Enable Power Saving Mode for Workouts
Depending on the type of workouts you do, and how much data you want to collect, you can take a lot of the load off your battery by switching on the one power-saving mode the Apple Watch already does have.
- On your Apple Watch, open the Settings app.
- Scroll down to the bottom and tap Workouts.
- Tap the toggle beside Power Saving Mode to turn it on.
As you can read from the description for this setting, this toggles off the Always-On display, cellular data, and the built-in heart rate sensor during walking and running workouts. You’ll still get calculations for active calories, distance, pace, and elapsed time, although the active calories may be slightly less accurate without the heart rate sensor.