LETTER TO EDITOR
Year : 2015 | Volume
: 8 | Issue : 1 | Page : 80--81
Need for revised protocol of heart rate variability for sequential evaluation of physiological changes in yoga
AV Vinay, D Venkatesh, Ravi Prakash
Department of Physiology, M.S. Ramaiah Medical College, Karnataka, India
Department of Physiology, M.S. Ramaiah Medical College, Karnataka
|How to cite this article:|
Vinay A V, Venkatesh D, Prakash R. Need for revised protocol of heart rate variability for sequential evaluation of physiological changes in yoga.Int J Yoga 2015;8:80-81
|How to cite this URL:|
Vinay A V, Venkatesh D, Prakash R. Need for revised protocol of heart rate variability for sequential evaluation of physiological changes in yoga. Int J Yoga [serial online] 2015 [cited 2020 Aug 13 ];8:80-81
Available from: http://www.ijoy.org.in/text.asp?2015/8/1/80/146072
Yoga is an ancient practice of lifestyle  having eight limbs as described in Patanjali Yoga Suthra.  Each one of these helps in subtly balancing health of an individual. In recent years, lot of importance has been given to three aspects of yoga that are asana, pranayama, and dhyana, in harmonizing the physiological status of an individual, as some important quantifiable change in the physiological parameters with their short-term practice have been recorded. In other aspects of yoga, however, to demonstrate a significant change it requires regular practice for quite a long duration. However, we suggest that these changes can be better evaluated if they are monitored on a regular basis as the changes, which may set in various physiological parameters can be sequential.
Most of the studies on changes in heart rate variability (HRV) parameters in yoga are short-term, which are meant to gauge the cross-sectional change in HRV during or after an intervention. However, yoga is a lifestyle practice where changes setting in are slow and set in over a day-to-day basis. Thus, we are of the opinion that sequential recording during practice or at rest on day-to-day basis with short-term HRV protocol will be more fruitful as it will help us to see the sequential changes in HRV brought about by regular practice of yoga. In addition, we can mark the approximate duration from which beneficial effect starts setting in. Added advantage of this type of recording would be that the HRV values will fall under a narrower range. Autonomic changes in heart are highly variable and amount of stress, which the person goes through on a daily basis, is also variable. This sequential recording on a daily basis will give us the trend of modulation in an individual at rest. This will help to determine the trending of autonomic changes over a period of time by HRV. With respect to yoga practice, sequential recording of HRV can also help in gauging the effect of other aspects of yoga like Yama, Niyama and also Prathyahara as the changes due to these are relatively slower (as compared to the commonly practiced Asanas and Pranayamas) as well as steady on regular practice as evidenced by subjective changes of improvement in the health status of regular practitioners. 
Yoga practice shows changes in the time domain parameters of HRV demonstrated by the increase in overall HRV in terms of SDNN and also change in parasympathetic activity expressed in terms of RMSSD, NN50, and PNN50.  On sequentially recording these changes, we will be able to specify the degree of beneficial effect which can be obtained and the level at which it hits a plateau phase, since the time domain parameters have a limit and technically cannot increase after a limit. A regular monitoring of HRV after discontinuing yoga practice will help us to gauge the time taken for decay in the beneficial effect. On the other hand, frequency domain parameters of HRV have following parameters low frequency (LF), high frequency (HF), and LF/HF ratio. A change in LF suggests alteration in sympathetic system; whereas change in HF represents the alteration in parasympathetic system. LF/HF ratio gives information about the balancing act of sympathetic and parasympathetic system. Yoga helps in increasing the autonomic modulation toward parasympathetic dominance by either increasing parasympathetic activity  or by decreasing the sympathetic tone in an individual or at times both. The yoga is a form of lifestyle which reduces the sympathetic tone, but still it helps in maintaining the sympathetic stimulation at an optimal level so as to reap the positive benefits of its practice. Upon sequential recording of these parameters, we will be able to gauge the optimal level of sympathetic stimulation, which is required for the optimal performance of an individual and also that when it levels off (does not decrease beyond a level).
Thus, short-term repeated assessment of HRV is helpful in evaluating time required for beneficial effects to set in and to assess the maximal beneficial effect derived out of its practice in maintaining better cardiac health. This can also be used to determine or shelf life of these benefits on discontinuing the practice of yoga.
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