My Garmin Vivoactive 3 does sleep & resting HR tracking, and it is okay.
On sleep:
- If I go to sleep pretty shortly after getting into bed, the total sleep hours seems about right. But if I end up binge watching Netflix / Amazon Prime because I can’t fall asleep, the total sleep hours is way off
- If you nap frequently, it doesn’t count that as “sleep”, so your total sleep time will be consistently off
- On the sleep breakdown - deep, light, rem, etc. - I have no idea (and no way to figure out) if it is accurate, close to accurate, or just random numbers, so I don’t look at that at all.
On resting HR:
- Garmin use some algorithm to figure out resting HR number it reports - it isn’t the lowest HR measured - and I haven’t seen anything that explains this algorithm, so that doesn’t give me a whole lot of confidence in the number
My anecdotal perception is that the total sleep and resting HR trends don’t correlate well to how I do on any specific ride. But I also find that my perception of fatigue doesn’t correlate well with performance.
For me, I actually seem to perform best when TrainingPeaks shows me with a TSB between ~ -5 and -30 (yes, negative). When I have a positive TSB - especially for several days, I’m usually pretty flat.