You can check whether a workout has already been completed directly from the workout library and the workout detail page.
Open the workout library
Tap Workouts from the bottom menu, then select the Classes section.
Identify new workouts
If you have not completed a workout before, the button at the bottom of the workout page will say Start and the completion icon in the top right will not be highlighted.
Identify completed workouts
If you’ve already finished a workout before, the completion icon in the top right will be highlighted and the button at the bottom will say Restart.
Note: For a workout to appear as completed, you need to mark it as complete at the end of the session.