of three specific assessments: mean RR interval, RMSSD, and the non-linear SD1 parameter, normalized against a reference database. Only the final aggregated Z-score will be reported as the endpoint for this measure. | Average score measured during one 10-minute period starting at approximately 35 minutes (Stress Induction) after Baseline during the single experimental Day 3. |
| PNS index during Intervention Blocks | This outcome measure is reported as a single composite score (standardized Z-score) representing the aggregated modulation of vagal activity. The final value is automatically calculated by Kubios HRV Scientific software from the mathematical combination of three specific assessments: mean RR interval, RMSSD, and the non-linear SD1 parameter, normalized against a reference database. Only the final aggregated Z-score will be reported as the endpoint for these measures. | Average score measured during two 10-minute periods starting at approximately 10 minutes (First Intervention) and 55 minutes (Second Intervention) after Baseline during the single experimental Day 3. |
| Change in Systolic Blood Pressure (SBP) | Measured in millimeters of mercury (mmHg) using an automated sphygmomanometer. This metric serves as functional hemodynamic endpoint to verify the hypothesis that coherent breathing enhances baroreflex sensitivity and stabilizes blood pressure. | Measured at 5 time points: at Baseline (0 minutes), and approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| Change in Subjective Mental Tension (VAMS) | A specific assessment of subjective mental tension intensity. Participants mark their current feeling on a 100 mm visual analogue scale (0-100), where 0 indicates "no tension" and 100 indicates "maximum tension" . Only this individual scale value is reported as the endpoint for this measure. | At Baseline (0 minutes), and at approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| Change in Subjective Calmness (VAMS) | A specific assessment of subjective calmness intensity. Participants mark their current feeling on a 100 mm visual analogue scale (0-100), where 0 indicates "no calm" and 100 indicates "maximum calm" . Only this individual scale value is reported as the endpoint for this measure. | At Baseline (0 minutes), and at approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| Change in Subjective Relaxation (VAMS) | A specific assessment of subjective relaxation intensity. Participants mark their current feeling on a 100 mm visual analogue scale (0-100), where 0 indicates "no relaxation" and 100 indicates "maximum relaxation" . Only this individual scale value is reported as the endpoint for this measure. | At Baseline (0 minutes), and at approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. |
| State-Trait Anxiety Inventory (STAI-Trait) | Measures the participant's stable tendency to respond with anxiety. Scores range from 20 to 80. This trait measure will be used to analyze how personality-level anxiety influences the physiological response to the stressor and breathing tasks. | At Baseline only (at the start of the experimental session on Day 3). |
| Respiratory Rate (RESP) | Objective verification of respiratory frequency (breaths per minute) derived from RR interval data using the Kubios RESP algorithm. This measurement is used as a manipulation check to confirm participant adherence to the assigned breathing protocols (6 bpm for the experimental group and 15 bpm for the sham group) and to ensure the internal validity of the experimental blocks. | Average respiratory rate measured during two 10-minute periods starting at approximately 10 minutes (First Intervention) and 55 minutes (Second Intervention) after Baseline during the single experimental Day 3. |
| 40843749 | Background | Siebieszuk A, Plonski AF, Baranowski M. Breathwork for Chronic Stress and Mental Health: Does Choosing a Specific Technique Matter? Med Sci (Basel). 2025 Aug 13;13(3):127. doi: 10.3390/medsci13030127. |
| 22608857 | Background | Smeets T, Cornelisse S, Quaedflieg CW, Meyer T, Jelicic M, Merckelbach H. Introducing the Maastricht Acute Stress Test (MAST): a quick and non-invasive approach to elicit robust autonomic and glucocorticoid stress responses. Psychoneuroendocrinology. 2012 Dec;37(12):1998-2008. doi: 10.1016/j.psyneuen.2012.04.012. Epub 2012 May 18. |
| 28469586 | Background | Shilton AL, Laycock R, Crewther SG. The Maastricht Acute Stress Test (MAST): Physiological and Subjective Responses in Anticipation, and Post-stress. Front Psychol. 2017 Apr 19;8:567. doi: 10.3389/fpsyg.2017.00567. eCollection 2017. |
| Apr 2, 2026 |
| Prot_SAP_ICF_000.pdf |
| ID | Term |
|---|---|
| D040701 | Stress Disorders, Traumatic, Acute |
| ID | Term |
|---|---|
| D040921 | Stress Disorders, Traumatic |
| D000068099 | Trauma and Stressor Related Disorders |
| D001523 | Mental Disorders |
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