Effects on Heart Rate Variability and Salivary Cortisol of Slow Paced Breathing for Stress Management

Heart rate variability is commonly analyzed in the frequency domain to assess autonomic modulation. Imbalances between sympathetic and parasympathetic systems can affect cardiovascular and emotional health. Techniques such as slow-paced breathing, which activates the vagus nerve, can help restore this balance and are easily accessible, especially for teenagers in a school environment. This study evaluated the effects of slow-paced breathing of adolescents by measuring Respiratory Sinus Arrhythmia (RSA), salivary cortisol and Depression Anxiety Stress Scale-21 (DASS-21). For this, the RR intervals from ECG recordings collected during the slow-paced breathing protocol and RSA indices were analyzed in three distinct five-minute periods (REST, Slow-Paced Breathing and POST). Saliva samples were collected for analysis of salivary cortisol before and after respiratory therapy. The findings indicate that slow-paced breathing was able to modify the physiological response to stress, providing an acute reduction in heart rate, activation of vagal modulation, and consequently relaxation. The analysis of the correlation between salivary cortisol concentration and the Stress construct of the DASS-21 confirmed the reduction in stress levels after slow breathing exercise, suggesting that acute sessions of slow-paced breathing can help adolescents manage stress and promote relaxation in an accessible and non-invasive manner.