For my part, my Garmin estimates my lactate threshold heart rate. Whatever its accuracy, I find it's as good a number as any to set zones around. Otherwise, I h

For my part, my Garmin estimates my lactate threshold heart rate. Whatever its accuracy, I find it's as good a number as any to set zones around. Otherwise, I have a good estimate of my max heart rate from a couple of times I've hit it incidentally, such as during a race. Max heart rate hurts, and it's not a place to go to during normal training.