How to Activate the Vagus Nerve. This video guides you through the 4-2-6-2 breathing exercise (Inhale for 4, hold for 2, exhale for 6, hold for 2), a simple way to activate your vagus nerve and calm your body. How It Works to Activate the Vagus Nerve. The longer exhale signals your parasympathetic nervous system (your “rest and digest” mode) to relax and reset. When you exhale, your vagus nerve releases a neurotransmitter called acetylcholine, which slows your heart rate and activates your paras