The 25 Best Exercises to Tone Your Abs (and None of Them Are Crunches)

• Get on all fours, with your knees under your hips and your hands under your shoulders. Remember to keep abs engaged and keep your back flat.
• Reach out with your right hand and extend your left leg out behind you.
• Round your back and head to connect your right elbow with your left leg under your body. Extend right hand and left leg back out.
• Repeat for a total of 15 times, then switch sides.

See the quadruped in action here.