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

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.

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