Heart Rate Dynamics during Shambhavi Mahamudra- A Practice of Isha Yoga

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A study was designed to quantify and compare the instantaneous changes of heart rate variability (HRV) during Shambhavi Mahamudra, a practice of Isha yoga.
It includes major stages viz. Sukha pranayam, 'AUM' chanting, rapid breathing, and relaxed sitting.
The standard lead II electrocardiogram (ECG) signals were acquired from eight healthy, yoga practitioners while performing various stages of Shambhavi Mahamudra. The short-term HRV were extracted from ECG, and analyzed using time, frequency-domain and Poincaré plot methods.
The results showed a combination of increased sympathetic tone and withdrawal of vagal tone during Sukha pranayam, an increased sympathetic tone during `AUM' chanting, and withdrawal of vagal tone during rapid breathing.\
The HRV descriptors were not significantly different during relaxed sitting