Breathing is the only autonomic function you can consciously control — making it a direct lever on your nervous system. Long exhales activate the parasympathetic branch; short, powerful breaths activate the sympathetic branch.
What's actually happening
Exhale length
Longer exhales increase vagal tone, slowing heart rate via the baroreflex.
CO₂ regulation
The urge to breathe is triggered by CO₂ buildup, not lack of oxygen.
Nose vs mouth
Nasal breathing produces nitric oxide, dilating blood vessels and filtering air.
Consistency
5–10 min daily of coherence breathing does more long-term than occasional sessions.