Delete old activity on iPhone and Apple watch 3

Data can be deleted selectively using the Health app on your iPhone. For example:

- Go to the Health Data tab > Fitness > Stand Hours > Show All Data > Edit (upper-right) - then either tap on Delete All (upper-left) or delete individual data points by tapping on the minus sign next to them > when finished, tap Done (upper-right).

Alternatively, to remove all Health and Activity data from your iPhone, you can reset and partially restore your iPhone. Note that this involves the permanent loss of all sensitive data on your iPhone and watch, including Health data, HomeKit data, and saved passwords:

• Unpair your watch from your iPhone via the Watch app:

  Unpair your Apple Watch and iPhone - Apple Support

• Make an unencrypted backup of your iPhone:
  • This must be done via iTunes on a computer (because iCloud backups are encrypted as standard);
  • Do not select the option to Encrypt iPhone backup;
  • How to back up your devices using iCloud or iTunes - Apple Support
• Erase all content and settings on your iPhone:

  On your iPhone: Settings > General > Reset > Erase All Content and Settings.

• Restore iPhone from the unencrypted backup:

  Restore your device from an iCloud or iTunes backup - Apple Support

• Pair and set up your watch:
  • Choose to restore the watch from backup when offered the option during set up. This will restore most of your data and settings, with some exceptions (eg Apple Pay cards, passcode).
  • Set up your Apple Watch - Apple Support