Effect of 21 days of yogic exercises ( <i>Suryanamaskar</i> ) on orthostatic and neurovestibular responses following 4 hours of head-down tilt

Objectives: The practice of yoga is known to modulate autonomic and postural physiology. Exposure to microgravity leads to adaptive changes in all physiological systems, notably in cardiovascular (CVS) and neurovestibular. Head-down tilt (HDT) is an effective earth-based analog for simulating the effects of microgravity on the cardiovascular system. It also simulates the effects of cephalad fluid shift on the neurovestibular system. Suryanamaskar includes a sequence of static and dynamic exercises which are known to affect the autonomic and vestibular systems. This study aimed to evaluate the effects of yogic exercises ( Suryanamaskar ) on HDT-induced changes in CVS and neurovestibular physiology. Material and Methods: Ten age-matched, healthy male participants took part in the study. Initial baseline data of their CVS responses to head-up tilt and coriolis time interval (CTI) estimation following eight orthogonal head movements in Barany’s Chair mode of the AirFox ® DISO Simulator were recorded before and after 4 hours of HDT. The participants practiced 12 sets of Suryanamaskar under supervision for 21 days. Thereafter, the same physiological parameters were recorded after exposure to 4 hours of HDT. The findings were then compared using repeated measures analysis of variance. Results: Mean age of the participants was 34.2 ± 3.9 years. The findings suggested that there was a significant reduction in heart rate (−5.8 beats/min) and systolic blood pressure (−3.1 mmHg) on exposure to HDT after yogic intervention. The comparisons of diastolic blood pressure and CTI pre and post- Suryanamaskar practice, however, did not yield statistically significant results. Conclusion: The effect of HDT on CVS physiology can be potentially altered by the practice of Suryanamaskar , primarily by improved orthostatic tolerance due to autonomic stabilization. However, influence of Suryanamaskar on the neurovestibular effects of short exposure to HDT, especially the effects on the semi-circular canals, needs further research. This has operational significance in the current world scenario, as we see private astronauts being sent on sub-orbital and orbital flights for a very short experience of microgravity