Can Fitbit accurately measure the heart rate during exercise?

It's not as accurate during exercise, but still provides general trends and effort levels. It works very well for resting heart rates. I have a Fitbit Charge HR and a Polar HR monitor with chest strap. read more

They connected volunteers to an electrocardiogram (EKG), which is the most accurate way of measuring heart rate. Then, volunteers wore the trackers — the Apple Watch, Mio Fuse, Fitbit Charge HR, and Basis Peak — while exercising on a treadmill at 2, 3, 4, 5, and 6 miles per hour. read more

I can sit on an exercise bike in the gym with heart rate monitors built into the handles and it will tell me that my heart rate is around 130-140 yet the Charge HR says that my heart rate is under 100. read more