Any ideas why my workouts seem to be backwards?

[mamir5]

Whenever I have a lackluster tired workout my Fitbit says I'm killing it and I know it's way overestimating. Then when I have a killer cardio workout where my machine is reading 180bpm+ for an hour my Fitbit reads it as under zones the entire time, maybe 120bpm. I tried moving it further up my wrist and making sure it's tight (not overly so). I guess it's not a big deal but it just bothers me that there isn't any consistency. I have the inspire 2. I also tend to use the elliptical so maybe the movement is confusing it, but it does pick it up as elliptical.

[alexthecat]

@mamir5  I've found that the motion of my arms on the elliptical seems to interfere with my Fitbit reading my heart rate correctly. The device keeps sliding around and that interferes with heart rate detection. My solution is to push the Fitbit higher up my wrist and use an adjustable knotwork bracelet to keep it there. It looks like this. 

I've also used a headband or bandana to prevent my Fitbit sliding around when I exercise.