Body Battery and Deep Sleep

Some people say the body battery reflect how they feel. To me it sounds like something Garmin made up. If you're serious about such metrics, it is worth publishing an academic paper. Same thing with sleep tracking. You're actually lucky to have so much deep sleep, I never get more than half an hour, and sometimes... nothing, even if I feel well rested after waking up.

I'm testing a Fitbit that costs half as much now, and it's worlds apart. We'll never be able to measure brain activity on our wrists, but at least it's something that looks fully plausible. Yet again, your chart surprisingly isn't too bad.

I had a fitbit before and it said I hardly dreamt at all. I seem to dream a lot, so the Garmin seems more plausible to me. That's the most deep sleep I've ever recorded, and some of it seems wrong (waking up in the middle of a deep sleep).  I normally record less than half an hour. I'm still puzzled as to if deep sleep isn't restorative, what is it? It's like these two measures aren't co-ordinated, and I'd have thought that deep sleep would have meant slower breathing, and it doesn't. I suspect it detects REM sleep by twitching movements or something, but none of the things the watch can measure seem (HR, breathing) seem to be different in deep sleep to other stages. 

I think it measures that you are keeping still. I sleep quite regularly (alarm 7 in the morning, even in weekends), and my sleep measurements seem quite accurate, both regarding when I sleep, and how deep.

Bear in mind that in order to see all your stats you will have to pay Fitbit every year and use only one device on your account.

I have had Garmin va4s, Samsung Active2 & Polar Ignite; The Garmin VA4s is a terrible embarrassment in comparison, kinda like very old android or windowsphone that crashed intermittently, had to be reset, reinstalled, a need to turn the device off and on again after each activity, for basic functinality to resume... And dont forget forced to troubleshoot each application yourself for batterydrain etc... Thank god that time has passed ;) ;)

Ignite is no better.  I have used one for the passing two years.  Polar has replaced it four times because it kept behaving poorly.  After their last update, my Ignite start recording sleep before I went to bed.  Polar, who started activity trackers first, should be embarrassed as the poor performance their current devices are demonstrating.  Garmin does have its issues too, but no one should say that it cannot be compared to what Polar is putting out currently.

Dreaming can happen in both Deep and REM sleep stages (just finished a course on sleep studies and found it interesting enough to remember.)   Deep sleep restores physical energy while REM restores mental energy (they used that term in the course.)  Sleep states are generally determined by heart rate, heart rate variables, and breathing rate.  Since everyone has different sleep patterns, it is best to compare how you normally sleep (average numbers) to a single night rather than to someone else's patterns.  If you feel rested when you wake, you are probably getting enough deep sleep.