Vagal tone

Vagal tone describes the baseline activity of the vagus nerve, the primary parasympathetic pathway connecting the brainstem to organs including the heart, lungs, and gut. Higher vagal tone is associated with efficient heart-rate slowing during exhalation, faster post-stress recovery, and lower systemic inflammation. It is commonly estimated from RMSSD or high-frequency HRV. In longevity contexts, strengthening vagal tone through breathwork, exercise, and sleep is considered a modifiable resilience factor.