Fitbit not accurately tracking my heart rate during high intensity exercise

[SplashyMetal]

I am a 49 yo woman in good shape, at least according to my Fitbit. However, I have basically never seen my heart rate hit 140, even when I am gasping for breath. It's very unusual to even see it hit 130. I have a hard time believing I *never* get to 75% max heart rate. Furthermore, when I see it on my Phone app, it seems to cap at 125.

i have tried wearing the Fitbit higher or lower on my wrist while I exercise. I've tried keeping my hand movements to minimum while speed walking. I've tried swimming (that does raise my heart rate, but doesn't seem to get to the phone). Yesterday I took a very hard spin class and it didn't register as a workout at all! (It did track as calories burned, but it didn't auto detect that I was breathing hard for 45 minutes).

is there anything else I can do, or is this just a bug in the Inspire 3? Should I be wearing the detector on the inside of my wrist?

I have to say, this app seems to have gotten significantly worse after the last major update. It takes longer to sync and the GUI is terrible. I don't know if that's related.

[alexthecat]

@SplashyMetal I train with my Fitbit and a chest strap heart rate monitor at the same time. I find readings to be quite similar between the two devices, as long as the Fitbit isn't sliding around on my wrist. If it is, that definitely introduces error. I usually tie a bandanna around my wrist to keep the Fitbit from moving. 

Be aware that it is not possible to get an accurate heart rate while swimming. The water interferes with the Fitbit measuring your heart rate.

Also, Fitbits do not automatically track Spinning. You need to start and end those sessions on your device.