The relaxation effect of prolonged expiratory breathing.
Level 3 - non-randomized controlled study
Small non-randomized within-subject experimental physiological study.
PubMed 30046408 · doi:10.4081/mi.2018.7669
What was done
Ten healthy men aged 21–28 years were evaluated across two breathing conditions following spontaneous breathing: prolonged expiratory breathing (6 seconds expiration, 4 seconds inspiration) and rapid breathing (1 second expiration, 1 second inspiration). High frequency (HF) power and the low frequency to high frequency (LF/HF) ratio of heart rate variability were measured to assess autonomic modulation.
What was found
The abstract reports that parasympathetic nervous function was significantly activated during prolonged expiratory breathing and significantly suppressed during rapid breathing. No quantitative values, effect sizes, or p-values are reported in the abstract.
Why it matters
This paper provides preliminary experimental evidence that lengthening the expiratory phase of breathing acutely shifts autonomic balance toward parasympathetic activation.
Limits
The sample size is very small (n=10) and restricted to young healthy men, limiting generalizability. The abstract does not indicate whether breathing condition order was randomized or counterbalanced. Heart rate variability is an indirect measure of autonomic tone, and no psychological or clinical relaxation outcomes were measured.
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