136 to 150 beats per minute: according to Kaiser Permanente's target heart rate calculator, this is the sweet spot that I'm supposed to go for when I'm exercising. My latest run I averaged 131 bpm, according to my new FitBit Surge. So that's encouraging how close I am.
But how important is being in your "target heart rate" as a goal? According to the Mayo Clinic your perceived exertion actually maps pretty closely to your heart rate. That is, if you feel like you are working hard, it's likely that you are in your target heart rate for exercise. If it feels easy and relaxed, you are probably below. And if it you feel like you are going to die, you are past your recommended heart rate.
That said, monitoring your heart rate is a more objective and trackable measure over time. As I run more and more, I find that a short run of a couple of miles doesn't feel that difficult, unless I really push it or I'm going uphill the whole way. Same with dancing. Right now house dancing leaves me exhausted and breathless. But as I get better at it, I might find it feeling easier and more relaxed. Tracking my heart rate can help me understand if I'm still getting the same benefits from these activities as I used to, or if I need to change it up.