Conquered the Plank? Try the Ab Wheel — These 4 Exercises Will Make Your Whole Body Shake

"This is a staple of our core training as a progression from the plank," Eric and Ryan told POPSUGAR.

• On your knees, hold the ab wheel directly below your shoulders.
• Roll the ab wheel forward slowly, engaging your core as you do. Roll forward until your arms are fully outstretched and your back is flat.
• Use your core to pull your arms back in, rolling slowly back to the starting position.
• This completes one rep.

For this ab wheel variation, which takes a step up in difficulty, you'll simply elevate your knees on a raised surface, such as a mat. "This increases the range of motion of the ab wheel rollout and in return, creates a more challenging position to stabilize and resist extension," Eric and Ryan told POPSUGAR.

• Kneel on your knees on a raised surface, such as stacked mats, holding the ab wheel directly beneath your shoulders.
• Roll the ab wheel forward slowly, engaging your core as you do. Roll forward until your arms are fully outstretched and your back is flat.
• Use your core to pull your arms back in, rolling slowly back to the starting position.
• This completes one rep.

After conquering the first two exercises, Eric and Ryan recommended this elevated plank march on the ab wheel to get your lower body involved as well. It's challenging for both your abs and your balance.

• Get into a high plank position with both hands on the ab wheel and your arms directly below your shoulders.
• Lift your left leg slowly, keeping your foot flexed and core engaged so your back doesn't sag.
• Set your left leg back down, and repeat with your right leg.
• This completes one rep.

Eric and Ryan called the standing ab wheel rollout "the king of all ab wheel exercises." It's very challenging, so they recommended a slight modification: from a standing position, roll out into a full extension against a barrier, which will allow you to come to a stop. Then, drop to your knees and roll back.

• Set a barrier, such as a block or barbell, on the ground.
• From a standing position, bend from your hips to set the ab wheel on the ground, slightly bending your knees.
• Roll out the ab wheel slowly, going as far as you can without allowing your back to dip. Engage your abs the whole time to stabilize.
• Once you hit the barrier, drop to your knees. Slowly roll the ab wheel back.
• This completes one rep.