Why it made the list: This harder version of the Russian twist works the obliques while requiring the upper abs to contract isometrically. To recruit the obliques, you either need lateral flexion (bending to your side), trunk rotation (twisting), or sucking in your belly. Doing your twists works the trunk-rotation function of the muscle, so really focus on the contraction. Try to get a little crunch on either side after the rotation to up the ante.
When you're doing exercises to strengthen these muscles, think of the abs and core as one unit. Even when you do exercises that recruit more of one muscle than the others (for example, side planks that really fire up the obliques), you'll notice that you still have to engage your entire midsection to do them right, which is proof that these muscles are never working completely alone. It's important to show equal love to all of the muscles of the core so that this unit can power itself properly from all angles.
Once you've reduced the layer of body fat to the point where you can find your six pack, performing specific ab and core strengthening exercises will make them much more visible. Once you understand how to safely exercise your abs, you'll find core exercises are most effective when the torso works as a solid unit and both front and back muscles contract at the same time, and you perform multi-joint movements.
Start by placing your heels on a low bench and holding two light dumbbells (begin with 3 pounds). Place a rolled-up towel under your lower back to increase the range of motion of your upper abs. Point your toes. From this start position, raise your upper body to the position shown in the second photo. Breathe normally. Now press the weights overhead. Keeping your arms straight, press your heels hard into the bench, then lower your upper body and allow the weights to arc behind your head.
When it comes to working the core, many people focus on abdominal muscles, and neglect their obliques (or what you may know as “side abs”). But, says Barrett, these clandestine muscles are just as important: they “keep everything tucked in.” To get a good oblique workout in, head to the pulley machine and start doing some Paloff presses. If you don’t know how to perform the exercise, read our comprehensive guide on mastering the move.
But instead of just trying to perform as many reps as possible, slow down and really focus on the quality of the movement—especially the eccentric, or downward motion, of the exercise, he says. “The eccentric contraction is the most important phase when sculpting any muscle.” Plus, focusing on quality over quantity will help protect your back (some experts say crunches can be potentially troublesome for guys with back issues.)