I moved from a simple VivoSport to the VivoActive 3 specifically because I want to be able to track a variety of parts of workouts. I found there are some training plans that look useful, and have tried those as well as used the watch to track walking, rebounding and strength training. I pretty much have the ST workout deal clear. But the running plan sometimes is confusing me. The plan clearly displays next steps in the workout, but it's not obvious how to acknowledge that I am starting that next step. On the VivoSport I think it was always true you would double-tap on the display to go on. With the VivoActive, sometimes using the button takes me to the menu to edit widgets. Other times the watch responds by displaying the aforementioned red square or green arrow. (I see them appear sometimes in other activities on the watch also). WHAT do these do, or what do they mean? FWIW I am not listening to music at the time and have no BlueTooth connected.
I do really like the VivoActive in many ways, and this is not all that HUGE a problem, but it IS pretty annoying. I can't find anything in the User Manual, yes, I did look.