Work out with Apple Watch
The Workout app 
on your Apple Watch gives you tools to manage your individual workout sessions. You can set specific goals, such as time, distance, or calories. Your Apple Watch tracks your progress, nudges you along the way, and summarizes your results. You use the Fitness app on your iPhone to review your complete workout history.
watchOS 9 offers several new Workout enhancements. They include the following:
Heart Rate Zones: Monitor the intensity of a workout by viewing Heart Rate Zones on your Apple Watch. Heart Rate Zones are automatically calculated and personalized using your health data, or you can create them manually.
New workout views: See important metrics for different training experiences. Turn the Digital Crown for new views of metrics like Activity rings, Heart Rate Zones, Running Power, Elevation, Splits, and segments.
New running metrics: (Apple Watch SE and Apple Watch Series 6 and later) Running form metrics, including Stride Length, Ground Contact Time, and Vertical Oscillation, can be added as metrics in Workout Views.
Custom workouts: Tailor work and recovery intervals to suit your training style. Receive alerts for pace, heart rate, cadence, and power.
Multisport workout: For triathlons, or activities with any sequence of swim, bike, and run, the Multisport workout uses auto-detection to easily switch between workouts. Details of the different workouts are automatically recorded, along with the transition times between them.
Running power: (Apple Watch SE and Apple Watch Series 6 and later) Apple Watch measures the effort you put into your run, displays the amount of power you’re expending (measured in watts), and helps you stay at a sustainable level.
Race Route (watchOS 9.2): If you routinely run or cycle the same route, you can race against your last or best result in an Outdoor Run or Outdoor Cycle workout.
Automatic track detection (watchOS 9.2): When you’re at a track and start an Outdoor Run workout, you’re prompted to begin a Track workout, where you choose a lane to run in and, optionally, receive lap alerts that show distance, time, and pace as you complete each lap.
Swimming enhancements: Kickboard detection has been added as a new stroke type for Pool Swim workouts. Also, swimmers can now track their efficiency with a SWOLF score—a stroke count combined with the time, in seconds, it takes to swim one length of the pool.
See Calibrate your Apple Watch for improved Workout and Activity accuracy for information on how your Apple Watch is calibrated.
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