Activity green ring not filling while non-workout outside walk or cycle [Apple Watch 2] After my Apple Watch 1 I decided to switch to the Apple Watch 2 and gave my GF also an Apple Watch 2. The strange thing is: My green activity ring is filling during my day without starting a workout (just walking stairs etc) but my GF's watch barley updates the green ring. 

Example:
We are walking in the city next to each other. We both have around 2000 steps and walked 2K without a workout. My green ring is at 40%, hers is at 3%. 

How is this possible? We set the same movement goals.
The watch uses your heart rate to decide whether you're exercising. Maybe your heart rate increases over the threshold and hers isn't?

More info: http://www.imore.com/apple-watch-activity-tracking-5-tips-you-need-know