If you create a client a regular workout and have them do an exercise for a certain amount of time, you aren't able to increase the time in the progression spreadsheet unless that exercise is a "cardio" exercise. Obviously you can label the exercise as such but then it adds a ton of extra categories for the client that don't apply to the exercise. You also can't edit exercises from the Trainerize library, so if you are using one of those and want to have the client do it for time, there won't be any way to increase the time the following week.