Effects of Nature-Based Virtual Reality and Binaural Beats on Heart Rate Variability and Relaxation: A Controlled Within-Subject Study

Psychological stress contributes to cardiovascular risk through dysregulation of the autonomic nervous system. Immersive virtual reality environments and binaural auditory stimulation have each shown stress-reducing effects, but their combined physiological impact remains insufficiently investigated. The DESTRESS research program (NCT05036538) evaluates these interventions in cardiac surgical patients. To isolate intervention-specific mechanisms independent of medical conditions, the VRELAX study was designed as a non-clinical sub-study with a randomized cross-over design in adult participants. Each participant undergoes two experimental conditions in counterbalanced order. A 30-minute immersive nature-based virtual reality exposure combined with binaural beats decreasing from alpha to delta frequency range (10-1 Hz). And a everyday cognitive activities without relaxation intervention. Sessions are separated by a 1 day intervention-free interval to reduce carryover effects. Heart rate variability is continuously measured using a validated chest-strap sensor. Subjective stress is assessed pre- and post-condition visual analogue scales. The primary outcome is HF-power of heart rate variability as an indicator of parasympathetic activation and physiological relaxation. Secondary outcomes are additional HRV parameters (root mean square of successive differences (RMSSD), number of successive normal-to-normal intervals differing by more than 50 milliseconds (NN50), percentage of successive normal-to-normal intervals differing by more than 50 milliseconds (pNN50), normalized high-frequency power of heart rate variability (HF%)), subjective stress ratings, and feasibility of independent intervention use based on participant instruction. By investigating physiological relaxation mechanisms in a non-clinical population, the study allows interpretation of intervention-specific effects independent of disease, medication, or perioperative factors. The findings will provide mechanistic context for the clinical DESTRESS trial and evaluate whether an easily implementable immersive relaxation procedure may serve as a preventive approach for reducing everyday and work-related stress.