IMMEDIATE EFFECTS OF 90 DEGREE VERSUS 45 DEGREE INVERSION ON CEREBRAL HEMODYNAMICS AND HRV IN YOGA PRACTITIONERS: A RANDOMIZED CONTROLLED STUDY

Abstract

Background: Inverted yoga postures are believed to influence cerebral circulation and autonomic nervous system regulation by altering gravitational blood flow dynamics. Practices such as 90° inversion and 45° inversion are traditionally used in yoga for promoting physiological balance and relaxation. However, scientific evidence comparing the immediate cerebrovascular and autonomic effects of different inversion angles remains limited.

Aim: To investigate the immediate effects of two inversion postures—90° inversion and 45° inversion on cerebrovascular hemodynamics and cardiac autonomic function in healthy yoga practitioners.

Methods: This randomized controlled study included 40 healthy yoga practitioners aged 18–35 years who had at least six months of yoga practice. Participants were randomly assigned to either the 90° inversion group or 45° inversion group. Each participant maintained the posture for approximately turn on I thought yesterday he only gave Roshan only completely3 minutes under supervision. Physiological assessments were conducted at three time points: baseline (supine rest), during the posture, and post-intervention recovery.

Assessment: Cerebrovascular hemodynamic parameters—Peak Systolic Velocity (PSV), End-Diastolic Velocity (EDV), Mean Flow Velocity (MFV), Pulsatility Index (PI), and Resistance Index (RI)—were measured in the left Middle Cerebral Artery using Transcranial Doppler ultrasonography. Cardiac autonomic activity was assessed through heart rate variability (HRV) analysis, including time-domain and frequency-domain parameters.

Results: Both inversion postures produced significant changes in cerebrovascular and autonomic parameters across the pre, during, and post phases. Mean flow velocity and end-diastolic velocity increased significantly during inversion, while pulsatility index and resistance index decreased, indicating improved vascular compliance. 90° inversion produced stronger autonomic and hemodynamic responses during the posture, whereas 45° inversion showed a more gradual recovery pattern with sustained reductions in vascular resistance.

Conclusion: Both 90° inversion and 45° inversion significantly influence cerebral circulation and autonomic nervous system activity, though with different physiological patterns. 90° inversion induces stronger acute regulatory responses, while 45° inversion promotes a more sustained reduction in cerebrovascular resistance during recovery. These findings suggest that different inversion angles may offer distinct therapeutic applications for improving cerebrovascular regulation and autonomic balance.

Keywords: Yoga, Inversion Postures, 90° inversion, 45° inversion, Cerebral Blood Flow, Transcranial Doppler, Heart Rate Variability, Autonomic Nervous System.