Apple Watch - Getting weight lifting to count towards "move ring"?
Make sure you are using the Workouts app on the watch as this will make the heart rate monitor get your heart rate more often. Therefore, it won't miss any spikes from lifting and moving about.
Make sure your watch is securely fitted so the heart rate monitor can get an accurate measurement!
Lastly, it's a bit hard for a device on your watch to know that you are using weight resistance, etc. so don't expect much. Perhaps we'll see some updates from Apple about this, here's hoping!
It doesn't seem like the Move ring can be filled with that sort of activity, though it would be nice. However, I don't do any weight lifting myself, but I do remember that just doing what may have been simplified bicep curls close to my body was able to fill it a little, and actually significantly upped the distance I had gone that day, as though the watch thought I was running.
For the time being, you're right that you'll have to use third party apps. This may help. It offers a few different options. I didn't read very far down, but it looks like you can use either Gymaholic or Fitlist based on personal preference, though Fitlist seems more popular in the thread.
Right now, third party apps won't be able to fill the "Move" ring. However, with the release of watchOS 2 this fall, you may have more luck. Developers will then be able to access health data on the watch, using sensors such as the heart rate monitor, etc., and creating their own haptic buzzes. I'm not positive that this new openness for developers will cover the Activity app, but it might. Time will tell.
There's also this, which again is not guaranteed. You can never quite know with rumors regarding Apple.
I suppose all of this adds up to say that for now, you'll have to use third party apps and their nonnative services, meaning that the Activity app will not be integrated with your weightlifting. But after a bit of waiting, come fall, you'll almost definitely see a whole bunch of native fitness apps pop up in the App Store, with weightlifting apps likely being among them.
Select and run an "Other" workout type. When you're done with the workout, choose "Name Workout" and then select one of the other activity types such as "Strength Training".
Once you've done this, "Strength Training" will appear as a top-level option for your next workout
At the end of an Other workout, you can choose a name for your workout from a list of options. This can help categorize different types of activity, like dance, strength training, or cross training.
https://support.apple.com/en-gb/HT204523#endorpause