Hold for 30 seconds, or as long as you can. Mountain climbers involve the same type of lower-body motion as the reverse crunch. Begin in plank position. Bend one knee, bringing it toward your chest.

Skip the crunches! Try these 7 standing core exercises for a stronger, sculpted midsection—no floor work required.

It’s a common fitness dilemma: You’re banging out crunches ... lower abs workout. Lie on your back with right leg and arm straight on the floor and at a 45-degree angle from body, left leg ...

Place your hands by your temples, with your elbows pointing out to the side. Lift your left knee, and at the same time, bend ...