Many people notice their heart rate feels slower and more settled during or after box breathing. Here is what researchers propose about this relationship.
The heart rate naturally speeds up slightly during inhalation and slows during exhalation — a normal phenomenon called respiratory sinus arrhythmia (RSA). Slow, rhythmic breathing tends to amplify RSA — the fluctuations become more pronounced as the breath slows.
During the holds in box breathing, the heart rate stabilises briefly. Some researchers propose that the combination of slow breath pace and structured holds produces a more consistent heart rate variability pattern than slow breathing alone. This is an active area of study.
The sensation of a calmer, steadier heartbeat many people experience is consistent with what RSA research would predict. Whether this translates to meaningful clinical benefits for heart health is a separate and more complex question that requires proper medical evaluation.
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