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rate of a healthy 21-year old male slowed to 34 beats per minute while doing kumbhaka with uddiyana bandha after three weeks of practice-0. Heart rate was normal before and after the practice.
Radiological and direct observation indicated that the expanded chest during the practice of mahabandha (combination of jalandhara, uddiyana and moola bandhas) avoided physical pressure on the heart and blood vessels, and maintained blood flow to and from the head''. The researchers also reported that the shape of the heart indicated good venous return. Contraction of the abdominal muscles greatly increases venous return and cardiac output". In fact, pilots discovered early in aviation that undesirable effects of G-forces could be alleviated in part by tightening of the stomach muscles and taking a deep breath, thus enhancing venous return to the heart.
Conclusion More research is required to validate pranayama scientifically and help understand how it aids wellbeing. Some of the studies mentioned here are preliminary and often research is hampered by lack of funding and access to practitioners and equipment. Innovators have tried to develop new methods of measuring subtle changes and processes, but it is also important that the various strands are collated. When science uses the experience handed down by yogis for thousands of years it is tapping into a vast resource that may uncover new insights into life and how it works.
References
Elliott, Stephen & Edmonson, Dee, The New Science of Breath - Coherent Breathing for Autonomic Nervous System Balance, Health, & Well Being, RN. 2 Ornish, D., Brown, S., Scherwitz, L.W., Billings, J.H., Armstrong, W.T., Ports, T.A., McLanahan, S.M., Kirkeeide, R.L., Brand, R.J., & Gould, K.L. (1990), 'Can Lifestyle Changes Reverse Coronary Heart Disease?' The Lancet, 336, 129-133.
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