After you’ve mastered two sets of 15 reps to fatigue, you can add an additional set or you can progress to a heavier weight level in the 8 to 12 rep range. Increase your weight by up to 5 percent. For example, let’s say you’ve been lifting 40 pounds for 15 reps for two sets. To progress, you would increase by 2 pounds and lift 42 pounds for 8 to 12 reps for one set.
The challenge with lower weight ranges is that it is difficult to find small weights to add the incremental poundage. If you’re working on machines, look for the small 5-pound bars that you can rest on top of the stack. If you’re working with dumbbells with narrow handles, you can hold more than one in your hand.
Another way to progress your program is to add variety by performing more exercises for each muscle group. This continues to stimulate the muscle by working the muscles through different movement patterns and by requiring more muscle fibers to work.