Hi
Apple has not disclosed details of the algorithm that is used by Apple Watch for awarding Exercise credit.
To credit progress towards your Exercise goal, the Activity app aims to identify activity that equals or exceeds the intensity of a brisk walk. This requirement applies both during general daily wear and when recording workouts via the Workout app. Exercise credit is awarded for each minute during which this requirement is met.
The definition of a brisk walk varies by person and depends on your personal information. To check that this is accurate:
On your iPhone, in the Watch app, go to: My Watch (tab) > Health > Edit - tap and adjust items, then tap on Done.
When recording specific fitness activities, be sure to use the Workout app (or a third-party app that shares data to Health) and to choose the activity type that most closely matches your workout, including choosing Other for workouts that are neither included within nor sufficiently similar to those in the main list. This enables your watch to use the most appropriate sensors and data sources when tracking results.
For example, with Apple Watch (first generation) and Series 1 models, the watch can access Location Services data from the paired iPhone if it is taken along during outdoor walking, running and cycling workouts. Series 2 and Series 3 models have built-in GPS.
For the most accurate results, it may also help to check your Location Services settings:
On your iPhone, go to: Settings > Privacy > Location Services:
- Check that Location Services (the main setting at the top) is turned on.
- In the list of apps beneath, check that Apple Watch Workout is set to While Using.
Also enable options under System Services including Motion Calibration & Distance, Wi-Fi Networking and Mobile Network Search.
Resetting your existing calibration data and recalibrating your Apple Watch can improve the accuracy of estimations made by Activity app and Workout app. More information and instructions are available via the link below. (Resetting your calibration data can be equally as helpful for Series 2 & 3 models and will not erase your Activity history):
Calibrating your Apple Watch for improved Workout and Activity accuracy - Apple Support
If your Apple Watch is worn too loosely, it can believe that it has been removed, causing activity to not be tracked.
For the best performance from your Apple Watch - including the most accurate readings from the heart rate sensor, which is used continually during workouts - be sure to wear your Apple Watch snugly (but not too tightly) during your workouts. Apple suggests tightening your Apple Watch band before workouts and loosening it again afterwards:
Your heart rate. What it means, and where on Apple Watch you’ll find it. - Apple Support
If you would prefer to receive Exercise credit for the full duration of workouts, regardless of their estimated intensity levels, then track them via the Workout app using "Other" as the activity type. This will credit one minute of Exercise for each full minute of the workout. Active calories will be estimated at a rate equivalent to a brisk walk or based on data recorded by the heart rate sensor, whichever is higher. However, note that neither distance nor a route map are recorded for outdoor workouts under this workout activity type.
More information:
Use the Activity app on your Apple Watch - Apple Support
Work out with your Apple Watch - Apple Support