Acute Effects of Two Slow-Paced Breathing Protocols With and Without Inspiratory Breath-Holding on Heart Rate Variability: A Randomized Controlled Trial

Background/Objectives: Slow-paced breathing (SPB) is associated with changes in heart rate variability, although these responses are strongly influenced by respiratory patterns; the effects of incorporating an inspiratory breath-hold into an SPB protocol remain insufficiently characterized. This study evaluated the immediate effects of two SPB protocols on heart rate variability (HRV) and cervical pressure pain thresholds (PPT).

Methods

A single-blind, randomized, controlled trial was conducted with 60 healthy adults (aged 18–65) stratified by age and sex, and allocated equally (n = 20 per group) to: Protocol 1 (6 s inhalation, 6 s hold, 6 s exhalation), Protocol 2 (6 s inhalation, 6 s exhalation), or a sham control (general respiratory education). Interventions lasted 5 min. Primary outcomes were time-domain HRV indices, root mean square of successive differences (RMSSD) and standard deviation of normal-to-normal (SDNN), recorded using a Polar H10 chest strap. The secondary outcome was PPT at the fourth cervical vertebra (C4) measured via digital algometry.