us, the killer apps for the Apple Watch are its health and fitness features. watchOS 9 improves that already impressive collection with new SWOLF efficiency ratings for swimmers, better tracking of triathlons, significantly improved running features including form monitoring and an option to save favorite routes, and the ability to build your own custom workouts directly from your Watch. The new Heart Rate Zone training is particularly welcome, bringing the Apple Watch up to speed with rivals’ dedicated running watches.
