Pairing an Apple Watch changes the mix of activity data in Apple Health, but it does not simply disable every fitness sensor on your iPhone. Apple Health can receive records from the iPhone, Apple Watch, and third-party apps, then organize overlapping data by source priority.
That distinction matters when activity in Zolt looks different after you add a Watch.
How Apple Health handles the sources
Apple says the iPhone can continue to capture steps and walking information with its built-in sensors. A paired Apple Watch contributes its own Activity, workout, and heart-rate records. When several sources contribute the same data type, Health uses its source-priority rules to organize them. Read Apple's guide to Health data sources.
You may therefore see a different total because the Watch becomes an important source, the devices covered different parts of the day, or a third-party app also wrote activity.
What to check first
Open Health on the iPhone, then inspect the affected data type.
- Go to Browse or Search, then Activity.
- Open Steps, Workouts, or the missing measurement.
- Scroll to Data Sources and Access.
- Check which devices and apps supplied records.
- Open Show All Data to inspect the affected time period.
Do not unpair the Watch as a first troubleshooting step. Source inspection is faster and avoids unnecessary setup.
Common explanations
The Watch was left behind. The iPhone may still record steps when carried, but Watch-only measurements such as continuous heart rate will be absent.
The phone was not carried. The Watch may record activity, but the iPhone cannot count movement while it is elsewhere.
A workout app wrote a duplicate. Two records can describe the same session. Review source access before deleting anything.
Permissions changed. Zolt needs read permission for the relevant Health categories.
Sync is still in progress. Give Health and Zolt time to finish syncing, then reopen the app.
If Zolt still looks wrong
Compare the source record in Health with the same period in Zolt. If Health is missing the data, fix the device, source, or permission first. If Health is complete but Zolt is not, contact support with the affected dates and screenshots.