It was the hardest stretch of the race, 1,000 feet of what seemed like nearly vertical incline between me and the finish line. As I approached the summit, my heart felt like it was about to burst through my chest. I didn’t need my Fitbit to tell me I was working hard on this hill, but I looked down at my wrist and there it was: 185 beats per minute. I had reached my peak heart rate.

Heart-rate tracking is a standard feature on many fitness trackers such as the Apple Watch ($399 at Amazon), Galaxy Watch and most Fitbits, but they rarely explain what to do with that information.

(Read More)