First, consider auto-recognize which has been around for many years. It applies to 8 exercise types which fitbit claims it can recognize based just by the wrist movement pattern. In the phone app, you can set the minimum length of time (at least 10 minutes) for this activity to count as an exercise session, or you can set this activity to never be recognized. For instance, some people who never swim find it helpful to set 'Swimming' to 'Ignored' to prevent housework form being incorrectly recognized as swimming. This auto-recognize is good at recognizing walking or running and gives you credit for a day of exercise, and gives you a workout summary with some details. But my personal belief is that for other exercise you are better off using the Exercise App on your wrist to be sure the exercise is recognized and you can classify as you wish. Auto-start is much more recent. It has been on the "smart watches" for a while but has recently been added to several "trackers". It works for these few exercise types: bike, elliptical, rowing, run, spinning, walk. As soon as fitbit recognizes these exercise types, it starts the Exercise App and all the options you have selected in the Exercise App. The Exercise App is when you start the exercise session from your fitbit device and choose the exercise type first. Before you then start the exercise if you swipe up from the little arrow at the bottom of the screen, you get to see several option that apply just to this exercise choice that will apply every you do this type exercise, such as having 3 different stats of your choice show on the screen, choosing a goal of time, AZM, etc, GPS on or off, and several others. If you have auto-start set to on, I don't suppose it makes any difference if you have auto-recognize to on or off. If you have-recognize on and auto-start off, you will still get your run recognized as a workout. I forget if there is someplace else that sets to turn GPS on as a default. But you will not get any other of the defaults you have set in the Exercise App such as showing the 3 stats on screen, etc. That turned out longer and more complicated than I expected. I hope it made some sense and someone appreciated it.
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