RSA is the natural variation in heart rate that is primarily driven by breathing patterns and the regulating influence of the vagus nerve on the heart. For example, inhaling inhibits the activity of the vagus nerve, increases heart rate, and decreases HRV. Exhaling activates the vagus nerve, decreases heart rate, and increases HRV.
RSA is also influenced by the baroreceptors (pressure sensors that help regulate your heart rate and blood pressure) and the limbic system in the brain (your emotion center).
RSA is considered an accurate window into the autonomic nervous system (ANS). The greater the “rhythmic” variation in heart rate, the healthier the system. A simple way to think about this is, if at rest heart rate is varying between 80 and 60 beats per minute (bpm), that is better than varying between 65 and 70 bpm. High RSA (more variation) is indicative of resilience and health; low RSA is indicative of vulnerability to stress and disease.
RSA naturally decreases with age. Interestingly, it is possible to increase RSA through slow breathing, meditation and exercise.
###