It’s to many steps (clicks) to start and end a exercise in a workout. Now the procedure is a 6 click setup for each exercise if you use the app (iPhone)
1. Click on exercise 2. Start video 3. Click on fullscreen 4. Turn mobile sideways 5. When video stop click on back to return to list. 6. Remember what comes next as no marking indicates next exercise (in a long list also scroll down). Now begin from step 1.

Ultimate would be a 1 click procedure. Click on exercise, video starts automatically and goes to full screen automatically when you turn your phone. When video end you automatically come back to right place for next exercise in list. Then click 1 time and procedure starts over.