Inhalation/Exhalation ratio modulates the effect of slow breathing on heart rate variability and relaxation.
Level 3 - non-randomized controlled study
Within-subject experimental trial; randomization is not explicitly specified in the abstract
PubMed 25156003 · doi:10.1007/s10484-014-9253-x
What was done
Thirty participants performed four instructed breathing patterns combining two respiration rates (6 or 12 breaths per minute) with two inhalation to exhalation ratios (0.42 or 2.33). Autonomic activity was measured using the high-frequency component of heart rate variability, alongside self-reported scores for relaxation, stress reduction, mindfulness, and positive energy.
What was found
The abstract provides no numerical data, confidence intervals, or p-values. Breathing with a lower inhalation to exhalation ratio resulted in greater self-reported relaxation, stress reduction, mindfulness, and positive energy compared to a higher ratio. Lower respiration rate on its own was associated only with higher positive energy scores. The low ratio also increased high-frequency heart rate variability power, but this autonomic effect was present only during the slow 6 breaths per minute pattern.
Why it matters
These findings suggest that prolonging the exhalation phase relative to inhalation, rather than reducing breathing rate alone, is a key driver of the parasympathetic and psychological benefits of slow breathing.
Limits
The study sample was small (n = 30), and the abstract does not report participant demographics, baseline health, or whether pattern order was randomized. No numerical values or effect sizes are reported, and only acute, in-session effects were measured.
Cited by
- supports Exhaling slowly stimulates the vagus nerve and activates the parasympathetic nervous system.