If you're doing standing free-weight exercises like squats, deadlifts, and overhead presses, your abs are probably getting a lot of training already. But if you still can't see them, implement this 30-minute plan on your off days. Over the course of a month, you'll vary the exercises and intensity each week so that you build functional core strength, endurance, and power—as well as carved—out abs. Each workout consists of only three moves.
Frequency: Perform each workout (I, II, and III) once per week for one week, resting or performing your other weight training on days in between. For example, you could do an upper-body workout on Monday, perform ab workout I on Tuesday, and do a lower-body workout on Wednesday. You could then do ab workout II on Thursday, another upper-body day on Friday, and ab workout III on Saturday (Sunday you'd rest).
How to Do It: Perform the exercises as straight sets, completing all the prescribed sets for an exercise before moving on to the next one.
Weight: Use the heaviest weight that allows you to complete all the prescribed repetitions for each set.