Short Breathing Exercises Blunted Heart Rate and Anxiety Under Stress

The trial enrolled 66 adults aged 18 to 39. They were randomly placed in one of three groups of 22: normal breathing, prolonged exhalation, or box breathing. A randomized trial is the strongest design for testing whether an intervention causes a change, though this one was small and short.

Box breathing follows a four-part cycle: a 4-second inhale, a 4-second pause, a 4second exhale and a 4-second pause. The prolonged exhalation method used periodic "physiological sighs." These are single deep breaths with a long exhale, mixed in with normal breathing.

Each person did their assigned breathing for 5 minutes just before a stress test. They did it again for 1 minute during the test, between the presentation and a mental challenge. The stressor was a modified, virtual version of the Trier Social Stress Test, a widely used lab method. Participants prepared a 5-minute job pitch, then delivered it over Zoom to a prerecorded video of two judges with neutral expressions.

The test worked as a stressor. According to the authors, it significantly raised heart rate, state anxiety (a self-reported measure of how anxious a person feels right now), salivary alpha-amylase and secretory immunoglobulin A. Alpha-amylase is a saliva enzyme often used as a marker of the body's "fight or flight" activity. Secretory immunoglobulin A is an antibody found in saliva.

Both breathing methods reduced the post-stress rises in heart rate, state anxiety and alpha-amylase compared with normal breathing. The authors conclude that brief breathing practice can buffer acute physiological stress responses. Their wording is cautious: the findings support short-term effectiveness for subjective and peripheral markers of stress.

The limits matter. Heart rate variability, which tracks the variation in time between heartbeats, did not differ across the three groups. Cortisol, the best-known stress hormone, did not differ either. Performance on the Stroop color-word task and on mental arithmetic was also statistically unchanged. So the breathing eased how anxious people felt and some body signals, but it did not improve thinking scores in this test.

Other cautions apply. The stress test was modified from the standard version, with a prerecorded panel, a shorter preparation time and breathing breaks built in. The authors call these meaningful deviations from the validated protocol. Participants were healthy and free of diagnosed anxiety, depression, ADHD and cardiovascular or metabolic disease. Results may not carry over to people with those conditions, or to real-world stress. Effects were measured only in the short term. The study did not test whether the habit changes long-term health.

The researchers framed the work around high-stress jobs such as law enforcement, firefighting and military service. The practical point for the wider public is modest: for a known stressful event, a few minutes of slow breathing appears to take the edge off some of the body's immediate reaction.

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Larger trials in real-world settings, in people with anxiety or heart conditions, and over longer follow-up.

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