Core Performance Essentials: Workout

[mattyst18]

I have recently purchased Core Performance Essentials and have progressed to Level 2. My question is about the time exercises. Does it call for one rep of the prescribed time or 6, 8, 10 or 12 reps of the prescribed time? Through level one I was doing the amount of reps while holding for the amount of time. (Ex) I was doing 10 reps of 20 sec. per exercise in Level 1-Stage D. Should I just do one rep of the prescribed time or both?