Heart rate during exercise

[batspocky]

Hi all - just checking in to see if anyone else has noticed something like this, or knows why it might happen.

I just bought an exercise bike and I've been using it for 25-30 minute spinning sessions. I wear a Fitbit Charge HR and I like to track my heart rate, etc. to ensure that I'm being smart about how I exercise. I've noticed that when I ride the bike, this thing happens where my heart rate will start out pretty low and even for the first 1/4 or even 1/2 of the ride, and then all of a sudden it will jump up into the peak range. Here are two pictures of what I'm talking about:

I try to keep my RPMs even throughout the ride - usually in the 80-85 RPM range. And while I do try to make small adjustments during the ride to simulate going up and down hills, it doesn't appear that the jump in heart rate is related to this at all. And it's not like an SVT where it just randomly jumps up and stays there...it goes back down quite normally post-workout.

I just can't figure out why it would take so long for my heart rate to go up, and why it happens when it does.

Any thoughts?

[kaff]

I use a stationary bike at the gym. I check my heartbeat on the fitbit and with the bike pads provided and they are always exactly the same. The same thing happens to me...my heart rate is relatively low for a while and then after a while it goes up and stays up. Don't know why, esp since I feel more stressed when I start than when I've been moving a while.

[mahmoudhany]

Hello @batspocky and @kaff
I couldn't really find the guide of the Charge HR, but I have the Charge 2's.
They had actually mentioned that exercises that cause you to bend your wrist, like biking, could interfere with the heart rate signal.
You can check it yourself here on page 5: Charge 2 manual
So I assume that the same issue should be in Charge HR as both use the same technology.
Hope that have helped you.