[neillyons]

I looked at the Apple watch but choose Garmin as it has a physical button to start and stop my run. I don't know if this is still the case but with the Apple watch I think you have to tap the touch screen. Takes too long, especially when every second counts on a 400m lap round the track :-P

[aldur]

I discovered this recently, but can start/stop by clicking the crown and the side button at the same time.

[tzs]

You can stop a workout by telling Siri "end workout".

I'd expect that you can also start one with Siri but have never actually tried, mainly because the idea of using Siri to start/stop workouts never occurred to me until reading this thread, which I happened to be doing this morning while doing a workout on my treadmill.