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Box breathing (4-4-4-4, tactical breathing)

Box breathing, also called square or tactical breathing, uses equal phases of inhaling, holding, exhaling and holding, and is widely promoted for acute stress. A 2026 systematic review found eight small randomised trials with mixed protocols: in several, box breathing gave short-term improvements in perceived stress, anxiety and mood, while physiological effects were inconsistent. In head-to-head studies it has not shown a clear advantage over slow breathing at about six breaths a minute, prolonged exhalation or cyclic sighing. No claim here reaches moderate certainty, because the trials of box breathing itself are few, small, short and use varied protocols and outcomes.

Evidence retrieved up to

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4 research claims

Marks

What the research shows

In small randomised trials of adults, short sessions of box breathing were followed by short-term improvements in perceived stress, state anxiety and mood compared with usual breathing or passive control, though results were not uniform across studies.

No known concerns at usual amountsBenefit

Who this is about

adults, mostly healthy volunteers and students

Details and sources

Practical note

Graded low: randomised trials, downgraded for imprecision (eight small trials in the 2026 systematic review, no pooled estimate) and inconsistency (varied protocols, populations and outcomes, effects described as non-uniform). Most studies tested a single session or a few minutes a day; the pattern in recent trials was about 4 seconds for each of the four phases, practised for 1 to 5 minutes.

Safety note

Breath holds are part of the pattern; a breathwork meta-analysis found no adverse events attributed to breathwork in the trials that reported on them, and its authors advise that clinicians consider whether breathwork may worsen symptoms of some mental or physical health conditions.

Sources

In a randomised trial of adults, box breathing practised before a laboratory social stress task blunted the rise in heart rate, state anxiety and salivary alpha-amylase compared with normal breathing, while heart rate variability and cortisol did not differ between groups.

No known concerns at usual amountsBenefit

Who this is about

adults undergoing a laboratory stress task

Details and sources

Practical note

Graded low: one randomised trial of 66 participants (22 per arm) with a modified virtual stress test, downgraded for imprecision and for inconsistency with other studies in which heart rate and heart rate variability responses were mixed. A crossover laboratory study of tactical breathing also found lower physiological arousal than with prolonged exhalation.

Sources

In head-to-head studies of healthy adults, box breathing has not shown a consistent advantage over other breathing techniques: breathing at about six breaths a minute raised heart rate variability more than square breathing, prolonged exhalation gave better task performance under stress, and mood and stress effects were similar across techniques.

No known concerns at usual amountsUnclear

Who this is about

healthy adults and students

Details and sources

Practical note

Graded low: a randomised trial and several within-subject comparisons, each small and mostly single-session, downgraded for imprecision and indirectness of short laboratory outcomes. In the one-month remote trial, the exhale-focused cyclic sighing arm showed the clearest gains in mood against mindfulness meditation; box breathing was one of three breathing arms.

Safety note

In one within-subject study, breathing at six breaths a minute led to mild over-breathing.

Sources

In military cadets, box breathing after maximal exercise was followed by faster recovery of high-frequency heart rate variability than spontaneous breathing, but effects on task performance are mixed, with slower reaction times after box breathing in one real-life study of students.

No known concerns at usual amountsUnclear

Who this is about

military cadets and tactical trainees

Details and sources

Practical note

Graded very low: single small randomised trials in specific groups, downgraded for imprecision, indirectness (surrogate recovery markers, simulator tasks, a student sample for the reaction-time finding) and inconsistency between performance outcomes. Tactical breathing is taught to military and police personnel; a marksmanship trial reported better first-shot scores with tactical breathing, but its abstract does not describe the breathing pattern used.

Sources