This is my second week on the 12-week program and I have noticed some results! To gain mass you want to use heavier weights with lower reps. I have done some modifications to the plan. I go to the gym Monday-Friday and I have three days of cardio. Monday: Cardio and an AB workout (just google 'core workouts' and find one that fits your needs), Tuesday: Legs and Calves, Wednesday: Cardio/Back & Biceps, Thursday: Shoulers & Triceps, and Friday: Cardio/Chest. I was dying the first week and I think it's a good workout with some tweeking to fit YOU! Also, invest in a good protein supplement to take before, during, or after each workout!
HOPE THIS HELPS!!!