Immediate effect of yogic postures on autonomic neural responses

Aim: The aim of this study is to identify the autonomic responses after immediate yogasana practices. Materials and Methods: Ten male (n = 10) yoga practitioners having more than 8 years of experience in yogasana practice were selected as subjects. Before and after immediate practices of six specific yoga postures were assessed on three different consecutive days for 15 min, 22.5 min, and 30 min. Heart rate variability (HRV) low frequency, HRV high frequency (HF), HRV amplitude, galvanic skin resistance (GSR), and blood volume pulse were assessed under the condition of autonomic neural activity and measured using NeXus-10 device. Results: Findings of the data generalized increasing of GSR (47.93% and 14.40%) and HF HRV (7.74% and 6.69%) and decreasing of low-frequency HRV (5.43% and 5%) immediately after 15 min and 22.5 min practice of yogasana, which indicates parasympathetic (vagal) activation. However, in the case of 30-min yoga practice, it decreased the GSR (11.03%) and HF HRV (2.59%), increased low-frequency HRV (2.23%) which, in turn, indicates the sympathetic activation. Discussion: The possible mechanism of vagal activation is an increase of baroreceptor sensitivity, tissue oxygenation, nervous system metabolism, and activation of vasodilation. It may be attributed to the activation of the head ganglion of the autonomic nervous system and inhibition of the posterior hypothalamic area. The sympathetic activation depends on the release of epinephrine and norepinephrine hormones, activation of vasomotor center, central neural integration, and peripheral inhibitory/excitatory reflex mechanisms. Conclusions: Immediate yogasana practices may enhance the parasympathetic (vagal) dominance, which increases autonomic flexibility and associates with a calm mental state.