This Sprinter Situp Challenge Will Carve a Perfect Obliques

It's worth training your body to do this well, too, both so you can twist and rotate at your torso more effectively, and because it'll give you that refined six-pack look you may be craving, too. Twisting your torso requires obliques, intercostal muscles, and serratus muscles to work with your abs, and it brings out the details in those muscles. And one of the easiest ways to train that is with the Sprinter Situp to Hollow Rock Challenge from Men's Health fitness director Ebenezer Samuel, C.S.C.S.

This countup game looks simple and requires just your bodyweight (translation: it can be done anywhere) but it's deceptively challenging. You start in the hollow hold position, already a position of core work, and transition to a twisting sprinter situp, pushing your obliques into action. Then you land in a corkscrew hollow rock, an ultra-challenging position for your abs and obliques. "From this stance," says Samuel, "you're twisting and continuing to twist, a new challenge for your abs and obliques to work together."

The best part: You don't need any equipment at all.

Start in a hollow body position: Lie on your back. Press your lower back into the ground. Lift your shoulder blades off the ground one inch, and your legs off the ground all without letting your lower back lose contact with the ground. Tighten your abs to drive your lower back into the ground.
Do a sprinter situp, contracting your abs then bringing right elbow to left knee; your right leg stays straight. Do 1 rep.
After that one rep, keep your right elbow connected to your left knee; you're now in corkscrew hollow rock position. Do one hollow rock, then return to hollow body position.
Do 2 sprinter situps; after the second one, stay in corkscrew hollow rock position and do 2 hollow rocks. Continue this pattern, laddering up to 5 sprinter situps and 5 corkscrew hollow rocks.
Rest 30-45 seconds. Do 3 sets per side.

The entire blend of moves challenges you to both rotate and own rotation, says Samuel, and it'll force perfect sprinter situp reps. "By forcing you to go right into corkscrew hollow rock position after a sprinter situp, you have to own sprinter situp position," he says. "It prevents you from being sloppy with your sprinter situps; I often see people forget to really touch elbow to knee. You can't do that when you know you have to get elbow to knee and keep them there at some point. It makes every rep better."

Try the Sprinter Situp to Hollow Rock Challenge anytime, anywhere for an ultra-quick core workout. You can also use it at the end of any full-body or bodypart workout. "It's a quick ab burn you can do anytime," says Samuel. "That's one of its best parts."

For more tips and routines from Samuel, check out our full slate of Eb and Swole workouts. If you want to try an even more dedicated routine, consider Eb's New Rules of Muscle program .