Apple Watch users can now track their heart rate zones during workouts, a feature that can help them optimize their exercise routine and monitor their progress. This feature is especially useful for those who are training for a specific event or goal, such as running a 5K. With this information, users can adjust their intensity levels to reach the desired heart rate zone and achieve their fitness goals.

Source: https://www.cnet.com/tech/mobile/5k-season-is-here-to-train-smart-enable-this-apple-watch-feature/#ftag=CAD590a51e