Earlier this year my employer provided us with the opportunity to do a three-day Firstbeat Lifestyle Assessment. This provided me a chance to do three days of “double self-quantification”, and compare the results of the much hyped Firstbeat to my daily driver, the Oura ring.
Firstbeat Bodyguard 2 measures your body’s signals 24/7, whereas Oura ring does most of it’s tracking during your sleep. Both of the wearables focus heavily on HRV (links to Oura’s and Firstbeat’s HRV info pages), but when it comes to sleep, there’s a lot more to look at.
The problem is that Firstbeat system operates pretty much in a black box. You can’t get any immediate feedback from the device, as all your data is put together and analyzed after the tracking period, and then sent back to you as a simplified report. What you get is five data points about your sleep, and one of those is an arbitrary score which we don’t really know how it’s formed:
- Restorative effect of sleep (score)
- Length of sleep
- Recovery during sleep (time and percentage)
- Quality of recovery (HRV)
As for Oura ring, the list of sleep data variables collected per night is pretty impressive:
- Total sleep, plus
- Sleep stage cycles and the amount of REM, Deep and Light sleep
- Timing, plus
- Wake-up time
- Time in bed
- Resting heart rate (graph + min/avg/max)
- HRV (graph + min/avg/max)
- Body temperature deviation
- Respiratory rate
And of course Oura, like Firstbeat, summarizes the night with a Sleep score. But comparing what we can, some differences did still come up between the data from the two platforms. If you’re doing a similar comparison yourself, note that Firstbeat “starts the day” from morning, so their sleep data for e.g. Friday is from Fri-Sat night, while Oura’s sleep data for Friday comes from Thu-Fri night.
Before delving into the results, here’s a short summary of the three days that were tracked. This is important to know as it gives context to the results:
- Friday: Normal office day. Only a 30-minute resistance band session, as I was recovering from unusually strong and early pollen season. Sauna in the evening.
- Saturday: Drove/sat in a car for about 6 and a half hours. 3 portions of alcohol during the day.
- Sunday: 1-hour sessions of bodyweight exercise and yoga. Sat at the computer the evening.
If there’s one biomarker that everyone should monitor, it’s their nightly heart rate variability. In fact, there are companies devoted to analyzing only that one metric, and it has proven to be useful to regular Joes and athletes alike. Measuring HRV during the night has two main advantages: you can’t consciously affect the result with e.g. altering your breathing pattern, plus as most of your recovery does happen during the night, HRV is a great indicator of how thorough that recovery has been.
Assuming Firstbeat’s report’s HRV is the average HRV of the night, the results between the two platforms are very close to each other. The difference between HRV data was just 0.66 ms on average! I’d put that in the margin of error and call the results identical. Again, the three-day sample size is a limiting factor, but still.
Length of Sleep
The length of sleep is a bit tricky one to measure, since we humans don’t really have an unequivocal off-switch. So it comes down to the builders of these wearables to design which markers they want to use to determine when exactly does a person fall asleep.
During all three nights, Firstbeat consistently thought that I slept more than what Oura tracked. On average, Firstbeat estimated my length of sleep to be 27 minutes longer than Oura’s estimates. Comparing Firstbeat’s results to Oura’s “time in bed” numbers didn’t match either. In fact, Firstbeat always had a result which was in between Oura’s total sleep time and time in bed values.
Recovery During Sleep
Firstbeat reports the amount of recovery during sleep both in hours and also as a percentage score. I couldn’t find information what do they consider to be “recovery during sleep”, and their reported times did not match anything in my Oura data.
Oura does give a Recovery index (how long it takes for your resting heart rate to stabilize) percentage, but that didn’t seem to correlate with Firstbeat’s percentage values either, not even in terms of overall trend.
I’m guessing Firstbeat just calculates the amount of sleep that has occurred when HRV has been above some predetermined threshold.
Firstbeat’s report does include a daily lowest heart rate. Oura provides that as well, but for each night. During those three days, Oura’s averages were 53 and Firstbeat’s 51, so again the results were practically identical. Other HR data is incomparable, since Firstbeat’s report doesn’t show separate sleep HR. I consider lowest resting heart rate still comparable, since it’s highly unlikely that I’d reached those numbers while awake.
One curious thing that I noticed was that when I overlapped the sleep cycle visualization from Oura’s data on top of Firstbeat’s summary graph, I got this:
At first glance it might not look like much but notice how REM sleep happened the same time that Firstbeat’s graph turned red. (Firstbeat’s graph is a bit challenging to read, as colors indicate different things and the height of the graph indicates the “strength of reaction”. So during that night, it went back and forth between high levels of green recovery and low levels of red stress.) I’ve certainly noticed before from my Oura ring’s data that during REM sleep – dreaming, that is – heart rate tends to spike. Unfortunately, I couldn’t replicate this overlap of REM sleep and stress with the two other nights’ data, so with this limited dataset I’m just going to file this under “interesting coincidents”.
When comparing the activity data, Firstbeat Bodyguard 2 had an obvious (and expected) advantage over my second generation Oura ring. However, when it comes to sleep data, I feel like the scale starts to tilt a bit in Oura’s favor. I’m not necessarily doubting Firstbeat’s tracking capabilities, but it’s too much of a black box solution to really provide me with tangible information. Oura’s mobile app goes into really granular level of sleep data and it makes n=1 studies possible.
Of course Oura’s power, and most wearables for that matter, comes when analyzing long term trends. In that sense it’s a bit unfair to compare it to the bulky Firstbeat Bodyguard 2 system, which isn’t intended to be used for months or years. But I’ll give props to Firstbeat for the fact that I now after my colleagues got their Lifestyle Assessment reports, a lot of them have been starting to take stress, recovery and sleep more seriously. “Quantified self” isn’t a fringe topic in our office anymore, and one colleague even ended up ordering an Oura ring because of this!
I know that at times I might seem to be highly critical of the Oura ring, but I assure you, it’s all in good faith. After I got my Oura ring, I’ve managed to increase my average nightly sleep by over 30 minutes, and I’m close to being consistently doubling the amount of deep sleep compared to the first month or two of my tracking! (By the way, if you’re looking to increase your deep sleep, read this great guide by Dr. Olli Sovijärvi, MD, available in English and in Finnish.) So I try to maintain my criticism constructive, as after all I’m selfishly encouraging the Oura team to keep developing and updating their product – a product that I continuously use.