Good Morning,
I am looking for a Rabbit Hole and figured this was the perfect place 
- I want to learn and explore more about HRV, the Apple Watch and overall health, but especially the connection to the autonomic nervous system and the connection to mental and physical fitness.
Tons of apps out there but I am looking for some insight from the folks here - especially links to some scientific papers or research based articles.
Thanks !
Commenting because I too would love to learn about HRV, but I’ve not found anything simple enough for me to understand.
@geoffaire - Here is a start - with some decent links to science based articles. Heart Rate Variability (HRV) as a digital biomarker for Mental Health and the promise of Apple Watch - MyHealthyApple
I’m curious what your HRV would report when you exercised. Would exercise push you from chronically to extremely low, and then it would crawl back up to chronically low? Or would it show roughly the same number after exercise?
I went through a period like this and I actually did have a health problem. I was able to return to normal readings after three months. Hope you are healthy and it’s a miscalibration.
A few years ago, I was considering using HRV in a research project, and so I did a quick search in Devonthink to find any articles I might’ve saved. This open-access article might be a good place to start: Heart Rate Variability and Cardiac Vagal Tone in Psychophysiological Research – Recommendations for Experiment Planning, Data Analysis, and Data Reporting
The Apple Watch has probably come a long way in the time since, but at the time, I found Biostrap to be a good consumer-level product for obtaining clinically valid HRV. You might add the word “biofeedback” into your HRV searches to get more relevant info/articles.
At a very basic level, here’s my understanding of how to think about HRV. HRV is a measurement of how consistently the heart beats. If it beats very consistently (
- - - think a metronome), the variability is low. If the heart beats inconsistently - - - - , the variability is high. As far as I know, we don’t fully understand the causes or implications of low vs high HRV. Sleep and many other factors affect HRV.
There are theories that attribute a low HRV to the autonomic nervous system responses, but the jury is out on whether they are valid. You might look into Poly Vagal Theory and also search for its critics. Here’s one article I found quickly: Toward understanding respiratory sinus arrhythmia: Relations to cardiac vagal tone, evolution and biobehavioral functions.
Neat question! I’ll be following to see what others have learned.
IANAD, but I’d reach out to mine with a quick note if I were you. You can even start it with, “I imagine you’ll laugh at me because all I have is my Apple Watch data to go on, but I noticed this and wanted to mention it in case it’s meaningful to you.”
IAAD and at best this is investigational.
If a patient has other cardiac symptoms/issues, then your doc will proceed with a workup based on those.
If you are otherwise healthy without symptoms or signs of cardiac disease, your doc will politely smile and move on.
When considering the use of any general purpose fitness device for health screening rather than simply for fitness, it is really helpful to do some reading on the concept of Bayesian analysis as it applies to screening tests. If you study a healthy population using a screening tool of low specificity, then you have a high risk of false positive findings. The harm from further testing to follow-up those false positive findings often exceeds any benefit of the screening - both in the sense of medical harm and economic harm.
https://towardsdatascience.com/bayes-theorem-for-medical-test-f1fb12b579c6
This is great stuff… Thank you all. I definitely found my rabbit hole!
Although this is a heart measurement - my understanding is that it really is giving us information about our autonomic nervous system and it’s an indicator that there’s some level of stress that the body is responding too.
Correct
And while it’s interesting to play with on your iPhone, IMHO the likelihood of yielding useful, actionable medical diagnostic or treatment info from this is nil.
Maybe at best it can give you input regarding your general level of stress similar to biofeedback. Interesting but not likely to be actionable information.