If the user toggled the permission (turned off and turned on again) in Settings "Privacy & Security -> Research Sensor & Usage Data -> Optical Sensor -> apps and studies with access", will the holding period get reset ? The 24 hours holding period is counting from the calendar day 24:00 or the time startRecording() got called ? I tried the following step but got a empty export, any ideas why ? Delete the app Install the app from Xcode with dev profile Called startRecording() and wait 24 hours exactly During the 24 hours, I wore my watch for around 12 hours, and update the app in place(without change the Xcode build number) for couple times. Export from system settings "Optical Sensor -> Export All Current Collected Data"