I've noticed a similar problem. I do my cardio on a treadmill, and essentially do the exact same program each time. I've noticed some pretty wild fluctuations too. Like, this morning, I dropped the speed 0.2 km/h...my heart rate, according to my fitbit, went from 134 to 112, within seconds, then back up to 130. At that point in the workout, there's no way I'd have been 112....the 130's was the more accurate number for sure.
As I'm trying to lose weight, my goals are set one of two ways; active zone minutes and/or calories burned. If the heart rate isn't accurate, how do I know whether I'm actually hitting my zones? Also, I've had days where I can achieve my goals (both) within a 30 minute workout, and other days where it's taken 35 or more minutes, and it's all random.
If the fitbut is only reading the heart rate at certain intervals, then I can understand the issue...and would expect that it works itself out over the length of the workout (as my heart rate at any one given couple second point in time isn't necessarily all that relevant during a 30-40 minute workout)...but would like to know for sure. Or am I wearing the device too loose, or too tight, or is there another problem altogether.
