Yoga, the cardiovascular and the nervous system.

Research has shown that yoga causes improvements in cardiac function, lowering resting heart rate and blood pressure and helping to prevent heart disease. There are a number of ways which yoga practice may create these changes.

The autonomic nervous system is the part of the nervous system which controls the involuntary functions of the body such as heart rate, digestion, respiratory rate, salivation, perspiration, urination, breathing and swallowing. It can be broken down into two further subsystems, sympathetic and parasympathetic. The sympathetic nervous system, also referred to as the “fight or flight response” prepares the body for action in response to threat. It increases the heart rate, blood pressure, sweating, and pupil dilation. Conversely the parasympathetic nervous system reduces the heart rate, stimulates digestion and returns the body to homeostasis.

If there is insufficient blood flow to vital organs, higher pressure is required in arteries, and this is achieved by increased activation of the sympathetic nervous system. This can cause sympathetic activity to predominate, resulting in high blood pressure, which can cause Coronary artery disease. Yoga helps to prevent by this by increasing blood flow around the body, Woodyard (2011), keeping blood pressure down.
Stress can also cause the same shift in autonomic activity described above, resulting in damage to the cardiovascular and respiratory systems. Yoga promotes relaxation. This combined with breathing exercises activates the parasympathetic nervous system and decreases sympathetic activity, Krishna et al (2014). It is suggested that this shift may be caused by inhibition within sympathetic areas of the hypothalamus, Desikachar (2005).

Additionally, muscles are able to absorb more oxygen when they are stretched, as was demonstrated in a study by Krishna et al. (2014). This reduces the effort required by the heart and also energizes the body, this improving cardiac function.

Remember that the heart is a muscle just like any other and need to be exercized to keep it in good condition. During the Bikram series we work intensely then rest for several seconds, so the heart rate is brought up and then down in short intervals, which is a great way of strengthening the muscle and keeping the heart healthy.

References

1. Bandi Hari Krishna, Pravati Pal, Pal G.K., Balachander J., Jayasettiaseelon E., Sreekanth Y, Sridhar M.G., and Gaur G.S. (2014). Journal of Clinical Diagnosis Research. Jan 2014; 8(1): 14–16. Published online Jan 12, 2014 [Last accessed 26/05/2014]

2. Catherine Woodward (2011) Exploring the therapeutic effects of yoga and it’s ability to improve quality of life. International Journal of Yoga. 2011 Jul-Dec; 4(2): 49–5 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3193654/#__ffn_sectitle [Last accessed 26/05/14]

3. Desikachar K, Bragdon L, Bossart C. The yoga of healing: Exploring yoga’s holistic model for health and well-being. International Journal of Yoga Therapy. 2005;15:17–39.