If you're in good health, your watch may actually be doing a good job measuring your heart rate. When you go cycling, it just takes that long for your heart ra

If you're in good health, your watch may actually be doing a good job measuring your heart rate. When you go cycling, it just takes that long for your heart rate to increase significantly enough to trigger the watch's activity detection software. The way I see it, the problem isn't a question of accuracy so much as the watch trying to guess activities it has no business guessing. The watch should focus on things that it's good at: gathering a reasonably accurate consumer grade heart rate and maybe showing notifications or the time if it has a display. Leave activity detection to something with more situational understanding.