Breathwork and Stress: Investigating the Mechanisms of Action and Effectiveness of Breathing Interventions in Modulating the Psychophysiological Response to Acute Stress Test

Condition(s) studied

Investigational drug(s) / intervention(s)

Coherent 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

Sham 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

Study 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.

Eligibility

Primary outcome measure(s)

• 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.

Trial sites (1)

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