Hi
To track and record the most accurate results for workouts on your Apple Watch, be sure to use the built-in Workout app (or a third-party fitness app that shares data to the Health 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.
To record workouts that are neither included within nor sufficiently similar to those in the main list of activity types - including when tracking strength training / weights workouts - choose "Other" as the activity type. For "Other" workouts, Apple Watch credits one minute of Exercise for each full minute of the workout and Active Calories at a rate equivalent to a brisk walk or based on data recorded by the heart rate sensor, whichever is higher.
When saving an "Other" workout, tap on "Name Workout" to label your activity from a range of options, which include "Strength Training".
For convenience, the workouts that you do most often will be offered as Quick Start options within the Workout app, including previously saved Other workouts with their saved names pre-selected.
For the best performance from the heart rate sensor during workouts, ensure that you wear your watch snugly (but not too tightly) on the top of your wrist. Apple suggests that you consider tightening the band before starting a workout and loosening it again afterwards.
Keep in mind that the sensor is likely to give better results for workouts that involve rhythmic (eg running) rather than irregular (eg boxing) movements. Other issues that can impact sensor performance include skin perfusion and wrist tattoos:
Your heart rate. What it means, and where on Apple Watch you’ll find it. - Apple Support
For workouts that involve flexing your wrists (such as when lifting weights), it may also help to move your watch a little higher up your arm, away from the flexing joint.
After being saved and synced to your iPhone, workout data can be reviewed via the Activity app (Workouts tab) and the Health app on your iPhone.
More information and instructions:
Use the Workout app on your Apple Watch - Apple Support
Work out
Use the Activity app on your Apple Watch - Apple Support
Use the Health app on your iPhone or iPod touch - Apple Support
