Multiscale cardiorespiratory complexity reveals autonomic signatures of Rajyoga meditation

IntroductionMeditation offers a tractable model for probing altered states of consciousness, yet consistent physiological markers remain elusive. This study characterized within-subject autonomic and respiratory modulation across pre-meditation, during-meditation, and post-meditation states in trained Rajyoga practitioners using multiscale heart rate variability (HRV) metrics and HRV, respiration coupling. Sex-stratified analyses were presented exploratorily to summarize state-dependent effects.MethodsA single-lead electrocardiogram (ECG) was recorded from 55 Rajyoga practitioners (31 male, 24 female) during three consecutive 10-min states: pre-meditation, during meditation, and post-meditation. After artifact correction, 27 HRV indices spanning time-domain, frequency-domain, and non-linear dynamics, including multiscale entropy (MSE 1, 20), were computed in Kubios HRV Scientific. State-dependent effects were tested using Friedman tests with Bonferroni-adjusted post-hoc contrasts, and cardiorespiratory coupling was assessed through correlations between respiration frequency and low-frequency (LF) and high-frequency (HF) HRV powers.ResultsMeditation was associated with robust state-dependent modulation. Time-domain indices and frequency-domain powers increased during meditation with partial post-session recovery, while selected non-linear features shifted significantly. Respiration frequency was reduced, and HRV, respiration coupling was strengthened, consistent with increased parasympathetic engagement. Exploratory sex-stratified summaries indicated potential differences in effect magnitudes that warrant confirmation in studies powered for interaction testing.DiscussionThese findings identify a reproducible physiological signature of the meditative state by integrating HRV magnitude, complexity, and cardiorespiratory coupling. The results support the usefulness of multiscale cardiorespiratory analysis as an operational marker of altered consciousness induced by Rajyoga meditation.