You have to enter your heart rate recordings manually, which is best if you used a Polar HRM. That can be done by going to Log, then Heart, and find out the values of your Resting, Normal, and Exertive heart rates each time you have them strength tested.
Active HRMs like Samsung Galaxy Fit/Gear 2 are not entirely reliable as they are worn on the wrist and the values go all over the place. So it wouldn't appear too good to have one built on a FitBit right now. I even tried the Withings Pulse O2 and that wasn't entirely reliable either. Only if it's linked to a Polar or ANT+ HRM would it be more reliable as it's closer to your heart.
