Heart Rate Variability is a big deal – greater variability correlates strongly with cardiac health, low variability correlates strongly with depression and anxiety*. The rabbit hole at scholar.google.com on HRV is deep and fascinating.
I’ve been tracking my own HRV for many years using a stand alone device called the EmWave. Now though with the advent of bluetooth heart rate monitors and iPhone apps, you can get a whole lot more info pretty easily.
Here’s the deal though: you need to use a really high-quality bluetooth heart rate monitor to get decent data. I had been using a cheap Jarv heart rate monitor for years to track my heart rate while running, riding, doing intervals, etc. And it works just fine for that stuff (if a bit flakey at times and does seem to run the battery out pretty quickly, but, you gets whats you pays for).
I paired up my Jarv with an HRV app on my iPhone though and it reported my variability as wicked low. At first I was concerned that maybe I didn’t have high HRV I thought I had. Then I tried the HRV app with the much more expensive Polar H7 and my HRV #s were way up there.
It appears that the way the Jarv reports the intervals between beats (R-R) is not quite reliable when compared to the way the Polar does the same reporting. I only found one other link on the inter webs that noted the Jarv under-reported HRV and since not everyone may have multiple monitors around to test with, I just wanted to note here that if you start tracking HRV and want reliable data, don’t use the Jarv heart rate monitor. Spring for the Polar one.
* by way of example of just how fascinating the rabbit hole is here: Low HRV correlates with depression but while antidepressants (specifically SSRIs) may alleviate the symptoms of depression, they do not increase HRV. It would be interesting to see a study on whether or not Cognitive Behavioral Therapy (CBT) – which is shown to be as effective as medication in long-term alleviation of depression – causes an increase in HRV.