Acute Stress Reaction, Healthy, Healthy Adult Participants, Stress Biomarkers
Conditions
Keywords
Breathwork, Coherent Breathing, Resonance Breathing, Heart Rate Variability, Maastricht Acute Stress Test (MAST), Cortisol
Brief summary
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: * Does slow, steady breathing at 6 breaths per minute lower physical stress markers (like heart rate variability and cortisol) better than faster, but structured breathing or just sitting still? * Is the calming effect caused by the specific breathing rhythm or simply by performing a structured, relaxing activity? Researchers will compare three groups to see if the specific rhythm of "coherent breathing" offers unique benefits: 1. Group (Interventional): Coherent Breathing: Slow breathing at 6 breaths per minute. 2. Group (Sham Breathing): Regular breathing at 15 breaths per minute (matching a natural pace). 3. Spontaneous Breathing (Control Group): Natural, unguided breathing. Participants will: * Complete a one-day preparation phase to become familiar with the breathing technique. * Visit the research center for one experimental session. * Perform their assigned breathing method before and after a stress test. * Take the Maastricht Acute Stress Test (MAST), which involves putting a hand in cold water and doing mental math. * Provide saliva samples and have their heart rate variability, and mood measured multiple times.
Detailed description
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: * Heart Rate Variability: RR interval (time duration between successive heartbeats, specifically the time intervals between each R-wave peak) data is collected using a Polar H10 heart rate monitor. To ensure data integrity and redundancy, the signal is recorded simultaneously through two mobile applications: Elite HRV and Kubios HRV. All subsequent advanced HRV analyses, including time-domain, frequency-domain, and non-linear indices (e.g., PNS/SNS Index \[Parasympathetic Nervous System Index and Sympathetic Nervous System Index\], RMSSD \[Root Mean Square of Successive Differences\]), are performed using Kubios HRV Scientific software. * Biochemical Markers: Salivary cortisol levels are measured to assess the hypothalamic-pituitary-adrenal (HPA) axis response using ELISA kits. * Psychological Scales: Subjective stress and anxiety are tracked using the STAI-VAMS. 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: 1. Coherent Breathing (6 bpm): Guided nasal diaphragmatic breathing (5.5 s inhale / 5.5 s exhale) focused on inducing cardiorespiratory resonance. 2. Sham Breathing (15 bpm): Guided breathing at a natural pace (2 s inhale / 2 s exhale) to control for the effects of a structured intervention. 3. Spontaneous Breathing (Control): Passive resting with eyes closed, serving as a neutral baseline for the natural course of the stress response.
Interventions
BEHAVIORALCoherent Breathing (6 bpm)
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
BEHAVIORALSham Breathing (15 bpm)
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
Sponsors
Medical University of Bialystok
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
SINGLE (Subject)
Masking description
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
Intervention model description
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.
Eligibility
Sex/Gender
ALL
Age
18 Years to 60 Years
Healthy volunteers
Yes
Inclusion criteria
* Healthy adults * Aged 18 to 60 years * Willingness to participate in all study phases, including preparation and laboratory session. * Professionally active individuals or university students.
Exclusion criteria
* Severe chronic diseases, including metabolic disorders (e.g., diabetes) and mental disorders. * Cardiac arrhythmia, history of heart attacks, strokes, or heart surgery. * Regular use of medications such as anxiolytics or beta-blockers (excluding hormonal contraception) * Pregnancy. * Current participation in other scientific experiments. * Significant previous experience with breathing techniques or current independent breathwork/meditation practice (defined as regular practice for more than 7 days/monthly within the last 12 months). * Professional sports practice. * Raynaud's disease * Inability to abstain from alcohol, caffeine, and nicotine for the required periods before the experiment
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in Root Mean Square of Successive (RMSSD) | 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. | 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. |
| Change in PNS Index | 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. | 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. |
| Change in Salivary Cortisol Concentration | 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. | 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). |
| Change in STAI-State score | 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. | 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. |
| Change in Mean HR | 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 measured in beats per minute (bpm). This serves as a fundamental indicator of physiological arousal and autonomic nervous system activity. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in SNS Index | 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. | 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. |
| Change in Diastolic Blood Pressure (DBP) | 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 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. |
| Change in Subjective Stress (VAMS) | 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. | 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. |
| Mean Heart Rate (Mean HR) during Experimental Blocks | 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. | Continuous monitoring of mean heart rate (bpm) during active interventions and stress induction to evaluate real-time physiological reactivity and recovery dynamics. |
| SNS Index during Stress Induction | Average score measured during one 10-minute period starting at approximately 35 minutes (Stress Induction) after Baseline during the single experimental Day 3. | 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. |
| Change in Standard Deviation of NN intervals (SDNN) | 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. | 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. |
| SNS index during Intervention Blocks | 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. | 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. |
| Change in LF power log (ln LF) | 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. | The natural logarithm of the HRV absolute power in the low-frequency band (0.04 - 0.15 Hz). |
| Change in Log-transformed High-Frequency HRV Power (ln HF) | 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. | The natural logarithm of the HRV absolute power in the high-frequency band (0.15 - 0.40 Hz). |
| PNS Index during Stress Induction | Average score measured during one 10-minute period starting at approximately 35 minutes (Stress Induction) after Baseline during the single experimental Day 3. | 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. |
| PNS index during Intervention Blocks | 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. | 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. |
| Change in Systolic Blood Pressure (SBP) | 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 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. |
| Change in Subjective Mental Tension (VAMS) | At Baseline (0 minutes), and at approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. | 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. |
| Change in Subjective Calmness (VAMS) | At Baseline (0 minutes), and at approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. | 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. |
| Change in Subjective Relaxation (VAMS) | At Baseline (0 minutes), and at approximately 25, 45, 60, and 75 minutes after Baseline during the single experimental session on Day 3. | 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. |
Countries
Poland
Outcome results
None listed