Hi
To record workouts on your Apple Watch and record the most accurate results (including credits towards your Move (calories) goal), be sure to use the Workout app (or a third-party fitness app) and to choose the activity type that most closely matches your workout.
This enables your Apple Watch to use the most appropriate sensors and data sources when estimating results, including using tailored calorie calculations for certain workouts.
Apple Watch uses different sensors and data sources to track the results of workouts, depending on the activity type. For example, with Apple Watch (first generation) and Series 1 models, the watch can access GPS data from the paired iPhone if it is taken along during outdoor walking, running and cycling workouts. Series 2 has built-in GPS.
During general daily wear and when using the Workout app to record workouts when GPS data is either not relevant or not available (eg Indoor Walk), the Activity app and Workout app track your arm motion (measured by the accelerometer) when estimating results including pace and progress towards the Exercise goal.
For the best results, allow the arm on which you are wearing your watch to swing naturally as you move around during daily wear and to move as expected during workouts.
Estimations also depend, in part, on your personal information. To check that this is accurate - and to update it over time:
On your iPhone, in the Watch app, go to: My Watch (tab) > Health > Edit - tap and adjust items, then tap on Done.
Calibrating your watch can improve the accuracy of estimations made by Activity app and Workout app. More information and instructions for calibrating your watch are available via the link below. The article also includes instructions for resetting existing calibration data and starting afresh. Resetting your calibration data will not erase your Activity history.
For the best performance from the heart rate sensor (data from which is used when estimating calories) during workouts, ensure that you wear your watch snugly on the top of your wrist. Apple suggests that you consider tightening the band before starting a workout and loosening it again afterwards:
Your heart rate. What it means, and where on Apple Watch you’ll find it. - Apple Support
To receive Exercise credit for the full duration of your workouts regardless of their estimated intensity levels, track them via the Workout app using "Other" as the activity type. This credits one minute of Exercise for each full minute of the workout. Active calories are estimated at a rate equivalent to a brisk walk or based on data recorded by the heart rate sensor, whichever is higher.
More information:
Use the Workout app on your Apple Watch - Apple Support
Use the Activity app on your Apple Watch - Apple Support