A symmetric cycle used by Navy SEALs and in CBT for anxiety: 4 s inhale, 4 s hold, 4 s exhale, 4 s hold. It rapidly regulates arousal and acute anxiety.
5 minutes, 1–3 times a day. You can start with 3 s cycles for each phase and work up to 4–5 s. Especially useful before predictable stressful situations.
In practice
5 minutes, 1–3 times a day. You can start with 3 s cycles for each phase and work up to 4–5 s. Especially useful before predictable stressful situations.
Precautions
Very safe. It may cause dizziness at first; sit down. Do not force the breath hold in pregnancy, severe COPD, acute glaucoma, or poorly controlled hypertension.
Effect by goal · level of evidence
Acute anxiety and arousal
improvesModerateRCT (AA)
Reduces acute arousal
Stanford randomized trial 2023: 5 min/day for 28 days significantly reduces anxiety and improves mood. Acute effect after the first session.
Acutely increases RMSSD and HF-HRV, similar to other slow breathing. Effect lower than 5.5 breaths/min in maximizing HRV but easier to sustain because of its symmetrical rhythm.
Cognitive performance under stress
improves (modest)Low-moderatemilitary trials (AA)
Operational use
Documented in military/tactical programs: improves decision-making under extreme stress. Extrapolation to civilian settings is reasonable but lacks double-blind RCTs.
Information, not medical advice. Scientific evidence reflects the quality of the studies.