I am starting an experiment to track my heart rate variability (HRV) because I want to see how it is influenced by various treatment strategies. I decided to start this thread so I can share my experience with others.
According to wikipedia, HRV is:
So, HRV is a very finely tuned measurement of the time from one heartbeat to the next. If person A and person B both have a heart rate of 60 beats per minute, it is very likely that they still have a different HRV. Person A could have a heart beat exactly once every second, whereas person B might have a heart beat at 0.97 second, then 1.05 second, then 0.91 seconds that ultimately averages out at 60 BPM. In this scenario, person A would have a very low HRV whereas person B would have a high HRV.
A high HRV is desirable as it suggests that the autonomic nervous system can adjust quickly to varying demands on the body. Moreover, a high HRV suggests that a person has good vagal tone, whereas a low HRV suggests poor vagal tone. Good vagal tone is desirable as it suggests that the autonomic nervous system is more capable of balance between parasympathetic and sympathetic states.
By measuring my HRV I hope to be able to track which treatments improve or worsen HRV, and by proxy learn what increases or worsens vagal tone. My aim is to increase my vagal tone and thereby, hopefully, contribute towards rebalancing my autonomic nervous system. There have been a couple of studies of HRV in CFS, and in particular how HRV influences sleep quality. It seems that patients with a higher HRV typically sleep better, whereas those with lower HRV are more likely to wake frequently in the night and feel unrefreshed in the morning. This is probably because the parasympathetic nervous system is more active in the patients with a high HRV, so they are able to get restorative sleep.
I am measuring my HRV using a heart-rate monitor strapped around my chest which connects to an iPhone app via bluetooth. I also own a Fitbit HR, which monitors heart rate via the wrist, however the Fitbit is not sufficiently accurate to measure the minute differences in heart beats needed to get an accurate HRV measurement.
There are a number of different ways to calculate HRV, however the value I will be focusing on here is the rMSSD (root mean square of successive differences), because it is supposedly a good way to measure HRV over short time intervals of a minute or two.
Here is a very rough idea of normal rMSSD values from an article by HRV4Training so you can get an idea of what the values mean:
70 to 120 - Young, highly athletic people
60s - Young, physically active people
Mid-30s to 50s - Young, sedentary people
20s - Patient populations (e.g. chronic heart failure patients)
Further analysis of normal values by HRV4Training can be found here.
I have only just started measuring my HRV so I do not want to share my results yet as it is good to get a few measurements so I can establish my baseline. Needless to say, however, that after being bedridden for two years my HRV is not looking too good! The best time to take measurements for the purposes of establishing a baseline is first thing in a morning, so I will establish my baseline over the next few days then report back.
The first treatment intervention I will test is a trans-cutaneous vagus nerve stimulator, which should arrive in the mail later this week. Vagus nerve stimulation supposedly directly increases vagal tone and should have a measurable impact on HRV.
According to wikipedia, HRV is:
the physiological phenomenon of variation in the time interval between heartbeats. It is measured by the variation in the beat-to-beat interval.
So, HRV is a very finely tuned measurement of the time from one heartbeat to the next. If person A and person B both have a heart rate of 60 beats per minute, it is very likely that they still have a different HRV. Person A could have a heart beat exactly once every second, whereas person B might have a heart beat at 0.97 second, then 1.05 second, then 0.91 seconds that ultimately averages out at 60 BPM. In this scenario, person A would have a very low HRV whereas person B would have a high HRV.
A high HRV is desirable as it suggests that the autonomic nervous system can adjust quickly to varying demands on the body. Moreover, a high HRV suggests that a person has good vagal tone, whereas a low HRV suggests poor vagal tone. Good vagal tone is desirable as it suggests that the autonomic nervous system is more capable of balance between parasympathetic and sympathetic states.
By measuring my HRV I hope to be able to track which treatments improve or worsen HRV, and by proxy learn what increases or worsens vagal tone. My aim is to increase my vagal tone and thereby, hopefully, contribute towards rebalancing my autonomic nervous system. There have been a couple of studies of HRV in CFS, and in particular how HRV influences sleep quality. It seems that patients with a higher HRV typically sleep better, whereas those with lower HRV are more likely to wake frequently in the night and feel unrefreshed in the morning. This is probably because the parasympathetic nervous system is more active in the patients with a high HRV, so they are able to get restorative sleep.
I am measuring my HRV using a heart-rate monitor strapped around my chest which connects to an iPhone app via bluetooth. I also own a Fitbit HR, which monitors heart rate via the wrist, however the Fitbit is not sufficiently accurate to measure the minute differences in heart beats needed to get an accurate HRV measurement.
There are a number of different ways to calculate HRV, however the value I will be focusing on here is the rMSSD (root mean square of successive differences), because it is supposedly a good way to measure HRV over short time intervals of a minute or two.
Here is a very rough idea of normal rMSSD values from an article by HRV4Training so you can get an idea of what the values mean:
70 to 120 - Young, highly athletic people
60s - Young, physically active people
Mid-30s to 50s - Young, sedentary people
20s - Patient populations (e.g. chronic heart failure patients)
Further analysis of normal values by HRV4Training can be found here.
I have only just started measuring my HRV so I do not want to share my results yet as it is good to get a few measurements so I can establish my baseline. Needless to say, however, that after being bedridden for two years my HRV is not looking too good! The best time to take measurements for the purposes of establishing a baseline is first thing in a morning, so I will establish my baseline over the next few days then report back.
The first treatment intervention I will test is a trans-cutaneous vagus nerve stimulator, which should arrive in the mail later this week. Vagus nerve stimulation supposedly directly increases vagal tone and should have a measurable impact on HRV.
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