Corgel said these work your transverse abdominis, meaning your deep core.
- Start resting on all fours with a dumbbell on the left side of your body.
- With your palms flat, rise up off your knees onto your toes into a high plank position. Your legs should be straight. The wider your feet are apart, the more stability you'll have while doing the exercise.
- Squeeze your glutes, keep your hands directly underneath your shoulders, and contract your abs (keeping your belly button pulled in) to prevent your butt from sticking up.
- With your head and spine in line, look about one inch out in front of you, and don't tuck your chin.
- Maintaining this form, grab the dumbbell with your right hand and pull it underneath your body until it's on your right side. Be sure not to rotate your hips.
- With control, grab the dumbbell with your left hand and pull it underneath your body until it's back on your left side.
- This counts as one rep.