Breathe better, live better: the science of slow breathing and heart rate variability.

Background: Slow breathing and heart rate variability (HRV) biofeedback have gained attention as non-invasive methods for enhancing autonomic regulation and promoting vagal tone. These techniques are associated with improvements in cardiovascular, respiratory, and neural outcomes, offering potential therapeutic applications for stress-related and chronic conditions.

Methods: A scoping review was conducted by analyzing six studies focusing on slow breathing and HRV biofeedback. The included studies involved healthy adults aged between 18 and 60 years, free from major cardiovascular, respiratory, or neurological disorders. Studies were identified through systematic searches in MEDLINE (PubMed), Scopus, Web of Science, and other databases. Population characteristics, intervention protocols, and outcomes related to HRV, respiratory sinus arrhythmia (RSA), baroreflex sensitivity, and neural synchronization were extracted and synthesized. Interventions were applied both acutely (single or short-term sessions) and chronically (ranging from daily sessions over 4-8 weeks).

Results: All six studies demonstrated significant improvements in HRV parameters, particularly the high-frequency (HF) band, reflecting enhanced parasympathetic activity. RSA increased significantly in studies utilizing tailored breathing patterns, especially those emphasizing longer exhalations. Baroreflex sensitivity improved in interventions combining HRV biofeedback and slow breathing, indicating better cardiovascular adaptability. One study reported neural synchronization between HRV and cortical potentials with decelerated breathing. Across studies, these interventions promoted relaxation, enhanced autonomic flexibility, and stabilized cardiovascular function. Autonomic flexibility refers to the dynamic ability of the autonomic nervous system to adapt to internal and external stressors by shifting between sympathetic and parasympathetic dominance.

Conclusions: Slow breathing and HRV biofeedback are effective, non-invasive interventions for improving autonomic regulation, vagal tone, and stress resilience. These techniques hold promise for managing chronic conditions and enhancing cardiovascular and mental health. Standardization of protocols and long-term evaluations are needed to optimize clinical implementation.