I was quite happy to get the new Venu 2, mainly because of the new sensor and I was quite surprised to see the new feature Garmin Health Snapshot.
I track my HRV with other applications and I was pleased to see that I would have the opportunity to track it in a bit more convenient way.
But I was curious to see if the data is reliable, so for the last 2 weeks, I tracked my HRV with three apps:
- EliteHRV (by Garmin HRM Dual chest strap) - I used it in the morning and in the evening, multiple times.
- HRV4Training (by the integrated HR Sensor on my Galaxy Note 9) - I used it only once, every morning.
- Welltory (by the integrated HR Sensor on my Galaxy Note 9) - I used it only once, every evening.
The results and some stats can be found here:
https://docs.google.com/spreadsheets/d/1FxhswnFcUb2E_PaM0412ljncU1_DgBEkkbfEO3Sb-u8/edit?usp=sharing
As you can see, there are a couple of problems.
1. There are very big differences between the “real” RMSSD and SDNN that was taken from EliteHRV with chest strap but also with the finger measurements.
I mean… I think we can all agree that the chest strap is the gold standard here and when there is about a 12 ms difference on average with a standard deviation of about 12 ms, this means that the Garmin Venu 2 result is probably not accurate.
2. There is very little correlation between the RMSSD and SDNN from Venu 2 and the other apps.
This is a problem because, even if the number RMSSD is not 100% accurate, if there was a good correlation (at least r > 0.7 and r < -0.7), we would know that the difference is relatively constant and we can use the Venu 2 result as a proxy.
With so weak correlation coefficient, we just can’t do that.
3. There is very little to no consistency and reliability between consequence measurements with Venu 2.
I know that the Heart Rate Variability is supposed to be… variable, but not in the matter of 1-2 minutes between measurements, with absolutely no change in conditions. And this is shown by EliteHRV.
If the first measurement from Venu 2 gives me RMSSD of 44 ms and 2 minutes later in the same conditions gives me 16 ms, while EliteHRV with the chest strap gives me 10.92 and 11.89 ms, this means that I absolutely cannot know what is my real HRV if I count only on Venu 2.
The results are almost as bad between Venu 2, HRV4Training, and Welltory.
Also, in the tab named Garmin Health Snapshot, you can see all the measurements solely from Venu 2. In the correlations table, you can see that the only strong correlation is between RMSSD and SDNN, which is supposed to be like that because they use the same RR interval data in their formulas, and between the HR and Stress, which means that the higher my heart rate is, the higher the stress and the other way around.
But there is only a moderate correlation between RMMSD and HR, which I’m not sure is a good thing. If RMSSD is derived from HR and RR intervals, I think there should be quite a strong relationship.
Overall, I’m quite happy with Venu 2, although there are a couple of other bugs that reduce the reliability of the heart rate data. These bugs were the same in my previous watch - Vivoacitve 4.
But the functionality “Garmin Health Snapshot” is just not working right now. First, the HRV data it’s not accurate, and second, it’s not consistent and reliable. Not to mention that very often the watch won’t report the RMSSD and SDNN data, also the PulseOx.
I think Garmin can and should fix this with software updates.
All of this is just my opinion and the data from only one person, so I may be wrong.
Edit: As of the 8th of January, 2023, I just want to mention that after a couple of updates, the Health Snapshot functionality improved greatly. The reported HRV values are very consistent after back-to-back tests. I didn't compare them with other HRV software but I feel much more confident in the reported values now.
